THE UNIVERSITY OF MICHIGAN COLLEGE OF ENGINEERING Department of Mechanical Engineering Student Project Reports INVESTIGATION OF DESIGN MEANS FOR HOME LAUNDRY APPLIANCES Basil G. iaskaras Jam'es C. McCall Robert 0,, Rice ORA Pr'j ect.. 07494 under contract with: WHIRLPOOL CORPORATION BENTON HARBOR, MICHIGAN administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR July 1968

TABLE OF CONTENTS Page COMPUTER SIMULATION OF THE TRANSIENT-STATE VELOCITY EXTRACTION DRYING EQUIPMENT (Basil G. Kaskaras) 1 1. Introduction 1 2. Simulation Method 3 3. Work Previously Compiled and Present Effort 4 4. Analytical Study 7 5. Computer Program Subroutines 16 A. Solve Subroutine 16 B. CALMAC Subroutine 17 6. Approximation Methods 19 7. Need for Experimental Data 20 8. Corclusion 20 9. Term Dictionary 21 10. References 22 INVESTIGATION OF CLEANING METHODS FOR HOME DISHWASHERS (James C. Mcall) 23 1. Introduction 23 2. Problem 23 3. Information on Cleaning Methods 24 A. Impact Cleaning 24 B, Solvent Cleaning 24 C. Emulsion and Diphase Cleaning 26 D. Vapor Decreasing 27 E. Ultrasonic Cleaning 27 F. Salt Baths 29 G. Brush Systems 29 4. Evaluation of Basic Cleaning Methods 30 A. Discussion of Evaluation 32 B. Impact Cleaning 32 C. Solvent Cleaning 32 D. Emulsion and Diphase 33 E. Vapor Degreasing 33 F. Ultrasonic 33 G. Salt Bath 33 H. Brush System 33 5. Cleaning Methods and Their Adaptability for Use in a Dishwasher 34 A. Impact Cleaning 4 B. Solvent Cleaning 34 iii

TABLE OF CONTENTS (Continued) Page C. Emulsion and Diphase 34 D, Vapor Degreasing 34 E. Ultrasonic Cleaning 35 F. Brush System 35 6. Feasibility of Building Dishwashers Using Various Cleaning Methods 35 A. Impact Cleaning 35 B. Solvent Cleaning 35 C. Emulsion and Diphase 36 D, Vapor Degreasing 36 E. Ultrasonic 356 F Salt Bath 36 G. Brush System 36 7. Proposed Dishwashers 37 A. Water Impact System 37 B. Solvent 37 CO Emulsion 37 8. Appendix 43 9. Bibliography 44 WHIRLPOOL VACUUM EXTRACT COMBINATION WASHER/DRIER ANALYSIS OF THE VARIABLES IN THE EXTRACT AND DRYING CYCLES (Robert 0o Rice) 46 1. Introduction 46 2. Conclusions 46 35 Re sul.t s 46 4. Result Uncertainty 50 50 Mechanisms of Moisture Extraction 50 6. Single Piece of Cloth Computer Program 52 A. Mechanical Extraction 52 B Drying 5 C. Falling Rate Period 56 D. General Procedure 57 E Specific Procedure 57 7. Machine Computer Program 61 A. Mechanical Extraction 61 Bo Drying 62 8. Experimental Procedures 64 A. Mechanical Extraction 64 Bo Heat and Mass Transfer Coefficients 67 iv

TABLE OF CONTENTS (Concluded) Page APPENDIX A. GRAPHS 1 - 8 71 APPENDIX B. FLOW DIAGRAM AND PROGRAM LISTINGS 81 APPENDIX C. COMPUTER PROGRAM NOMENCLATURE 88 v

COMPUTER SIMULATION OF THE TRANSIENT-STATE OF VELOCITY EXTRACTION DRYING EQUIPMENT Basil G. Kaskaras 1. Introduction This work represents an attempt to complete a computer program that will simulate the operation of a Whirlpool washer dryer laundry appliance. A successful simulation program will enable the elimination of costly prototype testing. The program at hand is flexible enough to allow the programming of different configurations of the components that make up the system. My task was to evaluate the work already in existence, establish the validity of the steadystate solution, and proceed into the transient-state operation of the system, (Fig. 1). 1

B~ ~~~~~~~a t t IU~~~~~~~~~~~~~~~U U) r s t;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~U 3~~~~~ e~~~~~~~~~~ 3 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~z ~E,,IIIi vi~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'~~~-s"~-c *~~~~~~~~~~~~~~~~4L..s ) ~;r~ 2~~~~~~~~~~~~C:

2. Simulation Method In writing a program that will simulate a complicated system, care must be taken to make the program general enough to allow for future modifications. The program at hand is of a general nature. It is based on the following logic: suppose that the system is working at an initial level of operation (steady state) at time equal to zero, as defined by the physical factors affecting the total performance, such as geometry of the components, fluid medium characteristics, and other parameters. This is the instant corresponding to the starting of the machine. Suppose now that over a period. of time following zero time an external excitation occurs, such as an instantaneous decrease in the quantity of fluid flow. This may be due to a decrease of the inflow nozzle area at the perforated plate location, caused by the turning around. of the clothes in the drum. This decrease in fluid flow will affect the system, causing a decrease in the power and. efficiency of the blower and a pressure rise across this same component. It will similarly affect all other components of the machine (see Ref. 8). Any excitation in the drum, therefore, causes a sweeping change in the system. This change proceeds from component to component (starting with the component immediately connected. to the drum, such as the nozzle in Fig. 1, and. ending with the one just before reentrance into the drum, such as the heater in Fig. 1) in small time intervals until it has affected the whole system. At this point, the system has reached a second steady state of operation that is certainly different than that at time zero. We see then that the system goes through a steady-transient-steady sequence of states over time. The exact nature of the transient response is not known.

It may have any of the forms shown in Fig. 2 or any other. Knowledge of this exact nature, however, is not necessary for the purposes of this computer program although it certainly is desirable. To simulate this transient state, an 8 approximation method has been devised. STEADY STATE STEADY STATE TIME Fig. 2. Steady-tpansient steady-state representation curve. It is understood that any subsequent excitation will result in another transient state followed by another steady state, and so on, for as long as the system is working. This is the time it takes to dry the clothes. Thus the overall transient state of the system is approximated by determining the conditions in the system at subsequent instants of time as affected by the turning around of the clothes in the drum that cover or uncover larger or smaller portions of the perforated plate area at these subsequent time instants. 3. Work. Previously Compiled and Present Effort At the start of this project, a great deal of analytical and programming material was already available, having been compiled by former graduate students, D. Lane, V. Wedeven, and J. Robinson (see U of M student project reports 07494-2-P 4

and 07494-3-P). The outcome of that work was a quite well-shaped computer program. In the beginning of the present effort, the program was fed into the computer and compilation was achieved along with some initial calculations that led to a solution for the steady-state operation of the system. Obviously, there was no card punch error and the program was in accordance with the computer language (MAD) requirements. I began by making an evaluation of the flow diagram and rechecking the analytical work. The flow diagram was judged to be good even though it could be written differently. However, such an effort was considered to be of no real value as it would. lead only to neatness not simplicity. The system simulated by it is too complicated to be described by a simple procedure. A very general flow diagram is shown in Fig. 3 (for a more detailed, diagram see Ref. 8). In Fig. 3, the box calling for the determination of a new perforated plate area clearly indicates the need for another computer program which will provide the present computer program with a new inlet area at each subsequent instant of time. (For such a program see Robert Rice's report.) Equation errors, found by checking the analytical work, may be due to three factors: errors due to lack of care in transferring from the literature to the program, derivation errors, and, errors due to unit conversion factors. All three types of errors were encountered in this program at various points and corrected. Only that part of the theoretical work that was found to be incorrect appears below, superceding the work done by the previously mentioned students. That part of the work that checked correctly with their work will not be repeated here as it can be located in their reports.

H(UM -P ~ ~ ~ ~ )0 4- 0 u o COO r-d u *H 0 0H )0 0 H 0 HH 0)C)P4|0) o | 4 r?' 0 0 P4 c C z 0 I - ) 1 b 0 o + U 0 0 0C ) 0 )0 03 U 0 o c o rl O O a) Q Q) CH O 0 *H Cco co.^~~~~~~~ _(U.~~~~~~~~~ \4-3 4' 0 d - 01 il ^.H C) )t M | ir-io 0 r 0| ) 4 C) r 43 rd \i 034, 04' 0 q- 0 - 0 r0).0 0)0 k rl ~rl rl~~~~~~~~~~~~E4 q. P

4. Analytical Study A. PIPES Adiabatic flow with friction in pipes is considered. Gas flow through a pipe or constant area duct is analyzed subject to the following assumptions: 1. Perfect gas (constant specific heats). 2. Steady one-dimensional flow. 3. Adiabatic flow (no heat transfer through walls). 4. Constant friction factor over length of pipe. 5. Effective pipe diameter D is four times hydraulic radius (cross-sectioned area divided by perimeter). 6. Elevation changes are unimportant as compared with friction effects. 7. No work added to or extracted from the flow. The controlling equations are continuity, energy, momentum, and the equation of state. The momentum equation must include the effects of wall shear stress and is conveniently written for a segment of duct of length 5x (Fig. 4): A- T nD~x =du pA - (p + dp 6x) A - TnDSx = pVA(V + - 6x - V) dx dx To7rD8x -,, (p+.d.8x)A pA dxji-{d V 4~v-,dV 8x1 ael x Fig. 4. Segment of duct of length 6.x 7

Upon simplification dp + dx + pVdV = 0 (P. 1) Since T, = pfV2/8, where f is the Darcy-Weisbach friction factor, dp + 2 dx + pVdV = 0 (P. 2) 2D For constant f, or average value over the length of reach, this equation may be transformed into an equation for x as a function of Mach number. Dividing Eq. (P. 2) by p, dp f pV2 pV - + - dx + dV 0 (P. 3) p 2D P P each term is now developed in terms of M. By definition M = V/c V2 = M2 kp (P. 4) or = kM2 (P. 5) for the middle term of the momentum equation. By rearranging Eq. (P. 4) dV =kM V (P. 6) Now to express dV/V in terms of M, from the energy equation V2 V2 h h + I- - = CpT + - (P 7) h"no = +2 = P 2 Diffe rent iating 8

cdT + VdV = 0 (P. 8) P By dividing through by V2 = M2kRT cp d.T +dV R kM2 T v 0 Since cp k R k-1 get dT d-V T = -M2(k-1l) (P. 9) Differentiating V2 = M2kRT and dividing by the equation, dV dM + dT (P. 10) V M T Eliminating dT/T in Eqs. (P. 9) and (P. 10) and simplifying dM dV -_ _dyV k-i- (P. 11) (ku)M2+l which permits elimination of dV/V from Eq. (P. 6) yielding PV kMdM - dV = (P. 12) (kl)M2+l And finally, to express dp/p in terms of M, from = = pRT and G = pV pV = GRT (P. 13) By differentiation 9

dp dT _ dV p T v Equations (P, 9) and (P. 11) are used to eliminate dT/T and dV/V: (k-l)M2+l dM dp (= _- - )M (P. 14) p2 M P 2-)M +1 Equations (P. 5), (P. 12), and (P. 14) are now substituted into the momentum equation (P. 3). After rearranging, f 2(-M2) d ~dx 3 ki 2 kM [(- )M +1] 2 dM k+1 dM = I? M3 -- T — (P 15) M[(k-)M2+l] which may be integrated directly. By using the limits x = 0, 3 = M,, x = L, M = M fL _ k+l M2P D JM - — Rn __ ^ — D kM2 I (P. 16) Mo 2(k )M2+1 or, 2 fL 1 ( +l k+l ((k-l)M2+2 D k O2 " 2k L\M (k-l)MO2+2 From Ref. 4, p. 224 L V2 V2 f - = k D 2g 2g Therefore L (kk)(D) (P. 18) 10

For computer adaptation of Eq. (P. 17), in accordance with the half-interval technique, the equation becomes [DLMAC] = k k+l-)M+2. 19) o^ * ^ -^ ^'"(^ {t ^ (P. 19) k\0 42M2 2k ~nL\~M/(k-l)Mo2+2 It is therefore possible to calculate the downstream pressure P2 using the relation P2 = RT,2 >1/2 P2 "2 \(P. 20) M2 2 k-1'k(l )M" 2 where, m, = downstream mass rate of flow T2 = stagnation temperature M2 = downstream Mach number R = perfect gas constant k = specific heat ratio The following relations also hold: T2 - 02 (P. 21) Tl+2 1+ - 2 P2 = L (P. 22) P2 RT2 0 2 -l 2 k/k-l Po 2 = P c + (P. 24) V = C2M2 (Ph 24) where ca = /kgRT2. (P. 25) 11

On the other hand, for rough pipes the following equations apply i ro = 1.74 +2 log16 - (P. 26) fL 1 2 PI 2 1 [1 - () - 2 log P (P. 27) D kM1 P while for smooth tubes f = 0.00357 + 030 3 (P. 28) (2 Rey) fkL 1 k+l (k+l)M2 - = ( - 1) + 2 n (P. 29) I M7-1) 2 k-l 2 2[1l+-M2] where D = hydraulic diameter f = friction factor B. HEATERS For turbulent flow (Rey > 6000) over banks of tubes regardless of whether they are staggered or arranged in-line, the equation o.6 ~. o0.33 c5 Pr 0 (H.1) kf where hc = film coefficient of heat transfer D = outside diameter kf = fluid thermal conductivity Pr= Prandtl number 12

kLf = fluid viscosity Qmax = mass velocity at minimum area, (fbm/hr-ft2) holds in reality, provided that the tube bundle has ten or more transverse rows. The values of the empirical coefficient cH depend on the tube arrangement and the Reynolds number. The frictional pressure drop in 2bm/ft2 for flow over a bank of tubes is given by 2 0 14 f'Gmax N 0.14 = p(2.09x108) b (H 2) where p = mass density, ~bm/ft3 f' = empirical friction factor N = number of transverse rows s = fluid viscosity of the stream ib = fluid viscosity of the fluid at the wall For staggered. tube arrangements and Rey > 1000 f' ~2+S 0i' o-18 maxDo. 0 0...25 (H. 3) ST-D 1-O" ~\ b For in-line tube arrangements and Rey > 1000 0.08 SL/Doa 1 Npr = (tC//Kf) = Prandtl number 15

2. JH = G N2/p = Colburn J factor where M 4M = Ac nD2 DG 3, Rey = Reynolds number hcD 4. = f Nusselt number 5. f = ((Ap/L)/(G2/2gcDp)) = friction factor where gc = conversion factor = 32.17 (ft;-bm/lbf-sec2) Ap L P frictional pressure drop per unit length For flow normal to banks of staggered. tubes, 2000 < Rey < 3.2 x 104 j = 0.33 Rey-0~4 (H. 5) where the fluid properties are evaluated at the mean film temperature TM = 0.5(Tb+Tw). For flow normal to banks of tubes in-line, 2000 < Rey < 352 x 10 jH = 0.26 Rey-0~4 (H. 6) where the fluid. properties are again evaluated at TMO For flow across staggered tubes, Rey > 1000, the friction factor is f' - [1 + 0.470 (xT-l) 108] Rey-o16 (H. 7) where transverse pitch ST T tube outside diameter Ho0D(N) 14

For flow across in-line tubes, Rey > 1000 = [0.176 + 0.32 XL(XT-1)-n] Rey0'15 (H. 8) where longitudinal pitch SL L tube outside diameter HDO(N) n = 0.43 +XL The definition of longitudinal and transverse pitch is illustrated in Fig. 5. Longitudinal pitch Flow || direction Transverse pitch (a) Longitudinal pitch Minimum flow area Transverse pitch I -I — + -t- -4 — + —Flow direction ~ - - -4 — 4- (b) Fig. 5. Definition of longitudinal and transverse pitch (a) for tubes in-line and (b) for staggeredtube arrangement. Since the Calrod heater actually used in the Whirlppol appliance under study can be represented by a staggered tube type of heat exchanger, the appropriate equations are used in the computer program. 15

5o Computer Program Subroutines Ao SOLVE SUBROUTINE This subroutine is used. to solve for the Mach number at a point if the following quantities are known at that point: stagnation temperature, stagnation pressure, area, and mass rate of flowo The following relations are known to be true: c = Tg (S. 1) V M = c (S. 2) P =P( k-1 M2)(k/k-l) = P( + 2 (S. 3) T T(1 + k-M2) (S. 4) p = pRT (S. 5) pVA (S. 6) Equation (SO 3) gives: k-, 2 k -k-l M (k/k-l) PO n= pRT(1 + -- M2 k-1 M)(k/k-l ) A RT(I + 16 (k/k-l RT( +6

= AM kg ~m Ig +( k-l 2) ( +k/k-l ) \g (1 + ((k )/2( )) m 0, k-1 (kSH)/2(k-l)) - AM\I-r(' + -" )M since k 1 k+l k-l 2 2(k-i) where m = mass rate of flow A = area V = velocity p = density R = gas constant T = temperature To = stagnation temperature P = stagnation pressure M4 = Mach number k = specific heat ratio For listing, see the Appendix. This function also incorporates the half-interval approximation technique as explained in this report. B. CALMAC SUBROUTINE The derivation of this function is given here for clarification purposes. This subroutine is used to solve for the Mach number at a point if the following 17

quantities are known at that point: stagnation temperature, pressure, area, and mass rate of flow. The following relations hold: c = kRTg (C. 1) V M c (C. 2) T = T(1 + k M2) (C. 3) p = pRT (CQ 4) m pVA (C. 5) From solve subroutine 1 have: P =P(1 A k-l M2) (/k-) =m (1o k-1 M2 ((k+l)/(2(k-l)5 Po = P(l + k^ M) k k- (1 + -~ M ) Consequently, To -k- 21/2 P (1 + k M2)12 AM 0 -(+-~-M2 m 0 1 1AT k I k-l M — Squaring both sid.es and transposing, get M 2 RT [1 + M2] M2 = ) ~ or *~[~ 2 RTo k) M4 + M2- () kg 0 (C, 6) where the symbols are the same with those used in the SOL3VE function.8 18

6. Approximation Methods The large number of idealized equations used in this program will, of course, lead into results that are not close to actual test data within the required accuracy. Consequently, approximation techniques are needed. that will compel the program to give accurate results. The half-interval technique is usable here when one of the quantities involved in an equation is unknown and is to be calculated so that the equation is true within specified. limits of accuracy. The solution is found. by means of an iteration looping. Example: Assume that we have the equation A = B where one of the factors b of the right member B is unknown. Also assume that for our purposes the equal sign of the equation must hold true within 2% of accuracy, that is,.98 A = B and b is known to be a number within the interval X...Y. Then by setting b (1) = X b(2) = Y x +Y b (3) = the equation.98 A = B will be satisfied after a certain number of iterations. In this program, approximately ten such iterations are being used. For an actual application of the above approximation procedure, see the SOLVE function in the Appendix. 19

7. Need. For Experimental Data Certainly experimental data should, be made available for purposes of comparison with the program output. At the present time, the lack of such data is not a critical factor since the program output values are undoubtedly incorrect. In the future, however, convergence of the program output within reasonable values will make the necessity for experimental data increasingly obviouso Such data will afford a check at each instant of time at every location of interest within the system. 8, Conclusion This program presents the same hazard. that all such large programs presentr,; That is, since the result of each equation is used in a large number of other equations for simultaneous solution of the system, in a chain reaction manner, an error at one point may later become highly magnified, thereby making the iprogram incorrect and futile. Consequently, when the small deviation fro:. reality of the idealized, equations used. in the program is — aken. into account., it is 6not expected. that the program will approach accurate valueso Therefore, it! is necessary to use approximation techniques that will cormpel tihe program to produce resuL.,;ts that are close to experimental values within tolerable limits of accuracyo The degree of agreement of the computer program results wi7th experimental values wwill dictate whether or not the program will (1) eliminate costly prototype test...ng, (2) simply give an indication of what is happening in the system, or (3) be of no value at all. 20

9. Term Dictionary (For a Complete Listing See Ref. 8). ALPAM - parameter used. in pipe calculations DFRI - parameter used. in pipe steady-state analysis DJiMAC - error measure in pipe Mach number calculations N - location in system between two consecutive components SCONC - parameter in SOLVE function 21

10. References 1, Arden, Bruce W., The Michigan Algorithm Decoder, revised. ed., Computing Center, University of Michigan, Ann Arbor, 1966. 2. Barron, Randall, Cryogenic Systems, McGraw-Hill, New York, 1966. 3. Kreith, Frank, Principles of Heat Transfer, International Textbook Co., Scranton, Pa., 1965, 4o Loitsianskii, L. G., Mechanics of Fluids and. Gases, Pergamon, New- York, 1966. 5. Shames, Irving H., Mechanics of Fluids, McGraw-Hill, New- York, 1962. 6. Shapiro, Archer H., The Dynamics and. Thermodynamics of Compressible Fluid Flow, Ronald Press, New York, 19535 7. Streeter, Victor L., Fluid Mechanics, McGraw-Hill, New York, 1962. 8. University of Michigan Student Project Reports 07494-3-p, Office of Research Administration, University of Michigan, Ann Arbor, December 1967. 22

INVESTIGATION OF CLEANING METHODS FOR HOME DISHWASHERS James C. McCall 1. Introduction It would be advantageous if a dishwasher could be built that might be smaller, cost less, require less power, handle more materials, clean better, clean faster, or clean in less time, or accomplish many of the above. This project involved the investigation of cleaning methods that would hopefully be better in some of the above aspects. The following paper is a presentation of all the work that led to the design, construction, and operation of a water impact dishwasher that could handle solid "abrasives" to create more mechanical scrubbing action. All the work is presented, hoping it may be of benefit to the reader. At the beginning of the project it was decided that a thorough investigation be done on all present-day cleaning methods. Later one would be picked to be built, and tested, but at no time would limitations of power, cost, and size be considered in the investigation or selection of any cleaning method. The feasibility of building a successful dishwasher using each type of cleaning method was also considered. On the basis of feasibility, water impact, emulsion, and solvent.dishwashers were proposed for selection of one to be built and tested. The water impact system with the additive was selected. It should be realized that most information available on cleaning refers to assembly-line parts cleaning. The information presented here will be consistent with that available, but these methods are certainly adaptable to cleaning dishes. 2. Problem The problem chosen for this project was to study all cleaning methods that might be useful for cleaning dishes and then select one to be built and tested. The dishwasher need not be conventional in any respect and it could conceivably clean only certain types of dishes with certain soils. This way the dishwasher could conceivably clean only pots and pans in a separate compartment that could eventually be incorporated with a conventional dishwasher. Cost, pQwer, and: size were not considered as factors since they could be handled at a later time 23

if such further work is considered desirable or necessary. Only the ability to clean and the feasibility and practicality of building and testing one in the laboratory were considered. 3. Information on Cleaning Methods A. IMPACT CLEANING Impact cleaning includes any type of mechanical scrubbing action achieved by.impact of particles and/or fluids. The conventional dishwasher is included in this, but its cleaning action is largely due to the chemical action of the detergent. Hence, it is more of a chemical cleaner than impact cleaner. Impact cleaning is done with many abrasives including sand, steel grit, steel shot, mud, synthetic or artificial abrasives, rubber slugs, and sawdust. (15:144-151)* Fluids include air, steam, and water. Sand is a good abrasive that can give a mild scrubbing action. When considering an impact system that uses a mechanical scrubbing action, one must be careful not to overrate the mechanical scrubbing action and assume that it will damage materials such as those found in kitchenware. Most sand blasters actually use an artificial abrasive that is much more abrasive than sand. Sand is used to clean delicate artwork and is almost the universal abrasive for glass,. vitralite, china, etc. (15:132) To give glass a fine frosting, it is necessary to resort to steel grit, (15:132) Vibratory finishing, included in impact cleaning, generally uses a barrel that contains an abrasive and the parts to be cleaned Rotary and vibratory motion creates a scrubbing action that is good for ceramic and plastic parts. The vibratory motion is created by offset weights or shafts where the amplitude is controlled by the weight. Water can be added to create a more mild scrubbing action and chemical compounds can also be incorporated. (12141 —142) B. SOLVENT CLEANING Solvents are often used to clean parts either by a dip tank method or by a spray system similar to the type of action used in a dishwasher. Solvents can be used hot or cold and are often reclaimed by distillation. *This notation is used to refer to the reference in the bibliography found at the end of this paper. The first number refers to the reference number and the second number refers to the page number. 24

Many commercial solvents are available. Best known is probably perchlorethylene, used for dry cleaning. Other solvents include trichlorethylene, methyl chloroform, trichlorothrifluoroethane, methylene chloride, fluorinated hydrocarbons, petroleum solvents, and Dow Chlorethane. A dirt-shearing action can be achieved by vertical agitation at 60-120 cycles per second with a five-minute normal cleaning action for some applications. (2:64) Solvent systems are used to clean clothes, metals, plastics, and other materials. Du Pont's Freon T-F is used in conjunction with ultrasonic dip baths to do precision cleaning of particles 1/40 the size of human hair for gyroscopes. It is nonflamable, nonexplosive, and virtually nontoxic. Its advantages include natural stability in resisting degradation, unlimited reuse of recovered solvent, and its ability to be combined with other solvents. (14:95) (For discussions on trichlorethylene, perchlorethylene, methyl chloroform, trichlorotrifluorethane, methylene chloride, and fluorinated hydrocarbons see 16:136 and the following pages.) Solvents tend to be expensive, but the effects of high cost can be reduced by distillation reclaiming. With distillation reclaiming, the solvent is generally hot when used. Petroleum solvents present a fire hazard and do not produce a high degree of cleaning. (16:137) The fire hazard makes petroleum solvents impractical for kitchen use. Alkaline cleaning is in effect a detergent action. (16:157) Surface active agents are used to bolster the efficiency of a cleaner and reduce the need for high alkalknity. (1:97) Alkalies include metasilicates, pyrophosphates, nonionic and ionic synthetic detergents. (1:98) Contrary to popular belief, alkaline cleaners can be used on aluminum. (1:97) Cold solvents have many advantages which are listed below: (13:58) 1. Equipment costs are lowered. 2. Contaminates that tend to set do not harden. 3. No time is needed to heat parts to temperature. 4. Design and installation are simplified. 5. Additives (wetting agents and rust preventives) that cannot withstand heat can be used. 6. Solvent breakdown is minimized. 7. Parts do not have to be cooled before handling. 25

C. EMULSION AND DIPHASE CLEANING Emulsion and diphase cleaners are solvent cleaners. They are considered separately here since they are handled differently and react differently. Emulsification occurs when a dilutent such as water is added to an emulsion concentrate. The two immisicible liquids are intimately combined as a stable solution in which the particle size of dispersed solvent phase varies from 1 to 10 microinch in diameter. Reduction of particle size during emulsification and maintenance of condition during the serviceable life of solution is governed by a surface-activating agent. (16:139) There are three types of emulsion cleaners. 1. Emulsifiable Solvent (16:138). An emulsifiable solvent is a diluted or undiluted petroleum solvent. It is effective in removing tightly adherent and heavy soils. It is normally used in a room temperature immersion bath, followed by a hot rinse that removes the loosened soil, but leaves a thin oily film. 2. Stable Emulsion (16:138-139). In a stable emulsion the dilutent is water. Stable emulsions simultaneously remove water soluable and solvent solu — able oils; however, they also leave thin oily residue. Stable emulsion cleaners may be used up to 180~F. Maximum effectiveness is achieved in spray systems, but it also performs well in soak-type cleaners. A stable emulsion has the ability to disperse a soil once it has been removed, thus preventing redeposition. 3. Diphase Cleaners (16:139). Diphase cleaners differ in that two distinct phases are present upon dilution. One is the solvent which may be the heavier or lighter fraction; the second is water. The solvent removes oils and wets the metal. The water dissolves water-soluble contaminates and wets mineral oils. Again a thin oily residue is left even after a hot rinse. Operating temperatures are limited by low-flash points. Emulsifiable solvents and stable emulsion cleaners contain four ingredients (16:139): 1. Organic solvent - usually a hydrocarbon such as kerosene or naphtha. 2. Acid soap or fatty acid which serves as emulsifying agent. 3. Blending agent which serves as wetting agent, providing a homogeneous and stable mixture of solvent and emulsifying agent. 4. Surface activating agent to increase cleaning effectiveness. 26

D. VAPOR DEGREASING Vapor degreasing is primarily used for the degreasing of metal parts by condensing a solvent vapor on the metal parts. Solvents with low boiling points could be used to clean dishes in a system that by its nature would reclaim the solvent by distillation. Vapor degreasing systems require no mechanical action and can consist of systems that use the following phases: 1. Vapor 2. Warm liquid + vapor 3. Boiling liquid + warm liquid + vapor 4. Vapor + spray and vapor (16:136) The advantages of vapor degreasing are: 1. Parts emerge dry. 2. It penetrates blind holes, etc. 3. Solvent cost is independent of soil removed due to redistillation. 4. System requires little space. (5:44) Trichlorethylene ("tri") and perchlorethylene ("per") are commonly used for vapor degreasing but both require volatile stabilizers. Both dissolve a wide range of soils, such as greases, waxes, resins, tars, gums, and fats. They are inert to metal, have low toxicity, and are nonflamable and inexpensive. Their properties include low latent heat value (low distillation cost), chemical stability, and ability to support cavitation in ultrasonic degreasers. Perchlorethylene has a fairly high boiling point (parts emerge too hot to handle), but tri has a lower one. Tri needs an additive to remove water, and both must periodically be checked for acidity and oil content. Both can have a neutral or alkaline solution. (5:.45-47) The limitations of tri and per include the inability to remove hard cakedon soils. Some soils react with solvents and consequently must be removed beforehand. (5:50) The solvents may attack some plastics and the vapors that,escape can be harmful if they come in contact with something hot. (9:129-130) E. ULTRASONIC CLEANING Ultrasonic cleaning is presently receiving much attention due to its 27

ability to clean and sterilize. It removes soil from 10 micron to submicron range. (17:62) It is generally used in conjunction with a tank-type system. Its main problem has been its high cost. (4 32) Ultrasonic cleaning has four critical components and processes for cleaning: 1. The generator, which produces electronic or rotary energy at resonant frequency of the transducer, generally converts line power to radio frequency power of desired frequency. (10:1) It can be an electronic oscillator with a 60-watt to many kilowatt output and is rated in average power or pulsated power (4 times average power). (18:52) 2. The transducer, which converts radio frequency power to mechanical energy at the same frequency, expands and contracts at the frequency of the generator. (10:1, 18:51) There are two types of transducers; the electrostrictive which expands and contracts in response to voltage alterations, and the magnetostrictive material which experiences a change in length when subject to a magnetic field. (17:51) Two common transducers are barium titanate, usually used at 40 kc/sec, and magnetostrictive materials, generally used at 20 kc/sec but do go up to 50 kc/sec. (18:51) The transducer is connected to the generator by co-axial conductor. (18:44) The frequency must be low enough to allow the bubbles to grow. (18:46) 3. A necessary process is the transmission of radio frequency power to the fluid. 4. Cavitation, which is the formation and collapse of microscopic bubbles, "literally blast(s) off the dirt." (18:45) As the bubbles form, the pressure is suddenly reduced in the area, releasing dirt and solid particles from- the surface of the parts. The collapse of bubbles causes liquid pressures up to 100 atm. (2:25) Cavitation depends on surface tension, pressure, density, temperature, and viscosity. It is a stressed liquid (beyond tensile strength) that suddenly collapses on compression phaseo (101) This creates a scrubbing action. Implosion is the collapse of bubbles during the pressure reduction. (18:~51) The cavitation can produce transducer errosion. (17:47), The liquid only accepts a certain amount of power from a plain radiating surface if the power becomes too high in the immediate vicinity of the radiating surface, one can get cavitation of the radiating surface. (17:54) Up to 20 watts per square inch may be used. The average power rather than peak power determines cleaning. (7:220) When the transducer is at one end of the tank, the other end must be at a node (odd-quarter wavelength) to produce a stable standing wave. (17 56).A solvent or detergent is generally used along with water. (1.8 51) However, water is sometimes a better solution than detergent. (8:127). Some solutions will not support cavitation and must be degassed. Hot or cold solvents can be.used but sonic action normally heats the solution. (18:52) The power required to produce cavitation increases as frequency increases with 20 to 100 kc/sec the best and 40 kc/sec generally chosen to provide high levels of cavitation at low-power levels. (18:54) The solution can be reclaimed by dis28

tillation or filtering. (18:56) A solution with a high-surface tension is desirable. (11:111) Mechanical agitation, such as shaking the parts basket, is desirable to remove dirt from parts. (8:127) Small parts can be cleaned by putting them in a glass beaker which is immersed in the tank, (18:54) usually made of stainless steel. (17:54) Tank size is based on ratio of transducer capacity (installed watts) to solution volume. (8:126) Different sized parts and various soils require various frequencies; the frequency used is also dependent on where the soil is. (17:4647) When baskets are used for parts, they should be greater than 1/4 inch mesh or less than 200 mesh. (17:60) Other considerations not yet mentioned in design include transducer location (if more than one transducer is used, they should be located as close together for maximum effectiveness) (8:127) and part orientation. English manufacturers of decorative flatware use ultrasonic. (11:111) See Ref. 3 from some applications including fragile glass.) Ultrasonic energy cavitates aluminum foil due to cold working by pressure differentials. (4:33) This may present some problems with cleaning aluminum pans in an ultrasonic dishwasher. Ultrasonic cleaning is safe, but one cannot put his hands in the tank for long periods of time since prolonged immersion results in burns. It does produce some noise but is not dangerous or objectional. (18:56) F. SALT BATHS Salt baths operate at high temperature, often with such salts as sodium hydride, Krolen No. 1, or Krolen No. 4. Due to the corrosive nature of salt and the difficulty in handling salt and cleaning dishes at high temperature, little information was collected on this subject. Reference 16 gives more information. G. BRUSH SYSTEMS A wide variety of things are cleaned by brush systems. Well-known examples are automatic car washes and thel.glass cleaners that are sometimes used to clean bar glasseso Apparently, due to technical simplicity of brush systems, no information is available. Obviously a brush system that would clean dishes would involve a complex system of brushes if it were to handle dishes of various shapes. 29

4. Evaluation of Basic Cleaning Methods Each cleaning method discussed in the preceding section can certainly clean dishes, but each has different advantages. Practicality of use for a dishwasher is not being considered at this time. In order to evaluate all the cleaning methods on an equivalent basis, a common basis for evaluating is given below. Present-day dishwasher may not hold up to the criteria listed, but this does..not invalidate the criteria, Also, evaluating each method means predicting performance on the basis of what is presently known. Although predicting is always subject to error and criticism it was felt that this is the best that could be done on what is known from an extensive literature search. Criticism and disagreement are certainly in order. A.. Cleanliness - dishes must appear to be clean 1. no deposits of food 2. no greasy or oily films 3. no spotting of glassware B. Sanitize - dishes must not contain any microorganisms (immediately after being cleaned) that are likely to cause infection. This requires no towel drying and may be accomplished in one of two ways: 1. Heat* a. 10-sec rinse at 170~F b. 2-min immersion at 170~F c. 1/2 min immersion at boiling temperature 2. Chemical - There are many chemicals available to sanitize dishes. The only important point is whether or not.one of these can be used in conjunction with each cleaning methodo C. Materials that can be cleaned - Some materials suffer damage either by heat, chemical action, or mechanical scrubbing action. The materials considered are shown.in Table I. D. Dishes or color designs should not be damaged. Table I contains an evaluation on a point basis of the above mentioned criteria. Ten points is the highest and means approximately 100% chance of success. Under sanitizing, the x's correspond to accomplishing sanitizing by the particular method indicated in the lefthand column. Each criterion is considered separately and it should be realized that any single dishwasher may not accomplish *This information was taken from an article titled "Sterilization of Dishes and Utensils in Eating Establishments"; however the article was discarded by the library before a complete bibliography was obtained. This information is also available in articles such as references 613 and 1911lo 50

) —, 4 00 0:,: XX 00000 000 0.;.ri ri H HH r- H rH o co rl c a o o x x x o0- o oooooco o c O H- OO O 0 > X 0\000 0 0 4-D r-1 r —00, - r-O::r- r- r-OOOO r-O r-H 0 (D:-. o 0\ o o o X X o o o o 0 co3 co a) r-1 r — r- A - 4 rl r-4 r-i r-4 C 0) HI r - @ 0 O n X X > 00 0 00 00 O O <0 P4 EQ PI r-4 r- ( r-4r-I r- r-Ar-4 iA 0 co ) S 1 o 0 (1) m X 03 *Q H P -H - Hq ) *H 4.1. *ri - P — 4 C) Pi rl 0 ri HlH l r-H r r-H O r H H bOO O Pi 0 H.t *O co o 0 (Cj co coH d r ~: 0c O r-i 4)4 0 0 ID H 0 ) o: a) q-P 0 U) 4-4 V CO X c iO -^ *H r0 0 0 H ) 0 C O O CO 0 V.* H-0U *H ( O U* 0) 0 I 0 ~(S O 1 O u ) O O?C * H C) CO TJ u 1 o0 b.0 C. H *H 4-) 4: 0 rO * CO O 4-O OCQ r- Cfj O or- a) 0 CO 4-' 0 -1 c 4C)^U R ObO c - 1.0 i-H JH r- C) 4- o H1?-, ) C) CO ( rd b cO ) 4-) - - dco P 4- i d cCO 4 ( co *rQ C)U H P- VCO P C0 4+ H0 > Ord *HOOO 00 4 IOH OHO40 Hr-ZZ *H0 r C) co 1120 r- * *H. C 0 HOt H 0) n U H W p a'H O C\ 0 13-P U C) S 0 1 51

all the criteria that are rated at 10. It is felt that each criterion rated at 10 could be accomplished but perhaps at the expense of other criteria that are also rated at 10. A. DISCUSSION OF EVALUATION The following discussion presents the author's reasons for assigning the values to the evaluation criterion as shown in Table I. B. IMPACT CLEANING As previously discussed, impact cleaning is used to clean a wide variety of materials, and impact cleaners can be made abrasive enough to clean a wide variety of hard-to-clean soils. On this basis, it is easy to imagine that impact cleaning can clean any type of soil found on dishes and a 10 was given for each cleanliness criterion. An impact dishwasher could use water at any temperature, thereby sanitizing by heat under the first two criteria. The third criterion (immersion) would probably be unreasonable since a dip tank is not used in this process. Chemical sanitation would be simple since it would probably only involve adding one of many available sanitizing agents. Many materials including glass, vitrolite, and china are cleaned by impact cleaning and hence it is felt that all materials listed in Table I can be handled and were rated 10. One obvious problem is achieving a balance between too much mechanical scrubbing action ruining the dishes and not enough mechanical scrubbing action to clean the dishes. It is felt that water with particles in it will eventually lead to errosion of color designs on some dishes such as glasses. Therefore, 9 is assigned to "no damage being done to dishes or color design." C. SOLVENT CLEANING Solvents clean a wide variety of materials-with a wide variety of soils to a high degrees hence, a rating of 10 is assigned to each cleanliness criterion, Sanitizing, either by heat or chemical action, should not present any problem, and each criterion is assigned a value of 10. As previously mentioned, plastics may suffer some damage from solvents. They are assigned a value of 8 while all other materials are assigned 10. 52

It is conceivable that a solvent could be used that would not damage dishes or color designs, so a value of 10 is assigned to that criterion. D. EMULSION AND DIPHASE As mentioned previously, emulsions tend to leave a thin oily film even after hot rinses. They receive only a 5 under "no greasy or oily films." The other problem with emulsions is that after some use and exposure to air they tend to turn to acid which in turn tends to ruin color designs. Therefore, "dishes or color designs should not be damaged" only received a value of 7. E. VAPOR DEGREASING Vapor degreasing is primarily for degreasing and may present some prob-. lems with food deposits and spotting of glassware; these are assigned values of 7 and 9, respectively. Sanitizing either by heat or chemical action should not present any problem. Vapor degreasing generally is high-temperature cleaning. This may present some problems with plastics which are assigned a rating of 7. F. ULTRASONIC Ultrasonic cleaning is a highly effective way to clean many materials. However, it may pit aluminum, which is assigned a value of 9. All other criteria received a value of 10. G. SALT BATH A salt bath dishwasher may present some problems with cleaning a wide variety of soils and spotting of glassware; hence "no deposit of food" and "no spotting of glassware" each are assigned values of 9. Salt bath cleaning also presents some problems with materials that can be cleaned and these materials as shown in Table I received low values. The salt may hurt some materials but it is not known whether it will harm color designs or dishes in general, so a value of 10 was given to that criterion. H. BRUSH SYSTEM A brush system should be able to accomplish everything that is in the 5533

criteria column except that it may not be able to remove hard caked-on soils; hence, this criterion is assigned a value of 9 while all other criteria received 10. 5. Cleaning Methods and Their Adaptability for Use in a Dishwasher Up to this point, the only concern for cleaning methods is whether or not they can clean dishes. This section discusses the possible problems and advantages of building a dishwasher using each type of cleaning method. A. IMPACT CLEANING Impact cleaning is very flexible. It can be accomplished with nozzle blast, mechanical blast, or tumbling. Many fluids can be used plus a wide variety of additives. As previously mentioned, impact cleaning is used to clean glass, vitrolite, and china. Due to the above-mentioned options and its present use to clean materials found in the kitchen, impact cleaning is certainly adaptable to cleaning and sanitizing dishes. Sanitizing could be accomplished either by heat or chemical action. B. SOLVENT CLEANING Solvent cleaning has found wide usage in assembly-line parts cleaning and dry cleaning; however solvents present a safety problem. It is still a basically reliable way to clean to a high degree and is adaptable to cleaning dishes. C. EMULSION AND DIPHASE Emulsion and diphase cleaning have not been. given much attention because they leave a thin oily film. Emulsions also tend to turn to acid, which might run dishes. It is felt that because of these reasons, emulsion or diphase cleaning may not be adaptable to clean dishes. D. VAPOR DEGREASING Vapor degreasing is actually a solvent cleaning system where the solvent is in the vapor phase. It is generally done at elevated temperatures and may not be adaptable to cleaning dishes. Also solvent vapors generally present a safety and handling problem, making their adaptability to dishwashing difficult. 34

E. ULTRASONIC CLEANING Ultrasonic cleans and sterilizes to a high enough degree to be used for sterilizing surgical instruments. It also cleans a wide variety of parts and materials. Obviously ultrasonic could be adapted to cleaning dishes. F. BRUSH SYSTEM Brush systems are relatively simple and an excellent way to clean many items. However, in order to clean dishes, a brush system would have to handle many different sizes, weights, and shapes, unless used for only a few types of dishes; hence a brush system would either be very limited in the dishes it could handle or it would be extremely complex. This would tend to make brush systems hard to adapt to cleaning dishes. 6. Feasibility of Building Dishwashers Using Various Cleaning Methods This section discusses the feasibility of building various types of dishwashers in the laboratory using the cleaning methods discussed previously. Feasibility is taken to mean whether or not a dishwasher can be built that meets the.criteria used to evaluate the cleaning methods. A. IMPACT CLEANING The many ways to build and operate an impact dishwasher make it particularly feasible to build in the laboratory. Laboratory work would mainly consist of building and testing a particular apparatus. It would also include investigation of possible damage or wear to dishes or color design. B. SOLVENT CLEANING Solvent cleaning can be accomplished with a hot or cold solvent using an immersion tank or spray system. Any system would be feasible and practical to build and laboratory work would include investigation of various solvents and the method in which to use and handle them. Laboratory work would also have to investigate whether or not all plastics could be cleaned with any particular system. 35

C. EMULSION AND DIPHASE Emulsion and diphase cleaning can use three different types of cleaners in immersion bath or rinse systems. An emmulsifiable solvent is very effective in removing tightly adherent and heavy soils. However, laboratory work must be able to come up with a system that removes the thin oily film left by emulsion and diphase cleaners. Laboratory investigation would also have to investigate possible damage to plastics and color designs on dishes. D. VAPOR DEGREASING Vapor degreasing is another flexible process in that the solvent may be used in many or a combination of phases. This system is mainly used for degreasing metal parts, but a suitable solvent may be applicable for cleaning dishes; however, hard caked-on soils may not be removed and some plastics may be damaged by the solvent or temperature at which a given system is operated. E. ULTRASONIC Ultrasonic cleaning is very effective and is useful for a wide range of soils and materials. This process is presently in wide use for specialized cleaning where its high cost is justifiable. Many companies today are doing research and development to lower the price, which is its big fault. Laboratory work would be very feasible and would need to include a cost-reduction study. F. SALT BATH A salt bath could be a very effective cleaning process and would be very easy to build in the laboratory. Practical problems that must be overcome include an apparatus that would not be attacked by the salt, a salt that would not be harmful to dishes, and a rinse system that would remove salt and soil from the dishes. G. BRUSH SYSTEM Brush systems are easy to build and many chemical additives could be used to clean and sanitize the dishes. Laboratory work would include the development of a brush system or systems that could handle a reasonable variety of dishes and the investigation of various bristle compounds for expected lifetime. 36

7. Proposed Dishwashers After reviewing all material up to this point, it was felt that three systems were the most promising; water impact, emulsion, and solvent. All three appeared to be equally good for cleaning dishes and reasonably adaptable. Sketches were made of possible ways to build each system (Figures 1, 3, and 4). A discussion of each system is included below. A. WATER IMPACT SYSTEM In the water impact system (Figure 1), the separator is necessary to keep the additive from getting into the drain and clogging it. If the pump that handles the abrasive cannot pump enough water, the nonabrasive pump could assist the abrasive pump by recirculating water to the nozzles. Other possible pump arrangements are shown in Figure 2. B. SOLVENT The solvent system chosen (Figure 3), incorporates an electric evaporator for solvent reclaiming. A preheater is used to reduce the electricity consumption for evaporation-and a water condenser is used to condense the vapor. C. EMULSION A possible emulsion system is shown in Figure 4. As can be seen, the only change from the present dishwasher is the emulsion reservoir system. This system could also be used for a cold solvent that is not reclaimed and is pumped to the drain after each wash. In cooperation with Whirlpool representatives, it was decided that within the span of time available, there was sufficient interest in the water impact system to warrant its being built and tested. To have desired flexibility with pump arrangements and the ease of mounting equipment on the testing apparatus, a casing was built (Figure 5), instead of rebuilding a conventional dishwasher. Presently the system is being worked on, and testing will be started when equipment problems are solved. A similar system would involve a water rinse followed by an air-abrasive cleaning cycle. This system would be very similar to "sand blasting" and would have the advantage of being able to accomplish a higher velocity of the additive without the danger of dislodging dishes due to high fluid impact. 37

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8. Appendix During the early stages of this project, much information was collected and is presently in this paper; however, many references that were educational, informative, and interesting to the author were not directly useful in writing this paper. These references that may be useful to the reader are presented in bibliographical form. Anonymous, "Two Alkaline Cleaners can Handle Most Jobs," Steel, 147, No. 2 96-98 (July 11, 1960). Beaudt, Eugene C., "In-Line Cleaning Saves Time," Iron Age, 189, No. 2, 64-65 (January 11, 1962). Bulat, T. J., "Evaluating Sonic Energy Cleaning," Air Engineering, 4, No. 6, 32-35 (June, 1962). Graham, A. K., William Blum Lecture, "Faraday's Laws Applied to Cleaning," American Electroplaters Society Technical Proceedings, 41-44, 228 (1960).,,,., -- r " Koonty, D. E., D. O. Feder, and C. O. Thomas, "Cleaning in Electronic Industry," American Electroplaters Society Technical Proceedings, 188-198, 252-253 Paulson, S. E., "Ultrasonic Cleaning of Plastic Frames," Machinery, 98,790-791 (April 5, 1961). Pickup, J., "Some Advantages of Automatic Plant Using Solvents for Degreasing," Metal Finishing Journal, 7, No. 77, 187-191 (May, 1961). Putner, T., "Methods of Cleaning Glass by Vapour Degreasing and Ultrasonic Agitated Solvents," British Journal of Applied Physics, 10, No. 7, 332336 (July, 1959)o Rand, B., "Faster Cleaning of Oily Fabricated Parts," Products Finishing, 26, No, 8, 54-58 (May, 1962). Steen, D. S., "How to Get Most from Ultrasonic Cleaning," Plant Engineering, 13, No. 12, 112-115, 208-209 (December, 1959). Steen, D. W., "Ultrasonic Cleaning," Metal Industry, 96, No. 18, 355-357 (April 29, 1960). 45

9. Bibliography 1. Anonymous, "Two Alkaline Cleaners can Handle Most Jobs," Steel, 147, No. 2, 96-98 (July 11, 1960). 2. Beaudit, Eugene C., "In-Line Cleaning Saves Time," Iron Age, 189, No. 2, 64-65 (January 11, 1962). 3. Bulat, T. J., "A Guide to Sonic Energy Cleaning," Ceramic Age, 76, No. 2, 24-28 (August, 1960). 4. Bulat, T. J., "Evaluating Sonic Energy Cleaning," Air Engineering 4, No. 6, 32-35 (June, 1962). 5. Fullerton, R. C., "Vapor Degreasing, A Study of'Tri and Per,'" Products Finishing, 26, No. 2, 44-47, 50 (November, 1961). 6. Harvey, John R., Our Health in Your Hands, Dept. of Public Health, Attleboro, Mass. 7. Heim, R. C., Ultrasonic Cleaning Tests for a Variety of Driving Waveforms, 1960 IRE International Conventional Record Part 6, IRE, New York, 1960. 8. Jacoby, Walter, "Factors to Consider When Installing Ultrasonic Cleaning," Plant Engrieering, 16, No. 4, 126-127 (April, 1962). 9. Linsley, H. E., "Vapor Degreasing," American Machinist/Metalworking Manufacturing, 105, No. 8, 127-140 (April 17, 1961). 10. Osterman, H. F., Ultrasonic Pickling and Cleaning, Society of Automotive Engineers No. 483B, S.A.E., Inc., New York, 1.962. 11. Osterman, H. F. and A. V. Santa Lucia, "Ultra Sonic Agitation Gives New Life to Pickling and Cleaning Baths," Metal Progress, 78, No. 2, 110-114 (August 1960). 12. Polucha, A. H., "Vibratory Finishing," American Machinist/Metalworking Manufacturing, 105, No. 8, 141-142 (April 17, 1961). 13. Rand, Burton, "Improved Processing Equipment Results in Faster Cleaning of Oily Fabricated Parts," Products Finishing, 26, No. 8, 54-58 (May, 1962). 14. Redstroke, W. N., "New Solvent Cleans Selectively," Iron Age, 189, No. 21, 93-95 (May 24, 1962). 44

15. Rosenberger, William A., Impact Cleaning, 1st ed., penton Pat. Co., Cleveland, Ohio, 1939. 16. Spencer, Lester F., "Chemical Cleaning of Metal Parts," Machine Design, 35, No. 15, 134-141 (July 20, 1961). 17. Thomas, Richard W., "Ultrasonic Cleaning; Theory and Applications," Products Finishing, 26, No. 3, 44-47 (December, 1961). 18. Tint, Gilbert, "Ultrasonic Cleaning Fundamentals," Products Finishing, 25, No. 9, 54-56 (June, 1961). 19. University of Michigan School of Public Health, Proceedings of the Inservice Training Course on Food Handling, Jung 19-21, 1947. 45

WHIRLPOOL VACUUM EXTRACT COMBINATION WASHER/DRYER ANALYSIS OF THE VARIABLES IN THE EXTRACT AND DRYING CYCLES Robert O. Rice 1. Introduction This report is a description of a computer program that simulates the water extraction and drying process in the Whirlpool vacuum extract combination washer/dryer. The report includes the experimental data taken and the two computer programs written to simulate the process. Although the simululation is not at this time as accurate as would be needed for design use, this study has shown the feasibility of simulating this process in the combination washer/dryer. It is hoped that further work in. this area will allow this type of simulation to aid the designer. 2. Conclusions The moisture extraction process in the Whirlpool vacuum extract combination washer/dryer can be represented by two general categories. First, mechanical extraction which is characterized by a pressure drop across the cloth that causes the water to be removed in droplet form. Second, drying which is characterized by heat and mass transfer equations. The heat and mass transfer coefficients, and the constants for mechanical extraction can be determined experimentally. A computer program simulation of the process using experimentally determined constants can be written to simulate the moisture extraction in the Whirlpool vacuum combination washer/dryer. 3. Results Two computer programs have been written to simulate the water extraction and drying process in the vacuum extract, combination washer/dryer.

The first program simulates a single piece of cloth during water extraction and drying. CLOTH INLET EXIT AIR AIR The comparison of the test results with the computer program simulation is shown on page 48. The difference in the two results is due to a programming error which allows the' extraction process to continue too long. This error can be corrected as shown in the program listing in Appendix B. The second computer program simulates the water extraction and drying process for the vacuum extract washer/dryer machine. EXIT AIR\ I 5) ^INLET (CLOTHESAIR The comparison of the test results with the computer simulation is shown on page 49. The results of the drying portion do not fit the test data very well because further experimental data is needed on the factors involved in the tumbling process. The accuracy of the program in fitting the experimental data is a function of the limits set on the factors ROR and JKR (see p. 59). These two factors should equal zero, but because of the computer they are set arbitrarily small. The smaller they are set, the more iterations the computer must make and the longer the program takes to run. The length of execution time has been the biggest limitation of the program. It is possible that this limitation can be eliminated by specifying a range of inlet temperatures, thereby reducing the number of iterations the program must make. 47

1.0 0.9- 0. 8- B-gsTest Data 0. 7 - - "..O.Program Pr 0.6 0.5 0.4 NL. Single Piece of Cloth 0.2 0.1 _ TIME (SEC):48

l.O0 0.9 x\ 0.8 - __o Program 0.7- Test Data 0.6 0.5 0.4 Z Machine j 0.3 - 0.2 0. 10 TIME (MIN) &9

4. Result Uncertainty In the mechanical extraction experimental results, the following possible errors were recognized: (a) The data did not conform exactly to the straightline drawn for this portion of the curve. Some of this difference can be attributed to the drying that was occurring at the same time, while any other must be attributed to the inaccuracy of measurement of the initial mass of water. This measurement was difficult because water is easily lost in the move from the weighing scale to the system before the pressure drop across the cloth was created. (b) In measuring the pressure drop across the orifice and the cloth, the inertia forces in the manometer could have introduced error due to the rapid change that had to be measured. In the drying portion of the mechanical extraction, the following possible errors were recognized: (a) As discussed in the experimental procedure section, it was difficult to obtain an accurate measuring system for the wet bulb temperatures. The instrument used to check the validity of these results was the sling psychrometer. (b) The recording instrument used for the wet and dry bulb temperature was a potentiometer. The millivolt readings were recorded on paper rolls by the instrument, then converted to temperatures by use of a millivolt-temperature conversion table. Although the introduction of large error seemed possible in this conversion, the computer program and data comparison seem to indicate that this did not occur. 5o Mechanisms of Moisture Extraction The process of water extraction can be broken down into two main mechanisms. The first is mechanical extraction, and the second is by vaporization. In mechanical extraction, water droplets are removed from the cloth by body and surface forces. The body forces are due to gravity, and the surface forces are created by placing a pressure drop across the cloth. The following model was used to represent this processo 50

WATER RESEVOIR MULTIPLICITY. OF TUBES Continuity Equation dm pAAP d = - pAV = - KAP dt C dm/dt = mass rate of change of water liquid p = density of the water A = area of the tubes AP = pressure drop across the cloth C = constant K = constant The moisture extraction by vaporiation can be represented by Fick's Law for diffusion. AIR CROSS SECTION OF FIBER WATER VAPOR 51

Fick s Law Rate = - D 7-s D = diffusion coefficient aC/0S = concentration gradient This equation is analogous to the heat transfer equation (Rate - K 6X but in the case of diffusion, the effective film thickness cannot he measured directly, so the equation is rewritten analogous to the heat transfer equation as~ Rate = Hmtx (Psat - Pvap) Hmtx = mass transfer coefficient Psat = saturation press of the water liquid Pvap = vapor pressure of the water vapor in the air 6. Single Piece of Cloth Computer Program A computer program has been written to simulate the water extraction and drying process to determine what effect variable changes in the process will have. A. MECHANICAL EXTRACTION This is the process by which water is extracted from the cloth mechanically by creating a pressure drop across the cloth with a blower. The following equations, representing this process, were determined experimentally (p. 64). oo0065Pc -.0222Pcri i MWL2 = MWL e for MWL/MWLI c = e MWLi = mass of water liquid in the cloth at time T MWL2 = mass of water liquid in the cloth at time T2 MWLI = initial mass of water in the cloth P = initial pressure drop across the cloth CI Program Notation c = 271,828 P.(- o0222*PCI) 52

X2 =.0065*PCI WHENEVER MWL/MWLI.G. C MWL - MWL*(2.71828.P.(-X2)) 2. PC PCI(MWL/MWLI) PC = pressure drop across the cloth at time T PCI= initial pressure drop across the cloth Program Notation PC = PCI*MWL/MWLI 35. VAI = VF/1 5- PC/PI VAI = velocity of the air entering at time T VA = maximum velocity of the air entering AIF Program Notation VAI = VAIF*(1.35 - PC/PCI).P..5 B. DRYING This is the process by which water is extracted from the cloth by the vapor pressure gradient between the cloth and the air. The system for the drying process was considered as shown below: AIR _ O__.-Tai Toe AIR, C j UF Lit rI Mc IM — M__* MMwl L ____J _ Mwv I M^~~wvi ^[Q M|wve 53

TAI = temperature of the air at the inlet TA = temperature of the air at the exit AE MWVI = mass of water vapor at the inlet NVL = mass of water vapor at the exit MC = mass of the cloth L mass of iquid water in the cloth MW = mass of liquid water in the cloth MW = mass of water vapor in the cloth The following four assumptions were made about the system. 1. The temperature of the water vapor at the inlet and exit equals the temperature of the air at the inlet and exit, respectively. 2. The mass of the cloth, water liquid, and water vapor in the cloth are all at the same temperature. 3. The temperatures involved in the heat transfer to the cloth are the temperature of the cloth (Tc) and the average of the inlet and exit temperatures (TAVE). 4. The change in mass of the water vapor in the cloth during the process is equal to zero (MWvc = 0). The basic equations used to define the process ares Continuity Equations 1. M = MAE = mass flow rate of air at the inlet AT MAE = mass flow rate of air at the exit 2. VC = MWL MW' = MVC = change in the mass of water vapor in the cloth MWL = change in the mass of water liquid in the cloth MWin = change in the mass of water vapor transported from the cloth to the air 54

Energy Equation: 35. Q + MAIHAI + MWVIHWVI = U + MEAE + MWEHW Q = heat transfer rate from the system U = change in internal energy of the cloth, water liquid, and water vapor in the cloth. H = enthalpy of the mass per pound mass Program Notation ROR = MDAI*HAI + MWVI*HWVI - (UD + MDAE*HAE + MDWVE*HWVE) Heat Transfer Equation: 4. QAC ACLHHTX(TAVE-TC)MAI QAC = heat transfer rate from the air to the cloth ACL = area of the cloth HHTX = heat transfer coefficient of the cloth Program Notation QDAC = ACL*HHTX*(TAVE-TC)*MDAI Mass Transfer Equation: 5- L = AHMTX (PSPV)MAI( 144) ML = MT = mass of water vapor transported from the cloth to the air HMTX = mass transfer coefficient of the cloth PS = saturation pressure of the water vapor at the temperature of the cloth P = vapor pressure of the water vapor in the entering air Program Notation MDWL = ACL*HMTX*(PS-PV)*MDAI*144 55

Equations Derived from Assumptions: 6. U = QAC - MWL(HV-HF) from assumption 4 (VC=O) H = enthalpy of the water vapor per pound mass v HF = enthalpy of the water liquid per pound mass Program Notation UD = QDAC - MDWL*(HVTC-HLTC) 7. U = CCMcTC + HMWL + HFMW from assumptions 1, 2, and 4 CC = specific heat of the cloth U = changes in internal energy of the mass of liquid water in the cloth per pound mass Program Notation JKR = UD - (CC*MC*TDC-MDWL*HWLTC+HDWLTC*MWL) C. FALLING RATE PERIOD In this period the drying rate decreases because the mass of water that diffuses to the surface of the fibers is less than the mass of water that could be removed by the vapor pressure gradient between the water in the cloth and the air. The following equations for this period are taken from the Chemical Engineers Handbook (pp. 15-39). 7 M=R = WW- WE)/WC -WE) MR = mass rate of water removed in the falling rate period W = mass of water in the cloth/mass of the cloth WC = critical mass of water in the cloth/mass of the cloth WE = mass of water in the cloth in equilibrium with the mass of water in the air/mass of the cloth

Program Notation W = MWL/MC WHENEVER W.LE. WC,MDWL = MDWL(W-WE)/(WC-WE) D. GENERAL PROCEDURE The following procedure is used for the program. At a given time T, the mass of water removed due to mechanical extraction is determined. Next temperatures, pressures, and mass necessary to calculate the heat and mass transfer rates, and the rate of change of internal energy in the cloth are found. These values are held constant over the time internal and the mechanical extraction water removal, temperatures, pressures, and masses at time T+l are calculated. This procedure is re~peated until the mass of water liquid in the cloth is in equilibrium with the air. E. SPECIFIC PROCEDURE 1. Data Input The following data must all be entered as input, but may be entered in any order. TAI - temperature of the inlet air (~F) VAIF - volume flow rate of air when the cloth is dry (cu ft/min) ACL - area of the cloth MWVI - mass of water vapor entering (lb water vapor/lb dry air) MWLI - initial mass of water in the cloth TOTPA - total pressure of the inlet air and water vapor PCI - initial pressure drop across the cloth (in. of water) MC - mass of the cloth (lb) CC - specific heat of the cloth TC - initial temperature of the cloth (~F) WC - critical moisture content of the cloth (mass water/mass cloth) WE - equilibrium content of water in the cloth with the air (mass water/mass cloth) PTIME - the interval in seconds between the printing of output (this must be an integer) Example - two cards /TAI=76.,VAIF=90o.,ACL=.196,MWVI=.006,MC=. 02,MWLI=.07,TC=65., /CC=.5,PCI=12.,TOTPA=l4.7,WC=.25,WE=.O1,PTIME=l * 57

2. Sample Calculations of Program Operations Using Example Data The program first calculates the constants used later in the iterations. C= 2.71828.P.(-.0222*PCI) =.775 X2 =.oo65*PCI =.078 PV = MWVI*TOTPA/(.622 + MWVI) =.0845 Then the iterations of time are started by setting time = 1. With time = 1, the water extracted by mechanical extraction, the pressure across the cloth, and the volume flow rate of air entering are calculated. MWL = MWL*(2.71828.P.(-X2)) =.0648 PC = PCI*MWL/MWLl = 11.1 VAI = VAIF*(1.35 - PC/PCI).P..5.= 58.6 Next the program begins the calculations to find the exit temperature of the air. This is an iterative process and only one iteration will be shown. The first step is'to assume a value of the exit temperature and make all calculations using the assumed value. TL = TC = 65 TR = TAI = 76 TAE =.5*(TR + TL) = 0.75 TAVE =.5*(TAI + TAE) = 73.25 PS = PSATT.(TC) =.3056 From steam tables external function ARHO = 2.698*TOTPA/(TAVE + 460) =.0746 MDAI = VAI*ARHO/60 =.073 QDAC = ACL*HHTX*(TAVE - TC)MDAI =.218 MCWL = ACL*HMTX*(PS - PV)*144*MDAI =.00601 HLTC = HFT.(TC) = 33.05 From steam tables external function HVTC = HGT.(TC) = 1090.2

UD = QDAC - MDWL*(HVTC - HLTC) = -6.13 HAI = 119.5 +.24*(TAI - 40) = 128.1 HAE = 119.5 +.24*(TAE - 40) = 126.8 MDWVI = MWVI*MDAI =.000263 MDAE = MDAI =.073 MDWVE = MDWVI + MDWL =.00627 MWVI = HGT.(TAI) = 1094.9 HWVE = HGT.(TAE) = 1092.4 These results are now used to check for a balance in the energy equation. ROR = MDAI*HAI + MDWVI*HWVI-(UD + MDAE*HAE + MDWVE*HWVE) = 3.32 Since the energy equation does not balance, the program sets TL = TAE and goes through the process until ROR is less than.1. If ROR had been less than zero, the program would have set TR = TAE and repeated the process. When ROR has been found to equal zero, the change in the temperature of the cloth is found. The procedure is generally the same as to find the exit temperature. Given that the exit temperature was found to be 72.5, TLI = 35 TRI = TAI = 76 TDC =.5*(TRI + TLI) - TC = -9.5 TCTDC = TC + TDC = 55.5 Hwltc = HFT.(TC) = 33.05 MDWLTC = HFT.(TCTDC) - HFT.(TC) = -9.48 JKR = (UD- (CC*MC*TDC-MDWL*HWLTC + HDWLTC*MWL) = -4.6 With this not zero, the program would go though the same type of iteration process that it did in the previous section. 59

5. Results Format The results are printed out in a format as follows: TIME, MWL, PC, -VAI, TC, TAE, TAVE, sec lb lb/in.2 ft3/min ~F ~F ~F RESULTS-SINGLE PIECE OF CLOTH COMPUTER PROGRAM TIME MWL PC VA I TC TE TAVE 1.0641 1.1.099' 58.6753 58.0625 o7. 75CC 71.8750 2.0589 10.1715 63.7906 55C.5000- 6o2.5"4-69 -69.2734 3.0540 9.3355 68.0701 55.50CO 60.625C 68.3125 4.0495 8. 5679 71.7753 55. 5000 60.6250 68.3125 5.0491 8.4913 72.1344 55.5000 60.6250 68.3125 6.0486 8.4144 72.4934 55.5000 60.6250 68.3125 7.0482 8.3371 72.8525 55.50CO 60.6250 68.3125 8.0477 8.2594 73.2116 55.50C00 60.25C 68.3125 9. 473 8.1813 73.5706 55.50CC 60.6250 68.3125 10.0468 8.1028 73.9297 55.5000 o60.250 68.3125 11.046'3 8.0240, 74.2888 55.5000 60.625C 68.3125 12.0459 7.93447 74.6478 55.50CO 60.6:250 68.3125 13.0454 7.8651 75.0069 55.5000 60.625_C 68.3125 14.0449 7- 1 75 3......7'5- 575. 50CO 60. 250 6-8. 312.5 15.0445 7.7048 75.7251 55.50CC 60.625 68.3125 16.0440 7..6240 76.0842 955O. 50C 60.6250 68.3125 17.0435 7.5428 76.4433 55.5000 60.6250 68.3125 18.0430 7.4613 76.8024 55.50CO 60.6250 68.3125 19.0426 7.3794 77. 16.15 55.5000 60.6250 68.3125 20.0421 7.2971 77. 5206 55.50CO 60.6250 68.3125 21.0416 7.2144 77.8798 55.5000 60.6250 68.3125 22.0411 7. 1314 78.2389 55. 5000 60.6250 68.3125 23.0406 7.0479 7'8. 5980 55.50CO 60.6250 68.3'125 24.0401 6.9641 78.9571 55.50CO 60.625C 68.3125 25 0396 6.8799 79.3163 55. 5000 60. 6250 68. 3125 26.0391 6.7953 79.6754 55.5000 60.625C 68.3125 27.0386 6. 7103 80.0345 55.50CO 60.625C 68.3125 28.0381 6.6250 80.3937 55.5000C 60.6250 68.3125 29.0376 6.5392 80.7528 55.5CCO 60.625C 68.3125 30.0371 6.4531 81.1120 55.50CO 60.625C 68.3125 31.0366 6.3666 81.4711 55.50CC 60.6 250 68.312_5 32.0.361 6. 2797 81.8303 55.5000 60.6250 8.8,3125 33.0356 6. 1924 82.1894 55.5CCO 60.6250 68.3125 34.0351 6.1048 82.5.486 55. 5000 60.625C 68. 3125 35.0346 6.C167 82.9078 55.50CO 60.6250 68.3125 36.0.341 5.9283 83.2669 55.5000 60.6250 68,3125 37.0335 5.8395 83.6261 55.5000 60.6250C 68.3125 38.0330 5.7503 83.9853 55.5000 60.6250 68.3125 39.0325 5.6608 84.3445 55.5000 60.6250 68.3125 40.0320 5.5708 84.7037 55.500C 60.6250 8 31.25 60

7. Machine Computer Program A computer program has been written but not completed for the vacuum extract combination washer/dryer. The factors still needed for the completion of this program are the average time the cloth covers the nozzle and the average thickness of the cloth covering the nozzle. The program as of this time has the same procedure as the single cloth program except for the changes discussed below. A. MECHANICAL EXTRACTION 1 MWLN M LMCN/MC(60)K MWLN = mass of water liquid at the nozzle MWL = total mass of water liquid in the clothes MC = mass of cloth at the nozzle CN MC = total mass of the clothes K = percentage of the time the clothes cover the nozzle Program Notation MWLN MWL*MCN/MC*60*K -.0065PCI(60 )K -.0222PCI 2. MWLN2 =-LN, e for MwNL/MI C = e Program Notation C = 2.71828.P.(-.0222*PCI) X2 =.39*PCI*K WHENEVER MWL/MWLI.G. C MDWLN = MWLN(l-2.71828.P.(-X2)) SMWL = MWL - MDWL 61

B. DRYING I. QAC = A HTX(TAVE - TC)MAIKI(K) KI = number of thicknesses of one piece of cloth covering the nozzle on the average Program Notation QDAC = ACL*HHTX*(TAVE - TC)*MDAI*KI*K 2. MWLN = ACLT X(PS P)144M KI(K) Program Notation MDWLN = ACL*HHTX*(PS - PV)*144*MDAI*KI*K 3. Output Format TIME, MWL, PC, VAI, TC, TAE, TAVE, sec lb lb/in.2 ft3/min F F F 62

RESULTS-MACHINE COMPUTER PROGRAM TIME MWL PC VAI TC TAE TAVE 1 14.8023 11.5427 62.2981 64.5889 71.5313 73.7656 2 14.2270 11.0947 65.2258 64.1685 71. 3642 73.6821 3 T*_6735 10.6636 67.9243 63.7480 71*.19S34 73.5967 4 13.1408 10.2486 70.4234 63.3276 71.C22i6 73.5113 5 12.6283 9.8494 72.7472 62.90i2 7C.95C9 73.4754 6 12.1353 9.46.53 74.9150 62.4868 70.7833 73.391-7 7 11.6609 9.0957 76.9430 62.0864 70.6158 73.3079 8 11.6493 9.0865 76.9932 61.,7061 70.4563 73.2282 9 11.6378 9.0773 77.0425 61.3657 70.3048 73.1524 10 11.6265 9.0684 77. 0908'610554 70.16c.2 73. 0846 11 11.6154 9.0596 77.1383 60.7651 70.1623 73.0811 12 11.6044 9.0510 77.1851 60. 5049 70.0489 73.0244 13 11.5936 9.0424 77.2311 60.2646 69.9472 72.9736 14 11. 5830 9.0340 77.2765 60.0444 69.8534 72.9267 15 11.5724 9.0257 77.3214 59.8442 69.7674 72.8837 16 11.5619 9.0174 77.3658.59.6641 69,6E92 72.8446 17 11.5516 9.0093 77.4096 59.5039 69.6188 72.8094 18 11.5413 9.0012 77.4531 59.3438 69.5562 72.7781 19 11_.5311 8.9932 77.4962 59.2036 69.4937 72.7468 20 11.5210 8.9853 77.5389 59.0835 69.4389 72.7195 21 11.5109 8.9774 77.5813 58.9634 69.3920 72.6960 22 11. 5009 8.9695 77.6235 58.8633 6932451 72.6'725 23 11.4909 8.9617 77.6653 58.7632 69.3060 72.6530 24 11.4810 8.9540 77.7010 58.6731 69.2669 72.6334 25 1'1.4 711 8.9462 77.7484 58. 5830 69. 2317 72.6158 26 11.4613 8.9385 77.7896 58.5029 69 1Cf5 72.5982 27 11.4515 8.9309 77.8306 _58.4329 69.1:652 72.5826 28 11.4417 8.9232 77.8714 58.3628 69.1278 72.5689 29 11.4320 8.9156 77.9121 58.3027 69.11C5 72.5552 30 11 4223 8.9081 77.9526 58.2427 69. C7C 72.5435.31 11.4126 8.9005 77.9930 58.2026 69.0C63_5 72.531 8 32 11.4030 8.8930 78.0333 58. 1626 69.0479 72.5240 33 11.3934 8.8854 78.0734 58.1226 69.0323.72.5161 34 11.3837 8.8779 78.1135 58.0825 69.C166'72.5083 35 11.3741 8.8704 78.1535 58.0425 69.01CC 72.5005 36 11.3645 8.8629 78.1934 58.0125 68.8 E53 72.4927 37 11..3549...85.-8.55 78.2332. 579824 68. 7 36 72.4868 38 11.3454 8.8480 78.2730 57.9624 68.9619 72.4809 39_ 11..3358 e...8406 78.3127 57.9424 68. 9541 72.4770 40 111.3263 8.8331 78.3523 57.9224' 68.9462 72.4731 65

8. EXPERIMENTAL PROCEDURES Ao MECHANICAL EXTRACTION The equations for the mechanical extraction were determined by measuring the pressure drop across the cloth and the pressure drop across the orifice in the experimental set-up (Figures 1 and 2). The measurements were accomplished by placing a U-tube manometer across the flow orifice and across the cloth and recording the pressure drop versus time. The mass of water liquid was also recorded versus time for different initial pressure drops across the cloth. Two techniques were used in recording these quantities. First, because of the rapid change in pressure drop with time, the pressure drop across the orifice and across the cloth were recorded versus time, and then plotted versus each other eliminating the time (Graph 5)0 Secondly, it was found in recording the change in the mass of water liquid that the amount of water that could be removed by mechanical extraction was affected by removing the cloth from the system, weighing it, and replacing it. In order to remove this error, the cloth was removed after a given time and weighed. Then it was resoaked in water, and placed in the system with the same pressure drop for a different time period. In this way it was possible to obtain the results as plotted in Graphs 1 -4. The following equations were then determined from the graphs: 1. Graphs 1, 2, and 3 - 0065PCIT MWL = MWLI e, whenever MWL/MWLI > C MWL = mass of water liquid in the cloth MWLI = initial mass of water liquid in the cloth PCL = initial pressure drop across the cloth Defining this equation in terms of one-second intervals -o 65Pci MWL2 = MWLI e 2. Graph 4 -0222PPC C = e 5. Graph 5 P0 = POF*(5 - Pc/PcI 64

'a n, I- -1 FU LJ i - U*UUU LL PU O't' 0 0"' r) < I I m 3 ~ ~cn m ID ~ ~ ~ O C-i - -uin n.- n- D 0 HcrH L. 1 ) )1.1 U W Z) "' L.. IL I J =fit 2 222~~~~~j

Or CL'rTHr ExPER IMENTAL SET6UP MACHINE Figure 2 66

PO = pressure drop across the orifice at time T P = maximum pressure drop across the orifice OF PC = pressure drop acorss the cloth at time T C PC = initial pressure drop across the cloth CI Defining this equation in terms of the velocity of the incoming air VA = VAIF 5 PC/CI V = velocity of the air entering at time T AI VAIF = final velocity of the air entering B. HEAT AND MASS TRANSFER COEFFICIENTS The experimental set-up for measuring the heat transfer coefficient, mass transfer coefficient, and drying times to check the validity of the computer program simulation of the drying process for a single piece of cloth is shown in Figures 1 and 2. The tube was made of six-inch diameter galvanized heating duct, twenty-five feet long. The length of the tube was necessary to provide for uniform flow through the orifice and uniform mixing of the heated air approaching the test cloth. The temperature measurements were made with thermocouples, and recorded versus time. The following quantities were measured: 1. The wet and dry bulb temperatures of the inlet air (TWI,TDI) 2. The wet and dry bulb temperatures of the heated air (TWH,TDH) 3. The wet and dry bulb temperatures of the exiting air (TWE,TDE) 4. The temperature of the cloth (TC) 5 The pressure change across the orifice (P) The wet bulb temperatures apd the dry bulb temperatures at the exit were difficult to obtain. The wet bulb temperatures created a problem since they dried while the cloth was drying. The system that gave repeatable results was using a U-tube as a reservoir for the wet bulb and a cigarette lighter wick for the bulb. 67

THEMOCOUPLE WICK HEATING _ /U-TUBE DUCT WATER In measuring the dry bulb temperature, a shield had to be made for the thermocouple since it became wet from the droplets removed from the cloth during mechanical extraction. The type of shields that were used are shown below:: -— TEST CLOTH e THERMOCOUPLE i\, MOVABLE I ~ ~/' SHIELD SHIELD The movable shield for the thermocouple was used because it was found to give the most repeatable results. When these quantities were plotted versus time, the following input variables to the computer program were calculated. 68

1. Volume flow rate of air Q = AoO /2Gc P/p A0 = area of the orifice C = coefficient of discharge p = density of the air 2. The mass transfer coefficient (HMTX) HMTX = MWVAI/(PS - P MWVT = mass of water vapor transported from the cloth. This is obtained by using the psychrometric chart, THTHD,T EW TED, to.obtain the difference in the amount of water per pound of dry air in front of and behind the test cloth. MAI = mass flow rate of air entering P8 = saturated pressure at the temperature of the cloth (obtained from TC) P = vapor pressure of the heated air (obtained from THDTHW) From Graphs 6, 7, and 8, the following results were obtained: T = 53 TAI = 76 Al T 66 TAE = 56 AlE MW =.0042 PS =.1990 PV =.0849 ACL =.196 MTX/MAI =.00132 69

3. Heat transfer coefficient (HHTX) Using the assumptions discussed in the computer program section: QAC = ACH T(TAVE - TC) QAC = heat transfer rate from the air to the cloth TAVE = 1/2 (TDH + TDE) ACL = area of the cloth QAC = (CCMCTC + HFWWL + HFMWL) + ML(V V - HF) CC = specific heat of the cloth MC = mass of the cloth HV = enthalpy of the water vapor per pound mass at the temperature of the cloth HF = enthalpy of the liquid water per pound mass at the temperature of the cloth TX= (CMTc + HFMW L + HF L + L(Hv HF))/(TAVE- TC)ACL From Graphs 6, 7, and 8, the following results were obtained: TC = 5 TAI =76 T = 66 TAVE TAE= 56 AE MWVT =.0042 See mass transfer coefficient TC = 0 ACL = 196 HHTX/MA = 1.79 70

APPENDIX A GRAPHS 1 - 8 71

I1.O0 0.9IS400 0.8. 0.7 0.6 0.5 0.4 -p 8.3 -.0059 PCIT 3- | MwL/MwLI > 0.3 -=x-10.P 2 /M e-.0066 PCiT WL /MWLI eOPC ---- P = 12 ~ CI= —.00655 P T 0.2- MWL/MWLI e --- P = 16 CI 1-.0065 P T MWL /MWLI= e 0. I I I 0 10 20 30 TIME (SEC) Mass of water in cloth vs. tim Graph 1. Single piece of cloth Initial mass of water in cloth te) 72

1.0 0.9 0.8 0.7 ~ 0.6 -- 0.5 0.4- -~- PC = 14.5 -.0059 PC T 3 I~~ MWL /MWLI = e 03 - PC- = 16.0 0.3 2 W -.0065 PC T MWL /MwLI = e -x- Pc, =18.0 MWL /MWLl =e-00659 PC T WL WLIe 0.2 0.1 I I I I I 0 20 40 60 80 100 120 TIME (SEC) ( Mass of water in cloth Graph 2. Two pieces of cloth Initial mass of water in loth vs time) 73

1.O0 x 0.9 6 XXm —x-mA__mLm P 6 0.8-x -x C 0.8 0.7 - X XPi = 12 0.6 0.5 0.4 PCI 6 _ /M ~ -.00189 (Kt) MWL /WLI = e 3 0.3- PCI =12 -.0035(Kt) MWL/ MWLI = e 0.2 0. I I I I I 0 10 20 30 40 50 60 TIME (MIN) / Mass of water in clothes Graph. Machine \Initial mass of water in clothes vs tme). 74

I.0 0.9 0.8 0.7 0.6 \ 0.5 Ce -.0222 Pr, 0.5 0.4 0 0.3 0.2 o Single Piece of Cloth x Two Pieces of Cloth o Machine 0.I I I I I 0 10 20 30 40 INITIAL PRESSURE DROP ACROSS THE CLOTH ( P ) INCHES OF WATER Graph 4. End of mechanical extraction - C. Mass of water in cloth Initial mass of water in cloth 75

ao u- U. 0 0r CL 0 0.8 Q _0 OF 0.7 U) 0.6 Q: CL LJ 1.0 ---— x 0.9 0 _j 0.8 < U 0.7 \ 0.6 [J 0.5 CL) U 0.42 \ i 0.3 j 0.2\ u_ 0.1 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 PRESSURE CLOTH/ INITIAL PRESSURE OF CLOTH (PC/PC) Pressure drop across the orifice Pressure drop across the cloth Grap rA —h 5 VS. Graph 5. Final pressure drop across the flow orifice. Initial pressure drop across the cloth 76

80 TDI 70 0 so I o: 60 LU 0i LJ H 0 o 0 0 0 0 0 Xo X T O L X X X._ X TWI,TWE 50 x Temperature of Cloth 30 Exit Temperature 40 I l l I I 0 40 80 120 160 200 240 Graph 6. Temperature of cloth (inlet and outlet air vs. time). 77

TDI 70 60 w 6-.O a a:: LLJ 0 o o 2 o LJ 1- 0 0 0 0 G 00' o o o 00oo o X X T TWE X50 -x-X- X x" x 50 xTemperature of Cloth lExit Temperature 0 80 160 240 320 400 480 560 TIME (SEC) Graph 7. Temperature of cloth (inlet and outlet air vs. time).,78

80 TDI 03 x 70 0 IL 0 i, c 0 D-.O' 60. o I0 J'Exit Temperature XI I I I I I ---— X —- I I I I I 0 20 40 60 80 100 120 140 160 180 200220240 260280 TIME (SEC) Graph 8. Temperature of cloth (inlet and outlet air vs. time). 79

APPENDIX B FLOW DIAGRAM AND PROGRAM LISTINGS 81.

Data I ~ ~ A AH PTOT 22M,:,P —^^.A -- Pv H.x A.01=^"^c- HH~C=17 -(0ULP =C=TX2 = C,0065 PCI. t.g. 10,000 T T, --— "~'^A H ~'~m ^:WLAI >c HAI: -.1' -*. HGT (TC) | TC 55- TAVE= C5(T+T) - (TAE +i.( TTI l TT IF ~"F PS = PSATT.(Tc) PA = 2.698 PT/(TAVE+0) - VAIA/ -- -— | Q AC - ^HRTX(AVE-^^)AI | —- U - QAC - MWL( UGT.(TC)- HFT.(TC)) 9-5 H + =119. +.24 (TAE-4O) H HGT.(T) -- | =M + | M = i | | 1 = L TAI = 119.) + 2.4(TAI-40) HWVE -HGT.(TC) ROR= MAII + knHWVL - (U + MAEHAE + NWHWVETETDC = TC + T( L —I TC =.5(TR1 + TL1) - TC L- j TR1 = TAI L —I TL1 = 55 ROR.I^^-*1^ —[ROR 6 HWLTC = k*(TCl t fwLTC - IHFT(TCTDC) - HFT.(TC) |- JKR = - (CC - LHWLTC + MWLT(}AWL IJKRI <01 Print Format p —-- I = I + K T — MYL, WE +.01 TC> — I = -- TC = TCTDC ^ — ML = WL " MWL 83

SINGLE PIECE OF CLOTH PROGRAM REAG AND PRINT DATA VECTOR VALUES X(1)=l.,2.,3.,4.,5.,6.,7.,8.e,.,10.,11.,12., 9 13.,14.,15.,16.,17.,18.,19.,20.,21.,22.,23.,24. VECTOR VALUES Y( 1 )=.0886,.C21,.961,.10C1,.104 1,.1082,.1126 9,.11711.1217,.1260,.1315,.1367,.1420,.1483,.1532,.1593, 9.1652,. 1716,.1780,.1845,.lC18,.2037,.2063,.2130 INTEGER TIME,PTIME,I PRINT CCMMENT$TIME MWL PC VAI TC TAE 9 TAVE$S VAI =0. C= 2.71828.P. (-.0222*PCI) MWL=MWL LI X2=.0065*PCI HHT X= 1 -79 - HMTX=.00132 PV=MWVI*TOTPA/(.622-+MWVI).. -THROUGH Sit FCR TIME =IITIME.G.10000 rOrrO a O \ Z.WHENEVER MWL/MWLI.G.C 3.MWL=MWL*(2. 71828. P. (-X2)) da..END OF CONDITIUNAL... 61~? WHENEVER VAIF-VAI.C..1 c 0\(", _ PC=PC [*IMWL/MWL I VAI=VAIF*(( 135-PC/PCIP 5) _\ E Z. IJ) LfVYlU 4W LE, C ^ftlf END OF CONDITIONAL TL=TC __ _ \\ TR=TAI S2 _ TAE =.5*(TR-+TL).. c... j j.. I ^.)......c TAVE =.5* (TAI+TAE) WHENEVER TC.LE.35,TRANSFER TO S7 WHENEVER TC.LE.55. T=TC-32. PS=TAB.(T,X(i),Y(l),,1,1i,24,1) TRANSFER TO Sli END CF CONDITIONAL PS=PSATT.(TC) Sll ARHO=2. 698* TOTP A/(TAV E+46C.) MDAI=VA I*ARHO/60._ QDAC=ACL*HHTX*(TAVE-TC) MCAI MDWL=ACL*HMIX*( PS-PV)* *4.MCAI _ W=MWL/MC WHENEVER W.LE. WC,MDWL =CDWL *(W-WE)/(WC-WE) HVTC=HGT. (TC) HLTC=:HFT. (TC) UD=QDAC-MDWL *(HVTC-HLTC) HAI=119.5+.24*(TAI-40.) HAE=119.5+. 24( TAE-40. MDWVI=MWVI*MDAI MDAE=MDAI MDWVE=MDWVI+MCWL HWVE= HG'T.(TAE) HWV1=HGT.(TAI) ROR=MDAI*HAI+MDWVI*HWVI-( LD+MCAEHAE+MOWV-E*HWVE) 84

WHENEVER.ABS. ROR.L..1, TRANSFER TO S3 WHENEVER ROR.L.O. TR= T AJE TRANSFER TO S2 O TH ERWI S E TL=TAE TRANSFER TO,2 END OF CONDITI'O NAL S3 TL1= 35. TR 1 =TA I S4 TDC=. 5(TR 1+TL1)- TC TC TFC=TC+TDC HWL TC = PFT( TC) HDWLTC=HFT. (TCTOC)-HFT. 1C ) JKR = ( UD-( CC MC*.TDC-.M.DL *_HtW L TTC- i+0L'T C M _ W WHENEVER. ABS. JKR.L. 1,TRANSFER TO 56 WHENEVER JKR.L. O..._ TR =TCT CC OTHERWISE TL I=TCT UC TC=TC TDC I= I+PT IME END OF CONDIT IONAL HENVE W LE. WT+RANS.OWFE, RANF R Fs S4 S6 MWL=MW=L-N3W. TC=TCTDC ______WHENEVER I,E. TIME PRINT FGt<!AT$1H,T'4-,6F8..4 * $,['TlMEM:.WLPC,VAI,TCTAtETAVE I=I +PTIME _. END. OF CON'DITIONAL S. CON.TINUE.. __ _ PRINT CCMM-EN $ TIME GRE 1ER THAN 1000 $ S7 END OF PROGRAM 85

MIACHI NE PROGRAM REAC AND PR IINT DATA VECTOR VALUES X(1)=l.,2.,3.,'4.,5.,6.t,7.,8.,9.,10.tll.,12., 9 13.,14.,15., 16.,17,18., 19. 220.,21.,22., 23,24. VECTOR VALUES Y( 1)=.O886,.C 21,.0961,.1001,.lO41,.082,.1 1 26 9,.1171,.1217,.126C,.1315,. 136 7,.1420,.1483,.1532,.1593, 9.1652t,.1716,.1780,.1845,.1918,.20377,.2063,.2130 INTEGER TIME,PTIME,I PRINT CCMMENT$TIME MWL PC VAI TC TAE 9 TAVE$ I= ____________ VAI=O. C= 2.71828.P.(-.0222*PC I X2=. 39*PCI*fK W L=MW I _ _ L _ H'TX=2.02 HMTX=.00132 _ ________________ PV=MWVI*TOTPA/(.622+MWVI) THROUGH Sl,FOR TIME=1,1,TIME.G.10000 MWLN=MWL*MCN/MC*60.*K WHENEVER MWL/MWLI.G.C _ MDWLN=MWLN*(1-2.71823.PI.(-X2)) MWL=MWL-MDWLN __ END OF CONDITIONAL - - __WHENEVER VAIF-VAI.C..1 PC=PCI*MWL/MWLI VAI=VAIF*( ( 1.35-PC/PCI).PF..5) END OF CONDITIONAL TL=TC _____ ___ __ _______ TR=TAI S2 TAE=.5* (TR+TL)__ TAVE=.5*(TAI+TAE) WHENEVER TC.LE.35,TRANSFER'TO S7 ___ __ WHENEVER TC.LE. 55.'T=TC- 32. PS=TAB.(T,X(l),Y(1),1,1,l,24,1) TRANSFER TO Sll END OF CONDITIONAL PS=PSATT. (TC) S'11 ARHO=2 698*TOTP A/(TfAVE+460.) MDA I=VA I*ARHO QOOAC=ACL*HHTX*(TAVE-TC)*MCAI*KI*K MDWLN=ACL*HMTX*(PS-PV) *144*MDAI*K11*K W=MWL/MC WHENEVER W.LE. WC,MDWLNh=tCWLN*(W-WE)/(WC-WE) HLTC=HFT (TC ) HVTC=HGT. (TC) ____ __ UD= QDAC-MDWLN* (HVTC-HLTC) HA =119, 5+- 24* (TA I-40. ) HAE= 119. 5+ 24*( TAE-40. ) MDWV I=MWVI __ _AI MDAE=MDAI MDWVE=MDWV I +MDW LN ___ HWVIT=HGT.(TAI) 86

HWVE= HGI'.(TAE) ROR= MD AI*HA -+MDWV I*HWV I- ( tD+MOAE*HAE+MD ~VE*HNVE) WHENEVER.ABS. kOR.L..1, TRANSFER TO S _ ___ WHENEVER ROR.L.O. TR=TAE TRANSFER TO S2 OTHERWISE TL=TAE TRANSFER TO S2 END OF CONDITIONAL S3 TL1I= 35. TR1=TAI S4 TDC=.5*('TRI+TI 1)- TC_ TC TOC=TC+TDC HWLTC = HFT.(TC) HD4WLTC =HFT ('CT DC) -HFT. (IC) JKR= (LID-( CC_-MCT DC-M WLN'F L IC+HOWLTC*MWL) ) WHENEVER.ABS. JKR.L..1,TRANSFER TO S6'WHENEVER JKR.L.O TRI=TCTDC OTHERWISE TL= TCTDC END OF CUNDITI.iNAL TRANSFER TO S4 S6 MW'L=MWL-MDWLN C=' CT DC WHENEVER I.E. TIME PR INT FORMAT$IH tt14,OF8.4 *$I,, MEvM L PCVAItTCTfAE7TAVE I=1+PTIME END OF CONDITIONAL WHENEVER W.LE. WE+.Ol*WE,TRPANSFER TO S7 SI CONTINUE PRINT COMMENT$ TIME GkRE'ER THAN 1000 $ S7 END OF PiR OGRA87

APPENDIX C COMPUTER PROGRAM NOMENCLATURE SINGLE PIECE OF CLOTH ACL - area of the cloth ARHO - density of the air at temperature TAVE C - the limit on the mass of water that can be removed mechanical extraction CC - specific heat of the cloth HAE - enthalpy of the air at the exit temperature HAI - enthalpy of the air at the inlet temperature H.HX - heat transfer coefficient of the cloth HMTX - mass transfer coefficient of the cloth HLTC - enthalpy of the water liquid in the cloth at the HWLTC temperature of the cloth HVIC - enthalpy of the water vapor in the cloth at the temperature of the cloth HDWLTC - change in the enthalpy of the water liquid in the cloth due to the change in the temperature of the cloth HW/E - enthalpy of the water vapor at the exit temperature HWVI - enthalpy of the water vapor at the inlet temperature MC - mass of the cloth MDAE - mass flow rate of air at the exit MDAI mass flow rate of air at the inlet MDWL - change in the mass of water liquid in the cloth MWL - mass of water liquid in the cloth 88

PC - pressure drop across the cloth PCI - initial pressure drop across the cloth PTIME - time between the output printout PS - saturation pressure at the temperature of the cloth PV - vapor pressure of the water vapor at TAVE QDAC - heat transver rate to the cloth TAB.( ) - external function to interpolate the values of PS for temperatures below 55~ TC - temperature of the cloth TDC - change in the temperature of the cloth TCTDC - TC + TDC TAI - inlet temperature of the air TAE - exit temperature of the air TAVE - average temperature of the air across the cloth TOTPA - the total pressure of the air and water vapor TL2TRTLIITRI - limits for the iterations to find TAVE and TDC UD - change in the internal energy of the cloth, water, and water vapor W - ratio of the mass of water liquid to the mass of the cloth WC - critical ratio W WE - the ratio of W where the water in, the cloth is in equilibrium with the water vapor in the air VAI volume flow rate of air VAIF - final volume flow rate of air 89

MACHINE MWLN - mass of water liquid at the nozzle MDWLN - change in the mass of water liquid at the nozzle MCN - mass of cloth at the nozzle K - percentage of time that the cloth covers the nozzle KI - the average number of thicknesses of cloth that cover the nozzle STEAM TABLES EXTERNAL FUNCTION HGT.(T) - enthalpy of saturated water vapor at temperature T HFT.(T) - enthalpy of saturated water liquid at temperature T PSATT.(T) - saturation pressure of water at temperature T 90