ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR INVESTIGATION OF HEAT TRANSFER PERFORMANCE OF NAVY FREON-12 CONDENSERS A SERIES OF U.S. Report No. 39 Edwin H. Young Assistant Professor of chemical Engineering Garen Balekjian Dennis J. Ward Marvin L. Katz Luis Gonzalez Research Assistants Project 1592 WOLVERINE TUBE DIVISION CALUMET AND HECLA, INCORPORATED DETROIT, MICHIGAN December 1955

I ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - TABLE OF CONTENTS Page ABSTRACT iii INTRODUCTION 1 DESIGN PROCEDURE 2 DISCUSSION AND RECOMMENDATIONS 5 APPENDIX A - Evaluation of CN for Run No. 28, Figure A of York Test Data 6 APPENDIX B - Evaluation of the Tube Wall Resistance for Trufin No. 195049-53 9 APPENDIX C - Calculation for Variation of (1/Deq)/4 with ho for Trufin No. 195049-53 Tube 10 APPENDIX D -Calculation of Total Outside Area of 4-FootLong Tube 12 APPENDIX E - Evaluation of the Performance of Unit No. 9 14 L ii

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGA ABSTRACT This heat transfer investigation was made to determine the minimum number of Freon-12 finned tube condensers required to cover a range of heat duties from 21,000 to 1,180,000 Btu per hour for the Navy Department. The design procedure is outlined and the unit specifications for eleven condensers are presented using a finned tube 5 feet long with land sections at 2, 3, and 4 feet from one end. N iii

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN This report was originally issued as Report No. 36 in February, 1955, and was reissued in May, 1955, with minor corrections. It is being reissued in December, 1955, with revisions and additions. iv

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - INTRODUCTION The condensation of Freon refrigerants provides a favorable application for finned tubes. Compact units using integral finned tubes have found wide usage throughout the refrigeration industry. The Navy Department has indicated interest in the use of Trufin type S/T tubes for replacing the plaintube condensers currently being used. Test data on the condensation of Freon-12 have been obtained by the York Corporation on six condensers tubed with 5/8-inch O.D. 18 BWG CuproNickel plain tubes and three condensers tubed with 3/4-inch O.D. 16 BWG 9010 Cupro-Nickel Trufin tubes having 19 fins per inch. The plain-tube test data had been used to prepare the standardized program currently being used by the Navy Department. Figure 1 presents the predicted heat-transfer performance of 24 plain-tube condensers with shell diameters varying from 6 to 20 inches and tube lengths varying from 1.5 to 8 feet. The number of units required to cover the desired range of heat duties from 21,000 t6 1,180,000 Btu per hour can be reduced effectively by using finned tube units with plain ends of the same O.D. as the plain tubes. These tubes can be rolled into tube sheets and supported in the same manner as the plain tubes. The York Corporation had analyzed their original test data obtained from the three finned tube condensers and had prepared rating curves from which the heat-transter performance of a given unit could be determined. On the basis of these rating curves, the Navy Department has completed a preliminary program which includes seven finned tube condensers with shell diameters varying from 6 to 16 inches and tube length of 2.5 and 5 feet. Table I gives the shell and tube specifications for the Navy Department condensers. Figure 2 gives the predicted performance of each unit within the range of water flow rates of 2 and 6 feet per second. The following are the important considerations in numerical order of importance that the NaTvy Department desires to be included in a standardized finned tube program: 1. minimum number of tube lengths to carry in inventory, 2. minimum number of head sizes required, 3. minimum number of shell diameters, and 4. maximum length of tube 6 feet, and preferably shorter. 1 I 1

~;1 - ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHGANN This investigation was made to determine the minimum number of finned tube condensers required to cover the range of heat duties from 21,000 to 1,180,000 Btu per hour. DESIGN PROCEDURE The procedure used to determine the performance of the recommended condensers is that suitable for the design of condensers using Trufin type S/T tubes. This method has been indicated previously., Equation (1) relates the heat duty, Q, of a heat exchanger with the overall heat transfer coefficient, Uo, the total outside area, A, and the mean temperature difference, ATav: Q = Uo A Tav (1) For a given condenser the heat duty is also related to the water throughput and the temperature rise: Q= Wt C At. (2) In equation (1), Uo including an inside fouling factor, ri, is defined by equation (3): J1 1 J-.mmXfAo Ao Ao _ -+ + "P r + (3) U0 ho kmAm Ai Aihi The essential steps of the design involve the determination of the correct AT driving force and the overall coefficient Uo from the individual resistances in equation (3). For this application AT a AT - (Tsv-tl)- (Tsv-t2) ATav M= Tm TsV v t' (4) sv- t2 1-Balekjian, G. and Young, E. H., "Use of Finned Tubes in Condensing Butyl Heads and Isopropyl Alcohol," University of Michigan, Engineering Research Institute Report No. 33 for Wolverine Tube Division of Calumet and Hecla, Inc., June, 1954..1 I 2 -— ~ —-- — ~ - Crr~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-Il

I - ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN The water-film coefficient is obtained from V o.8 hw = 150 (1+0.011 tw) tO (5) 0.2 di Evaluation of the tube wall resistance is shown in Appendix B. The outside condensing film coefficient is calculated from the following equation: -3 2 1/4 ho0.725 CNf 1), *o f (6) In equation (6), (1/Deq)l/4 is defined as follows: 1/4 Af 1/4 Ar/ 4 ( 1.3 ef (; ( + + (7) CN and N are functions of the number of tubes in the condenser and the tube layout. For a triangular tube layout N = 0.40 x~054 (8) CN is a correction factor applied to the condensing coefficient for the average tube in the bundle as predicted by the Nusselt equation, and it varies with N and the material condensed. In this investigation the variation of CN with N for Freon-12 was established from the test data obtained by the York Corporation for 8-, 12, and 16-inch shell condensers and given in Figure A of their test data. Evaluation of CN is shown in Appendix A for rin No. 28 of Figure A. Figure 5 indicates the CN values calculated from the test data, along with the suitable lines used for subsequent designs. The two points appreciably below the upper line represent run Nos. 6 and 29 (Figure A of test data) at 1.97 feet per second water velocity. The lower line was used to determine the condensing coefficient values with water velocities of 2 feet per second, while the upper line was used for water velocities above 2 feet per second. In this investigation shell diameters and header baffle clearances conform to the Bureau of Ships Specification No. 5000-S5902-F-841623-B. The tube selected is 90-10 Cupro-Nickel with 18 BWG (0.049 inch) wall thickness, 2 Young, E H.,, et al., "Condensation of Freon-114 on a Horizontal 19 Fin/ Inch Tube," University of Michigan, Engineering Research Institute Report No. 32 for Wolverine Tube Division of Calumet and Hecla, Inc.,: January, 1954. j No - -- --- - -- 3

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Trufin type S/T 195049-53. Evaluation of ho from equation (6) and determination of Uo from equation (3) involve a process of successive approximation. This procedure is facilitated by using Figures 4 and 5. The preparation of Figure 4 includes fin efficiency corrections as is illustrated in the calculation given in Appendix C. Figure 5 presents the variation of the property group in the modified Nusselt equation (6) with the mean condensate film temperature, Tf. Appendix D presents the calculation of the total outside area for the 4-footlong finned tube having 2-inch-long land sections at 2 and 3 feet from one end, and 1-inch-long plain ends. The details of the design calculations are given in Appendix E for unit No. 9 with 10-1/4 inches I.D. shell and 5-foot-long tubes...The heat transfer performance of each unit was determined at water velocities of 2, 3, 6, and 10 feet per second for a condensing temperature of 105~F, and an inlet water temperature of 850F. Table II gives the characteristics of Trufin tube type S/T No. 195049-53. Table III gives the shell and tube specifications for the 11 Trufin units necessary to cover the specified range of heat duties. Figure 6 presents the tube sheet layout for the 6-1/8, 8-1/8, 10-1/4, 12-1/4, and 15-1/2-inch I.D. shell condensers. Figure 7 presents the performance of the 11 units selected by the Navy Department for the recommended standardized program. The performance of each unit from 2 to 3 feet per second and 6 to 10 feet per second water velocity is shown by dashed lines; the performance of each unit from 3 to 6 feet per second is shown by a heavy line. Figure 8 is the rating chart determined for the condensers designed in this investigation. It is based on the water temperature rise and flow rates, and the heat duties summarized in Table III. The nominal heat duty for a ton of refrigeration is taken as 15,000 Btu per hour. A comparison of the design procedure used in this investigation with that used by York Corporation for their recommendations indicates that the two methods give comparable results. The present method is preferred because in the evaluation of the condensing coefficient it accounts for the variation of the condensing film coefficient with the selected inside fouling resistance, water velocity and temperature, and number of tubes in the bundle. In their designs, York Corporation used a constant condensing coefficient for a given tube bundle obtained by averaging the four values calculated from the test data. J I 4

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN DISCUSSION AND RECOMMENDATIONS In order to cover the wide range of heat duties, eleven condensers were designed with five shell diameters and four different tube lengths. Table III summarizes the shell and tube specifications for the eleven condensers covering a range of heat duties from 21,000 to 1,300,000 Btu/hr. Figure 7 presents the performance of each unit as a function of the water throughput in gal/min. The desirable features of the designs summarized in Table III are: 1. Only five different head sizes and shell diameters are required. 2. The range of water velocities and temperature rise is suitable to prevent excessive tube-side fouling. 3. The eleven condensers enable the selection of a unit which for a specific requirement provides a reasonable capacity range. 4* In order to accommodate the various tube and shell lengths it is recommended that a single tube length be carried in inventory. A tube 5 feet long with lands at 2, 35 and 4 feet from one end will provide all the necessary tube lengths with plain ends of 1 inch and land sections of 2 inches in length. The required number of units for this program is more than that specified in Table I based on the performance of units within 2 to 6 ft/sec water velocity. In general, fouling on the tube side tends to become appreciable below 3 ft/sec, while erosion at the tube entrance and pressure drop became limiting factors at water velocities above 10 ft/sec. The CuproNickel alloy tubes specified in this application are suitable for use with tube-side water velocities up to 10 ft per second. This water velocity range increases appreciably the range of performance of each unit so that the required heat duties may be obtained satisfactorily with fewer units. The use of water velocities inside the tubes of up to 10 ft/sec is recommended for this particular application. L 5

- ENGINEERING RESEARCH INSTITUTE * UNIVEI APPENDIX A EVALUATION OF CN FOR RUN NO. 28 FIGURE A OF YORK TEST DATA 1. TUBE CHARACTERISTICS ZSITY OF MICHIGAN -. 6 Trufin No. 195065-53 19 fins per inch do = 0.739 inch dr = 0.624 inch di = 0.494 inch wall thickness = 0.065 inch (16 BWG) mean fin thickness = 0.016 inch A = 0..496 ft2/ft Ai = 0.1292 ft2/ft Ao/Ai.= 3.84 Acs = 0.00133 ft2/tube km= 27.5 Btu hr- ~F-ft 2. EXPERDIENTAL CONDENSING FILM COEFFICIENT a. Metal Resistance _ rm dm, mean diameter, = dm = 0.624-0.494 - 0.624'n 0.494 dr-di dr 0.560 inch Am = (3.14)(o.560) = 0.1468 ft2/ft (12) XfAo rm k A m m (9) (O.o65)(o.496) rm = 0.000665 hr- F-ft2 Btu (12)(27.5)(0.1468) b. Water Film Resistance - A0 Aihw 6

-ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN Number of tubes in bundle = 46. Water velocity, Vt = 5.96 ft/sec Average water temperature, tw = —.9892.48 = 88.73~F From equation (5), (8 hw = 150 (1+0.011x88.73) ( 44)0.2 (o.494) hw = 1422 -uhr- OF-ftz, and Ao Aih. 3.84 h- ~F- ft2 1422 - 0.0027 Btu c. Experimental Condensing Film Coefficient - ho 1 1 A0 ho Uo Aihw'm (10) Uo = 186.0, 1 = 0.00538 Uo 1 ho - 0.00538 - 0.0027 - 0.000665 ho = 0.002015, 1 h = 1 = 0 0.002015 496 Btu 2 hr- ~F-ft 3. EVALUATION OF CN From equation (6) ho = 0.725 CN / 3 2 1/4 / kfPfgc X% IfN At cfD'q f feq For, x = 46 tubes in the bundle, N = 0.40 (46)054 = 3.16, N/4 (3.16)1/4 = 1.3335, ATLM = 16.04~F (From Figure A of test data), Atcf = (16.04) (00 )= 6.0OF, c.00538 At1/4 cf = (6.o0)/4 = 1.566, Tf = Tsv - 1/2 Atcf, and (11) 7

-ENGINEERING RESEARCH INSTITUTE Tf= 105.06 -.= 102.0o6F. 2 From Figure 5,.~,~p2g ) 1/4 of F-)r = 406.7 From Figure 4, UNIVERSITY OF MICHIGAN at ho = 4 2.775 el Substituting in equation (6), h = (0.725)(406 7(.7)(.775) (1.53335)(1.566) CN = 392 CN From section (2c), 392 CN = 496 and CN = 496 392 This result is shown by the circular point at N = 5.16 in Figure 3. 8

- ENGINEERING RESEARCH INSTITUTE * UNIVERSIT APPENDIX B EVALUATION OF THE TUBE WALL RESISTANCE FOR TRUFIN NO. 195049-53 1. TUBE CHARACTERISTICS - Trufin No. 195049-53 Summarized in Table II'Y OF MICHIGAN L 2. METAL RESISTANCE - rm XfAo KAm dm 0.624-0.526 = 0.583 inch. in 0.624 0. 526 A = - -(3.4)(0-583) = 0.1528 ft2ft. (12) rm Em (o.049)(o.496) (12) (27.5) (0.1528) = 0.000482 hr-~F-ft2 Btu.1 9

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN APPENDIX C CALCULATION FOR VARIATION OF (l/Deq)1/ WITH ho FOR TRUFIN NO. 195049-53 TUBE The following calculation is made for one point on Figure 4. It involves evaluation of the outside film coefficient (ho) in Btu/hr-~F-ft2 outside area and the equivalent diameter (l/Deq)l/4 for an assumed value of the outside film coefficient (ho) in Btu/hr-~F-ft2 equivalent outside area. In equation (7), (1/4 eD Af = 1.3 ef - Ao Ar 1/4 AO rJ Af = (0.80) (o.496) = 0.397 ft2/ft A, = (0.20) (o.496) = 0.099 ft2/ft, and _ (0.597)(12) L, mean effective fin height = (i2)(19)(2)(0.759) (1)(19)(2)(04739). = 0.01414 ft. Substituting in equation (7), (1) 1/4 /, \1/4 _ (1.3)(.397) ( 1 1/4 (0.496)).0141_ (0.099) /12 1/4 ef + (0.496) K.624), and (D-' - = 3.02 ef + 0.417 To evaluate the fin efficiency from Figure 5 of Reference 1, do _ 0.79 - 1.182 and dr 0.624 i fin height, H = I(0.739 - 0.624) (2)(12) = o.oo48 ft For an outside fouling factor of ro = 0, the abscissa ieduces to 2hI H v - kmY. o(2) ho. (12) 0.oo0048 (27.5)(o..016). 003555 10

-- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - For an assumed value of ho = 800 Btu hr-~F-ft2 equivalent outside area abscissa = 0.0355 \800 = 1.003.. ef = 0.735 and 1 >1/4 eq = (3.02)(0.735) + 0.417 = 2.637 ~ Ae = ef Af +Ar (12) Ae = (0.735)(0.397) + 0.099 = 0.391 ft2ft ho = h, and Ao = (0'~91)(80. ) =6 f~~Btu ae (0.391) (800) = 630 Btu h = (0.496) hr-OF-ft2 outside area (13) This calculation gives one point on Figure 4 and other values of the assumed coefficient ho 0' is repeated for 11

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN APPENDIX D CALCULATION OF TOTAL OUTSIDE AREA OF 4-FOOT-LONG TUBE Total tube length = 4 feet 2-inch-long land sections at 2 and 3 feet 1-inch-long end sections, and Length rolled into tube sheet = 3/4 inch. At every land and end the reduction in the outside imperfect finning is: area because of 0.86 sq. inches 1.88 sq. inches Total reduction at start of finning operation, and at end of finning operation. in area = 0.86 + 1.88 = 2.74 sq. inches. The total outside area of the tube is obtained from the following equation: A = LlAo + L2A$ 2.74 (n+l), 144 (14) where: A n L1 = total outside area, ft2 = number of land sections = total length - 2(n+l) 12 ft, L2 = n + 1 ft 12 24 Ao = 0.496 ft2/ft, and A' = 0.1963 ft2/ft. For the 4-ft tube, L1 = 4 - = 3.5 ft and 12 L2 = (2) (2) + 1 = 0.75 ft 12 24 Substituting in equation (14), A = (3.5)(0.496) + (0.375)(0.1963) \-144/' 12

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN A = 1.737 + 0.0736 - 0.057 = 1.754 ft2 The outside area of the other tubes w a calculated similarly: Tube length, No. of Outside ft Lands Area, ft2 5 3 2.318 4 2 1.754 3 1 1.525 2 0 0.8992.1 153

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN APPENDIX E EVALUATION OF THE PERFORMANCE OF UNIT NO. 9 1. CONDENSER SPECIFICATIONS Shell I.D. = 10-1/4 inches, No. of tubes = 82, No. of tube passes = 2, Total outside area = (82)(2.318) = 190 sq ft, and Tube layout: 15/16-inch triangular pitch. 2. HEAT TRANSFER PERFORMANCE - at 3 ft/sec water velocity No. of tubes per pass = 82/2 = 41, Acst = (41)(0.00151) = 0.062 ft2/pass, Water flow rate = (0.062)(3)(3600)(62) = 41,500 lb/hr = 41,50 83 gal/min. (8.33)(60) From section (2) of Appendix B, rm 0.000482 hr-~F-ft2 Btu For the selected inside fouling factor, ri = 0.0005 A0 hr_~F-ft2 A ri = (0o.00)(3.59) = 0.001795 Aij' Btu - The overall coefficient is determined by successive approximations in the following manner: saturated vapor temperature = 105~F, inlet water temperature = 85~F, assume At water = 8.4~F, t2 = 85 + 8.4 = 93.4~F, ATa =ATM (105-85) - (10 93.4) 15.4F and nav LM o 105-85 in 105-95.4 14

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - tw = 85 + 93.4 = 89.2F. 2 From equation (5), (3)0.8 hw = (150)(1 + 0.011 x 89.2) ( 26) (0.526)0.2 = 817 Btu/hr-~F-ft2 ~Ao 359' hr-~F-ft2 Water-film resistance = - = 59 0.00439 t Aihw 817 Btu 1 R- — = 0.00459 + o.001795 + 0.000482 = 0.006667 Assume ho = 580 Btu/hr-OF-ft2, 1 = 1 = 0.00172, ho 580 Rt = 0.00172 + 0.006667 = 0.008387, At =..00172L 15.4 = 3.150F, cf - 0.008587 Atef1/ = (.15)1/ = 1.33, and Tf = 105 -315 = 103.4F. f2 From Figure 5, (kf pf gc1 405.2 /1 1/4 jD $ = 2.68 Fre 4 From equation (8), N = 0,40(82)0 54 = 4.31 and N1/4 (4 )1/4.. = (4.31) = 1.441 15

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN From the upper line of Figure 3, CN = i.40. C -i..4o Substituting in equation (6), Btu ho (0.725)(1.40)(405.2)(2.68) = hrF-ft 2 ~ =~ (1.441)(1-33) 57hr ~Fft2 Since the assumed and calculated values of ho agree satisfactorily, Btu U = = 119.2 -1.2.... Rt o.oo08387 hr-~F-ft2 (outside area) The heat duty obtained from Q = UO Ao ATLM is, substituting: Q = (119.2)(15.4)(190) = 348,500 Btu/hr.. The corresponding At of water = 48, 0 = 8.400F. 41, 500 Calculated At water checks satisfactorily with the assumed value of 8.4~F. 3. HEAT TRANSFER PERFORMANCE - at 6 ft/sec water velocity Water flow rate = (0.062)(6)(3600)(62) = 83,000 lb/hr 83,00 = 166 gal/min (8.33)(60) Assume At water = 5.90F, t2 = 85 + 5.9 = 90.90F, AT, = (105 - 85) - (105 - 909) = 16.8~F 105-85 n 105-90.9 t = 85 + 90.9 = 87.95~F, 2 (6)0.8 hw = 150 (1 + 0.011 x 87.95) 0.2 = 16408 (0. 26) 16

F- ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN Ao Aihw 3.59 = 0.00255, and 1408 Rt - 1 = 0.0025.1795 + 0.000482 = 0.004827 ho Assume h = 550, _1 = i = 0.00182, ho 550 Rt = 0.004827 + 0.00182 = 0.006647, 0.00182 5 =.98F Atf -14.5 5.98o tAcf = 00664 A j1/4,_ \14 1,.... Atcf -= (3.9b = ~.L 41 ana, Tf = 105 - 3298 103.01F. 2 From Figure 5, /3 2 1/4 /f3pf gcl = 406. m F e From Figure 4, 1 i 1/4 eq\ ^ = 2.72. Substituting in equation (6), ho (0.725) (14o)(4o6) (2.72) (1.441) (1.412) = 550 Btu/hr-~F-ft2 The calculated value of ho checks with the assumed value.... Uo = 0. 0 = 150.8 0.006647 Btu hr-~F-ft2(outside area) The heat duty is: Q = Uo Ao ATLM = (150.8)(g90)(16.8) = 481,000 Btu/hr. The corresponding temperature rise is: 17

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN = 481 ooo = 5.8F 83,090. The calculated At checks satisfactorily with the assumed value of 5.8~F. 18

TABLE I SHELL AND TUBE SPECIFICATIONS FOR NAVY DEPARTMENT FINNED TUBE CONDENSERS nit iShell Tube N o No. of Total Water Flow Rate Heat Duty O.D., Length, b Tube Outside Gal/Min Btu/Hr No In. Ft T s Passes Area, Ft2 2 Ft/Sec 6 Ft/Sec 2 Ft/Sec 6 Ft/Sec 1 6-5/8 2.5 12 4 13.9 4.1 12.2 19,800 34,250 2 6-5/8 2.5 20 4 23.2 6.8 20.3 32,900 57,400 3 6-5/8 5 20 2 46.4 13.6 40.7 65,800 115,000 4 8-5/8 5 38 2 88.o 25.7 77.2 124,500 220,000 5 10-3/4 5 68 2 157.2 46.0 138.0 222,000 395,000 6 12-3/4 5 102 2 236.0 69.1 207.3 335,000 596,000 7 16-13/16 5 196 2 454.0 132,9 599.0 640,000 1,158,000, _'" t __., r,,; i,,',,,,,,,,,,',,~ ~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tubes: Trufin Type S/T No. 195049-53. TABLE II TUBE CHARACTERISTICS OF TRUFIN TYPE S/T NO. 195049-53 MATERIAL: 90-10 CUPRO-NICKEL 19 fins per inch do = 0.759 inch dr = 0.624 inch di = 0.526 inch wall thickness - 0.049 inch (18 BWG) mean fin thickness = 0.016 inch Ao = 0.496 ft2/ft Ai = 0.138 ft2/ft Ao/Ai = 3.59 Acs = 0.00151 ft2/tube k = 27.5 Btu hr-~F-ft

TABLE II TUBE SPECIFICATIONS I FOR FREON-12 CONDENSERS SHELL AND Water Velocity Unit Shell Tube o. f No. of Total Water Veloity Unit Shell Tube No. of Total 2 ft/sec 3 ft/sec 6 ft/sec 10 ft/sec No. I.D., Length, Tues Tube Outside fse At ts _6 —-- - -- _t_ —— e in. ft Passes Area, ft PM Q Btu/hr GPM Btu/hr GPM Btu/hr GPM Q Btu/hr i. ft Pas ses Area, 0F GPM Q1 M Q, Bo GPM F1 G Q, Btu/hr Bthr I I ~ ~ ~ ~ ~ ~ ~ ~ ~ GMGM 1Buh 1 6-1/8 2 6-1/8 3 6-1/8 4 6-1/8 2 14 2 12.59 3 14 2 18.55 4 14 2 24.60 5 14 2 32.40 4.3 6.2 7.9 9.7 9.45 9.45 9.45 9.45 21,400 29,400 37,300 46,000 3.5 5.2 6.5 8.1 14.2 14.2 14.2 14.2 26,200 36,500 46,500 58,200 2.3 3.4 4.4 5.5 28.4 28.4 28.4 28.4 34,200 48,000 61,500 78,000 1.62 2.30 2.90 3.90 47.2 47.2 47.2 47.2 39,000 54,900oo 72,500 94,000 5 6-1/8 6 6-1/8 4 26 2 45.70 5 26 2 60.30 7.8 17.6 68,700 9.6 17.6 84,400 6.6 26.3 87,100 8.3 26.3 108,800 4.4 52.6 117,000 5.6 52.6 148,500 3.1 87.7 4.o 87.7 137,500 175,800 7 8-1/8 8 8-1/8 9 10-1/4 10 12-1/4 4 48 5 48 5 82 5 118 2 84.20 2 111.20 2 190.00 2 273.10 7.6 9.6 9.7 9.7 32.3 32.3 55.3 79.5 122,000 155,000 268,000 386,000 6.7 8.3 8.4 8.4 48.5 48.5 82.8 119.5 161,800 202,000 348,500 502,000 4.5 5.7 5.8 5.8 97.0 97.0 165.6 239.0 219,000 276,000 481,000 692,000 3.2 4.1 4.0 4.1 162.0 162.0 276.0 398.0 256,000 330,000 551,000 815,000 11 15-1/2 5 196 2 453.60 9.6 132.4 638,000 8.4 198.5 839,000 5.8 397.0 1,152,000 4.15 666.5 1,370,000

800,000 - - -- 6o00,000o —oo -- -oo 0,00,000 - 100,000- - - - - - -- - -__ ______/ ^II==100,000= I / E CONDENSER HEAT REJECTION FACTOR w / Ei REFRIGERATING EFFECT X FACTOR -EAT REJECTION /^.,/~ >^. — ^7' / I /4,8UBES REFRIGERATING EFFECT X FACTOR.*HEAT REJECTION~ I m z 0 LJ LL LU cn LU C) z z 0 10,000- -', -; / C 20,000 — 7-. 5/8"0D 6 TUBES__ 000/ LNOTH,oo __/ //-~.Tfi' I I... _ _tIvI I _ _ _ L.... o00 1.5800 1.5300 1.4800 1.4300 1.3800 1.3300 I.2800 I.2300 1.1800 YtS I 1.51,z z. I 5 6 7 6 9 10 15 20 30 40 14 12 10 6 5 4 3 2.5 WATER FLOW RATE,GPM WATER TEMPERATURE RISE, ~F -20 -10 0 10 20 30 40 50 60 SATURATED SUCTION GAS TEMP IN ~F FIGURE I PERFORMANCE OF FREON-12 CONDENSERS USING 5/8-INCH O.D. 18 BWG PLAIN TUBES

4,000,oc o — y UNIT NO. SHELL OD. TUBE LENGTH NO. OF TUBE NO. OF - -- - - INCHES FT. PASSES TUBES I 6 5/8 2.5 4 12 2,000,000 — - 2 6 5/8 2.5 4 20 7 / 3 6 5/8 5 2 20 4 8 5/8 5 2 38 5 10 3/4 5 2 68 I,00o,Oc 0 6 12 3/4 5 2 102 / /- - 7 16 13/16 5 2 196 " / 800,00c - I 400,00o 200,00 w ___ __ _ _ ____ _____ ___ _/" / i___ ___ _ ooJ n'~~A~~ ~ I -r 3 / /, 200 300 400 I 60 1 1C Ioo LI 11/IA / I/ /\.AA r I/ CONDENSER HEAT REJ....................... ECTION FACT( F z V / XV /\ 1 / X /A I I z 60,000 0 2 40,000/ ///-o I-a n-ooo T %,o,ooo./ / / /_ / x //I __I___1 REFRIGERATING EFFECT X FACTOR-HEAT REJECTOT B -.4LI 1.5800 1.5300 1.4800 1.4300 1.3800 1.3300 1.2800 1.2300 1.1800 I \N\l, I.,.......'..... -- 2- - I I 11.5 1 2 5 3 4 5 6 17 8 9 l 15 2U 30 40 0 60 U70 0 so o00 -z2 -o10 0 1 20 30 40 50 60 14 12 10 8 6 5 4 3 2.5 WATER FLOW RATE,GPM SATURATED SUCTION GAS TEMP IN ~F WATER TEMPERATURE RISE, ~F FIGURE 2. PERFORMANCE OF FREON-12 CONDENSERS USING TRUFIN NO. 195049-53 TUBES

2.0 1.8 z 0. 1.6 I'-.4 0 IL 1.2 z 0 a: ~ 0.8 I.0 0 0.8 0.7 0.6 ___1_____ j___~_ —- - -- - - SYMBOL WATER VELOCITY FT./SEC ~~ -__ 0- 3.3 X 4.7 I'2 3 4 5 6 7 8 9 IO 24 NUMBER OF TUBES IN A VERTICAL ROW, N FIGURE 3 RATIO OF EXPERIMENTAL TO THEORETICAL CONDENSATION COEFFICIENTS FOR FREON-12 O

3.5 3.4 3.3 3.2 3.1 S. I __I_____ I I______ _e_____e - _TRURNFIN NO. 195049-53 X -I OUTIIsID90-10 CUPRO-NICKEL TUBE OUTSIDE FOULING FACTORO KM ~ 27.5(TU)(FT)/(NHR)(FK)(SQ FT) -.4 I - -1* 2.9 - a S- 2 I _ I — 2.7 I I \1~ 9O XL II I I I I _ I a _ I.a — II I - - &.%7 0 100 200 300 400 OUTSIDE FILM 500 600 700 800 COEFFICIENT, ho BTU/HR-F-SQ FT OUTSIDE AREA 900 m000 -- - FIGURE 4 VARIATION OF(I f WITH OUTSIDE FILM COEFFICIENT DEQ

450 440 430 420 410 SATURATION TEMPERATURE * 105PF _LATENT HEAT OF VAPOR.*s5.5BTU/l w 4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444i4444444444i1444444TT N I I I ______ 90 IL - lM rrer.390 %99 A0 -.-. —. 370,' —-..I.. 380 i — 50 6O 70 8 0 90 00 110 120 130 140 IS0 CONDENSATE FILM TEMPERATURE, T *F F FIGURE 5 VARIATION OF PHYSICAL PROPERTY GROUP IN NUSSELT EQUATION WITH CONDENSING AND CONDENSATE FILM TEMPERATURES FOR FREON- 12

6'" I.D. SHELL TOTAL NO. OF TUBES - 14 1 6 /s" I.D. SHELL TOTAL NO. OF TUBES= 26 000 C \ ooooboeod 8 /" I.D. SHELL TOTAL NO. OF TUBES ~ 48 COMMON TO ALL UNITS TUBE SHEET THICKNESS = 3/4 INCH TUBE SHEET CENTER-LINE CLEARANCE, A 1/4 INCH TUBE O.D. 3/4 INCH TUBE PITCH ~ 15/16 INCH CENTER TO CENTER, TRIANGULAR TUBE TO TUBE CLEARANCE ~ 3/16 INCH TUBE PASSES a 2 00000 000->Oa oooooo oeooo 02 00 I S TOTAL0 OF T ooo Ioo ooT ooo / o oooloocoo 15" I.D. SHELL; TOTAL NO. OF TUBES = 196 0000 000 0 00000 00 12'/4 I.D. SHELL; TOTAL NO. OF TUBES 118 1O04" I.D. SHELL; TOTAL NO. OF TUBES = 82 FIGURE 6- TUBE SHEET LAYOUT FOR FINNED TUBE CONDENSERS

) I I Icu~PICCne w~ca I av /L. /S m w I. w Xn a z 0 C, 1,500,000 /. / UNIT NO, SHELL 1.0. TUBE LENGTH NO. OF NO. DF (INCHES) (FEET) TUBES TUBE PASSES I 6'/ 2 14 2 3 600 4 14 214 poooo0- oo —- 4 6 / 5 14 2 -/ - 900,000 6 6 4 26 2 ~900,000 -- -- ----— r~ 6ee 5 26 2 / ~ oo eve 4 48 2 / / / / 800,000 - 8ae 5 48 2 -- 9 )./4 5 82 2 ///4~ / / i 700,000 —o —------ I 12'4 5 118 2 7 / 700,000 600,000- _____ Z 400,000 150,000 - /_,o0,ooo - /..._ / /z /'2.0,000 —Z__ 0,000 —-___________________ 0,00 -/ /_____ _____ 20,000.'If 8 9 10 20 30 40 50 60 70 80 90 100 WATER FLOW RATE, GPM 300 400 500 6bU 700 800 FIGURE 7 — PERFORMANCE OF FREON-12 CONDENSERS USING TRUFIN NO.195049-53 TUBES

20 TUBE PASSES 2 INSIDE FOULING FACTOR'0.0005 19 _ OUTSIDE FOULING FACTOR ~ 0 NOMINAL TON OF REFRIGERATION 15,000 BTU/HR CONDENSING TEMP. 105eF INLET WATER TEMR * 85F 18 - WOLVERINE TRUFIN 195049-53 12' " _ ___ _ - SYMBOL TUBE LENGTH,F > 19-A- --- -- A 2 IL 0 4 v. * 9 4 x 7 7xx 8 r:-W - ---— n —- ~ Uk ~' ~ 6 - ~ X~ 5I 6 7 — 0 - u - 6.5 14 - \ 4.5 1 3 5.5 I10 - - - -- - --- -- A/Q, FT2 OUTSIDE AREA TON REFRIGERATION.3- ^ ____^-^ ___^ _________ TON1 REFRIGERATIONJ FIGURE 8 DESIGN CHART FOR FREON-12 CONDENSERS

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN NOMENCLATURE A Total outside area, ft2 Acs Cross section area of tube for water flow, ft2 Af Outside area of fins, ft2/ft Ai Inside heat transfer area, ft2/ft Am Mean metal heat transfer area Am (= d) ft2/ft 12 A0 Outside area, ft2/ft Ar Outside root metal area, ft2/ft CN Correction factor for condensing coefficient with N tubes in a vertical row Cp Mean heat capacity, Btu/lb-~F di Inside diameter of tube, inches do-dr dm -- - inches in; do Diameter over fins, inches dr Root diameter of tube, inches Do Diameter over fins, feet Deq Equivalent diameter of finned tube for condensing, feet Tsv-tf ef Fin efficiency, defined as r where tf and tr are the Tsv tr temperatures of the fin and root, respectively.1

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN - ho h o KM kpfpgc L f L LI L2 N Q ri Rt tl t2 Ts tw Tf At Atc ATav ATLM Inside heat transfer coefficient Outside condensing coefficient Outside condensing coefficient, Btu hr-~F-ft2 (inside area) _Btu hr-~F-ft2 (outside area).. Btu hr-~F-ft2 (equivalent area) Thermal conductivity of metal, Btu/hr-~F-ft Nusselt physical property group Length of finned condensing surface L (12)Af = ft do(N) (2) (12) Length of finned portion of tube, ft Length of plain or unfinned portion of tube, ft Average number of tubes in a vertical row Total heat duty, Btu/hr Inside fouling resistance, hr-~F-ft2(inside area)/Btu Total resistance to heat transfer, 1/Uo Inlet water temperature, ~F OutMet water temperature, ~F Temperature of saturated vapor, ~F Average water temperature, ~F Average condensate film temperature, ~F Temperature rise of water Temperature drop across condensate film, ~F Mean temperature difference, ~F Logarithmic temperature difference, ~F 1 1. - -- — - --

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN U0 Overall heat transfer coefficient, Btu/hr-~F-ft2 (outside area) Vt Water velocity inside tubes, ft/sec Wt Water side flow rate, lb/hr X Wall thickness drdi feet 24 x Number of tubes in bundle Y Mean fin thickness, feet X\ Latent heat of condensing, Btu/lb