ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR Report No. 36 INVESTIGATION OF HEAT TRANSFER PERFORMANCE OF A SERIES OF U. S. NAVY FREON-12 CONDENSERS EDWIN H. YOUNG Assistant Professor of Chemical Engineering GAREN BALEKJIAN DENNIS J WARD ALBERT J PAQUETTE MARVIN L KATZ. Research Assistants Project 1592 WOLVERINE TUBE DIVISION CALUMET AND HECLA, INCORPORATED DETROIT, MICHIGAN February, 1955

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE OF CONTENTS 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 1 1/4 APPENDIX C - Calculation for Variation of eq 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. 15 14 ii

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 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 sixteen condensers are presented using a finned tube 5 feet long with land sections at 2, 3, and 4 feet from one end. iii

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 plain tube 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 to 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 transfer 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 Navy 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. - L 1

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 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.1 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 = UA ATav (1) For a given condenser the heat duty is also related to the water throughput and the temperature rise: Q = Wt Cp At.(2) In equation (1), Uo including an inside fouling factor, ri, is defined by equation (3) 1 1 XfAo Ao Ao U0 + - ri + (3) Uo ho kmAm A ri 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 (T s-tl) - (Tsv-t2) av LM Tsv - t () In T - sv - 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. 35 for Wolverine Tube Division of Calumet and Hecla, Inc., June, 1954. 2

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The water-film coefficient is obtained from V o.8 hw = 150 (1+0.011 tw) t~ (5) 0.2 d1 Evaluation of the tube wall resistance is shown in Appendix B. The outside condensing film coefficient is calculated from the following 2 equation; ho = 0-725 CN N PftNt D (6) N" At2 fDeq In equation (6), (1/Deq)l/4 is defined as follows: 14 A= 1- 1/4 A /4 ^Y 1- 1 ef3 Ao~ (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 x54. (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 run No. 28 of Figure A. Figure 3 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. 3

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Trufin type S/T 195049-53. Evaluation of ho from equation (6) and the 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 filp 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. 15 with 16 inches I.D. shell and 4-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 85~F. Table II gives the characteristics of Trufin tube type S/T No. 195049-53. Table III gives the shell and tube specifications for the 16 Trufin units necessary to cover the specified range of heat duties. This table includes also additional units considered for possible use. Figure 6 presents the tube sheet layout for the 6-, 8-, 10-, 12-, and 16-inch condensers. Figure 7 presents the performance of the 16 units selected for the recommended standardized program. The units were selected on the basis of the overlap obtained with the performance at 3 to 6 feet per second water velocity indicted by the solid lines. 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. 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 4

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN DISCUSSION AND RECOMMENDATIONS In order to cover the wide range of heat duties, sixteen condensers were designed with five shell diameters and four different tube lengths. Table III summarizes the shell and tube specifications for the sixteen 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 sixteen 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, 3, 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 length. The recommended standardized program is based on the predicted performance of units within the water velocity range of 3 to 6 ft/sec. The required number of units 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 Cupro-Nickel alloy tubes specified in this application are suitable for use with t;ube-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 than those specified in Figure 7. The use of water velocities inside the tubes of up to 10 ft./sec. is recommended for this particular application, 5

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - APPENDIX A EVALUATION OF CN FOR RUN NO. 28 FIGURE A OF YORK TEST DATA 1. TUBE CHARACTERISTICS 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 Ao = 0.496 ft2/ft Ai = 0.1292 ft2/ft Ao/Ai = 3.84 Acs = 0.00133 ft2/tube km = 27.5 Btu hr- OF-ft 2. EXPERIMENTAL CONDENSING FILM COEFFICIENT a. Metal Resistance - rm dm, mean diameter,= = r d. d = 0~624-0o494 - 0.560 inch o. 0624 0 494 Am = (3e14)(0.560) = 0.1468 ft2/ft (12) rm = XfAo m - - km mA m m (9) r - (o.065) (o0.496) (12)(27.5)(0.1468) b. Water Film Resistance - = 0.00665 hr- F-ft2 Btu AO AiE 6

-- ENGINEERING RESEARCH INSTITUTE * UNI Number of tubes in bundle = 46. Water velocity, Vt = 5o96 ft/sec48 Average water temperature, tw = 2-.9 2 From equation (5), ( 608 hw = 150 (1+0.011x88.73) (5 4 -20.8 (o0.494)-' IVERSITY OF MICHIGAN = 88.73~F hw = 1422 hr BoFftu2 A 3.84 Aiha - 1422y=0.0027, and hr- OF-ft2 Btu c. Experimental Condensing Film Coefficient - ho 1 1 Ao ho Uo Aihw rm (10) Uo = 186.0, 1 = 0.00558 U0 1 - = 0.00558 - 0.0027 - o0.00ooo665 ho = 0.00201. 1 h = 1 0.002015 496 Btu hr- ~F-ftz 3. EVALUATION OF CN From equation (6) ho = 0.725 5f 2 1/4 N tcfDeqfg CLfN At cfD eq ^^ -^D For, x = 46 tubes in the bundle, N = 0.40 (46)0.54 = 5.16, N1/4 (3.16)1/4= 1.3335, ATLM = 16.04~F (From Figure A of test data), Atcf = (16.04).002015> 6.o00F,.00538 At1/4 (6.0)1/4 1.566 cf = T - 1/2 f = Tsv - 1/2 Atcf, and (11) 7

- ENGINEERING RESEARCH INSTITUTE Tf = 105.06 - 6o0 = 102.06 F. 2 From Figure 5. * UNIVERSITY OF MICHIGAN p ___ 1/4 From Figure 4, = 406.7 at ho = 496, ( / Ye^ = 2.775. Substituting in equation (6), h = (o.725)(406.7)(2-775) 0 (1.3335)(1.566) CN = 592 CN o From section (2c), 592 CN = 496 and C = 496 C 592- 1.27 4 This result is shown by the circular point at N = 3.16 in Figure 3. 8

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN APPENDIX B EVALUATION OF THE TUBE WALL RESISTANCE FOR TRUFIN NO. 195049-55 1. TUBE CHARACTERISTICS - Trufin No. 195049-55 Summawrized in Table II 2. NETAL RESISTANCE - r X f s-m KmAm 0.6 24 dm =.6ali. - 0.583 inch or 0.526 Am = (3.14)(0.583) = 0.1528 ft2/ft. (12) r = ((Q,049) ( 0. 96 = 0.000482 hr-oF-ftt (12)(27.5)(0.1528) Btu i 9

r -- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - APPENDIX C CALCULATION FOR VARIATION OF (l/Deq)1/4 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 (1/Deq)/ for an assumed value of the outside film coefficient (ho) in Btu/hr-~F-ft2 equivalent outside area. In equation (7), t 1/4 De C.-Y keq f (1/4 = 1.3 ef A. Ar 1/4 Ao Af = (0.80) (o.496) = 0.397 ft2/ft, Ar = (0.20)(0.496) = 0.099 ft /ft, and (0.397)(12] L, mean effective fin height = = 0.01414 ft. i - (12)(19)(2)(0.759) Substituting in equation (7), 1>1/4 (a),r1 1/4 eW (1-3.).397) l/4 c (0.496.0411 ef + (0.099) (0.496) t.2 1/4 0.6.24 anc = 3.02 ef + 0.417. To evaluate the fin efficiency from Figure 5 of Reference 1, d 0 7329' 1.182 and dr - 0.624 fin height, H = (739 -. 624) = 00048 ft. (2)(12) For an outside fouling factor of ro = 0, the abscissa reduces to H k1-Y —o-oo48 (2) h (12) H kmY =O.oo48 (27.5) (o.016) 0- 0 10

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN For an assumed value of = 800 Btu ho hr-OF-fVf equivalent outside area abscissa = 0.0355 80O = 1.003'. ef = 0.735 and, = (3.02)(0.735) + 0.417 = 2.637 Ae = ef Af + Ar, (12) Ae = (0.735)(0.397) + 0.099 = 0.391 ftft, A ho = A h and (13) h = (0.391) 0)= 650 Btu h (0.496) (80) hr-~F-ft2 outside area This calculation gives one point on Figure 4 and is repeated for other values of the assumed coefficient ho. j 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 area because of imperfect finning is: 0.86 sq. inches at start of finning operation, and 1.88 sq. inches at end of finning operation. Total reduction in area = 0.86 + 1.88 = 2.74 sq. inches. The total outside area of the tube is obtained from the following equation: 2.74 A = L1Ao + L2A - 21- (n+l), (14) where: A = total outside area, ft2 n = number of land sections, L1 = total length - 21( ft L2 = 2n+ 12 = 6 ft/ft, and Ao = 0.1963 ft2/ft For the 4-ft tube, L1 = 4- 6 3.5 ft and 12 L2 = (2)(2) + 1_ =.375 ft 12 24 Substituting in equation (14), A = (3.5)(o.496) + (o.375)(o.1963) (- i( 2+), \44 12

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN A = 1.737 + 0.0736 - 0.057 = 1.754 ft2 The outside area of the other tubes was calculated similarly: Tube length, No. of Outside ft Lands Area, ft 5 3 2.518 4 2 1.754 3 1 1.325 2 0 0.8992 13

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN APPENDIX E EVALUATION OF THE PERFORMANCE OF UNIT NO. 15 1. CONDENSER SPECIFICATIONS Shell I.D. = 16 inches, No. of tubes = 222, No. of tube passes = 2, Total outside area = (222)(1.754) = 389.5 ft2, and Tube layout: 1-inch triangular pitch. 2. HEAT-TRANSFER PERFORMANCE - at 5 ft/sec water velocity 222 No. of tubes per pass = 111, Ast = (111)(0.00151) = 0.1676 ft2/pass, Water flow rate = (0.1676)(3)(3600)(62) = 112,200 lb/hr = (112,200) = 224-4 gal (8.33)(60) min From section (2) of Appendix B, rm = 0.000482 hr F-.ft2 - Btu. For the selected inside fouling factor, ri = 0.0005 and AO A- ri = (0.0005)(3.59)= 0.001795 -r-Bt2 Btu The overall coefficient is determined by successive approximation in the following manner: saturated vapor temperature = 105 F, inlet water temperature = 85~F, assume At water = 6.80F, t2 = 85 + 6.8 = 91.8~F AT = ATiM = (105-85) - (10- 91.8) 16 4~F, and av l 05 105.85 =16.4F, nd. n 105-91.8 tX = 85 + 918 = 88.4~F. 2 14

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF Ml( From equation (5), 08 hw= (150)(1+0.011x88.4) (3)~'L (0.526)0.2 hr-OF-ft Water-film resistance = A- = 359 0.00442 hr BF-ft2 ~ 811 Btu 1 Rt h = 0.00442 + 0.001795 + 0.000482 = 0.006697 hr —F-ft2 =Btu CHIGAN - and Assume ho = W Btu 595 hr —-Ffthr-~F-ft2 1 = 19 = 0.00168, Rt 0.00168+0.006697 = 000838, Rtcf= 0.0016.9 =.8 Atcf -.00168 (16.4) = 3.290F c - 008 t1/4 (329)1/4 c ~f ": 29 = 1.347, and Tf = 105 - 3.29 = 103.4~F rom Figure,2 From Figure 5, kf32 1~/4 From Figure 4, = 405.6 11/4 Deq = 2.67 From equation (8), N =0.40(222)~054= 7.4 and N1/4 (7.4)1/4 = 1.65 15

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - From the upper line of Figure 5, CN= 1.685. Substituting in equation (6), h = (0..725)(1.685)(405.6)(2.67) = 596 Btu (1.65) (1.347) hr- ~F-ft2 Since the assumed and calculated values of hoagre satisfactorily, U 1 = 119. 4 Btu Rt 0.00838 hr- F-ft2 outside area For the assumed At water, condenser heat duty from equation (1), Q = (119.4)(16.4)(389.5) = 763,000 Btu/hr, and corresponding At water = 763,000 = 6.8~F 112,200 Calculated At water checks satisfactorily with the assumed value of 6.8~F. 3. HEAT-TRANSFER PERFORMANCE - at 6 ft/sec water velocity Water flow rate = (0.1676)(6)(3600) (62) = 224,400 lb/hr 224400 = 448.8 gal (853)(60) min Assume At water = 4.6~F t2 = 85+4.6 = 89.6~F ATLM = (105-85)-,105-89.6) 1.2 ~o? n (105-85) (105-89.6) tv = 85+89.6 = 87.5~F hw = 150(1+0.011x87.3) (.6) = 1405 (0.526)u~ =i47

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN o 3.59 0.00256, and Rto =- 0.00256 + o.oo1795 + 0.000482 = 0.004837 Assume ho = 550, 1 1 ho 55 0.00182 Rt = 0.004837 + 0.00182 = 0.006657 tc -- 00 (17.52) = 4.79F o.oo6651 At4= (4.79)1/4 = 1.48, and Tf = 105 - = 102.6~F!f From Figure 4, r4c 2 1/4 = 1 = 150 Btu6.2 From Figure 4, 1/4 7 F-2 o e 715a Substituting in equation (6), h = (0.725)(1.685)(496.2)02.715) (1.65)(1.48) 1 Corresponding, At water = 1,0253000 = 4.56OF The Calculatssumed At water of h checks satisfactorily with the calculated value oof 4 Btu6F. 0.006657 hr-~F-ft2 outside area For the assumed At water, Q = (150)(17.52)(389.5) = 1,025,000 Btu hr Corresponding, At water = l-023Q00O = 4.56 OF 224,400 Calculated At water checks satisfactorily with the assumed value of 4.6~F. 17

TABLE I SHELL AND TUBE SPECIFICATIONS FOR NAVY DEPARTMENT FINNED TUBE CONDENSERS - Shell Unit No. N.In. 1 6-5/8 2 6-5/8 5 6-5/8 4 8-5/8 5 10-3/4 6 12-3/4 7 16-13/16: Tube Length, Ft 2.5 2.5 5 5 5 5 5 No. of Tubes, - 12 20 20 38 68 102 196 No. of Tube Passes 4 4 2 2 2 2 2 = Total Outside Area, Ft2 13.9 25.2 46.4 88.0 157.2 236.0 454.0 iI Water Flow Rate Gal/Min 2 Ft/Sec 6 Ft/Sec 3.6 10.7 6.0 18.0 12.0 31.0 21.5 68.0 36.0 107.0 68.0 190.0 96.0 350.0 Heat Duty Btu/Hr 2 Ft/Sec 6 Ft/Sec 21,000 41,500 34,500 69,000 65,000 115,000 115,000 222,000 195,000 385,000 360,000 645,000 515,000 1,180,000 = Tubes: Trufin Type S/T No. 195042-53. TABLE II TUBE CHARACTERISTICS OF TRUFIN TYPE S/T NO. 195049-55 MATERIAL: 90-10 CUPRO-NICKEL 19 fins per inch do = 0.739 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 = 5.59 Acs = 0.00151 ft2/tube km= 27.5 Btu hr- ~F-ft

TABLE III SHELL AND TUBE SPECIFICATIONS FOR FREON-12 CONDENSERS ---'___l~~~~~~~~~ ___ l Water Velocity: Unit Shell Tube No of No- of Total 2 ft/sec 3 ft/sec 6 ft/sec 10/ft/sec No. I.D. Length, Tubes Tube Outside " BtAt Btu/hrA in. ft Passes Area, ft2 OF GPM Q1 Btu/hrGPM t GPM Q Btu/hr 25,40 12 2. 5, bO.5 5.5 5710 1 6 2 6 3 6 4 6 2 3 4 5 13 2 11.7 13 2 17.2 13 2 22.8 13 2 30.1 2.4 3.5 4.5 5.6 17.5 17.5 17.5 17.5 20,900 30,440 39,000 49,500 1.9 2.8 3.6 4.6 26.3 26.3 26.3 26.3 25,400 36,500 47,200 60,900 1.2 1.8 2.3 3.1 52-5 52.5 52-5 52.5 32,800 46,600 61,500 80,400 0.85 1.2 1.6 2.1 87.5 87.5 87.5 87.5 37,100 53,700 70,100 93,400 - 6 -2 5 6 3 6 6 4 7 6 5 6 6 26 2 25.4 26 2 34.4 26 2 45.6 26 2 60.2 26 2 69.6 6.2 17.5 7.8 17.5 9.6 17.5 54,400 68,700 84,400 3.7 5.2 6.6 8.3 9.2 26.3 26.3 26.3 26.3 26.3 48,200 68,800 87,100 108,800 121,500 2.4 3.4 4.4 5.6 6.4 52.5 52-5 52.5 52.5 52.5 62,900 90,700 117,000 148,500 168,000 2.4 5.1 4.0 87.5 87.5 87.5 104,000 137,500 175,800 8 8 3 9 8 4 10 8 5 -- 8 6 48 2 63.6 48 2 84.3 48 2 111.0 48 2 128.4 6.2 32.3 7.6 32.3 9.6 32.3 100,700 122,000 155,000 5.3 6.7 8.3 9.3 48.5 48.5 48.5 48.5 128,300 161,800 202,000 226,000 3.5 4.5 5.7 6.5 97.0 97.0 97.0 97.0 172,000 219,000 276,000 314,500 2.5 161.5 3.2 161.5 4.1 161.5 198,200 256,000 330,000 10 3 76 2 100.6 11 10 4 76 2 133.2 12 10 5 76 2 176.0 - 10 6 76 2 205.5 12 3 120 2 159.0 13 12 4 120 2 210.5 1.4 12 5 120 2 278.0 -- 12 6 120 2 321.0 5.3 7.8 51.1 199,200 6.8 9.6 51.1 246,000 8.4 9.3 5.4 7.8 81.0 316,000 6.8 9.6 81:0 389,000 8.5 9.4 77.0 77.0 77.0 77.0 121.5 121.5 121.5 121.5 202,000 259,500 322,000 358,000 324,500 411,000 515,000 567,000 3.6 4.5 5.8 6.5 3.5 4.6 5.8 6.6 154.0 154.0 154.0 154.0 243.0 243.0 243.0 243.0 274,000 546,000 443,000 501,000 431,000 555,000 710,000 805,000 5.2 256.0 410,000 4.1 256.0 526,000 3.2 404.0 658,000 4.2 404.0 850,000 15 16 4 222 2 389.5 16 16 5 222 2 514.5 -- 16 6 222 2 594.0 7.7 150.0 580,000 6.8 9.6 150.0 716,000 8.5 9.4 224.4 763,000 224.4 952,000 224.4 1,060,000 4.6 448.8 5.9 448.8 6.6 448.8 1,023,000 1,320,000 1,490,000 3.3 750.0 1,222,000 4.2 750.0 1,570,000

2.0 1.8 0. 1.6 OI-.4 IL 1.2 z 0 to P 1.0 0.7,,,.., -I ~ I' 11Ill ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~o- _ r I ~~~~~~~I I II I I 4111I11I VP I. I I. + I 6 1, 1 1.F F ______ - - - | -| -SYMBOL WATER VELOCITY =" -^~- T 1 r -I 2FT./SEC.....~_ X 4.7 I 1 1 11 11 I 0.6 2 3 4 5 6 7 9 9 0 NUMBER OF TUBES IN A VERTICAL ROW, N FIGURE 3 RATIO OF EXPERIMENTAL TO THEORETICAL CONDENSATION COEFFICIENTS FOR FREON-12 20

3.5 _____________ TRUFIN NO. 195049-53 90-10 CUPRO-NICKEL TUBE OUTSIDE FOULING FACTOR*O 3.3 -- - K - 2 7.5( ^. TU)(FT) t/(H"F)SQ FT) 3.2 3.12 - - - 2.9 - I II 26. 2.7 2.6 - 2.5 2.4 2.3 0 100 200 300 400 500 600 700 00 900 K100 OUTSIDE FILM COEFFICIENT, ho, BTU/.R-F-SQ FT OUTSIDE AREA FIGURE 4 VARIATION OF( D QWITH OUTSIDE FILM COEFFICIENT DEQ

450 440 430 420 410 SATURATION TEMPERATURE a 10eFP -LATENT HEAT OF VAPO*R.S.BTTU/LI - I L -- I -I. 400 0100%% ay I-A& Ark 9 0- -- - - - 970 --- - -- - -- - -- - -- - STO - I I I ---- I - I - I 560 -' - I I II n II I II II - IIIIIIIIIIIII - InI -III --- ---- s0 0O TO SO t0 100 110 I10 110 140 wO CONDENSATE FILM TEMPERATURE, T,*F FIGURE 5 VARIATION OF PHYSICAL PROPERTY GROUP IN NUSSELT EQUATION WITH CONDENSING AND CONDENSATE FILM TEMPERATURES FOR FREON- 12

20 19 18 17 IL * u. t16 Iu. C. 15.-4 _i U 14 13 12 II 10 4 SHELL I.D. 6", 8", 10", 12", & 16" TUBE PASSES 2 INSIDE FOULING FACTOR s0.0005 OUTSIDE FOULING FACTOR * 0 NOMINAL TON OF REFRIGERATION ~ 15,000 BTU/HR CONDENSING TEMP. * 105IO INLET WATER TEMP ~ 5 IF WOLVERINE TRUFIN 195049 - 53 SYMBOL TUBE a X 2 3 5 0 6 5 6 A/Q, FT2 OUTSIDE AREA TON REFRIGERATION 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 = 2dm ft2/ft 12 AO 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 0~, inches do ln ar 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 -twhere tf and tr are the Tsvtr temperatures of the fin and root respectively J L

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN hi Inside heat transfer coefficient- Btu hr-~F-ftZ (inside area) ho Outside condensing coefficient Btu. hr- F-ft2 (outside area) ho Outside condensing coefficient, Btu hr- F-ft2 (equivalent area) KM Thermal conductivity of metal, Btu/hr-~F-ft (I-) Nusselt physical property group L Length of finned condensing surface L = (12)Af = ft do(N)(2) (12) L1 Length of finned portion of tube, ft L2 Length of plain or unfinned portion of tube, ft N Average number of tubes in a vertical row Q Total heat duty, Btu/hr ri Inside fouling resistance, hr- F-ft2(inside area)/Btu Rt Total resistance to heat transfer, 1/Uo t1 Inlet water temperature, ~F t2 Outlet water temperature, ~F T Temperature of saturated vapor, ~F sv tw Average water temperature, ~F Tf Average condensate film temperature, ~F At Temperature rise of water Atc Temperature drop across condensate film, ~F ATav Mean temperature difference, ~F ATLM Logarithmic temperature difference, ~F 7 J3 6

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Uo 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 dr-di feet 24. x Number of tubes in bundle Y Mean fin thickness, feet X Latent heat of condensing, Btu/lb