ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR Report No 42 FOULING OF AN 11-FINS-PER-INCH COIL IN AN INTERNAL TANKLESS WATER HEATER Edwin Ho Young Associate Professor of Chemical and Metallurgical Engineering Clifford To Terry Luis Oo Gonzalez Marvin L.o Katz Dennis J Ward Research Assistants Project 1592 CALUMET AND HECLA, INCo WOLVERINE TUBE DIVISION DETROIT, MICHIGAN July 1956

---- The University of Michigan * Engineering Research Institute TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS ii ABSTRACT iv OBJECTTIE iv Io INTODUCTION 1 IIo THEORETICAL CONSIDERATIONS 2 III. FOULING MECHANISMS 3 IVo TEST APPARATUS AND PROCEDURE V ANALYSIS OF TEST DATA 7 Ao ANALYSIS OF WILSON PLOT DATA7 B ANALYSIS OF THE I. BR CAPACITY DATA 10 VIo DISCUSSION OF RESULTS 12 VII. CONCLUSIONS 16 APPENDIX A - SUMMARY OF WILSON PLOT DATA 18 APPENDIiX B - SUMMARY OF I BoRo CAPACITY DATA 19 APPENDIX C - WILSON PLOT RUN CALCULATION 20 APPENDIX D - I.BoRo CAPACITY RUN CALCULATION 22 REFERENCES2 ii

The University of Michigan Engineering Research Institute LIST OF ILLUSTRATIONS Table I II III Figure 1 2 5 4 5 6 Dimensions of Test Coil Noo 4 Typical Wilson Plot Test Run (Run No. 224) Typical IoBoR. Test Run (Run Noo 68) Solubility of calcium sulfate as a function of temperature. Wilson Plots for various fouling conditions. Effect of test procedure on Wilson Plot intercepts. l>ooRo capacity curves during 75-day test periodo i3oBRo capacity curves during 27-day test periodo Test coil after 75-day test period, before cleaningo Page 1 6 7 4 8 11 13 14 15 iii

iI L The University of Michigan * Engineering Research Institute ABSTRACT A finned-tube coil operating in a standard tankless hot-water heater was subjected to controlled fouling conditions. Heat transfer tests were made to determine (1) the variation of the fouling with time and (2) the effect of this fouling on the heat transfer performance of the coil. The results of this investigation indicate that (1) the inside fouling film has a much greater effect on the overall fouling resistance than the outside fouling film and (2) the water flow rate maintained through the inside of the coil influences the internal fouling rate. OBJECTIVE The purpose of this investigation was to determine the extent to which fouling affects the heat transfer characteristics of a finned-tube coil in an internal tankless hotwater heater. iv

L The University of Michigan ~ Engineering Research Institute I. INTRODUCTION It has been shown that clean finned-tube coils can be used to definite advantage over comparable plain-tube coils in internal tankless hotwater heaters.1 Under identical test conditions the amount of heat transferred with a finned-tube coil can be as much as four times that of a comparable plain-trube coil of equal length in which the OD of the plain tube is equal to the root diameter of the finned tube.1 This investigation was made in order to determine the extent to which fouling affects the heat transfer characteristics of a finned-tube coil. The tests were conducted in a standard tankless hot-water heater fabricated in accordance with the Institute of Boiler and Radiator Manufacturers' specifications.512 The coil used in this investigation is identified as test coil number 4 of Report Number 35.1 The tube and test-coil dimensions are tabulated in Table I. TABLE I DIMENSIONS OF TEST COIL NO. 4 a Do Dr Di Mean fin thickness Fin height Fins/in. AO Ao/Ai Total outside area No. of straight sections No. of U bends Total length Horizontal pitch Vertical pitch Do of copper leads =1.005 in. =.650 in. =. 546 in. 0.0186 in. = 0.1761 in. 10.925 1.032 ft2/ft 7.21 26.33 ft2 =20 = 19 25.59 ft =1.005 in. 2.625 in. 0.875 in. i 1. References are given on p. 23. 1

L The University of Michigan * Engineering Research Institute II. THEORETICAL CONSIDERATIONS The heat transferred through a finned tube can be related to the outside heat transfer area and mean overall temperature difference driving force by Q = UoAo(AT)mean (1) in which Q = rate of heat transfer, Btu/hr, Uo = overall heat transfer coefficient, Btu/hr-~F-ft2 outside surface area, Ao = total outside surface area, ft2, and (AT) = mean temperature difference, ~F. The overall heat transfer resistance is related to the individual resistances by 1 _ 1 r' rm(I',) ri(~' I (Ao) (2 - - r + r + o + rf + rm( ) ri ) hi in which ho = outside film heat transfer coefficient for a finned tube, Btu/hr-~F-ft2 outside surface area, r' = outside fouling film resistance for a finned tube, hr-~F-ft2 outside area/Btu, rf = fin resistance, hr-~F-ft2 outside area/Btu (see Equation 3), rm = tube root-wall resistance to heat transfer, hr-~F-ft2 mean metal area/Btu, A0 = outside tube surface area, ft2/ft of tube length, Am = logarithmic mean metal area between Di and Dr, ft2/ft of tube length, Ai = inside tube surface area, ft2/ft of tube length, hi = inside film heat transfer coefficient, Btu/hr-~F-ft2 inside surface area, and ri = inside fouling film resistance, hr-~F-ft2 inside area/BtuO The fin resistance3 is defined by 1 1_ 1. -t Ef (3) rf = + ro(-) ) f + Af in which Ef = fin efficiency. 2

--- The University of Michigan * Engineering Research Institute The effect of fouling on the performance of a finned-tube coil can be established by (1) determining the variation of the heat transfer characteristics of the coil with time, under fouling conditions, and (2) determining the values of ri and ro. III. FOULING MECHANISMS Fouling mechanisms in general are among the least understood of all heat transfer phenomena. The mechanisms of the fouling of heated or cooled surfaces from water are, however, believed to be qualitatively known. Scale formation or fouling from water may be divided into two types if the pH is controlled to 7.0 or above: (1) that due to temporary water hardness and (2) that due to permanent hardness.4 The mechanism of fouling caused by temporary hardness of the water involves the decomposition of calcium bicarbonate or magnesium bicarbonate upon heating. As water temperature rises, the bicarbonates liberate C02 according to the equations Ca(HCO3)2 -> CaCO3 + H20 + C02 (4) Mg(HCO3)2 — > MgCO3 + H20 + C02 (5) The resulting carbonates precipitate as a chalky white powder, which tends to form scale. The formation of scale due to water containing permanent hardness salts, such as calcium and magnesium sulfate, is not in general due to decomposition but to the decreasing solubility of the salts with increasing temperature. As shown in Fig. 1I the solubility of CaS04 reaches a maximum at about 40~C, after which it steadily decreases. For example, at 100~C the solubility of CaSO4 is 77% of the solubility at 40~C and 84% of the solubility at 10~C. Permanent hardness scale is harder and more adherent than the carbonate scale caused by temporary hardness. If the pH is permitted to drop below 7.0, another fouling mechanism involving corrosion of the iron walls of the container vessel is encountered. At high water temperatures, several salts become somewhat unstable. This instability leads to chain reactions typified by the following: 1o MgC12 + 2H20 -> Mg(OH)2 + 2HC1 2EC1 + Fe -> FeC12 + H2 FeC12 + 2E20 -> Fe(OH)2 + 2HC1 3

.22.21 0 N a E,.20 0 O.19 o en 0 0 U.1 0 -J 0 Uo.17.16.15 C I Ir I I I I I ^z r: ^:::1 1 1^^, -I m 0 3'+ In Za Q) 3 _. "I 00 3 5, rcu I^ ) 10 20 30 40 50 60 70 80 90 WATER TEMPERATURE, OC Fig,~ 1 Solubility of calcium sulfate as a function of temperature~ 100

- The University of Michigan ~ Engineering Research Institute ---- 2. Mg(N03)2 + 2H20 - Mg(OH)2 + 2HNO0 2HN03 + Fe -.- Fe(N03)2 + H2 Fe(N03)2 + 2H20 -> Fe(OH)2 + 2HN03 3. MgSO4 + 2NaC1 - MgC12 + Na2SO4 Mg2C12 + 2H20 - reaction 1. The Mg(OH)2 and Fe(OH)2 precipitate out of solution, causing scale. However, if the pH is maintained above 7.0 (such as by addition of NaOH), the acids formed in the above reactions are neutralized, stopping the chain reaction, In order to avoid the above reactions, the pH of the fin-side water was carefully controlled to a value of not less than 8.0 during the tests by adding sodium hydroxide to the tank water when necessary. In addition, the temporary and permanent hardness of the tank (fin-side) water was carefully controlled. The water flowing through the inside of the tubes was taken from the Ann Arbor municipal mains without further treatment. IV, TEST APPARATUS AND PROCEDURE The test apparatus described in Report No. 351 was used in this investigation. The procedure followed involved (1) the Wilson Plot method and (2) the I.B.R.2 capacity method. Both procedures are described in Report 355, pages 7-15. After initial Wilson Plot test data had been accumulated and analyzed, it was found desirable to add three copper-constantan thermocouples below the coil in the tank in order to obtain more exact Wilson Plots. Only the Wilson Plot data obtained after the addition of the thermocouples are presented in this report. The tank water was maintained at a pH of 8.0 or above and the total hardness was held at about 300 ppm. The pH was adjusted by the addition of a concentrated NaOH solution to the tank. The water hardness was maintained by the addition of CaC03, CaS04, MgSO4, and Mg(NOs)2 to the water when necessary. In order to maintain a constant tank water temperature throughout the test runs, a self-acting temperature controller was placed in the steamheating lines. The temperature-measuring bulb of this controller was inserted through the side of the tank at a distance of 3 ft above the steamheating coil. This measuring bulb actuated a control valve, regulating the amount of steam flowing to the heating coil. 5

The University of Micihigan T Engineering Research Institute - Two series of fouling tests were made on the test coil during the investigation. The clean coil was first allowed to foul for 75 days, with test data being taken throughout the test period. After modification of the test apparatus and acid cleaning of the test coil, a second, 27-day, test period was beguno The Wilson Plot data presented in this report were obtained during this second test period. After the accumulation of fouling during a test period, the test coil was acid cleaned. This treatment consisted of first removing the fouling film with a 5% sulfuric acid solution and then brightening the surface by treatment with a 5% K2Cr207 solution. The purpose of the acid cleaning was (1) to determine if the test coil could be restored to its original heat transfer performance by cleaning, (2) to determine if the test coil would refoul at the same rate, and (3) to make possible the separate determination of the inside and outside fouling resistances. To separate the inside and outside fouling resistances, the followin procedure was used~ 1o A Wilson Plot was made on the coil in the fouled conditiono 2o The coil was removed from the tank, acid cleaned and brightened on the inside only, and replaced in the tank. 35 A Wilson Plot was immediately made on the partially cleaned coi 4o The coil was again removed from the tank and the outside acid cleaned a-d brightened. 5. The coal was replaced in the tank, and a Wilson Plot was immediately made on the completely cleared coil, The data obtained in this manner were analyzed as indicated in. Section V of this report. A typical Wilson Plot test run is presented in Table IoL The Wilson Plot test results are tabulated in Appendix A. TABLE II TYPICAL WILSON PLOT TEST RLU" (Run No. 224) Tank Temperatures Inlet L20 Outlet H2O T0;... The co..le s Temp (C) TemT. (~C ) (TC) (~ ) A(mv (mv) C B(mv) 211 79.1 87.6 88.0 87 8 3562 3.62 3060 21oi 78.8 87.6 88,0 87.7 356o 3561 3.63 21-L 79.0 87.7 88.1 87.8 3563 3563 3561 2.' l79.0 87.9 88.1 87,9 3562 3562 3561 2iol 79.3 87.9 88.1 88.0 3563 3563 3 63 Avg 21o08 79-04 87.74 88,06 87.84 35620 3.622 35616 I I Lb of H20 = 140; Time = 7 min 37 sec *See Fig. 4g p. 9% Report No o 351. - 6

The University of Michigan Engineering Research Institute A typical IoB.R. capacity test run is presented in Table III. The capacity results are tabulated in Appendix Bo TABLE II TYPICAL I.B.R. TEST RUN (Run No. 68) Inlet H20 Outlet H20 Tank Temperature Temp. (C) Temp. (C) TA(OC)* TB(~C) T(C) 16o60 72.35 86.95 86.90 86.80 16.65 72.70 86.60 86.90 86.80 16.65 72.80 86.80 86.90 886.80 16.70 73.70 86.85 87.10 87.00 16.75 72.40 86.40 86.85 86.85 Avg 16.67 72.99 86.82 86.95 86.69,r 1_ _ sr ^, j". _ 7 11,inn 1!, _ _ ~,.... Lb of li2U = See Fig, 4,'75; Time = r min o ( sec po 9, Report No. 351, Vo ANALYSIS OF TEST DATA A. ANALYSTS OF WILSON PLOT DATA The Wilson Plot curves obtained with the test coil cleaned, partially cleaned (inside only), and fouled are presented in Fig. 2. The intercepts of these curves can be used to calculate the fouling factors on the inside and outside of the coil as follows: At the intercept,- = 0 tercept L tA~I intercept I h'A.0 0! + r Ao r f r r.- rm + --- + - + -- 0 (6) A0 A1 Am For the line corresponding to the tube cleaned on the inside only, ri = 0, the intercept (1/UoAo) = 0.0002170 Substituting into Equation 6, 1 r_ 0m 0.000217 = + () h A o AA Am Ao "*0 0 0I 0 Similarly, for the line corresponding to the tuhbe r. = 0, rO = 0, the intercept (l/UoAo) = 0.000205o 0 cleaned on both sides, Agaipn, substituting into 7

I 0 0:D 0 8 7 6 Tube fouled Tube cleaned (inside only) Tube cleaned (both 5.... sides) 2 C: -I 0 0 CQ Co 14 m Zs m _. VW Do 3' Gi r, n>'0 2 4 6 8 10 12 14 16 104/( +0.011 tw ) W08 F'igo 2o Wi.sonr PIlots for various fouling conditions 18 2C

-- --- The University of Michigan Equation 6, 0.000205 = * Engineering Research Institute 1 oAo rf AO Ao (8) Assuming ho is the same for both the fouled and unfouled conditions, and combining Equations 7 and 8, 0.000217 =.000205 + Ao Ao (9) Solving ro =.000012. Ao For the line corresponding to no cleaning (l/U0A ) = 0.000257. Substituting into Equation 6, of the tube, the intercept 0o 000257 =. + + ri + hoAo Ao A rm + -r Am Ao (L0) rt Ao o000012 and rf rm + Ao Am hoAo.r000205. Substituting these values into Equation 10 0. 000257 - 000205 +. 000012 + ri Ai ('l I ) So Lv.' rig, -.000040 Ai (after 27 days) Prom'1abLe 1, Total Ao = 6o 533 ft2 = 7o 21 A~i. T.T:ler efor e Total Ai 26533 7.2o 1 3565 ft2 3Sol-ving for the fouling, O =,000012 x 26. 533 = 000o516 hr- ~FEft2 outside area/Btu ri = Oo000040 x 3.65 = 0.000146 hr-~F-ft2 inside area/Btu. 9

The University of Michigan ~ Engineering Research Institute Taking the ratio of the fouling factors, rt O ooo000146 ri =. 0462, r Oo0000316 ~~~~or ri = 046 r the amount of fouling on the inside of the coil is less than half of that on the outsideo However, taking the ratio of the actual fouling resistances to heat transfer, ri/Ai 0o000040 1A = 3.33, r /A0 0.0000C12 " the inside fouling resistance to heat transfer is over three times the outside fouling resistanceo Thus, the inside fouling constitutes 3 3 x 100 = 77% 3.33 + 1 of the overall fouling resistance to heat transfer. Dhrring the course of the investigation it was noted that the Wilson Plot intercepts obtained from the test data tended to shift with variations in experimental procedure. Wilson Plot curves indicating this effect are given in Figo 35 This variation of the Wilson Plot intercepts is discussed further in Section VI. The Wilson Plot data obtained during the initial, 75-day, test period using the L.B.Ro test methods were not sufficiently accurate to allow direct computation of the fouling factor from the intercepts. Consequently, these runs are not included in this report. The second, 27-day, test was begun after acid cleaning of the test coil and modification of the test apparatus to include thermocouples located below the test coil.o The addition of these thermocouples permitted more accurate Wilson Plot test measurements. A typical calculation of a Wilson Plot test run is presented in Appendix Co... ANAL.YS-S OF T.E. 7.oRo CAPACITY DATA The IoBoRo capacity data are of a comparative nature and do not directly indicate the fouling resistance present on the tube. However, the variation of the capacity curves with time for a coil provides a qualitative.record of the fouling trend. Inasmuch as the Wilson Plots taken during the initial, 75-day, test period were inconclusive, the capacity data were used to determine the fouling trend during this test period. A typical calculation of a capacity-type test run is presented in Appendix D, 10

I 0 0 0 w 2X~~~~~~ ~~~12/12/55 H -— /L) 3~~a 12/23/55 | | \ \ \ 12/12/55 (H — L) 12/31/55 (H ---- L) 1/3/55 ( H --- L) 2 X 21 212 /8/55, 12/23/55, Legend: 112/28/55 (LH) X 12/12/55 A 12/16/55 o 12/28/55 V 12/21/ 55 a 12/23/55 o 12/28/55 4 1/3/56 H- L Test procedure high to low velocity L- H Test procedure low to high velocity O01. I,.-I t_ c: _< Q In - aD I" m~;D C" 3 m _. MQ 5<3 Mo M^ ~n< =1 4 I 1% 0 2 4 b b U1 12 14 1b It 20 104/1 + 0.011 t ) W0 8 Fig 3,, Effect of test procedure on Wilson Plot intercepts.

The University of Micihigan T Engineering Research Institute The capacity curves for the initial, 75-day, test period, with parameters of days of testing, are presented in Figo 4o The corresponding capacity curves for the second, 27-day, test period are presented. in Figo 5o Photographs of the test coil taken after the initial, 75-day, test period and before cleaning are shown in Figo 60 VI. DISCU'SSION OF RESULTS The analysis of the Wilson Plot data obtained during the second, 27-day, test period indicated that the inside fouling, although less than half as great as the outside fouling, constituted 77% of the overall fouling resistance to heat transfer. This emphasizes the importance of the inside fouling on the overall fouling resistance to heat transfer. The large outsideto-inside area ratio (7.21/1 for the test coil) greatly increases the effect of the inside fouling. As can be seen by examination of Equation 2, the inside fouling is multiplied'by the ouftside-to-inside area ratio to obtain the inside fouling resistance to heat transfer. As shown in Section V, the high hardness content of the tank-side water caused the outside fouling to be nearly twice as great as the inside foulingo The water flowing through the inside of the coil was taken directly from the City of Ann Arbor water mains and had a total hardness which varied from 85 to 115 parts per million (ppm). The recirculating-tank water was maintained at about 300 ppmo Thus, although the total hardness on the outside of the test coil was three times the'hardness on the inside of th e coil, the degree of fouling on. the outside of the coil was only about twice that on the inside of the coilo This indicates that the degree of fouling is not di.:rectly proportional to the hardness of the water in. contact with the metal, but also varies with other factors such as temperature of metal relative to the water, velocity of the water, etCo Figure 3 presents the effect of the'test procedure o.n the Wilson Plot intercept values The Wilson Plot curves which were obtained starting with the low-velocity runs and increasing the velocity for additional runs tend to be higher than the Wilson Plot c1,,t-res octained using the opposite experimental procedure (starting with a.iigh-velocity run and decreasing the velocity for each additional run). This effect of shifting the Wilson Plot curves is probably attributable to the removal of part of the fouling scale on the inside of the tube due to the erosive actiori of the water during the hi gh-velocity runs. For the series of runs starting with high velocities, part of the fouling film would be removed du'ring the first high-velocity run and would not be present throughout the remainder of the Wilson Plot test. For the Series of runs starting with low velocities, the fouling film would be present during the majority of the runs and would not be removed until the..-. —-----------— 12

I The University of Michigan 4 I 0 _j 02 0 Engineering Research Institute Start d/ // 0 / 2 days - 3 days -3/ /-.30 days // / -33 and 43 days ymbol Days from Date start 0 22 9/8/55 A 29 9/15/55 X 30 9/16/55 * 33 9/19/55 0 43 9/29/55 130 140 150 I i1 120 (TTANK -TINLET) F Fig. 40 IoBoR. capacity curves during 75-day test periodo 15 --

- C= -*\??* 3m (T)t z -J ( 0 I C) -F~-O m s ro m va 140 (TTANK T- NLET WATER) F 180 Fig. 5. I.B.R. capacity curves during 27-day test period.

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The University of Michigan * Engineering Research Institute higher velocities were reached. A comparison of Figs. 4 and 5 indicates that the total fouling present after the second, 27-day, test period was greater than that present after the 75-day test period. For example, at (Ttank Tinlet water) = 140~F the coil capacity after the initial, 75-day, test period was 4.05 gal/min, whereas after the second, 27-day, test period the capacity was 3.77 gal/min; this decrease in capacity was due to a greater degree of fouling present in the latter case. -Visual observation of the effect of acid cleaning the test coil indicated that the cleaning tended to roughen or pit the surface of the finned tube. Since fouling or scale can adhere more easily to rough surfaces, it would be expected that the fouling rate after cleaning would be greater than that for a new coil. A comparison of Figsi 4 and 5 indicates that the early stage or initial fouling rate during the second, 27-day, test period was greater than the initial rate during the 75-day test period. During' b -itei periods the coil capacity tended to decrease to a fairly constant, limiting value. However, during -'i:iSecond, 27-day, test period this limiting value was reached much more quickly than in the initial, 75-day, test period. As shown in Fig. 5, the acid cleaning and brightening treatment of the test coil failed to return the coil to its initial performance condition. This indicates that some of the fouling film was not removed from the coil surfaces during these treatments even though the coil was acid cleaned several times. VII. CONCLUSIONS The following conclusions were reached in this investigation: 1. In a finned-tube coil the inside fouling film has a much larger effect on the overall fouling resistance than the outside fouling film, due to the large outside-to-inside area ratio of the finned tube. 2. The degree of fouling of a finned-tube coil is not directly proportional to the hardness of the water in contact with the coil, but also varies with other factors such as the temperature of the metal relative to the water, the velocity of the water, etc. 5. The water flow rate maintained through the inside of the test coil has a large influence on the fouling rate. j L -

The University of Mnichigan T Engineering Research Institute 4. The total fouling present at the end of the 27-day test period was greater than that present after the earlier, 75-day, test period. This was attributed to the roughening of the surfaces of the test coil during cleaning. 5. The early stage or initial fouling rate during the second, 27day, test period was greater than the initial rate during the earlier, 75-day, test period. 6. The best acid cleaning and brightening treatment of the test coil failed to return the coil to its initial performance condition. 17

The University of Michigan * Engineering Research Institute APPENDIX A SUMMARY OF WILSON PLOT DATA Water Rate Avg Tank Avg Tank Inlet Coil Outlet Coil AT. 10-4 10 104 Date Run No. Temp. to Temp. from Water Temp. Water Temp. (F) (Ntuhr Ao.0 o emark Coil (~F) Coil ('F) ('F) ('F) 12/10/55 149 5510 190.36 183.38 100.48 143.20 62.90 23.55 142.2 2.67 4.40 150 464o 190.51 183.75 97.72 146.02 62.30 22.40 136.7 2.78 4.92 151 3190 190.12 183.40 91.40 152.81 59.30 19.58 125.3 3.03 6.65 Coil cleaned and 152 2350 190.35 185.40 84.23 159.26 58.20 17.62 115.1 3.30 8.69 placed in tank 153 1357 190.29 185.00 73.94 170.15 51.40 13.03 96.5 3.94 13.40 154 1930 190.65 185.40 80.42 163.44 56.20 16.01 108.1 3.52 11.80 12/12/55 155 6050 190.97 179.30 102.50 141.80 61.80 23.86 146.60 2.59 4.02 156 4765 191.30 179.10 98.10 145.50 61.5o 22.64 139.80 2.72 4.90 Two days of 157 3504 190.95 180.70 92.80 151.80 60.20 20.70 130.60 2.91 6.19 fouling 158 2500 191.30 182.10 85.20 158.70 59.10 18.40 118.40 3.21 8.18 159 1436 191.30 183.50 74.20 170.30 53.60 13.80 97.85 3.88 12.75 12/16/55 16o 6040 191.40 183.40 102.80 141.07 64.20 23.14 136.80 2.77 4.05 161 4765 191.10 182.20 99.05 144.57 63.20 21.70 130.40 2.91 4.89 Six days of 162 3150 190.85 185.80 91.00 152.10 62.70 19.25 116.60 3.26 6.82 fouling 163 2370 191.10 186.8o 85.70 158.20 6o.8o 17.18 107.40 3.54 8.55 164 1315 190.87 187.80 72.75 171.15 54.10 12.94 90.80 4.18 13.70 12/18/55 165 914 190.30 185.10 69.75 174.80 49.75 9.61 73.30 5.18 18.35 166 1180 1-91.50 186.50 73.20 170.85 54.4o 11.54 80.40 4.72 14.85 167 1178 191.40 186.40 73.80 170.57 54.40 11.42 79.80 4.77 14.90 168 1616 191.30 185.30 81.27 163.43 57.80 13.29 87.40 4.35 11.60 Eight days of 169 2646 190.60 185.00 90.02 152.83 62.10 16.64 112.00 3.757.81 fouling 170 4300 190.50 183.70 100.05 143.67 63.30 18.8o 112.90 3.37 5.30 171 5400 190.50 183.20 104.12 140.62 63.20 19.70 117.50 3.21 4.43 172 6170 191.00 183.90 104.97 138.52 64.70 20.70 122.00 3.12 3.97 12/21/55 173 5990 189.80 179.70 104.80 139.00 62.10 20.50 125.20 3.03 4.07 174 4425 190.10 179.50 99.80 143.90 61.4o 19.45 120.10 3.16 5.20 175 3392 189.70 180.6o 95.30 148.40 60.70 18.00 112.90 3.37 6.42 Eleven days of 176 2600 190.10 181.80 89.60 154.30 59.80 1l.82 107.00 3.5 I7.95 fouling 177 2046 191.20 182.80 84.50 159.60 58.70 15.35 99.40 3.82 9.60 178 1600 190.50 183.20 79.00 165.40 55.60 13.82 94.48 4.02 11.70 12/23/55 179 3500 190.386 181.29 96.32 147.49 61.60 17.90 110.20 3.45 6.21 180 2680 189.71 18o.80 91.58 152.47 59.00 16.30 105.00 3.62 7.68 181 2015 190.46 182.49 86.11 158.11 58.60 14.50 93.90 4.04 9.6' Thirteen days of 182 1295 191.09 185.17 76.21 168.56 54.80 11.96 83.00 4.5 13. 1'. fouling 183 976 190.81 185.12 70.43 173.52 51.40 10.17.5.20 5.05 17.30 184 5960 190.13 180.80 105.40 138.38 62.90 19.56 118.20 3.22 4.0S 185 4875 190.44 18o.80 102.09 141.89 62.30 19.40 118.20 3.21 4.77 12/28/55 186 701 191.43 186.72 64.00 179.69 47.20 8.10 65.20 5.153 22.60 187 1232 191.33 186.93 73.31 170.20 54.90 11.94 79.00 4.81 14.40 188 2130 191.06 185.24 84.94 157.82 60.70 15.51 97.30 3.91 9.29 Eighteen days of 189 3645 190.87 184.01 97.43 146.95 62.70 18.06 104.50 3.47 6.05 fouling 190 4645 190.85 183.25 102.31 143.21 62.90 19.00 114.85 3.31 4.98 191 5920 191.50 183.42 104.07 131.81 65.20 20.55 120.00 3.17 4.11 1/3/56 192 5890 190.75 177.90 103.17 139.07 62.40 21.18 128.90 2.97 4.14 193 4985 191.25 181.00 101.83 142.15 62.80 20.10 121.40 3.13 4.73 194 3990 191.40 182.20 97.32 145.85 63.20 19.40 116.6o 3.26 5.64 Twenty four days 195 2730 190.70 182.50 90.50 152.90 61.00 17.10 106.30 3.57 7.65 of fouling 196 1553 190.75 184.70 79.60 165.40 56.20 13.32 91.00 4.22 11.97 197 1170 191.45 186.70 72.62 171.63 55.80 11.58 81.90 4.64 15.00 198 731 190.97 187.80 65.48 178.72 48.20 8.28 65.20 5.83 21.90 1/13/56 220 5820 191.10 181.80 101.85 141.45 63.70 25.03 137.00 2.'(77 4.16 221 4870 191.08 182.60 97.98 144.78 63.70 22.80 136.00 2.79 4.82 Coil cleaned on 222 3395 190.55 182.20 94.50 152.00 59.80 19.54 124.20 3.06 6.40 inside 223 2300 190.50 185.10 85.45 160.02 58.30 17.16 111.80 3.40 8.74 224 1103 190.58 i86.4o 69.87 174.57 50-70 11.55 66.50 4.38 1i.80 1/16/56 229 6170 189.30 177.60 103.02 14o.70 60.O 23.21 147.50 2.61 3.97 230 4900 190.13 180.10 99.45 145.05 61.00 22.34 139.00 2.73 4.7 Coil cleaned, 231 3055 189.35 180.70 89.58 152.83 59.70 19.33 123.80 3.07 6.98 both sides 232 1745 190.22 182.00 79.08 165.82 55.65 15i.14 104.50 3.64 10.91 233 1000 189.90 186.50 68.17 176.40 48.30 10.82 85.00 4.47 17.05 234 6025 180.13 172.00 105.44 138.35 53.20 19.84 142.00 2.68 4.03 Coil cleaned, 235 4550 180.03 171.70 102.32 142.60 51.50 18.32 134.20 2.83 5.08 both sides; tank 236 2143 180.60 174.50 87.70 155.85 49.50 14.60 112.00 3.39 9.27 temperature of 237 957 179.88 176.00 75.21 168.35 41.20 8.91 82.30 4.62 17.60 180~F i i 18

The University of Michigan * Engineering Research Institute APPENDIX B SUMMARY OF I.B.R. CAPACITY DATA Ttank Tate Twater in out Ttank - Coil Date Run No. Average Tank Inlet Water Outlet Water twater Twater in Capacity emarks Temp. (~F) Temp. (~F) Temp. (~F) ( F) (~F) (gal/min) 75-day test period 9/8/55 58 59 60 61 9/15/55 67 68 69 70 71 9/16/55 72 73 74-A 74-B 9/19/55 75 76 77 78 9/29/55 84 85 86 87 1/5/56 199 200 201 202 203 1/7/56 204 205-A 205-B 206-A 206-B 1/10/56 207 208 209 210 1/11/56 211 1/12/56 212 213 214 215 1/13/56 216 217 218 219 1/16/56 225 226 227 228 190.66 188.87 189.23 188.16 189.43 188.58 188.12 187.90 187.00 160.75 171.15 179.25 189.56 162.44 169.95 178.59 188.53 161.80 169.26 178.97 189.45 161.80 171.45 179.94 190.15 190.16 160.30 154.92 189.97 169.85 179.95 161.55 169.72 179.81 189.57 160.74 159.93 169.78 179.89 189.45 160.00 169.97 189.78 179.87 160.05 170.00 179.95 188.03 68.83 63.35 58.80 56.59 68.53 62.00 55.04 48.80 40.92 49.12 46.50 47.46 47.58 47.26 46.55 46.27 46.78 45.96 45.62 45.16 45.13 46.31 45.35 44.75 44.11 43.76 43.55 43.13 42.67 42.98 42.65 42.13 42.15 44.45 43.53 41.53 40.83 40.95 40.63 40.90 40.98 41.52 41.25 41.26 41.08 41.47 41.43 41.92 170.01 163.13 158.60 157.00 169.26 165.61 156.40 148.79 140.91 152.20 146.67 148.36 148.22 146.97 146.84 146.49 146.82 146.76 145.75 145.60 145.81 27-day test 146.59 145.61 146.75 144.52 144.11 143.65 143.13 142.13 143.12 143.00 142.33 142.40 144.34 143.84 141.28 141.13 140.90 141.15 140.25 141.55 142.25 141.43 141.51 140.80 140.55 141.52 142.05 101.18 121.83 99.78 125.52 99.80 130.43 100.41 131.57 100.73 120.90 101.61 126.58 101.36 133.08 99.99 139.10 99.99 146.08 103.08 111.63 100.17 124.65 100.90 131.71 100.64 141.98 99.71 115.18 100.29 123.40 100.22 132.32 100.06 141.75 loo.8o 115.84 100.13 123.64 100.44 133.81 100.68 144.32 period 100.28 115.49 100.26 126.10 102.00 135.19 100.41 146.04 100.35 146.40 100.10 116.75 100.00 111.79 99.46 147.30 100.14 126.87 100.35 137.30 100.20 119.23 100.25 127.57 99.89 135.36 100.31 146.04 99.75 119.46 100.30 119.10 99.95 128.83 100.52 139.26 99.35 148.55 100.57 119.02 100.73 128.45 100.18 148.53 100.25 138.61 99.72 118.97 98.87 128.53 100.09 138.52 100.13 146.11 2.59 3.21 3.78 4.22 2.52 3.01 3.67 4.46 5.07 1.34 2.70 3.36 4.41 1.69 2.42 3.26 4.20 1.75 2.54 3.52 4.23 1.55 2.43 3.05 4.17 4.56 1.671 1.224 4.415 2.512 3.33 1.97 2.64 3.57 4.40 1.970 1.965 2.86 3.70 4.72 2.34 3.57 5.69 4.50 2.39 3.58 4.80 5.86 Coil cleaned on inside Coil cleaned on inside and outside 19

The University of Michigan Engineering Res APPENIIX C WILSON PLOT RUN CALCULATION Run No. 224 —coil cleaned on inside W = (140)(600) = 1105 lb/hr (457.2) earch Institute TH20 in =; 21.08 Correction = -1.04 T1 = 20.04~C = 69.87~F TIH2 out = 79.04 Correction = 4-.17 T2 = 79.21~C 174.570F~ AtH20 = 174.57 69.87 1043. 70 F twater = 122.22F WO.8 = 270.6 104 = 104/(1 +.011 t)WO'8O 2.54 Wo0.8 15.80 TA Ttanr = 87.74 +.29 88.03~C A before coil.1 TB = 88.06 +.25 88.29~c TA + TB -+ TC 3 TC = 87.84 +.14 87.980c = 88. o~ c = 190.58~F The average thermocouple reading is Tthermocouple = lthermocouple TcA + TcB + T.CC 3 3.,620 +- 35622'~~ 35.616' / 3,620 +-: 3.6.2.. 3I616 - 3'619 mv (copper 3_ - ~ t______~ constantan) 20 -j

The University of Michigan Engineering Research Institute Therefore, Ttank leaving coil = 186.40~F AT1 = i90 58 -174057 16. 0FF AT2 = 186.40 -69.87 116.53~F ATLM AT2 - AT1 AT2 ri AT1 50.7~F Q = WCpAt20 = 1103 x 1o0 x o10470 = 115,500 Btu/hr Ao = 26.33 ft2,0 Q AoATLM 115,500 (26533) (50o7) = 86.5 Btu hr-ft-'F 104 no 0o 104 = 4.38 hr- " 4 38 tI Etu~ (86.5)(26.33) 21

The University of Michigan * Engineering Research Institute APPENDIX D I.B.R. CAPACITY RUN CALCULATION Ruir No. 68 TH20 in 16.67 TH20 out = 72.99 Correction = + 01 Correction +.13 T, = 16.68~C 62. 00~F T2 73.12~C = 163.61~F TA 86.82 +0.14 86.96~C TB = 86.95 +0.15 87.10~C = 86.69 +0.23 86 920~ 86.96 + 87.10 + 86.92 Ttank 3 86.99~0 = 188.58~F ATcoil = T2 - T = 163.61 62o00 10",!.610r rtank Twater in) = 188.58 - 62.00 126.58~F 75 x 3600 ~w 182.7 = 1478 lb/hr WCpATcoil 1478 x 1 x 101o61 150,200 Btll/nr K = - Q 50,000 3= 01 gal/min 22

The University of Michigan * Engineering Research Institute - I REFERENCES 1. E. Ho Young et al. The Investigation of Heat Transfer and Pressure Drop of ll-Fins-Per-Inch Tubes and Coils. Eng. Res. Inst. Report No. 35, Univ. of Mich., Ann Arbor, February, 1955. 2. "I.B.Ro Testing and Rating Code for Indirect-Storage and Tankless Water Heater Tested in Tank," The Institute of Boiler and Radiator Manufacturers, New York, New York, 1952. 3. W. H. Carrier and S. W. Anderson, "The Resistance to Heat Flow Through Finned Tubing," Heating, Piping, and Air Conditioning, May, 1944, pp. 304318. 4. F. V. Matthews. Boiler Feed Water Treatment, 3rd Edition. New York: Chemical Publishing Co., Inc, 1951. i i 23