Pin Fin Tubes

A division of Concept Engineering International, A Heat Transfer Focus Company
Heat Transfer Specialists, Manufacturers of Turbulators, Wire Wound Fin tubes, Brass and Naval Brass plates

Visit us at Stall C74 in the Thermal Processes Hall 6.1 at Achema, Frankfurt.





Steam Air Heaters


These fin tubes can be provided with Carbon Steel, Stainless Steel or Copper wire fins on Carbon Steel, Stainless Steel or Copper, Brass and Cupro Nickel tubes. To demonstrate the performance of these fin tubes against helical fin tubes we have done the following:

Tables giving maximum air velocity and performance for various tubes at different pressure drop points. (Measured in inches of water column.)

We have after analysis computed the following tables where we have generated the maximum airflow rate possible for every panel given a pressure drop limit. We have set the limit at .5", 1", 1.5" and 2" of water column. For this maximum airflow, we have given the corresponding heat transfer parameters. These tables allow us to optimize the tubes and airflow rates to get the desired results.

1) 0.5" Water Column

  Air Air side Air Udlinear LMTD Heat Load Outlet
Tube Velocity Pr Drop Co eff    temp
P4 700 0.463 40.06 24.70 85.95 218207.2 82.5
R2 600 0.430 44.04 31.25 82.02 206876.7 88.6
L fin 700 0.471 38.45 27.17 88.40 203700.0 77.3
S1 700 0.440 47.95 34.63 84.81 225038.0 84.3
S2 600 0.430 56.51 39.18 76.94 231272.5 96.1
S3 500 0.394 62.45 42.21 68.79 222815.3 107.20
S4 500 0.473 71.83 46.45 65.61233657.9 111.20
S5 400 0.432 84.1751.61 54.17 214466.5 123.90
T5 400 0.446 62.09 46.22 61.92 196467.8 115.60

2) 1 Water Column

  Air Air side Air Udlinear LMTD Heat Load Outlet
Tube Velocity Pr Drop Co eff       temp
P4 1100 0.994 51.60 28.65 93.00 274317.6 71.0
R2 900 0.954 56.55 37.07 88.14 263475.0 79.0
L fin 11000.996 47.78 32.23 94.80 259350.0 67.3
S1 1100 1.070 62.04 41.43 91.38 290418.9 73.7
S2 900 0.944 71.20 45.72 84.10 294701.7 85.4
S3 800 0.973 81.65 50.17 78.18 300556.7 94.30
S4 700 0.900 87.04 52.35 72.79 291828.4 101.90
S5 600 0.930 106.12 59.11 63.63 288196.1 113.60
T5 600 0.990 81.81 56.33 69.02 266402.5 106.90

2) 1.5 Water Column

  Air Air side Air Udlinear LMTD Heat Load Outlet
Tube Velocity Pr Drop Co eff       temp
P4 1400 1.495 59.06 30.82 96.39 305110.6 65.2
R2 1100 1.414 62.64 39.59 91.26 291611.6 73.9
L fin 1400 1.505 53.82 35.20 97.80 91900.0 62.4
S1 1300 1.485 68.23 44.10 93.65 316441.1 69.9
S2 1100 1.393 79.83 49.13 87.40 329181.2 80.2
S3 1000 1.493 92.73 54.15 82.35 342083.8 88.10
S4 900 1.453 100.44 56.92 77.91 340078.0 94.70
S5 800 1.598 124.94 64.53 70.33 347830.4 105.20
T5 700 1.341 90.85 60.47 71.68 297520.8 103.40

2) 2 Water Column

  Air Air side Air Udlinear LMTD Heat Load Outlet
Tube Velocity Pr Drop Co eff       temp
P4 1500 1.681 61.39 31.44 97.25 314706.3 63.7
R2 1300 1.963 68.21 41.75 93.71 315736.3 69.8
L fin 1500 1.695 55.65 36.09 98.60 301350.0 61.1
S1 1500 1.968 74.02 46.45 95.46 339915.3 66.8
S2 1300 1.927 87.81 52.04 89.99 359432.0 76.0
S3 1200 2.118 102.87 57.45 85.64 377322.3 83.0
S4 1100 2.128 112.60 60.62 81.88 380466.6 88.80
S5 900 1.994 133.64 66.77 73.01 373744.2 101.60
T5 900 2.195 105.78 66.74 76.45 350324.2 96.80

Analysis of the Data generated:

Performance of any Fin tube cooler is a combination of its Air side Coefficient and tubeside coefficient as given by the general formula:

Ud = hfi*hi/hfi+hi

Where:
Ud = overall heat transfer Coefficient
hfi = Heat transfer coefficient on fin side of the tube.
hi = Heat transfer coefficient inside the tube

From this formula it can be observed that any increase of the coefficient on one side (Air or tube) will lead to a less than proportional increase in the overall coefficient.

So to get a fair idea of the performance of a fin tube we have to look at both the Airside performance as well as the overall performance to see its individual impact as well as composite impact. We have accordingly in the interest of transparency, given both the airside coefficient as well as the overall coefficient.

The lower material consumption per meter of fin tube offsets in part its greater labour cost giving a surprisingly economical fin tube. When the lower length of fin tube required in any equipment is factored in, it becomes definitely very cost effective.

Now the findings:

1. In the general Airflow velocity range of 800 to 1200 the pressure drop of S1 pin fin tube is almost identical to the 10 FPI L fin tube. However the airside coefficient is higher by 26 - 30%. Similarly the overall coefficient is higher by 28% in the case of 3-bar steam in the tubes.

2. For S5 the overall coefficient is 220% and airside coefficient is 300% of the coefficient of the 10 FPI L fin tube. This implies a reduction to 40% in panel size for the same performance.

3. The wire fin tube hits the pressure drop limit at a lower airflow rate as compared to the L fin tube. However at this lower air flow it has a much higher coefficient than the L fin tube operating at the higher airflow rate giving a higher total heat load. This translates into significant power saving.

4. The outlet Air temperature achieved at different flow rates is higher for the S5 Panel by about 25 degrees centigrade. Again this implies that one can achieve the desired air temperature with a lower number of fin tube rows.

5. Again with the log mean temperature difference(LMTD) we are able to achieve an improvement of about 18-24 degrees between the 10 FPI L fin tube and S5. A tighter LMTD means a much more efficient heat exchanger.

6. Notwithstanding the tight LMTD achieved, the heat load for S5 is higher by 60-61% for S5 compared to the 10 FPI L panel.

7. While the difference is very large for S5 and 10 FPI L fin, it is also substantial when compared with S1, the lowest configuration.

8. Copper fins give a 15% higher airside coefficient and an 8 - 10% higher overall coefficient as compared to Stainless Steel or Carbon Steel fins.

In a nutshell, we can achieve a reduction in number of rows of the steam air heater, by approx. 50%. We can achieve a further reduction in weight as the wire fin tube is much lighter than the L fin tube. (If the same metal is used, by over 50%. In case the L fin is made of Aluminium the weight may be about the same). A significant reduction in power consumption is also achieved. We are able to substitute Aluminium strip fins with Stainless Steel wire fins without an increase in cost or weight.

Designing one's own heat exchangers

We have made it easy to design one's own heat exchangers by providing extensive data. Also by presenting the data in the form of 1x1 meter 3 row Panels, and expressing the coefficient in linear terms we have made it easy to predict performance by scaling up these panels in face area or number of rows. We have tried to make it intuitive.

For easy reference we have also given a graph comparing the same panel 3 kgs with 10 kgs steam. By isolating the airside coefficient, we have made it possible for designers to use the data for any other type of heat exchanger like Oil Coolers, Water Coolers or any other Air-Cooled heat exchangers.

The Data tables have given a color code to values where the typical allowable pressure drops are reached. (.5, 1, 1.5 & 2 inches of water column). This allows one to select the most appropriate tube and airflow rate for a given allowable pressure drop. This also allows one to easily optimize their fin tube type and panel sizing.

Air sup velocity Udlinear Air coefficient btu/hr. ft
fpm btu/hr. ft F deg C
  P4 R2 L fin S1 S2 S3 S4 S5 T5 P4 R2 L fin S1 S2 S3 S4 S5 T5
200 12.61 16.69 16.80 19.76 24.43 28.86 32.19 39.79 31.92 15.68 19.75 22.32 23.48 30.21 37.05 42.61 56.70 38.76
300 16.47 21.30 20.40 23.91 29.33 34.38 38.13 46.53 39.82 22.13 26.55 27.86 29.58 38.07 46.68 53.69 71.44 51.06
400 19.65 25.11 22.67 27.24 33.20 38.68 42.71 51.61 46.22 28.26 32.75 31.22 34.85 44.85 55.00 63.26 84.17 62.09
500 21.73 28.38 24.20 30.04 36.42 42.21 46.45 55.68 51.64 32.79 38.55 33.63 39.59 50.93 62.45 71.83 95.55 72.27
600 23.63 31.25 25.71 32.48 39.18 45.24 49.62 59.11 56.33 37.32 44.04 36.04 43.90 56.51 69.31 79.73 106.12 81.81
700 24.70 34.01 27.17 34.63 41.61 47.86 52.35 62.01 60.47 40.06 49.73 38.45 47.95 61.70 75.67 87.04 115.82 90.85
800 25.85 35.62 28.53 36.57 43.77 50.17 54.76 64.53 64.18 43.17 53.25 40.85 51.74 66.58 81.65 93.91 124.94 99.48
900 26.88 37.07 29.82 38.33 45.72 52.26 56.92 66.77 66.74 46.12 56.55 43.23 55.33 71.20 87.32 100.44 133.64 105.78
1000 27.81 38.38 31.0939.94 47.50 54.15 58.86 68.79 69.11 48.92 59.67 45.56 58.75 75.61 92.73 106.68 141.96 111.85
1100 28.65 39.59 32.23 41.43 49.13 55.86 60.62 70.58 71.28 51.60 62.64 47.78 62.04 79.83 97.89 112.60 149.81 117.65
1200 29.43 40.71 33.29 42.81 50.64 57.45 62.24 72.23 73.28 54.18 65.48 49.89 65.20 83.89 102.87 118.32 157.42 123.20
1300 30.15 41.75 34.28 44.10 52.04 58.91 63.74 73.75 75.14 56.66 68.21 51.90 68.23 87.81 107.68 123.86 164.81 128.54
1400 30.82 42.72 35.20 45.31 53.35 60.27 65.12 75.13 76.87 59.06 70.84 53.82 71.18 91.60 112.32 129.20 171.90 133.69
1500 31.44 43.63 36.09 46.45 54.58 61.55 66.41 76.43 78.49 61.39 73.38 55.65 74.02 95.27 116.84 134.41 178.86 138.67

Air sup velocity Air outlet temp
deg C
Heat load
fpm kcal/hr.
 P4 R2 L fin S1 S2 S3 S4 S5 T5 P4 R2 L fin S1 S2 S3 S4 S5 T5
200 107.3 108.8108.1 113.6 121.9 127.60 130.80 135.80 127.2 89234.5 90860.9 92400.0 96065.4 105064.7 111245.0 114714.6 120135.9 110811.3
300 101.3 101.9 99.7 104.6 113.3 119.60 123.30 129.70 120.9 124093.5 125069.3 124950.0 129460.6 143610.2 153856.4 159874.0 170282.9 155970.7
400 96.5 96.6 92.3 97.8 106.4 112.90 116.80 123.90 115.6 155049.1 155265.9 150150.0 157868.2 176517.4 190612.8 199070.0 214466.5 196467.8
500 91.2 92.2 85.7 92.4 100.8 107.20 111.20 118.50 111.0 179444.9 182155.6 169050.0 182697.7 205467.2 222815.3 233657.9 253445.6 233115.8
600 87.1 88.6 80.9 88.0 96.1 102.30 106.30 113.60 106.9 201997.5 206876.7 186900.0 204925.0 231272.5 251439.8 264450.9 288196.1 266402.5
700 82.5 85.7 77.3 84.3 92.0 98.10 101.90 109.20 103.4 218207.2 230350.9 203700.0 225038.0 254258.8 277407.8 291828.4 319531.2 297520.8
800 79.0 82.1 74.1 81.1 88.5 94.30 98.10 105.20 100.2 234200.0 247644.8 218400.0 243307.8 275401.9 300556.7 317037.4 347830.4 326145.2
900 76.0 79.0 71.5 78.3 85.4 91.00 94.70 101.60 96.8 248837.5 263475.0 233100.0 260059.6 294701.7 322025.0 340078.0 373744.2 350324.2
1000 73.3 76.3 69.3 75.8 82.7 88.10 91.60 98.30 93.7 261848.6 278112.5 246750.0 275401.9 312808.8 342083.8 361058.4 397381.1 372443.1
1100 71.0 73.9 67.373.7 80.2 85.40 88.80 95.30 91.0 274317.6 291611.6 259350.0 290418.9 329181.2 360191.0380466.6 419228.9 393586.2
1200 68.9 71.7 65.5 71.7 78.0 83.00 86.30 92.60 88.4 285593.9 303809.5 270900.0303809.5 344794.5 377322.3 398790.6 439775.6 412452.3
1300 67.0 69.8 63.9 69.9 76.0 80.80 83.90 90.00 86.1 296002.8 315736.3 281400.0 316441.1 359432.0 393260.9 415108.7 458099.6 430613.6
1400 65.2 68 62.4 68.3 74.1 78.70 81.80 87.70 84.0 305110.6 326362.1 291900.0 328639.0 372660.0 407573.1 431101.5 475881.5 447799.1
1500 63.7 66.4 61.1 66.8 72.4 76.90 79.80 85.5082.1 314706.3 336662.5 301350.0 339915.3 385454.2 422048.0 445630.6 491982.7 464334.1

Air sup velocity LMTD Air side pr drop in wc
fpm deg C
 P4 R2 L fin S1 S2 S3 S4 S5 T5 P4 R2 L fin S1 S2 S3 S4 S5 T5
200 68.71 67.54 65.2 63.63 56.15 50.24 46.46 39.43 50.680.055 0.049 0.07 0.038 0.051 0.067 0.081 0.115 0.113
300 73.23 72.79 72.2 70.78 63.88 58.33 54.77 47.81 57.110.11 0.11 0.128 0.083 0.112 0.147 0.178 0.25 0.253
400 76.66 76.59 78 75.74 69.41 64.21 60.87 54.17 61.920.18 0.194 0.194 0.147 0.196 0.257 0.309 0.432 0.446
500 80.29 79.61 82.3 79.48 73.59 68.79 65.61 59.34 65.780.262 0.301 0.273 0.227 0.302 0.394 0.473 0.66 0.692
600 83 82.02 85.8 82.41 76.94 72.5 69.49 63.63 69.020.357 0.43 0.368 0.325 0.43 0.56 0.671 0.93 0.99
700 85.95 83.91 88.4 84.81 79.75 75.53 72.79 67.22 71.680.463 0.583 0.471 0.44 0.58 0.753 0.9 1.243 1.341
800 88.14 86.21 90.5 86.84 82.08 78.18 75.53 70.33 74.030.58 0.758 0.587 0.572 0.751 0.973 1.161 1.598 1.743
900 89.99 88.14 92.1 88.58 84.1 80.42 77.91 73.01 76.450.708 0.954 0.711 0.721 0.944 1.22 1.453 1.994 2.195
100091.62 89.81 93.5 90.11 85.83 82.35 80.02 75.39 78.60.846 1.173 0.847 0.887 1.158 1.493 1.775 2.429 2.697
1100 93 91.26 94.8 91.38 87.4 84.1 81.88 77.49 80.420.994 1.414 0.996 1.07 1.393 1.792 2.128 2.904 3.25
120094.24 92.58 95.9 92.58 88.76 85.64 83.52 79.34 82.151.152 1.678 1.153 1.269 1.649 2.118 2.511 3.419 3.853
1300 95.35 93.7196.9 93.65 89.99 87.02 85.06 81.09 83.651.319 1.963 1.323 1.485 1.927 2.47 2.926 3.974 4.506
1400 96.3994.76 97.8 94.59 91.14 88.33 86.4 82.61 851.495 2.27 1.505 1.718 2.225 2.847 3.368 4.565 5.209
1500 97.25 95.7 98.6 95.46 92.16 89.44 87.65 84.04 86.211.681 2.6 1.695 1.968 2.544 3.25 3.842 5.196 5.963

Air sup Velocity
fpm
Ud/panel Air Coefficient
btu/hr panel Fbtu/hr paneldeg C
 P4 R2 L fin S1 S2 S3 S4 S5 T5 P4 R2 L fin S1 S2 S3 S4 S5 T5
200 3185 3284 3141 3694 45685396 6019 7438 5339 3960 3886 4173 4390 5648 6926 7967 10600 6483
300 4161 41913814 4470 5483 6427 7129 8699 6661 5590 5225 5208 5531 7117 8728 10039 13357 8541
400 4962 4942 4239 5093 6207 7231 7985 9649 7732 7138 6446 5837 6516 8385 10283 11827 15737 10387
500 5489 5585 4524 5617 6808 7892 8684 10410 8638 8282 7586 6288 7401 9522 11676 13429 17864 12089
600 5969 6150 4806 6072 7325 8457 9278 11051 9423 9426 8666 6738 8208 10565 12958 14907 19839 13685
700 6239 6693 5080 6475 7779 8947 9788 11592 10116 10118 9787 7189 8964 11536 14147 16273 21653 15197
800 6529 7010 5333 6836 8184 9381 10238 12064 10736 10904 10480 7638 9674 12448 15264 17557 23360 16641
900 6789 7295 5575 7165 8548 9770 10641 12484 11165 11647 11129 8082 10345 13312 16325 1877824986 17694
1000 7023 7554 5812 7467 8881 10123 11005 12861 11561 12355 11743 8518 10984 14136 17338 19944 26541 18711
1100 7237 7792 6026 7745 9186 10444 11333 13196 11924 13033 12328 8933 11599 14925 18302 21051 28008 19680
1200 7433 80126225 8004 9468 10740 11636 13504 12258 13683 12887 9327 218915684 19233 22121 29430 20609
1300 7614 8216 6409 8245 9730 11014 11916 13788 12569 14311 13424 9704 12757 16417 20132 23158 30814 21502
1400 7783 8407 6581 8472 9974 11269 12175 14047 12859 14917 13941 10061 13308 17125 21000 24155 32139 22363
15007940 8586 6748 8685 10204 11507 12417 14290 13130 15505 14441 10404 13840 17812 21845 25129 33440 23196

In our study we have isolated the airside and tube side coefficient and dealt with how to enhance both to get the optimum result.
The relevant literature can also be downloaded from the following websites

Stream Air Heater
catalog
Fin tube catalog Air cooled heat exchanger catalog Turbulators catalog