By: Brittany Watton & Jeff Philippart Heat Exchanger Design By: Brittany Watton & Jeff Philippart

Design Criteria Design a heat exchanger to dissipate 1MW of thermal energy for the High Performance Computer Center. It must be less than 20 ft long and compact. The current piping has a diameter of 14 inches The potable water has a temp of 57 degrees exiting the reservoir and cannot change by more than 3 degrees. It flows at 10^6 gal/day. Liquid to disperse heat is at 90 to 100 degrees F and flows at 5*10^6 gal/day. Pressure drop should be minimized.

Design Considerations Fluid Choice- Water is the best choice because of its high heat capacity and thermal capacity, it is also cost effective and easily accessible Tube material- Copper was chosen for its thermal performance and corrosion resistance The Pitch Ratio was chosen to be 1.25, this makes the space between tubes .25 times the tube size. The number of baffles was chosen to be 4.

MatLab Code Description Three parameters were varied to achieve 18 independent results. 1- The arrangement was altered, the script prompts the user to select a triangular or square layout for the tubes. 2- The number of passes is then selected as either 1, 2 or 3 3- The last option is pipe diameter; .5”, .75” and 1” are all standard sizes which make them easier to purchase. One of the above is chosen as the last parameter.

Cost Analysis Triangular Layout pipe size (in.) cost per pipe # pipes total cost 1 $108.50  105  $11,392.5 0.75 $70.00  188 $13,160.0  0.5 $43.70  423  $18,485.1 Square Layout pipe size (in.) cost per pipe # pipes total cost 1 $108.50 91 $9,873.50 0.75 $70.00 162 $11,340.00 0.5 $43.70 366 $15,994.20 This does not show the total cost, it shows the relationship between the diameter of the pipes and the approximated total cost for the pipes. The smaller the diameter the more pipes that can fit in the space.

Results A smaller tube size results in a smaller pressure drop Square Arrangement (1 pass) Pipe Diam. (in.) # of tubes effectiveness q_max press. Drop hot (kpa) press. Drop cold total press. Drop 0.5 366 0.2473 4.043 0.547 2.719 3.2665 0.75 162 0.1932 5.1757 9.7286 1.6452 11.374 1 91 0.1254 7.9715 218.71 1.55 219.87 Square Arrangement (2 passes) press. Drop hot 354 0.1841 5.4324 4.1 6.8192 157 0.1234 8.1039 73.835 75.48 88 0.0701 14.2646 1675.6 1.155 1676.8 Triangular Arrangement (1 pass) 423 0.4987 2.005 0.42189 4.0225 4.447 188 7.412 2.426 9.8839 105 168.1 1.699 169.86 Triangular Arrangement (2 passes) 409 3.148 4.0255 7.174 182 56.179 2.4264 58.605 102 127.41 1.6992 127.58 One pass had a lower pressure drop than 2 passes The triangular arrangement also reduced the pressure drop

Recommendations For the lowest pressure drop the optimal design from the results devised would point to a square arrangement of tubes with diameters of .5” and a single pass. This would be the second most costly option but it fits within the design parameters and the efficiency would reduce the cost of use. This design is conducive for easy cleaning, the components can be cleaned with a brush and chemically

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