Question

A shell-and-tube heat exchanger uses cooling water in the tubes. There are two pressure gages installed on the the water side to the heat exchanger. Gage 1 (P₁) is installed on the inlet water line, which is connected to the lower nozzle, while Gage (P₂) is installed on the discharge water line, which is connected to the upper nozzle. Both pressure gages are very near the nozzle flanges. The pressure drop from each pressure gage to the exchanger channel is 1 psi. The vertical distance between the two pressure gages is 4’-8”. The current pressure difference in tube-side pressure drop (P₁ – P₂) is 6 psi. If the number of tube passes were changed from 2 to 4 (with no appreciable change in the exchanger tube count), the water side pressure drop P₁ – P₂ (psi) would be most nearly:

a. 34                                                         c. 20

b. 28                                                         d. 12

Answer 1

total pressure drop in tube side for shell and tube heat exchanger is given by following relation.

All the parameter remain same like diameter , frictional factor, g etc .. only n changes so pressure drop doubled because n change from 2 to 4

so pressure dropp = 6psi*2 = 12 psi

option (d) is correct