Question

City water will be cooled in a heat exchanger by sea water entering at 15°C. The outlet temperature of the sea water is 20°C. City water will be recirculated to reduce water consumption. The suction line of the pump has an inner diameter of 154 mm, is 22 m long, and has two 90° bends and a hinged check valve. The pipe from the pump to the heat exchanger has an inner diameter of 127 mm, is 140 m long, and has six 90° bends. The 900 bends are all made of steel with a radius equal to the inner diameter of the pipe, R/d = 1.0. The heat exchanger has 62 tubes in parallel, each tube 6 m long. The inner diameter of the tubes is 18 mm. All pipes are made of drawn mild steel (? = 0.0445 mm). The sea water flow rate is 120 m3/h. Assume that there is one velocity head loss at the inlet and 0.5 velocity head loss at the outlet of the heat exchanger. The elevation difference is 10.5 m. Calculate: a. The total pressure drop in the system (kPa and m liquid head = H m) b. The power of the sea water pump (pump efficiency ? = 60%). Plot the pumping power as a function of the sea water flow rate (for three flow rate values: 2,000 L/min, 2,500 L/min, and 3,000 L/min).

Answer 1