Consider a coupled shell-in-tube heat exchange device

Chapter , Problem 11.36

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Consider a coupled shell-in-tube heat exchange device consisting of two identical heat exchangers A and B. Air flows on the shell side of heat exchanger A, entering at Th,i,A 520 K and . Ammonia flows in the shell of heat exchanger B, entering at Tc,i,B 280 K, . The tube-side flow is common to both heat exchangers and consists of water at a flow rate with two tube passes. The UA product increases with water flow rate for heat exchanger A as expressed by the relation UAA a bm. c,A where a 6000 W/K and b 100 J/kg K. For heat exchanger B, UAB 1.2UAA. (a) For , determine the outlet air and ammonia temperatures, as well as the heat transfer rate. (b) The plant engineer wishes to fine-tune the heat exchanger performance by installing a variablespeed pump to allow adjustment of the water flow rate. Plot the outlet air and outlet ammonia temperatures versus the water flow rate over the range 0 kg/s . 11.3