Consider Problem 11.36.
(a) For m_c,A = m_h,B = 10kg/s, determine the outlet air and ammonia temperatures, as well as the heat transfer rate.
(b) Plot the outlet air and outlet ammonia temperatures
versus the water flow rate over the range 5 kg/s ≤ m_c,A = m_h,B ≤ 50kg/s.

Data From Problem 11.36

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 T_h,i,A = 520 K and m_h,A = 10kg/s. Ammonia flows in the shell of heat exchanger B, entering at T_c,i,B  = 280 K, m_c,B = 5kg/s. The tube-side flow is common to both heat exchangers and consists of water at a flow rate m_C,A = m_h,B with two tube passes. The UA product increases with water flow rate for heat exchanger A as expressed by the relation UA_A =  a + bm_c,A where a = 6000 W/K and b = 100 J/kg · K. For heat exchanger B, UA_B = 1.2UA_A.

(a) For m_c,A = m_h,B = 1kg/s, 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 variable speed 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 0kg/s ≤ m_c,A = m_h,B ≤ 2kg/s. 

Transcribed Image Text:

Air ThiA = 520 K mA = 10 kg/s A Water mA = MAB = 1 kg/s Pump Ammonia Tci,B= 280 K m. B = 5 kg/s B