APPROXIMATE SOLUTIONS FOR TRANSIENT-RESPONSE OF A SHELL AND TUBE HEAT-EXCHANGER

Abstract

Approximate solutions for the transient response of a shell and tube heat exchanger to step change in shell fluid temperature and tube fluid velocity are derived. It has been shown that other previously published limited or approximate solutions are derivable from the exact solutions. The limiting asymptotic "no wall" solutions for both response to shell fluid temperature and tube fluid velocity change are also deducible from a limiting tube wall time constant solution. Some of the approximate solutions presented include the use of simple exponential forms of equations that enable the quick estimation of the time required to reach a given degree of approach to the final steady state. The error between the exact and the approximate exponential form of solutions are in most cases less than 2%. All the previous derived exact and approximate solutions presented here are applicable to crosscurrent, cocurrent, or countercurrent flow heat exchangers with one infinite thermal capacitance rate fluid.