Abstract
The step response of a multi-pass crossflow heat exchanger was determined for variable inlet temperatures and mass flowrates. In every instance overall parallel and counterflow circuiting was considered. The energy balance equations were solved using an implicit central fmite difference method. Numerical predictions were obtained for the case where the minimum capacity rate fluid was subjected to a step change in inlet temperature while mass flowrates for both fluids were maintained constant. Under those circumstances it was demonstrated that for short times the transient response of a counterflow heat exchanger was nearly independent of the number of passes. Likewise the transient performance was calculated when a step mass flowrate change of the minimum capacity rate fluid was imposed, in the absence of any temperature perturbations. In that situation the transient heat exchanger response was influenced by the number of passes for both parallel and counterflow circuiting.