Equations for transient behaviour of parallel-flow multichannel heat exchangers

A set of partial differential equations is formulated which describes the transient behaviour of parallel-flow multichannel heat exchangers. In the model, the heat capacitance of walls is neglected and heat is assumed to be transferred only in the direction perpendicular to the direction of flow of fluids. The set is solved by the MacCormack predictor-corrector method for a sample four-channel heat exchanger. Three cases of transient behaviour of the exchanger are investigated: uniform initial temperatures in all channels, a step change in flow rate in one channel, and a step change in inlet temperature of one fluid. In the last two cases, the exchanger is initially at steady state.