A semi-analytical method for determining unsteady temperature field in a parallel-flow three-fluid heat exchanger

This paper presents a semi-analytical solution of a set of partial differential equations describing the transient temperature field in a parallel-flow three-fluid heat exchanger. The set of partial differential equations is Laplace-transformed and the resultant set of ordinary differential equations is solved analytically. The inverse of the solution is obtained numerically. Exemplary calculations are performed for the case of a step change in the inlet temperature of one fluid and steady state initial conditions.