A Numerical Finite Difference Method for Performance Evaluation of a Periodic-Flow Heat Exchanger

A numerical finite difference method is presented for calculating the fluid and metal temperature distributions for the periodic-flow type heat exchanger, accounting for the effect of heat conduction in the wall in the direction of fluid flow. Unlike previous solution techniques that use the Gauss-Seidel method based on a single element calculation, the method presented here uses a column of elements to compute the fluids and metal temperature distributions, and it allows variable or constant thermal properties (specific heats, densities, heat transfer coefficients, and thermal conductivities). Nonuniform mass flow rates and a nonuniform grid spacing may be employed. The present method reduces the computational time required for convergence and improves the numerical stability while allowing an arbitrary metal temperature distribution as a starting case. After qualifying the numerical method, illustrative results are presented for counterflow and parallel flow rotary regenerators with three different surfaces in the flow direction and variable fluid and material properties.