Computer simulation of thermoeconomic optimization of periodic-flow heat exchangers

Abstract

A computer simulation of heat transfer by the finite difference technique is presented for calculating the fluid and matrix temperature distributions and their effect on periodic-flow heat exchanger performance. The governing differential equations have been formulated in terms of characteristic dimensionless groups. In order both to secure a high degree of accuracy of the results and to save computational time, three modifications have been made to evaluate the finite difference mesh size for regenerator length, hot period and cold period. The geometry of the matrix of a periodic-flow heat exchanger is optimized using the unit cost of the exergy of the warm delivered air as the objective function. The running cost is determined using unit costs for the pressure component of exergy and for the thermal component of exergy. The ratio of the two unit costs is obtained from an air conditioning plant and a power station in which the regenerator is used. The effect of variation in the principle design parameters on the unit cost of the warm air and on the heat exchange effectiveness are examined, and recommendations are made for the selection of the most appropriate parameters for a regenerator of a given capacity.