OPTIMUM CONFIGURATION OF NATURAL CONVECTION SHELL-AND-COIL HEAT EXCHANGER WITH RESPECT TO THERMAL PERFORMANCE

摘要

The shell-and-coil heat exchanger, a type of natural convection heat exchanger that utilizes helical coils, has been investigated experimentally under steady state conditions. Four configurations namely, single coil, two, three and four coils were tested in eleven different arrangements, with the aim of obtaining an optimum configuration suited for application in a typical SDHW system. The geometric factor of most significant influence on the thermal performance is a dimensionless flow space S' defined as the ratio of the equivalent total flow space to an equivalent diameter of the coil. A general trend of increasing heat transfer coefficient with increasing S' was observed. Nusselt number for single coils is presented in the general form as a function of a modified Rayleigh number. The consideration of heat transfer coefficient is complemented by the use of modified effectiveness and the UA value for the suggestion of optimum configuration with respect to thermal performance.