The optimal hydraulic diameter of semicircular and triangular shaped channels for compact heat exchangers

Abstract

All heat pump cycles have one common feature that connects them to one another; this feature is the presence of a heat exchanger. There are even some heat-driven cycles that are completely composed of heat exchangers, every heat exchanger fulfilling a different, though critical role. The need therefore exists to optimize heat exchangers, more specifically Compact Heat Exchangers (CHE). This study deals with the optimization of such a CHE by determining an optimal hydraulic diameter of the micro-channels in a CHE, for minimal hydraulic losses. Two Computational Fluid Dynamics (CFD) models were developed for a single micro-channel that is present in a CHE. The first model had a semi-circular cross-section, the second a triangular cross-section. The results were verified by comparing it with existing experimental data. Following the verification of the results, the micro-channel was optimized by implementing an optimum diameter for the lowest pressure drop over the micro-channel. This was done for both the semi-circular and triangular micro-channel cross-sections.