Optimization of the thermal-hydraulic performance of zigzag-type microchannel heat exchangers using asymmetric geometry

Abstract

• Experiments study were conducted in MCHEs with asymmetric zigzag flow channels. • Nusselt number and friction factor correlations were obtained experimentally. • Thermal-hydraulic performance of MCHE with asymmetric configuration is enhanced. Experimental studies of a microchannel heat exchanger (MCHE) assembly with asymmetric zigzag flow channels on the hot and cold sides were conducted to investigate the water-to-water heat transfer and flow resistance characteristics. Compared to the cold side, the hot side flow channels were designed with a larger hydraulic diameter, resulting in fewer flow channels but a larger heat transfer area. Nusselt number correlations were established by fitting the heat transfer experimental data conducted in different Reynold and Prantl numbers. Similarly, the friction factor correlations were established by fitting the flow resistance data conducted separately to eliminate the uncertainties associated with heat transfer and heat dissipation. The overall thermal-hydraulic performance of the MCHE with symmetric and asymmetric structures was compared using the volume goodness factor and the area goodness factor. The comparison results indicate that the MCHE with asymmetric structure is superior to the MCHE with symmetric structure in terms of volume, weight and area effectiveness, and the higher the working temperature, the better the superiority. Specifically, within the experimental range of this study, the maximum volume goodness factor and area goodness factor of the asymmetric configuration are 3.35 and 2.72 times that of the symmetric configuration. This paper demonstrated a new method for optimizing the overall thermal-hydraulic performance of MCHEs with zigzag flow channels, that is, to adopt asymmetric structure on the hot and cold sides.