Single-Phase Flow in Meso-Channel Compact Heat Exchangers for Air Conditioning Applications

Abstract

Experimental study of the single-phase heat transfer and fluid flow in meso-channels, i.e., between micro-channels and mini-channels, has received continued interest in recent years. The studies have resulted in empirical correlations for various geometries ranging from simple circular pipes to complicated enhanced noncircular channels. However, it is still unclear whether the correlations developed for conventional macro-channels are directly applicable for use in micro-/mini-channels, i.e., hydraulic diameter less than 3 mm, with heat exchanger applications. A few researchers have agreed that similar results may be obtained for the laminar flow regime regardless of the channel size, but no general agreement has been reached for the transitional and turbulent flow regimes yet. In this study, different meso-channel air–liquid compact heat exchangers were evaluated and the experimental results were compared with published empirical correlations. A modified Wilson plot technique was applied to obtain the heat transfer coefficients, and the Fanning equation was used to calculate the pressure drop friction factors. The uncertainty estimates for the measured and calculated parameters were also calculated. The results of this study showed that the well-established heat transfer and pressure drop correlations for the macro-channels are not directly applicable for use in the compact heat exchangers with meso-channels.

Notes

^a n is equal to 0.3 for cooling and 0.4 for heating the fluid.

^b Deviation between experiment and correlation =|Experiment—Correlation|/Experiment.

^a Deviation between experiment and correlation = |Experiment – Correlation|/Experiment.