Experimental study of the single-phase heat transfer and fluid flow in mesochannels, i.e., between microchannels and minichannels, has received continued interest by researchers in recent years. The studies have resulted in empirical correlations for various geometries ranging from simple circular pipes to complicated enhanced non-circular channels. In spite of these extensive studies, it is still unclear whether the theories and correlations developed for conventional macrochannels are directly applicable for use in microchannels (Dh = 10–200 μm) and minichannels (Dh = 200 μm–3 mm) with heat exchanger applications. A few researchers have agreed that similar results maybe obtained for the laminar flow regime regardless of the channel size; however, no general agreement has been reached for the transitional and turbulent flow regimes yet. In this study, different mesochannel air-liquid compact heat exchangers were evaluated and the experimental results were compared with published empirical correlations. These compact heat exchangers were used in the secondary fluid loops of an automotive air conditioning system that used refrigerant R134a as the working fluid. 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 calculated. The results of this study showed that the well established heat transfer and pressure drop correlations for the macrochannels are not directly applicable for use in the compact heat exchangers with mesochannels.

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