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This paper presents a method to quantify the distribution of liquid refrigerant mass flow rate in parallel flow microchannel heat exchanger from the infrared images. Quantification is achieved by building the relationship between the liquid mass flow rate through each microchannel tube and the air side capacity calculated from the infrared measurement of the wall temperature. After being implemented in a heat exchanger model, the quantification method is validated against experimental data. This method can be used for several types of heat exchangers: evaporators, condensers etc., also it can be applied to various heat exchanger designs: different inlet/outlet locations, different flow configurations etc.

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Please cite this article as: Huize Li, Pega Hrnjak, An experimentally validated model for microchannel heat exchanger incorporating lubricant effect, International Journal of Refrigeration (2015), http://dx.doi.org/Highlights  A heat exchanger model comprehensively considering lubricant effect was developed.  An infrared thermography based method was integrated in the heat exchanger model.  New model showed superiority over models that ignore or overly simplify lubricant effect. ABSTRACT This paper presents the further development of Li and Hrnjak's (2013) microchannel heat exchanger model which includes the thermodynamic and transport properties of refrigerant-oil mixture. Effect of lubricant is accounted in boiling heat transfer, pressure drop and refrigerant distribution. A newly proposed infrared thermography based method is implemented in the model to describe the liquid refrigerant distribution in the inlet header of the microchannel heat exchanger. The new model is validated against experimental results (R134a-PAG 46 oil) at various oil circulation ratios (0.1%-8.3%). Simulation results also indicate that lubricant addition improves refrigerant distribution which is in agreement with experiments and the infrared thermography based method enables the model capture lubricant effect on capacity more comprehensively.

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