A graph theory-based modelling method for multi-splitting-merging-channel refrigerant-cooled evaporator in battery thermal management

•A model of multi-splitting-merging-channel evaporator is established.•The splitting and merging flows are described by a graph theory-based method.•All control volumes are normalized into only five types.•The average deviation between predicted and experimental temperatures is 1.0 °C.•Multi-split structure performs better than single-split and none-split. A multi-splitting-merging-channel refrigerant-cooled evaporator can provide non-uniform cooling capacity distribution to match a non-uniform distributed heat flux produced by a battery by properly arranged hierarchical refrigerant channel network, however the design of the refrigerant channels is extremely complex. The purpose of this study is to present a model to support the design of a multi-splitting-merging-channel refrigerant-cooled evaporator, and the model should have the functions of describing various channel network, predicting the refrigerant flow distribution in splitting and merging channels, and accurately presenting temperature distribution at unevenly distributed heat flux. In the model, the distributed parameter modelling approach is applied for predicting the thermal performance distribution; arbitrary kinds of control volumes are normalized into five standard types according to channel structures; the refrigerant flows with multiple splitting and merging are described by the calculation sequences of control volumes, which are generated based on the graph theory. Model validations are done on a small sized and a large sized evaporator samples by comparing the simulated results with the experiment data. It is shown show that, the average temperature deviations of the small sized and the large sized evaporator samples are 1.0 °C and 0.9 °C, respectively while their average pressure drop deviations are 2.8% and 2.1%, respectively. The validation result indicates that the accuracy of the proposed model is acceptable for engineering application.