Study On Pressure Drop Characteristic And Flow Separation Of The Reduced T-junction With Microchannel Flat Tube

Parallel flow heat exchanger is widely used in automobile air conditioning and heat pump,but the mal-distribution of each microchannel flat tube in parallel flow heat exchanger could greatly degrades its heat transfer performance.For single-phase flow,the theory and method of uniform distribution in parallel flow heat exchanger are relatively mature.However,for two-phase flow,due to the complexity of its flow and the immaturity of the theory,it has not developed a perfect theory and method to predict the flow distribution of the two-phase flow in parallel flow heat exchanger.Therefore,the study of pressure drop characteristics of two phase flow in parallel flow heat exchanger can develop and enrich the theory of fluid distribution in parallel flow heat exchanger,providing scientific basis for the optimal design of parallel flow heat exchanger and improving heat transfer performance in practice.The pressure drop characteristics of sing-phase in microchannel flat tube are studied by experiment.The experiment result shows that the friction factor of single-phase flow in microchannel flat tube is bigger than that in ordinary tube.Besides,the empirical correlation of friction pressure drop for the two-phase flow in the microchannel flat tube is proposed.The pressure drop characteristics of single-phase flow in the header are studied by experiment.It is found that the irreversible pressure drop of single-phase flow from the header into the microchannel flat tube is not only related to the flow separation ratio,but also inversely proportional to the upstream Reynolds number of the header.Besides,an irreversible pressure drop model is proposed to predict the flow of single-phase flow from the header to the microchannel flat tube.On the basis of the separated flow model,the parameter C of the gas-liquid interaction is modified so that it can predict the irreversible pressure drop when the two-phase flow flows from the header to the microchannel flat tube.The flow distribution characteristics of two-phase flow in the header are studied by experiment.The experimental results show that compared with the liquid phase,more gas phase will flow into the microchannel flat tube when the upstream quality in header is low.With the increase of the flow separation ratio,the quality of the header in upstream and microchannel flat tubes tend to be consistent.Based on the potential flow theory and complex function theory,a phase split model is established that is applicable to the stratified flow.