microchannel heat exchanger, reverse flow
Flash Gas Bypass with venting of reversed vapor is implemented in a R134a automotive air conditioning system. The mass flow rate of reversed vapor is measured by a flow meter placed on the venting line. The effects of microchannel geometries including channel length and channel diameter on the amount and frequency of flow reversal are investigated. A mechanistic model is developed to simulate the bubble dynamics inside of single microchannel tube. This model is validated against experimental data and used to explain the effect of channel length and diameter on flow reversal.