New approach to improve performance by venting periodic reverse vapor flow in microchannel evaporator

• A novel approach to vent periodic reverse vapor flow is proposed and explored.
• Visualized flow regime in transparent headers of a microchannel evaporator.
• Venting reverse vapor improves system COP up to 12%.

This paper presents a proposal for a venting reverse vapor in flash gas removal A/C system in order to improve refrigerant distribution and reduce pressure drop in microchannel evaporator and thus increase system efficiency. Introduction to the reverse vapor flow observed in parallel flow microchannel evaporator was presented in earlier IJR paper by the authors. An experimental comparison of the A/C system with new approach to an FGB system revealed that vapor venting provided a 5% increase of cooling capacity and 3% of COP when operated at identical test conditions, while the maximum COP improvement was approximately 10%–12% when capacity is matched by reduction of compressor speed. The improvement compared to direct expansion system was significantly higher.