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This paper experimentally confirmed the benefits of liquid extraction in microchannel condensers. Experiments are conducted on a mobile air conditioning (MAC) system. R134a is used as the working fluid. An extraction tube with valve is added to one condenser so that it can work in two modes: the conventional mode and the extraction mode. Two types of experiments have been conducted: the heat exchanger-level test and the system-level test. In the heat exchanger-level tests, for the same inlet and outlet enthalpy on the refrigerant side, the extraction mode generates more condensate than the conventional mode. The extraction mode also lowers the refrigerant outlet enthalpy compared to the conventional baseline at the same refrigerant flow rate. The effects of air-side conditions have also been explored. In the system-level test, the air conditioning system with the extraction-mode condenser achieves a higher COP than the baseline under the same superheat and refrigerating cooling capacity.

The present study reveals the characteristics of refrigerant flow in a microchannel condenser with the extraction circuitry. The extraction circuitry provides a potential to enhance the condenser performance at almost no cost – the condenser geometry is the same except for a few well-sized drainage holes in the header baffle. A microchannel condenser is modified to run in both the extraction mode and the conventional mode. A 1-D finite-volume model is built for the condenser and is validated with R134a experimental data. The capacities agree within ±5 % and the pressure drops agree within ± 25 %. Using this model, a numerical study is conducted on the condenser. A singleextraction-tube design and a double-extraction-tube design for the extraction mode are both simulated and compared. The flow characteristics in the extraction tube are revealed for a physically possible range of liquid separation efficiency. The effects of flow resistance in the extraction tube on the phase separation efficiency and the condenser performance are also studied.