Low-Cost Phase-Distribution Enhancement for Two-Phase Heat Exchangers

Military Environmental Control Units (ECUs) are one of the greatest consumers of electric energy in forward operating bases (FOBs). Microchannel condensers have replaced tube-fin coils in both military ECUs and commercial air conditioners to improve system efficiency. Flow into the condenser is single-phase superheated vapor and therefore uniform flow distribution through multiple parallel microchannel arrays is easily achieved. Manufacturers are interested in exploiting the same benefits by replacing the tube-fin evaporator coil with a microchannel heat exchanger. However, flow into the evaporator is a saturated mixture of liquid and vapor refrigerant, typically at a thermodynamic quality of 0.10.4, and therefore two-phase flow distribution through a multitude of parallel microchannels can be very non-uniform.In this proposal, Mainstream presents a solution to achieve uniform two-phase distribution in a microchannel evaporator. Proof of concept was demonstrated in Phase I, and refinement of the technology and integration into existing military products will occur in Phase II.