An Improved Heat Exchanger and An Oil Separator For CO2 Heat Pumps

ATEC, in collaboration with an OEM partner and University of Maryland's Center for Environmental Energy Engineering, propose to develop an innovative oil separator and a heat exchanger with a novel manifolding system for CO2 heat pumps. These twocomponents will eliminate some of the shortcomings of CO2 heat pump systems.Traditional oil separators cannot effectively remove oil from supercritical CO2. However, our oil separator combines the inertia separation mechanism with an electrohydrodynamic (EHD) separation mechanism to produce a device with a high separationefficiency over the entire operating range of CO2 heat pumps. Our Phase I experimental results with a prototype EHD separator showed a dramatic increase in oil separation efficiency using supercritical CO2. In Phase II, we will improve upon our designand develop a commercial-ready model.In the area of CO2 heat exchangers during Phase I, we developed an improved method for manifolding high-pressure heat exchangers. Our manifold overcomes the difficulties of fabricating multi-pass/multi-row heat exchangers that can withstand high pressure.Also, our manifolding system will make it easier to reduce two-phase flow maldistribution. During Phase II, we will design, fabricate, and test a superior heat exchanger for a 3-ton CO2 heat pump system.The two innovative components we are developing willovercome some of the major difficulties that CO2 systems are currently facing, thus improving the COP and energy efficiency of CO2 systems. Our EHD oil separator will allow effective oil circulation in the compressor while minimizing the deterioratingheat transfer performance and increased pressure drop of the presence of oil in microchannel heat exchangers. Our newly disclosed heat exchanger design will further increase heat transfer performance through a combination of an optimized manifold designand an improved flow path design to suppress two-phase flow maldistribution.