Oil separator, Droplet, Visualization, CFD, Impingement
Oil is needed for most of compressors in HVAC industry but oil circulating in the system is unfavorable for the heat exchanger performance and cycle efficiency. A common solution for oil issue is separating oil at the compressor discharge and returning it back to the compressor. For compactness, oil separation structure integrated into the compressor is more and more popular than traditional external oil separator. Therefore, analytical tools and design guideline of oil separation structure is important, especially for irregular geometry and realistic flow condition at the compressor discharge. As one of major mechanisms of droplet separation, impinging mechanism is studied by flow visualization and CFD simulation and presented in this paper. The video of oil mist flowing through the baffles and plates is captured by high speed camera and analyzed quantitatively. CFD simulation is carried out for investigating the flow field and performance of impinging separator. Refrigerant vapor is calculated in the first step and discrete phase model is used to track the droplet movement in the second step. Droplet size distribution and overall separation efficiency is used to validate the CFD simulation results. Both flow visualization and CFD simulation provide useful tools for oil separator design. The results and conclusions from this study give useful guidelines about how to reduce the oil circulation ratio by integrating oil separator in the compressor.