Lubricants in Heat Exchangers: A Slippery Slope

Once oil leaves the compressor, it circulates through all components before returning to the compressor to perform its primary lubrication objective.  Oil induced wetting, foaming, and pressure drop impact heat exchanger effectiveness and pressure drop, sometimes in ways which are counterintuitive.  Oil disproportionately accumulates in regions of the heat exchanger which have the greatest effect on distribution of refrigerant flow, therefore the impact of oil is much larger than its circulation ratio would suggest.  Infrared photography and high speed videos are used to demonstrate changes in distribution and subsequent effect on heat exchanger and system performance.