In an operating evaporator, oil will typically stay on top of which refrigerant?

In an operating evaporator, oil will typically stay on top of carbon dioxide, also known as R-744, due to its unique properties compared to other refrigerants. Carbon dioxide operates at higher pressures and has a lower density than many other refrigerants, resulting in a layer of oil accumulating above it in a mixture. This behavior is particularly relevant in systems where CO2 is used, as the oil is often not miscible with the refrigerant under certain conditions, allowing it to form a distinct layer on top.

In contrast, other refrigerants like R-22, R-410A, and R-134A can have different solubility characteristics with oil, either becoming fully miscible or not forming a distinct oil layer in the evaporator. Understanding these differences is crucial for efficient system operation and maintenance, as the behavior of oil within the refrigerant affects lubrication and heat transfer in the system.