Wettability of metal surface with oil/refrigerant mixture

Separation of oil from refrigerant is important to reduce the oil circulation rate in a refrigeration cycle. Since the oil separation depends on the droplet size of oil mist in a compressor and the condition of the oil film on the inner surface of the compressor shell, this study examined the wettability of a metal surface with the oil/refrigerant mixture and surface tension. The wettability of metal surfaces with PAG/CO2 mixture was evaluated by measuring the contact angle of droplets on the metal surface. The surface tension of the mixture was measured using a pendant drop method. It was found that the wetting of the metal surface with the oil/refrigerant mixture showed a complete wetting, and the contact angle decreased with the refrigerant concentration. Taking the Ohnesorge number into account, the initial spreading of oil mist on the metal surface under discharge conditions should immediately become a viscus-dominant condition. (C) 2020 Elsevier Ltd and IIR. All rights reserved.