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Surface tension, oil level and density measurement of oil/refrigerant mixture by maximum bubble pressure method.

Number: 2431

Author(s) : LEE G., FUKUTA M., MOTOZAWA M., KIMURA R., TSUJITA R.

Summary

Refrigeration oil is used for lubrication of sliding parts and sealing of compression chambers in refrigerant compressors. The refrigeration oil generally has solubility with refrigerant. Since property of the oil such as viscosity significantly changes with dissolution of refrigerant into the oil, it is important to monitor the refrigerant concentration in the oil/refrigerant mixture in the compressor shell. Surface tension is one of the properties which change according to the refrigerant concentration in the mixture and was proposed as an indicator to measure the refrigerant concentration at high temperature and pressure condition. In this study, the surface tension was measured by a maximum bubble pressure method. A Peltier pump was developed as a bubble generation pump for the maximum bubble pressure method. Peltier element was used to increase the pressure inside a copper container by heating it with applying electric current to the elements. The pump has no moving parts, easily controls the pressure by regulating the electric current, and generates bubbles steadily at capillary tubes immersed in the mixture. A 3-capillary method, which uses three capillaries of different immersed depths and inner diameters, can measure the surface tension, oil level and density of the mixture simultaneously. The 3-capillary method is applicable to the refrigerant compressors and it allows us to monitor the oil level and the surface tension of the mixture in the compressor shell. It was found that the influence of the density of mixture on the surface tension measurement is very small in the maximum bubble pressure method. The measurement accuracy of the oil level was ±10% by the 3-capillary method, and it has a feasibility to monitor the oil level in the compressor shell. A correlation between the surface tension of PVE/R410A mixture and the refrigerant concentration in oil was proposed.

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  • Original title: Surface tension, oil level and density measurement of oil/refrigerant mixture by maximum bubble pressure method.
  • Record ID : 30030724
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022

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