Effects of temperature and pressure on the surface tension of low viscose lubricants in high pressure atmospheres.

One possible way to increase the efficiency of a compressor is to reduce the friction and the leakage losses which occur e.g. at the piston rings. Besides the effects of the surface roughness of the cylinder wall also the thermophysical properties of the lubricant refrigerant mixture have an effect on the sealing quality inside the compressor. The thermophysical properties of lubricant refrigerant mixtures can currently only be determined by generalized calculation methods which need to be confirmed by measurements. In this paper the measurement results of the Laplace constant for a POE lubricant with different refrigerants are shown. The effects of different temperatures and pressures on the surface tension of the mixtures are discussed and reduced parameters are introduced. Approximations of the surface tension as functions of the temperature and pressure are shown and discussed in relation to the solubility effects of different refrigerants in POE lubricants.