Investigation of the effects of vapour quality and oil concentration on performance of a swash plate compressor

Abstract

SUMMARYThe main objective of the present study is to experimentally investigate the effects of vapour quality and oil concentration on the performance of a swash plate compressor for automotive air conditioning systems. R-134a is used as refrigerant. The compressor used is a typical automotive swash-plate-type compressor driven by a 10 hp variable-speed electric motor and lubricated by polyalkylene glycol (PAG) oil. The variables measured during the experiment are pressure, temperature, oil concentration, total mass flow rate and vapour mass flow at the inlet and outlet of the compressor. The experiment was performed at varying compressor speeds, compression ratios and vapour quality. The results revealed some unknown aspects of the compression process in an automotive air conditioning system. The vapour quality does not affect volumetric efficiency, but influences isentropic efficiency of the compressor. In the vapour quality range of 80-90%, isentropic efficiency decreases with increasing vapour quality. During the compression process, only a portion of the liquid refrigerant evaporates. However, at the outlet of the compressor, refrigerant/oil mixture never reaches steady state. The evaporation ratio decreases with increasing compressor speed, and with increasing vapour quality as well.

The effect of oil in refrigeration: Current research issues and critical review of thermodynamic aspects

“…In addition, because some refrigerants remain dissolved into oil, the true fluid quality at compressor inlet is always lower than unity, and some liquid is desorbed from oil during the compression process. This phenomenon may considerably affect the compressor isentropic efficiency, but not the volumetric efficiency (Wang et al, 2006a).…”

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

“…In fact, the destructive increase of cylinder pressure during wet compression can only occur when the vapor quality is under 0.4 at the compressor inlet, but this condition is rare [7]. In addition, the accelerated wear of a cylinder could be reduced by fully evaporating the droplets of liquid during compression [8]. Thus, the number of liquid droplets and a finite time required for heat transfer during compression, are considered to be important for preventing an abrupt increase in the pressure and a greater wear of the cylinder.…”

Characteristics of a multi-functional device and capillary flow of refrigeration systems

“…Thermodynamic properties at three lubricant concentrations (1%, 5%, and 1 0 %) were calculated using the model. 33 Wang et al (2006) and cooldown time. The system is a receiver/dryer type, and no IHX is taken into account.…”

“…and decreasing with compressor speed by Aprea et al (2003) and Wang et al (2006). Tassou and Qureshi (1998) attribute the increase to optimized compressors that have maximum volumetric efficiencies at design speed.…”

“…Therefore, compressor speed does affect the system performance. The pressure behaviour with compressor speed has been reported by many researchers including Tassou and Qureshi (1998), Shao et al (2004), Boyde et al (2000), Ratts and Brown (2000), Aprea et al (2003), and Wang et al (2006). However, not much attention was paid to the mechanism underlying the trend lines of discharge pressure and intake pressure with compressor speed.…”