Absorption and foaming dynamics of refrigerant R134a in polyolester oil

• Grant number: 07/07403-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2008
• End date: July 31, 2009
• Field of knowledge: Engineering - Mechanical Engineering - Thermal Engineering
• Principal Investigator: José Luiz Gasche
• Grantee: William Monte Verde
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil

Abstract

The solubility value of refrigerants in lubricant oils is of great importance to analyse the lubrication system of refrigeration compressors due to its high influence on the oil viscosity. In addition, the volumetric efficiency of the compressor is also modified by refrigerant solubility changes once this mixture has also the aim of sealing the existing compressor clearances. The solubility of refrigerant in oil has another important effect in hermetic compressors, which has been extensively used in small refrigeration systems. At the compressor start-up solubility reduction produced by pressure decrease causes oil foaming. In hermetic reciprocating compressors, where the oil is in the suction pressure, foaming can lead to liquid compression, yelding to valve failing. The main idea of this research project is to modify a experimental setup, substituting the test section, in order to study both the saturation and foaming dynamic processes of a mixture composed by a polyolester oil and refrigerant R134a. The saturation tests will be performed through the measurement of the instantaneous mixture height along time in order to obtain the dynamic behavior of the process and also through the measurement of the refrigerant and mixture masses at the final phase-equilibrium state to determine the refrigerant solubility. A digital video camera will be used to accomplish the foaming tests by measuring the height reached by the foam and its collapse time. Several tests will be performed for pressures varying between 4 and 6 bar and temperatures ranging from 20 to 40 C. (AU)