Experimental Techniques to Determine Oil Distribution in Automotive A/C Systems

This paper presents experimental techniques to determine the amount of lubricant in each of the major components of an R134a automotive A/C system using ND-8 (PAG 46) oil—compressor, condenser, liquid tube, evaporator and accumulator. Three different techniques are presented: Remove and weigh Flushing Mix and sample The advantages and disadvantages, as well as the suitability of each technique are discussed. The uncertainties of each technique applied to different components of the experimental system are presented. Applying these techniques shows that the overall amount of lubricant in the system can be determined with an uncertainty of ±2g which is less than ±1% for the experimental system. In addition, a new method to separate refrigerant and lubricant is presented which does not require a solvent, and allows reusing the lubricant after separation. This method has an accuracy of ±0.04g of refrigerant left in the lubricant after separation.