HOT SURFACE IGNITION OF R-32 AND R-410A REFRIGERANT MIXTURES WITH LUBRICATING OIL

Abstract

This study examines the flammability of refrigerant and oil mixtures. The flammability risk associated with refrigerants is an important property to consider prior to their use in residential and commercial HVAC systems. This research was conducted to compare the ignition characteristics of R-32 with R-410A, and the effects of lubricating oil. Unpiloted hot-plate ignition tests were carried out to determine ignition temperatures and quantify the flammability risks associated with these refrigerants. Additionally, computational fluid dynamic (CFD) methods were used to model the vapor temperatures and concentrations of an R-32 jet impinging on a hot-surface. The laboratory results indicate that R-32 will ignite upon contact with a 764oC surface. This is higher than the reported 648oC autoignition temperature of R-32. R-410A was found to ignite upon contact with a 790oC surface. Results with mixtures of refrigerant and polyolester (POE) oil were found to ignite at temperatures close to that of oil alone, 645oC. CFD predictions show that ignition is likely to occur along the edges of the apparatus, where the fuel vapor concentrations and temperatures are within the limits of combustion.