R-32, L-41, lubricant miscibility, COP, oil circulation ratio
Polyol ester (POE) lubricants of different viscosity ISO grades (32-80) and possessing distinctly different compatibilities (miscible vs. immiscible) were tested with R-410A, R-32, and L-41b. For each refrigerant-lubricant pair tested, the cooling coefficient of performance (COP), heating performance factor (HPF), and oil circulation ratio (OCR) were determined while operating at AHRI Standard 210/240 conditions A, B, C, H1 & H2. The results were correlated to the properties of the working fluids. Due to its higher density, yet comparable specific heat, R-32 showed increased cooling capacity compared to R-410A. However, the COPs of these refrigerants were similar because the capacity increase was offset by increased compressor power consumption. L-41b required the least compressor power, but also had the lowest cooling capacity and COP of the three refrigerants. Lubricant choice had minimal impact on cooling capacity. However, immiscible lubricants lowered cooling capacity by about 4% for R-32, condition B. A larger effect was observed in the compressor, where lubricants specifically designed for R-32 lowered discharge temperatures by 6 °C and reduced power consumption by up to 10%. For R-32-lubricant pairs tested under AHRI cooling condition B, the highest and lowest COPs measured were 4.19 (optimized ISO 68 POE) and 3.72 (commercial ISO 32 POE) ? a 12% improvement by replacing the standard R-410A lubricant.