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ISSN Online: 2379-1748
8th Thermal and Fluids Engineering Conference (TFEC)
AN EXPERIMENTAL INVESTIGATION ON SPRAY EVAPORATION OF R1234ZE(E)/POE-68 MIXTURE ON AN ENHANCED TUBE BUNDLE
Abstract
Refrigerant spray-type evaporators are used in refrigeration systems for several HVAC, desalination, petroleum refining, chemical, and biochemical processes. Tubes are assembled in bundles inside a shell: water is circulated inside the tubes while the refrigerant is sprayed through nozzles installed at the top of the bundle. In actual vapor-compression-based refrigeration systems, the compressors use lubricants which inevitably circulate with the refrigerant through the rest of the system components. The oil is an undesired and yet unavoidable contaminant in spray-type evaporators.
This paper describes the effect of lubricating oil on the heat transfer performance of spray evaporators for air conditioning and refrigeration systems. New data are provided for refrigerant and lubricant mixtures of R134a (HFC) and R1234ze (HFO) with synthetic polyester (POE) lubricant. The present study investigated the effects of heat flux, oil circulation ratio (OCR), and saturation temperature. The saturation temperature ranged from -6 °C to 10 °C (20 °F to 50 °F), and the heat flux varied between 3 kW/m2 and 20 kW/m2. The results indicated that an OCR of 0.8-1.2% enhanced the tube bundle heat transfer coefficient by as much as 20-30% at heat fluxes between 10-15 kW/m2. However, at a higher heat flux of 17 kW/m2, marked penalizations of the heat transfer coefficient were measured, particularly at low saturation evaporation temperature.
This paper describes the effect of lubricating oil on the heat transfer performance of spray evaporators for air conditioning and refrigeration systems. New data are provided for refrigerant and lubricant mixtures of R134a (HFC) and R1234ze (HFO) with synthetic polyester (POE) lubricant. The present study investigated the effects of heat flux, oil circulation ratio (OCR), and saturation temperature. The saturation temperature ranged from -6 °C to 10 °C (20 °F to 50 °F), and the heat flux varied between 3 kW/m2 and 20 kW/m2. The results indicated that an OCR of 0.8-1.2% enhanced the tube bundle heat transfer coefficient by as much as 20-30% at heat fluxes between 10-15 kW/m2. However, at a higher heat flux of 17 kW/m2, marked penalizations of the heat transfer coefficient were measured, particularly at low saturation evaporation temperature.