HEAT TRANSFER COEFFICIENT OF TWO-PHASE FLOW BOILING WITH LOW VAPOR QUALITY

摘要

The use of HCFCs refrigerants are gradually being replaced by HFCs and hydrocarbons refrigerants that haszero ODP (Ozone Depletion Potential). R-290 (propane) is a hydrocarbon refrigerant with C_3H_8 molecularstructure. In this research, the flow boiling heat transfer occurs inside small tube with diameter of 7.6 mmand length of 1.07 m. In order to determine the value of heat transfer coefficient, the experiment were carriedout for mass fluxes ranging from 200 kg/m~2s to 400 kg/m~2s, heat fluxes ranging from 5 kW/m~2 to 20 kW/m~2,and saturation temperatures from 5℃ to 15℃. This study analyzed the heat transfer through the local heattransfer coefficient along the flow for low vapor quality region. The boiling heat transfer coefficient of R-290 is influenced by heat flux, mass flux, and saturation temperature. In comparison to previous boiling heattransfer correlations, the correlation of Shah (1982) best fitted the experimental result with the meandeviation of 32.20%. A new correlation for boiling heat transfer coefficient was developed by modificationof F factor with regression method. The new correlation has smaller mean deviation of 22.46% incomparison with the present experimental result.