Theoretical and experimental study has been performed on heat transfer of airwater two phase laminar annular flow through a uniformly heated vertical small tube. Analysis ascertains that the mechanism of heat transfer...Theoretical and experimental study has been performed on heat transfer of airwater two phase laminar annular flow through a uniformly heated vertical small tube. Analysis ascertains that the mechanism of heat transfer is the evaporation of a very thin liquid film attached on the tube wall. The predictions of analytical solutions are quite good compared with the experimental results.展开更多
Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film eva...Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film evaporation characteristics of 90# gasoline, 93# gasoline and 0# diesel with different initial thicknesses were investigated at different en- vironmental fluxes and heating rates. The influences of heating rate, film thickness and environmental flux on fuel film evaporation for these fuels were found. The results showed that the environmental conditions in TGA were similar to those for fuel films in the in- ternal combustion engines, so data from TGA were suitable for the analysis of fuel film evaporation. TGA could simulate the key influencing factors for fuel film evaporation and could investigate the basic quantifi- cational effect of heating rate and film thickness. To get a rapid and sufficient fuel film evaporation, suffi- ciently high wall temperature is necessary. Evapora- tion time decreases at a high heating rate and thin film thickness, and intense gas flow is important to promoting fuel film evaporation. Data from TGA at a heating rate of 100℃/min are fit to analyze the diesel film evaporation during cold-start and warming-up. Due to the tense molecular interactions, the evapora- tion sequence could not be strictly divided according to the boiling points of each component for multi- component dissolved mixture during the quick evaporation process, and the heavier components could vaporize before reaching their boiling points. The 0# diesel film would fully evaporate when the wall temperature is beyond 250℃.展开更多
文摘Theoretical and experimental study has been performed on heat transfer of airwater two phase laminar annular flow through a uniformly heated vertical small tube. Analysis ascertains that the mechanism of heat transfer is the evaporation of a very thin liquid film attached on the tube wall. The predictions of analytical solutions are quite good compared with the experimental results.
文摘Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film evaporation characteristics of 90# gasoline, 93# gasoline and 0# diesel with different initial thicknesses were investigated at different en- vironmental fluxes and heating rates. The influences of heating rate, film thickness and environmental flux on fuel film evaporation for these fuels were found. The results showed that the environmental conditions in TGA were similar to those for fuel films in the in- ternal combustion engines, so data from TGA were suitable for the analysis of fuel film evaporation. TGA could simulate the key influencing factors for fuel film evaporation and could investigate the basic quantifi- cational effect of heating rate and film thickness. To get a rapid and sufficient fuel film evaporation, suffi- ciently high wall temperature is necessary. Evapora- tion time decreases at a high heating rate and thin film thickness, and intense gas flow is important to promoting fuel film evaporation. Data from TGA at a heating rate of 100℃/min are fit to analyze the diesel film evaporation during cold-start and warming-up. Due to the tense molecular interactions, the evapora- tion sequence could not be strictly divided according to the boiling points of each component for multi- component dissolved mixture during the quick evaporation process, and the heavier components could vaporize before reaching their boiling points. The 0# diesel film would fully evaporate when the wall temperature is beyond 250℃.
