As a natural working,fluid carbon dioxide (CO 2) has shown great potential in refrigeration and air conditioning industry. The heat transfer and pressure drop performance of supercritical CO 2 in pipes is necessary fo...As a natural working,fluid carbon dioxide (CO 2) has shown great potential in refrigeration and air conditioning industry. The heat transfer and pressure drop performance of supercritical CO 2 in pipes is necessary for gas-cooler design. This paper presents an experimental investigation of supercritical CO 2 heat transfer characteristics using temperature oscillation method.Considering the variable fluid temperature, an extended and more reasonable temperature oscillation model is built and used for heat transfer coefficient evaluation. The convective heat transfer coefficient of supercritical CO 2 flowing in an aluminum multi-channel flat pipe is measured for the first time.Experiments are performed under one typical pressure and temperature condition.The experimental setup and data acquisition as well as processing program are described in detail. New dimensionless heat transfer data in the form of Nusselt number via Reynolds number are given and analyzed.The results could be a good reference to gas-cooler design.The paper also supplies a general model or tool for determining local convective heat transfer coefficient which can be used more widely.展开更多
Although forced convection in porous media has been studied for many years, there are only relatively few investigations of convective heat transfer in porous metal with porosity higher than 0.9.This paper reports an ...Although forced convection in porous media has been studied for many years, there are only relatively few investigations of convective heat transfer in porous metal with porosity higher than 0.9.This paper reports an experimental study on convective heat transfer and pressure drop in high porosity porous aluminum.Four typical samples with the same porosity 0.92 but different pore density (10 PPI and 20 PPI) or material (A356 Al alloy and 6101 Al alloy) were used in the test.In order to measure volumetric convective heat transfer coefficient of air flowing in the samples, a single blow mathematical model was developed and the experimental setup was built.The air frontal velocity was located in 0.6 m·s -1 to 2.6 m·s -1.The effects of pore density and material on the heat transfer and pressure drop characteristics were discussed.The results showed that pore density affected the heat transfer coefficient and pressure drop drastically while the effect of material (and manufacture) was quite different for different pore densities.More work is to be done on the relations between the microstructure and the macro heat transfer performance of porous aluminum.展开更多
文摘As a natural working,fluid carbon dioxide (CO 2) has shown great potential in refrigeration and air conditioning industry. The heat transfer and pressure drop performance of supercritical CO 2 in pipes is necessary for gas-cooler design. This paper presents an experimental investigation of supercritical CO 2 heat transfer characteristics using temperature oscillation method.Considering the variable fluid temperature, an extended and more reasonable temperature oscillation model is built and used for heat transfer coefficient evaluation. The convective heat transfer coefficient of supercritical CO 2 flowing in an aluminum multi-channel flat pipe is measured for the first time.Experiments are performed under one typical pressure and temperature condition.The experimental setup and data acquisition as well as processing program are described in detail. New dimensionless heat transfer data in the form of Nusselt number via Reynolds number are given and analyzed.The results could be a good reference to gas-cooler design.The paper also supplies a general model or tool for determining local convective heat transfer coefficient which can be used more widely.
文摘Although forced convection in porous media has been studied for many years, there are only relatively few investigations of convective heat transfer in porous metal with porosity higher than 0.9.This paper reports an experimental study on convective heat transfer and pressure drop in high porosity porous aluminum.Four typical samples with the same porosity 0.92 but different pore density (10 PPI and 20 PPI) or material (A356 Al alloy and 6101 Al alloy) were used in the test.In order to measure volumetric convective heat transfer coefficient of air flowing in the samples, a single blow mathematical model was developed and the experimental setup was built.The air frontal velocity was located in 0.6 m·s -1 to 2.6 m·s -1.The effects of pore density and material on the heat transfer and pressure drop characteristics were discussed.The results showed that pore density affected the heat transfer coefficient and pressure drop drastically while the effect of material (and manufacture) was quite different for different pore densities.More work is to be done on the relations between the microstructure and the macro heat transfer performance of porous aluminum.
