The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-a...The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-air interfacial thermal resistance were reviewed especially. In the distribution of thermal resistance, the rank of the thermal resistance proportion （from max to min） is air flow heat transfer resistance, heat transfer resistance between refrigerant and wall, water film convection resistance and wall heat transfer resistance. When the heat flux is constant, the total resistance lowers nearly along with the increasing of air flow and water spray density. But there are a best air flow value of 2.98 m/s and a best spray water density of 0.064 kg/（m ·s） respectively, if continue to increase them, condensation performance is not significantly improved any more. The test results are available to improve the evaporative condenser performance and the designing lever.展开更多
The effective thermal conductivity of composites with ellipsoidal fillers is analyzed by using a homogenization method that is able to represent the microstructure precisely.In this study,various parameters such as th...The effective thermal conductivity of composites with ellipsoidal fillers is analyzed by using a homogenization method that is able to represent the microstructure precisely.In this study,various parameters such as the volume fraction,shape,and distribution of the filler are quantitatively estimated to understand the mechanisms of heat transfer in the composite.First,thermal boundary resistance between resin and filler is important for obtaining composites with higher thermal conductivity.Second,the anisotropy of the effective thermal conductivity arises from contact between filler in the case of ellipsoidal filler and produces lower thermal resistance.Finally,the filler network and thermal resistance are essential for the heat transfer in composites because the path of thermal conduction is improved by contact between neighboring filler particles.展开更多
The thermal choking phenomenon is of great importance in an inlet isolator in dual-mode ram jet/scramjet combustor. In some cases the choked flow creates a pseudo-shock wave including a shock train in it at the engine...The thermal choking phenomenon is of great importance in an inlet isolator in dual-mode ram jet/scramjet combustor. In some cases the choked flow creates a pseudo-shock wave including a shock train in it at the engine inlet and causes large amounts of drag and radically reduces the performance of the engine at high flight Mach numbers. The present paper describes a one-dimensional flow model taking account of the upstream boundary-layer as well as heat addition by using a mass-weighted av- eraging technique. The simple relationships for the flow field in a constant area duct in which the effect of the upstream boundary-layer is considered but the effect of the wall friction in the duct can be neglected are presented. The results of the calculation such as the maximum heat addition when the thermal choking occurs, the downstream Mach number and the static pressure ratio are presented and examined in detail.展开更多
文摘The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-air interfacial thermal resistance were reviewed especially. In the distribution of thermal resistance, the rank of the thermal resistance proportion （from max to min） is air flow heat transfer resistance, heat transfer resistance between refrigerant and wall, water film convection resistance and wall heat transfer resistance. When the heat flux is constant, the total resistance lowers nearly along with the increasing of air flow and water spray density. But there are a best air flow value of 2.98 m/s and a best spray water density of 0.064 kg/（m ·s） respectively, if continue to increase them, condensation performance is not significantly improved any more. The test results are available to improve the evaporative condenser performance and the designing lever.
文摘The effective thermal conductivity of composites with ellipsoidal fillers is analyzed by using a homogenization method that is able to represent the microstructure precisely.In this study,various parameters such as the volume fraction,shape,and distribution of the filler are quantitatively estimated to understand the mechanisms of heat transfer in the composite.First,thermal boundary resistance between resin and filler is important for obtaining composites with higher thermal conductivity.Second,the anisotropy of the effective thermal conductivity arises from contact between filler in the case of ellipsoidal filler and produces lower thermal resistance.Finally,the filler network and thermal resistance are essential for the heat transfer in composites because the path of thermal conduction is improved by contact between neighboring filler particles.
文摘The thermal choking phenomenon is of great importance in an inlet isolator in dual-mode ram jet/scramjet combustor. In some cases the choked flow creates a pseudo-shock wave including a shock train in it at the engine inlet and causes large amounts of drag and radically reduces the performance of the engine at high flight Mach numbers. The present paper describes a one-dimensional flow model taking account of the upstream boundary-layer as well as heat addition by using a mass-weighted av- eraging technique. The simple relationships for the flow field in a constant area duct in which the effect of the upstream boundary-layer is considered but the effect of the wall friction in the duct can be neglected are presented. The results of the calculation such as the maximum heat addition when the thermal choking occurs, the downstream Mach number and the static pressure ratio are presented and examined in detail.
