Experimental study of natural convection heat transfer across air layers bounded by a lower hot rectangular and a square corrugated plates to an upper cold flat plate has been carried out. The surroundings of this spa...Experimental study of natural convection heat transfer across air layers bounded by a lower hot rectangular and a square corrugated plates to an upper cold flat plate has been carried out. The surroundings of this space are adiabatic. The effect of the angle of inclination, the aspect ratio, the temperature potential and the Rayleigh number on average heat transfer coefficients are investigated within a range of 0°≤75°,, 2.33≤A≤6.33, 10°≤T ≤35°, and 3.29xl04≤RaL≤ 2.29x106. The developed correlation predicts well the experimental data within an error of ±15%.展开更多
Experimental and numerical researches were conducted to investigate the cooling performance of a single row of consoles （converging slot-hole） on a large-scale flat-plate model. The results show that the coolant flo...Experimental and numerical researches were conducted to investigate the cooling performance of a single row of consoles （converging slot-hole） on a large-scale flat-plate model. The results show that the coolant flow from a row of consoles shows good lateral uniformity of adiabatic effectiveness, with regions of slightly enhanced cooling occurring between the consoles. For the console cooling geometry, the interaction between coolant jet from inclined console and the mainstream flow results in reasonable vortices configuration. A pair of counter rotating vortices originate from the edge of slot, not from the centerline of film holes and the rotating direction is contrary to conventional cylindrical hole. The heat transfer coefficient ratio is a tittle bigger for the console case than conventional cylindrical hole, and the discharge coefficient for a console is larger than that for cylindrical film cooling hole.展开更多
A theoretical model is developed to predict the upper limit heat transfer between a stack of parallel plates subject to multiphase cooling by air-mist flow.The model predicts the optimal separation distance between th...A theoretical model is developed to predict the upper limit heat transfer between a stack of parallel plates subject to multiphase cooling by air-mist flow.The model predicts the optimal separation distance between the plates based on the development of the boundary layers for small and large separation distances,and for dilute mist conditions.Simulation results show the optimal separation distance to be strongly dependent on the liquid-to-air mass flow rate loading ratio,and reach a limit for a critical loading.For these dilute spray conditions,complete evaporation of the droplets takes place.Simulation results also show the optimal separation distance decreases with the increase in the mist flow rate.The proposed theoretical model shall lead to a better understanding of the design of fins spacing in heat exchangers where multiphase spray cooling is used.展开更多
The heat-transfer behaviour of the conduction cold plate system used for avionics is investigated in this paper. The steady-state temperature profile for the cold plate is derived and the relationship between the cool...The heat-transfer behaviour of the conduction cold plate system used for avionics is investigated in this paper. The steady-state temperature profile for the cold plate is derived and the relationship between the coolant mass flowrate, the heat load and the hashest cold plate temperature is established.A model is proposed to describe the transient thermal rosponse of the cold plate under thermal shock condition. The analytic solution of the transient heat transfer within the cold plate is provided. The results of this paper agree with those of the finite element method and can be used for the structural design and performance evaluation of cold plate system.展开更多
Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensienal discrete-hole film cooling arrangement. The effects of basic geometrical characteristics of th...Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensienal discrete-hole film cooling arrangement. The effects of basic geometrical characteristics of the holes, i.e diameter D, length L and pitch S/D were studied. Different turbulent heat transfer models based on constant and variable turbulent Prandtl number approaches were considered. The variability of the turbulent Prandtl number Prt in the energy equation was assumed using an algebraic relation proposed by Kays and Crawford, or employing the Abe, Kondoh and Nagano eddy heat diffusivity closure with two differential transport equations for the temperature variance ko and its destruction rate εθ The obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology. All implemented models for turbulent heat transfer performed sufficiently well for the considered case. It was confirmed, however, that the two- equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models.展开更多
文摘Experimental study of natural convection heat transfer across air layers bounded by a lower hot rectangular and a square corrugated plates to an upper cold flat plate has been carried out. The surroundings of this space are adiabatic. The effect of the angle of inclination, the aspect ratio, the temperature potential and the Rayleigh number on average heat transfer coefficients are investigated within a range of 0°≤75°,, 2.33≤A≤6.33, 10°≤T ≤35°, and 3.29xl04≤RaL≤ 2.29x106. The developed correlation predicts well the experimental data within an error of ±15%.
基金supported by the National Natural Science Foundation of China (Grant No. 50876041)
文摘Experimental and numerical researches were conducted to investigate the cooling performance of a single row of consoles （converging slot-hole） on a large-scale flat-plate model. The results show that the coolant flow from a row of consoles shows good lateral uniformity of adiabatic effectiveness, with regions of slightly enhanced cooling occurring between the consoles. For the console cooling geometry, the interaction between coolant jet from inclined console and the mainstream flow results in reasonable vortices configuration. A pair of counter rotating vortices originate from the edge of slot, not from the centerline of film holes and the rotating direction is contrary to conventional cylindrical hole. The heat transfer coefficient ratio is a tittle bigger for the console case than conventional cylindrical hole, and the discharge coefficient for a console is larger than that for cylindrical film cooling hole.
文摘A theoretical model is developed to predict the upper limit heat transfer between a stack of parallel plates subject to multiphase cooling by air-mist flow.The model predicts the optimal separation distance between the plates based on the development of the boundary layers for small and large separation distances,and for dilute mist conditions.Simulation results show the optimal separation distance to be strongly dependent on the liquid-to-air mass flow rate loading ratio,and reach a limit for a critical loading.For these dilute spray conditions,complete evaporation of the droplets takes place.Simulation results also show the optimal separation distance decreases with the increase in the mist flow rate.The proposed theoretical model shall lead to a better understanding of the design of fins spacing in heat exchangers where multiphase spray cooling is used.
文摘The heat-transfer behaviour of the conduction cold plate system used for avionics is investigated in this paper. The steady-state temperature profile for the cold plate is derived and the relationship between the coolant mass flowrate, the heat load and the hashest cold plate temperature is established.A model is proposed to describe the transient thermal rosponse of the cold plate under thermal shock condition. The analytic solution of the transient heat transfer within the cold plate is provided. The results of this paper agree with those of the finite element method and can be used for the structural design and performance evaluation of cold plate system.
文摘Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensienal discrete-hole film cooling arrangement. The effects of basic geometrical characteristics of the holes, i.e diameter D, length L and pitch S/D were studied. Different turbulent heat transfer models based on constant and variable turbulent Prandtl number approaches were considered. The variability of the turbulent Prandtl number Prt in the energy equation was assumed using an algebraic relation proposed by Kays and Crawford, or employing the Abe, Kondoh and Nagano eddy heat diffusivity closure with two differential transport equations for the temperature variance ko and its destruction rate εθ The obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology. All implemented models for turbulent heat transfer performed sufficiently well for the considered case. It was confirmed, however, that the two- equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models.
