A thermal multiphase lattice Boltzmann(LB) model is used to study the behavior of droplet impact on hot surface and the relevant heat transfer properties.After validating the correctness of the codes through the D^(2)...A thermal multiphase lattice Boltzmann(LB) model is used to study the behavior of droplet impact on hot surface and the relevant heat transfer properties.After validating the correctness of the codes through the D^(2) law,the simulations of intrinsic contact angle and the temperature-dependent surface tension are performed.The LB model is then used to simulate the droplet impact on smooth and micro-hole heated surface.On the smooth surface,the impinging droplet is reluctant to rebound,unless the intrinsic wettability of the solid surface is fairly good.On the micro-hole surface,however,the micro-holes provide favorable sites for generating a high-pressure vapor cushion underneath the impinging droplet,which thereby facilitates the continuous droplet rebound.For the continuously rebounding droplet.The time evolution of volume and temperature display obvious oscillations.The achievable height of the rebounding droplet increases as the intrinsic wettability of the solid surface becomes better,and the maximum transient heat flux is found to be directly proportional to the droplet rebounding height.Within a certain time interval,the continuous rebounding behavior of the droplet is favorable for enhancing the total heat quantity/heat transfer efficiency,and the influence of intrinsic wettability on the total heat during droplet impingement is greater than that of the superheat.The LB simulations not only present different states of droplets on hot surfaces,but also guide the design of the micro-hole surface with desirable heat transfer properties.展开更多
Droplet-based high heat flux dissipation technique under multi-gravitational environments has gained increasing research attention due to the increased requirements of heat dissipation in advanced air-/space-borne ele...Droplet-based high heat flux dissipation technique under multi-gravitational environments has gained increasing research attention due to the increased requirements of heat dissipation in advanced air-/space-borne electronics.In this paper,a threedimensional model was developed to investigate the impact of continuous droplets on liquid film under various Weber numbers and gravity loads.In other words,the effects of Weber number and gravity load on the flow and heat transfer characteristics were investigated.The results demonstrated that the dissipated heat flux was positively correlated with both Weber number and gravity load.A large Weber number indicated larger kinetic energy of a droplet,leading to a greater disturbance on the impacted film area.When the Weber number was doubled,the average wall heat flux could be enhanced by 36.3%.In addition,the heat flux could be boosted by 5.4%when the gravity load ranged from 0 to 1g.Moreover,a weightless condition suppressed the vapor escape rates on the heating wall where the volume fraction of the vapor on the wall could increase by 20%under 0g,leading to deteriorated heat transfer performance.The novelty in this paper lies in the accurate three-dimensional modeling of an aerospaceoriented droplet impacting two-phase heat transfer and fluid dynamics,associating macro-scale thermal performance to microscale thermophysics mechanisms.The findings of this study could guide the development of aerospace-borne spray cooling facilities for advanced aerospace thermal management.展开更多
The processes of heat and humidity transfer between air and water are what to be studied mainly in the paper, we put forward some main factors which influence the processes of heat and humidity transfer in the air was...The processes of heat and humidity transfer between air and water are what to be studied mainly in the paper, we put forward some main factors which influence the processes of heat and humidity transfer in the air washer. We come to the conclusion that we can change these main factors to achieve different heat and humidity transfer processes and decide processes of heat and humidity transfer of air and water with the initial temperature of spraying water in the air washer. All these results can make things convenient for the air conditioning management.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51901148 and 51874204)the Fund of the State Key Laboratory of Solidification Processing(Northwestern Polytechnical University),China(Grant No.SKLSP202006)。
文摘A thermal multiphase lattice Boltzmann(LB) model is used to study the behavior of droplet impact on hot surface and the relevant heat transfer properties.After validating the correctness of the codes through the D^(2) law,the simulations of intrinsic contact angle and the temperature-dependent surface tension are performed.The LB model is then used to simulate the droplet impact on smooth and micro-hole heated surface.On the smooth surface,the impinging droplet is reluctant to rebound,unless the intrinsic wettability of the solid surface is fairly good.On the micro-hole surface,however,the micro-holes provide favorable sites for generating a high-pressure vapor cushion underneath the impinging droplet,which thereby facilitates the continuous droplet rebound.For the continuously rebounding droplet.The time evolution of volume and temperature display obvious oscillations.The achievable height of the rebounding droplet increases as the intrinsic wettability of the solid surface becomes better,and the maximum transient heat flux is found to be directly proportional to the droplet rebounding height.Within a certain time interval,the continuous rebounding behavior of the droplet is favorable for enhancing the total heat quantity/heat transfer efficiency,and the influence of intrinsic wettability on the total heat during droplet impingement is greater than that of the superheat.The LB simulations not only present different states of droplets on hot surfaces,but also guide the design of the micro-hole surface with desirable heat transfer properties.
基金supported by the National Natural Science Foundation of China (Grant Nos.52106114,51725602,and 52036006)。
文摘Droplet-based high heat flux dissipation technique under multi-gravitational environments has gained increasing research attention due to the increased requirements of heat dissipation in advanced air-/space-borne electronics.In this paper,a threedimensional model was developed to investigate the impact of continuous droplets on liquid film under various Weber numbers and gravity loads.In other words,the effects of Weber number and gravity load on the flow and heat transfer characteristics were investigated.The results demonstrated that the dissipated heat flux was positively correlated with both Weber number and gravity load.A large Weber number indicated larger kinetic energy of a droplet,leading to a greater disturbance on the impacted film area.When the Weber number was doubled,the average wall heat flux could be enhanced by 36.3%.In addition,the heat flux could be boosted by 5.4%when the gravity load ranged from 0 to 1g.Moreover,a weightless condition suppressed the vapor escape rates on the heating wall where the volume fraction of the vapor on the wall could increase by 20%under 0g,leading to deteriorated heat transfer performance.The novelty in this paper lies in the accurate three-dimensional modeling of an aerospaceoriented droplet impacting two-phase heat transfer and fluid dynamics,associating macro-scale thermal performance to microscale thermophysics mechanisms.The findings of this study could guide the development of aerospace-borne spray cooling facilities for advanced aerospace thermal management.
文摘The processes of heat and humidity transfer between air and water are what to be studied mainly in the paper, we put forward some main factors which influence the processes of heat and humidity transfer in the air washer. We come to the conclusion that we can change these main factors to achieve different heat and humidity transfer processes and decide processes of heat and humidity transfer of air and water with the initial temperature of spraying water in the air washer. All these results can make things convenient for the air conditioning management.
