Study On Flow And Heat Transfer Of A Thermal Shielding Radiator

Armored vehicles,tanks and other military equipments show higher temperature than environment due to the large power of engine under working condition,and the phenomenon of local high temperature can be detected by the infrared guided weapons and the optoelectronic imaging satellites easily.This puts military equipment at extremely risk on the battlefield.In this study,the local high temperature equipment is simplified as a high temperature heat source,and a micro-channel thermal shielding radiator is proposed to shield the high temperature surface from infrared detection.The large temperature difference between the heat resource surface and cold face,the high temperature uniformity at the cool plate is pursued to improve infrared stealth capability of military equipments.In this paper,the effect of inlet and outlet modes on the performance of the heat insulator is simulated firstly.There are four kinds of inlet/outlet arrangements including C-type,Z-type,Y-type and I-type.And the results show that the pressure drop and flow distribution are high related with inlet/outlet modes,which leads to different uniformity of cold-plate temperature.By numerical results,it is found that I-type has the optimal pressure drop and uniform temperature by using the flow non-uniform coefficient and pressure drop.Secondly,in order to achieve better heat insulation performance,a cavity between the bottom plate and the micro-channel with non-uniform distributed ribs inside the thermal shielding radiator is proposed.The effect of the coolant flow rate and heat surface temperature on the heat insulation performance is evaluated.According to parameters such as the pressure drop,average,highest,standard deviation temperature of the cold plate sources,and thermal resistance,Reynolds number,and the heat source temperature,it is concluded that the cavity largely improves the heat insulation,and heat insulator with improved fin is more applicable to the condition of the high mass flow,while the heat insulator with uniform fin has the best heat insulation performance at medium and low flow rates.Finally,in view of the impact of cavity thickness on the performance of the cavity type heat insulator,the optimal cavity thickness of 0.2mm is obtained to maximize the overall radiator resistance and achieve the best temperature uniformity.In order to verify the results of numerical simulation,an experimental system is established.Firstly,the influence of different inlet/outlet arrangement on the temperature uniformity of cold-plate and the temperature difference between cold and hot plate was explored,and it was found that the heat insulation effect of I-type was the best under experimental conditions,but the pressure drop under the experiment was much higher than the result of numerical simulation due to the wall rough and local resistance at the junction.Based on the I-type inlet/outlet arrangement a comparative experiments were carried out to study the heat insulation performance of the cavity type heat insulator by parameters such as the flow pressure drop,heat transfer and heat insulation performance.Compared with traditional heat radiator,it is found that,with the cavity,the flow resistance drops while the temperature difference between the cold and hot surface increases.By comparison with the simulation results,it is found that,besides the pressure loss,the temperature related experimental data are better than the simulation.In summary,the additional thermal resistance caused by the rough surface improves the thermal insulation performance.Based on the geometry parameter of the improved designed heat insulator,the thickness of the cavity is taken as a variable,and the influence of flow rate and heat source temperature on its thermal insulation performance is numerically studied.It is found that there is an optimum thickness of 0.2mm for the cavity type heat insulator.Numerical and experimental results were used to study the flow and heat transfer enhancement of the heat insulation radiator.To enhance heat transfer,the side with channel should be close to the heat source.For the purpose of the thermal insulation,however,the cover plate with the cavity should be close to the heat source.