Thermal Response And Transport Characteristic Study Of Infrared Stealthy System

With rapid development of infrared detection technology,the all-around and all-weather reconnaissance of air and ground formed by high-precision and sensitive infrared detection technology poses a huge threat to the military targets on the battlefield.Researches on infrared stealth technology is of great significance,especially on the adaptive infrared stealth technology.At present,the adaptive infrared stealth system with the nucleus of changeable emissivity material induced by electricity cannot meet the application requirements in places with large temperature difference between day and night.In contrast,the adaptive infrared stealth system with changeable temperature material induced by electricity is obviously much more advantageous than these systems with changeable emissivity material.Therefore,this paper proposes a new scheme based on the adaptive infrared stealth technology with the electric cooling and changeable temperature system,based on which,a prototype of the infrared stealth system is designed and manufactured.Both of the thermal response and transport characteristics of the prototype were thoroughly studied by means of theory,experiment and numercical simulation.Performances of the system were tested and perspectives for further optimization were proposed.Firstly,the main components of the infrared stealth system include the thermoelectric cooler,the vapor chamber and the cold screen.The thermoelectric cooler can refrigerate quickly once powered on,which meets the rapid thermal response requirement of the system temperature.The vapor chamber with high-efficiency heat conduction and excellent synthermal performance can provide an excellent foundation for the infrade stealth performance.The system was integrated by various modules,improving the applicability of the system.Based on detailed heat transfer and hydraulic calculation,the size and structure of the system were determined,and a prototype with the ratio of width to height ratio of 4:3 was fabricated.The overall size of the prototype was 1400 mm× 1020 mm× 21 mm(Width × Height ×Thickness)and 192 modules in the prototype was arranged in 16 ×12 matrix.Secondly,a quasi three-dimensional unsteady heat transfer model of the vapor chamber is established based on control volume-based method.A one-dimensional unsteady heat transfer model of the thermoelectric cooler was established based on energy conservation.Results show that temperature decrease of the module varies greatly along with the environmental.The increasing the working current will improve the thermal response of the module to a curtain extent,while lower or higher working current will lower down the thermal response speed.In addition,lower temperature of inlet cooling water and higher flow rate would also elevate the thermal response speed of the module.To study the heat transportation characteristics of the system,the temperature distribution equation of the vapor chamber was established based on the thermal equilibrium state.Results indicated that the referigeration capacity generated by the thermoelectric cooler uniformly spread from the center of the surface to the surrounding area,with lower temperaturein the center and higher temperature around.It was worth noted that the maximum surface temperature difference is less than 1K.Then,the thermal response and thermal transportation characteristics of the prototype were further tested by a test platform.The experimental results verified the feasibility of the theoretical model with a maximum error of 9.4%.It was found that the surface temperature of the prototype decreased more quickly with higher flow rate and lower temperature of inlet cooling water.Besides,in spite of the abnormal data caused by control errors,the maximum temperature difference between surface positions was less than 1K,indicating the good uniformity of surface temperature.Finally,the physical model of the prototype was built in Gambit software and then exported to Fluent software for simulation.The curve of the surface temperature of the infrared stealth system with time and the temperature field of each component were obtained.The maximum error between simulation results and experimental results was 5.7% and the surface temperature field of the vapor chamber showed same distribution with teeoretical results.And it is found that the temperature of the vapor chamber surface increases from the center to the periphery and the maximum temperature difference of the surface is within 1K.This study provides theoretical and data support for the adaptive infrared stealth technology with changeable emissivity material induced by electricity,which would be helpful to promote the development of infrared stealth technology.