Implementation Of Precise Temperature And Humidity Control Based On Thermal Control Ground Simulation Cabin

In current temperature and humidity control system utilized in spacecraft andspace station, temperature is actively controlled while humidity is passivelycontrolled. Nevertheless, due to the coupling of temperature and humidity, thissystem isn’t reliable enough in humidity control especially when there is a highprecision control requirement for temperature and humidity. As temperature andhumidity control system is indispensable in a manned spacecraft’s environmentalcontrol and life support systems, its research and development is of greatsignificance. In addition, in the research of the convection heat transfer in spacecraftcabins, the lowering pressure method is usually used to suppress the effect ofnatural convection in ground experiments, but the choice of the pressure oftendepends on some unknown parameters, so that the suppression of natural convectioncannot be guaranteed. Therefore, this article implements researches on spacecraft’stemperature and humidity control systems and analyzes the effect of loweringpressure method.Aiming at the existing problems, this article adopts a ground experimentsystem in a sealed cabin, establishs a steady-state simulation model and a dynamicmodel for this system on the basis of equilibrium principle of heat and mass byingusing the lumped parameter method. Through analyzing the heat exchangers inmiddle-temperature and low-temperature circuits and change point in condensingdryers, we figure out how the ventilation quantity, and the human body humidityproduce rate and the flow distribution ratio of condensing drying branch influencessteady-state characteristic. By analyzing the dynamic response of temperature andhumidity under different conditions in the sealed cabin, the system’s dynamiccharacteristic is clear.Results testify that the lowest relative humidity at control target can be37.8%;the highest humidity produce rate of body can be16.29kg/day; the optimized systemtotal ventilation quantity is8m3/min; the optimal flow distribution ratio ofcondensing drying branch is0.255. We succeed in finding out that human body’shumidity produce rate is the critical influencing factor of the steady-statecharacteristics and therefore recommend the match of humidity produce and system.In addition, the system has sufficient ability to control temperature and humidity,can quickly achieve precise control of temperature and humidity when imposingreasonable control strategy. Even if the wet load exceeds the system’s control ability,you can enhance its conrol ability by regulating the flow distribution ratio ofcooling drying branch or heating ventilation circuit. The second way is the priority. Finally, the paper establishes a steady-state numerical model of flow and heattransfer for the manned spacecraft pressurized cabin. Considering the humancomfort, elimination of natural convection effect and energy consumption together,the optimum air rate is obtained through a comparative study of flow and heattransfer both in ground test condition and space condition. Critical pressure andGr/Re2are obtained through a comparative study of the convective heat transfercoefficient and temperature distribution both in ground test condition and spacecondition for various gas pressure of the cabin.