Study On Effect Of Humidity On Human Thermal Comfort Under Closed Weightlessness Environment

With the rapid development of the manned space technology,create a suitable for astronauts to live a long time and living environment in the manned spacecraft has become one of the main task of the study on human spaceflight engineering.Microgravity research on human thermal comfort is the foundation and basis of the cabin design of artificial environment and life support system.Currently,human thermal comfort research mainly has two directions,and one of them is studying cabin ventilation and air distribution.wind speed and temperature are used to evaluate indoor thermal comforts.Another direction is the study of the changes of the physiological function of human body under microgravity conditions which belongs to the category of aerospace physiology.Considering the above two research directions,paper not only combines temperature and wind speed,but also takes humidity,astronauts activity rate and human blood distribution into account for the thermal comfort evaluation system.CFD simulation is used to simulate temperature and humidity field in microgravity cabin and paper also devote to exploring cabin thermal comfort range under different staff activity rate.In this paper,the microgravity environment and numerical simulation methods are introduced firstly,then,principle and feasibility of thermal comfort evaluation by using standard effective temperature SET* is described.In order to illustrate the commercial CFD software FLUENT can be used to simulate non-existent of natural convection under microgravity conditions,2D and 3D modeling simulation are inplemented,and respectively compare with Ren Jianxun "cold flow test"and "constant temperature method” experiment which can eliminate of natural convection.According to the result,under natural convection,There is a redistribution of flow field and low-speed area distribute less than non-existent of natural convection condition.This phenomenon both exits in the simulation and experiment.Indicating that the computer simulation can seize the flow field characteristics of non-existent of natural convection under microgravity circumstance and demonstrate the feasibility of the computer simulation method.Then passage establishes a three-dimensional modelthe according tothe Columbus Laboratory and calculates air supply temperature and humidity.Calculation results as boundary conditions are applied to the simulation for sake of analysising of cabin humidity field distribution in different gravity situation.Studies show that under normal gravity,the humidity field distribution is much closer to the air supply value and water vapor distribution is the most important factors for cabin humidity field.Finally,UDF program is written to calculate standard effective temperature in order to combine relative humidity,personnel activity intensity and blood distribution to assess thermal comfort.The results show that the thermal comfort of human body feeling temperature increases with the increase of relative humidity.When the temperature is in the range of 24-27 degrees and relative humidity is in the range of20%-80%,as well as Flow velocity around the body is 0.2m/s,under such environment,human body in sleep state have the highest thermal comfort.On the contrary,human body in motion,which computing the standard effective temperature is slightly lower than the thermal comfort zone,prefers to a warmer environment.From the air flow rate,when the flow rate increases to 1m/s,the standard effective temperature decreases and human body feel "cool".On the opposite,when the flow rate reduces to 0.06m/s,the body feels "hot".The above conclusions are drawn without consideration of blood distribution.Microgravity effect will make the body’s blood to pool the upper limb,Thus reduce lower limb blood flow,which will make the upper limb thermal sensation temperature promote,and lower limb thermal sensation temperature decline.In this paper,the numerical simulation method and ground experiment are combined.by using FLUENT UDF(user defined function),standard effective temperature is introduced to evaluate manned space cabin thermal comfort.The temperature,velocity,humidity,staff activities,dress condition,blood distribution are converted to unified standard effective temperature value to estimate human thermal comfort in different environmental conditions.SET* calculation program has the characteristics of flexible adjustment and wide adaptability.The researchof this paper will provide some experimental parameters and basis for the research of human thermal comfort experiment under the microgravity.