Specification Of Thermal Boundary Conditions For Human Bodies In Densely Occupied Indoor Environments

When carrying out a CFD simulation for indoor environments, the thermal boundary of the human bodies is commonly set as a constant wall temperature or a constant heat flux. Such method was derived from the research of a single person. However, it may lead to distorted or even wrong results for crowded environments such as classroom, train or airplane, etc.This thesis proposed a method for appropriate specification of the thermal boundary conditions in densely occupied environments. By analyzing the existent research work, it is found that the radiant heat transfer is reduced 50%-75% on the sheltered body surfaces with the neighbors, in which the radiant heat transfer coefficient is 2-3W/(m2- ℃) and the radiant heat transfer amount is only 50% of that are not sheltered. The conclusion is the similar for self-sheltered human body surfaces even for a single person. This research selected one row of seated passengers in a aircraft cabin as the object of study and set the thermal boundary condition as wall temperature of 29.9℃ and wall thermal flux of 55W/m2 of human body, respectively. The obtained results were compared with those obtained based on the proposed method. The measured body surface temperatures and surrounding air velocity speeds and air temperatures were utilized as the evaluation standards.It can be concluded that the existent work cannot reflect the influences of the neighbors to the human body thermal conditions. If the thermal boundary of the human body is set as 55W/m2, the body surface temperature would be higher than the reality. The reason is the reduced radiation heat transfer on sheltered body surfaces. The mutual shelter for each other sitting side by side decreases the radiation heat transfer coefficient, leading smaller radiation heat transfer rate than that on body surfaces that are not sheltered. Hence, if the total heat release amount is fixed, an appropriate decrease in the radiant heat flux of sheltered body surfaces and a small increase in the total heat flux on the front trunk surface can make the result more reasonable. This is the case either in the temperature distribution of body surfaces or the total heat release to the surrounding environment.