Research On View Factors In Radiant Air-conditioning Rooms

Indoor environment has significant influence on work efficiency and life quality for people. And we could create a more comfortable and energy-efficient artificial environment by using radiant air-conditioning system. In the study of radiation heat transfer and thermal comfort in a radiant air-conditioning room, we need to solve accurately the view factors between some surfaces, such as human body, floor, ceiling, floor, window, and so on.View factors in radiant air-conditioning rooms could be usually thought into two categories: View factors between enclosure structure surfaces and View factors between the human body and enclosure structure surfaces. Firstly, this paper detailedly introduced the research status of this two kinds of view factor in the domestic and international related topics and overviewed various calculation methods of view factor. Then, this paper derived the calculation formulas of view facto r between enclosure structure surfaces by using algebra method and boundary integral method, respectively. In the fourth chapter, the human body in sitting posture was simplified to a hexahedron. And the hexahedron model dimensions are identified because the surface area of the simplified model is equal to the effective radiation area. Finally, this paper got the semi-analytical calculation formulas of view factor between the human body and enclosure structure surfaces by using boundary integral method. The results were drawn into chart for easy of use and were compared with Fanger’s result who used camera method to obtain the view factor between human body and environmental surfaces.In the fifth chapter, this paper studied the view factors between human body and enclosure structure surface by using numerical simulation method. Firstly, combined with the the discrete calculation formula of view factor and effective radiation area, the mathematical model of numerical simulation is developed to solve the view factor between the human body and environment surfaces. Then, According to the GB/T 10000.88(Human Dimensions of Chinese Adult), a standard three-dimensional human model in sitting posture was established and the parameters about the model were analyzed and compared with others. Finally, this paper solved the view factor between the human body and wall, ceiling and floor. The numerical results were used to be compared with the semi-analytical solution formulas in the fourth chapter. this paper found that, firstly, the view factors between human body and the front structure surfaces are much higher than the view factor between the human body and the rear structure surfaces. Secondly, the semi-analytical formulas of the view factor are in good agreement with the numerical simulation results for the ceiling. When the length and width of the ceiling are greater than 2m(3m), the relative error between semi-analytical results and the numerical simulation results is less than 8.6%(3.6%). Besides, the relative error is getting smaller gradually as the increase o f ceiling dimetion. For the vertical wall, the semi-analytical results are also in good agreement with numerical simulation results. When the length and width of the wall are greater than 1m, the relative error is less than 2.7%. And when the wall dimentions are equal to 4m, the relative error is close to 0. After that, the relative error increases gradually and tends to be stable as the increasing of the wall dimetions, but is always less than 3%. For the floor, the relative error is about 7.5% when the floor dimentions is greater than 1m. And this paper has modified the error to lower than 1%.