Influence Of Solar Radiation On The Cooling Capacity And Load Of Radiant Ceiling

As a new type of terminal, the radiation air conditioning system has been widely used for its comfort, energy saving and so on. As large scale of transparent envelope is used in buildings like airport terminal, shopping mall and office building, the room receives more solar radiation from outside. If radiant air conditioning system is applied in such circumstances, lots of solar shortwave radiation can be absorbed by cooling surfaces directly. Based on the radiant ceiling system, the influence of solar radiation on the cooling capacity and load of radiant ceiling were systematically analyzed in the paper, and absorption factor method is presented to calculate the solar shortwave radiation which is directly absorbed by cooling ceiling.First, the fundamental structure and characteristics of the ceil ing radiant refrigeration system were introduced in the paper, and design steps and key points of radiation air conditioning system was briefly introduced. Based on the thermal equilibrium between the indoor environment, the surface of the radiant ceiling and the cold water loop, The reasons for the enhancement of the cooling capacity of the radiant panel caused by the solar short wave radiation are explained by the theoretical formula. And then based on the heat transfer mechanism of air conditioned room, cooling load differences between radiant and air systems and the adaptability of load calculation method to calculate the load of radiant air conditioning system were discussed. Studies have shown that when the RTS method was used to calculate the load of radiant air conditioning system equipped in buildings where solar radiation inside was strong, the solar radiation which was directly absorbed by the cold surface and the portion which first to be absorbed by the building envelope and indoor objects, and finally to be released in the form of convection must be distinguished. Finally, absorption factor method is presented to calculate the solar shortwave radiation absorptivity of metal cooling ceiling on the base of analyzing the process where solar radiation was absorbed by the cold surface. Based on a typical office room installed radiant ceiling panel system in Changsha, the influence of room size on solar shortwave radiation was studied. The results show that, even if the south envelope is low-e glass, 20% solar radiation received by the room is absorbed by metal cooling ceiling. Therefore, the influence of solar radiation on the cooling capacity and load of it must be fully considered.