Study On Thermal Field Change Of Closed Space Environment Under Convection-radiation Heat Exchange

With the continuous improvement of the quality of life,people are increasingly demanding a more comfortable thermal environment in which they work and live.It is a main trend of using composite heating end for building heating in winter because the single heating method can not meet the requirements of thermal comfort for indoor person.Heating energy consumption is an important part of building energy consumption for the regions where need heating in winter.In order to meet both the demands of indoor heating and reduce the energy consumption,the study proposed a new composite heating end with air source heat pump as the heat source.This paper used CFD simulation software to simulate the indoor thermal environment and operation mode of the new composite heating end,followed by establishing the mathematical model and physical model via ICEM pre-processing software.By adjusting different structural parameters and operating parameters such as radiant panel area,radiant panel mounting position,air supply speed,radiant panel surface temperature,and air supply angle,we analyzed and compared the changes of indoor temperature field,vertical temperature difference and velocity field under different conditions,then determined the most suitable structural and operating parameters for the model combined with the calculated PMV values at 0.1 m around the human body.The simulation results showed that the air temperature in the room was higher under the conditions,such as the closer of the radiant panel placed to the ground or the outer wall,the larger areas of the radiant panel,the higher surface temperature of the radiant panel,and the higher the blowing speed.When the radiant panel was installed on the north wall,the radiant panel area was 2.0 m~2,the bottom was 0.7 m away from the ground,the panel surface temperature was 28?,the air supply angle was 60°and the fan air supply speed was 1.0 m/s,the indoor airflow movement verified better.Here,the PMV value at 0.1m around the simulator was between-0.5 and+0.5.The start-up characteristic simulation study showed that when the opening time of the composite heating end was earlier,the indoor heating effect was better and the indoor average air temperature was more stable.However,all the simulated starting schemes should meet the demands of the indoor heating at the early stage.Integrating the simulation of the system operation mode,it was found that the energy consumptions of the system were the lowest when switching points at 22?.Because of the uncomfortable feeling of human body in this office environment,the mode switching point was selected at the temperature of 20?in the end.It was calculated that in the same heating cycle,the composite heating can save energy by 13.0%compared with the simple use of the radiant panel for heating indoors.The research work of this subject provided a new view for composite heating,put forward a useful reference for optimizing the composite heating operation mode and some supports for the composite heating for low energy operation.