Experimental And Numerical Research On Indoor Thermal Environment With Radiant Floor And Optimization Of Operation Strategy

With the development of science and technology,the HVAC system not only needs to meet users’ requirements for the indoor environment,but also needs to meet the requirements of building energy efficiency.Especially in recent years,radiation air conditioning system have been promoted in the market,and the utilization rate in buildings with large windows has gradually increased.In the environment,both solar radiation and radiation air conditioning system will have a huge impact on the indoor thermal environment.Therefore,it is necessary to study the influence rules of these two factors,so as to formulate an effective operation strategy of radiation air conditioning to guide users and achieve the purpose of reducing energy consumption.This paper mainly studies the a projection area formed by solar radiation on the surface of radiant floor and its surface temperature law,and explores the influence of the projection area on the indoor environment.The indoor air temperature,mean radiation temperature,operation temperature and PMV were compared at different time and setting temperature of radiant floor to explore the influence degree on indoor environment.And the paper calculating heating capacity of different working conditions and energy consumption,the optimization strategy of radiant floor operation is proposed.Firstly,the paper introduced the research and development status quo of the radiant floor,then briefly expounds the research results of the effect of solar radiation on the heat transfer characteristics of the radiant floor,and analyzes the shortcomings of the existing research.Secondly,the composition of the radiation air conditioning system and the heat transfer process in the room,as well as the indoor thermal environment evaluation indicators such as air temperature,mean radiant temperature are introduced,and the corrected value of operation temperature and PMV-PPD is cited,which takes the solar radiation into account value,so that the evaluation results are closer to reality.Thirdly,the study takes the experimental room on the roof of a building in Changsha as the object,and uses the solar radiation and the setting temperature of the radiant floor as variables,which can obtain the variation rules of the indoor environment with time.Then,the CFD numerical simulation is used to obtain the floor surface temperature and the air temperature distribution rules of the working face with Z=0.75 m.Finally,based on the experimental and simulation results,the operation effect of the radiant floor system and the indoor environment is evaluated.The results show that the solar radiation forms a projection area on the floor surface,and the temperature is not uniform.The temperature difference between the two areas in winter is greater than 15 ℃,and the maximum temperature difference between the two areas in summer is 27 ℃.The uniformity of floor surface does not affect the uniformity of indoor air temperature;indoor air temperature and mean radiation temperature change regularly with the intensity of solar radiation and there is a delay effect,and solar radiation makes indoor air temperature and mean radiation temperature increase by 9 ℃ ～ 10 ℃;The correction values of operative temperature and PMV describe the indoor environment which is affected by solar radiation,and the change of the correction value of the operative temperature has no delayed effect relative to the solar radiation,indicating that the solar short-wave radiation has a more significant impact on the operative temperature than the convection and long-wave radiation.Therefore,the correction values should be used.Finally,this paper proposes that the radiant floor can effectively use the solar radiation energy to reduce the total heating or cooling capacity,which can reduce the energy consumption of air conditioning: the setting heating temperature of the radiant floor can be reduced by 6 ℃,and the total heating capacity of the heating system can be reduced by 47 kW;The setting temperature of the cooling system is increased by 6 °C,then the indoor temperature is only increased by 2 °C;According to the variation rules of solar radiation,it is proposed that the heating mode in winter should be operated by time period and intermittent operation mode,and the cooling mode in summer should be operated by time period.