Study On Optimization Of CRCP-DOAS Air Conditioning System Based On BES-CFD Co-simulation

With the continuous development of social and economic level,people have higher and higher requirements for the indoor comfort of living and working environment,which leads to high energy consumption in buildings.A more comfortable,healthier,more energy saving and green air conditioning system has become one of the key topics of current research.In recent years,the hybrid air conditioning system,which combines ceiling radiant cooling panel(CRCP)and dedicated outdoor air system(DOAS),has attracted more and more attention because of its high comfort and energy efficiency.At present,due to the lack of comprehensive guidance in the design of CRCP-DOAS air conditioning system,its indoor design parameters still follow the recommended value of convective air conditioning system,so it is inevitable that the system cannot achieve the expected effect of energy saving and comfort after being put into use.Load ratio(sensible load removed by radiant terminal / total indoor sensible load)has been widely studied by scholars,which is an important design parameter of the system,but all the researches are single objective optimization of load ratio based on energy consumption and thermal comfort respectively.However,in practical engineering applications,the energy efficiency,comfort,safety ought to be considered at the same time to optimize the load ratio.In addition,there is no detailed introduction and recommendation on the selection of indoor temperature design/control parameter type and reasonable value range in the national standard.In order to study the system energy consumption and indoor thermal environment of CRCP-DOAS air conditioning system under different design parameters,BES-CFD coupling simulation was introduced in this paper.Taking a residential building with CRCP-DOAS air conditioning system in Changsha as a research case,the energy consumption and indoor thermal environment of the system under different load ratio and different air supply temperature difference are analyzed.In addition,taking air temperature,mean radiant temperature and operative temperature as indoor environment control parameters respectively,the correlation between control parameters and indoor thermal comfort is analyz ed,so as to obtain the optimal control parameter type.And then the influence of different setting values of the control parameter on thermal comfort is analyzed.The results show that under the same air supply temperature difference,with the increase of load ratio,energy efficiency increases,while thermal comfort decreases.Under the same load ratio,with the increase of supply air temperature difference,energy efficiency increases,while thermal comfort decreases.The condensation risk of the system is less affected by the temperature difference of supply air and the load ratio,and there is no condensation risk under all design parameters.The optimal load ratio ranges under comprehensive consideration of energy efficiency,thermal comfort and safety are 46%～74%(4℃),16%～59%(6℃),3%～50%(8℃).In addition,all the three types of control parameters have a strong correlation with thermal comfort.Considering the system cost,air temperature is still a more appropriate type of control parameter for the system.Since the ceiling and floor of the house are both cooling panels,the radiant heat transfer between the human body and the surface is bigger,so the range of design air temperature to satisfy thermal comfort is bigger,varying from 26.2℃ to 28.8℃.The research results of this paper can provide theoretical guidance for the design of CRCP-DOAS air conditioning system in similar residential buildings.