Reserach On System Optimization Of The Hybrid System With Floor Radiant Cooling And Fresh Air Unit

In order to improve the indoor thermal comfort of buildings in the mid and down reach of Yangzi River areas with hot summer and cold winter,the radiation terminal has been widely used in recent years because of its high comfort and energy saving features.However,the radiation cooling system which is running alone has the problems of long response time and condensation.Radiation cooling+fresh air composite air conditioning system has the advantages of good indoor comfort,improving the cooling capacity of radiation terminal,improving the condensation problem of radiation surface and saving more energy than traditional air conditioning system,but the combined operation mode and fresh air parameters of the composite system are still unclear.Under this background,combined with theoretical calculation,numerical simulation and experimental test,this paper analyzes the operation mode of floor radiant cooling+fresh air composite system under different comfort needs,indoor comfort and operation parameters of floor radiant cooling+fresh air composite system under different fresh air parameters and the operation performance of existing fresh air unit under different outdoor conditions.In this paper,the control range of indoor temperature and relatively humidity in the intermittent operation of radiation and convection air conditioning system in the cooling season under two kinds of comfort needs is defined.Energy Plus is used to simulate the indoor thermal comfort of the compound air-conditioning system of fresh air+floor radiant cooling under two comfort needs,six startup modes and four shutdown modes.Through comparative analysis,it is concluded that when the indoor temperature and relatively humidity control range is acceptable,the economic operation mode of the compound air-conditioning system of fresh air+floor radiant cooling is that the fresh air unit and floor radiant cooling open at 18:00 p.m.in weekdays,the floor radiant cooling turnes off at 0:00 p.m.and the fresh air unit operates in cooling and dehumidification mode all night;on weekends,the floor radiant cooling turns on at 9:00a.m.and turns off at 0:00 p.m.,and the fresh air unit operates in cooling and dehumidification mode all day.When the control range of indoor temperature and relatively humidity is comfortable,the comfortable operation mode of the composite air conditioning system of fresh air+floor radiation cooling is that the fresh air unit and floor radiation cooling open at 16:00 p.m.in weekdays,and the rest are the same as the economic operation mode.Energy Plus is used to simulate the operation of the compound air conditioning system when the dry bulb temperature and moisture content of the fresh air are 16.3℃/10.4g/kg,17.3℃/11.1g/kg and 18.2℃/11.8g/kg respectively.The simulation results show that there is no condensation on the radiation surface under the three parameters,and the thermal comfort evaluation indexes LPD₁ and LPD₃ meet the level I comfort.When the fresh air parameters are 18.2℃/11.8g/kg,the indoor thermal comfort is similar to the other two conditions,and the system uses this parameter to run with the lowest energy consumption and the highest energy efficiency,which is the best fresh air parameters.Energy Plus is used to simulate the operation of split air conditioner in the cooling season under two comfort demands.The results show that when the indoor temperature and relatively humidity control range is acceptable,the energy consumption of composite system in the cooling season is 6.2%lower than that of split air conditioner,and the energy efficiency ratio in the cooling season is 17.5%higher than that of split air conditioner;when the indoor temperature and relatively humidity control range is comfortable,the energy consumption of composite system in the cooling season is similar to that of split air conditioner,but the energy efficiency ratio of composite system is 25.4%higher than that of split air conditioner.Through the experiment,the operation parameters of a ducted type air conditioner are tested when the outdoor dry bulb temperature and relative humidity are 27℃/71.7%and 35℃/81.3%respectively.The results show that when the outdoor parameters are 35℃/81.3%,the dehumidification capacity of the unit can not meet the wet load.Therefore,this paper puts forward a new type of multifunctional fresh air unit for radiant air conditioning,introduces its internal structure,working principle,four operation modes applicable to different needs and the actual operation method of each unit’s internal equipment under each operation mode,which provides a technical reference for the application and promotion of fresh air+floor radiant cooling composite system.