Optimization Of Intermittent Regulation Of Tube-embedded Building Envelope Cooling System In Residential Buildings

The radiant cooling system has many forms,this paper studied the tube-embedded building envelope cooling system,the system can also be called “Thermally activated building system”,it's structural form is that the cooling pipe is embedded in the concrete slab at the beginning of the building,the concrete is used as the carrier of cold quantity to participate in the thermal process of the room,for the air conditioning system,the whole tube-embedded building envelope is used as the ends of radiation to adjust the thermal environment of the room.The system has high comfort and potential of energy saving,at present it has been paid more and more attention by researchers at home and abroad.Because the physical properties of concrete material itself,the concrete has higher thermal inertia,and the thermal inertia performance is cold delay characteristics in the tube-embedded building envelope cooling system,there is a response time difference between the opening of the cooling system and the thermal environment of the room.Therefore,the tube-embedded building envelope cooling system is different from the convection air conditioning system in the control mode,it is the existence of concrete heat storage effect that the difficulty of the system to regulation is increased.But it also provides a new idea for the regulation strategy of the system,which provides the possibility of intermittent regulation.In the practical engineering application,in order to avoid the condensation phenomenon of cold slab when the room humidity is too large,it can bring unsafe factors to the system,the radiation cooling system is often combination with the displacement ventilation system.This paper is aimed at residential buildings to studies the optimization of the intermittent control strategy of the tube-embedded building envelope cooling system.In view of the structure shape and characteristics of the tube-embedded building envelope cooling system,this paper gives a brief overview of the system.In order to make reasonable intermittent cooling control scheme,this paper taken TRNSYS as the simulation platform,a typical residential building with three bed-rooms,two halls and two toilets as the research object,the tube-embedded building envelope cooling+displacement ventilation composite system is adopted,according to the rules of the residential building personnel work and rest time table,the room thermal disturbance factors are set.Through computersimulation,the dynamic response of the room thermal environment under the triple disturbance of external disturbance,internal disturbance and intermittent cooling is analyzed,based on the basis of comfort and energy consumption,in order to find the evaluation methodology of dual-objective optimization in terms of optimal energy consumption and comfort optimal,in this paper energy consumption index a and unsatisfactory index b are introduced,the best working points is the lowest point of energy consumption index a and unsatisfactory index b,the thermal process of the room was analyzed under different cooling time and different distribution of cooling time,and finally the optimal intermittent cooling scheme was obtained.The results show as follows: Firstly,on the basis of satisfying the room thermal comfort and system security,the existence of concrete heat storage effect makes the system can also adopt intermittent control strategy in residential buildings and realize the purpose of peak load transfer and utilizing the power price of trough.Secondly,after weighing the room comfort and energy consumption,this paper provides 2 cooling time scheme for tube-embedded building envelope cooling system of the residential building in Xi'an region,respectively for 6hours(18:00-0:00)and 8 hours(18:00-2:00).Thirdly,as for thermal process of the room,intermittent cold and external disturbances have great influence on the heat flux density of the cooling components,while the internal disturbance factor is not obvious.Under the same cooling time,using the different distribution of cooling time,controlled by the start-stop time the pump,can reinforce the concrete's ability of transferring heat between outside and inside,and releasing the cold energy stored in the concrete effectively.Based on comparative analysis,the best cooling time distribution scheme for residential building is obtained.Fourthly,under the condition of different distribution of cooling time but the same cooling time,it is not the case that the more frequent start and stop of the pump,the greater amount of cold will be carried by the embedded pipe,the specific working conditions should be particularly analyzed.Fifthly,during the simulation,if the heat flux density of non-cooling envelope is always negative,it indicates that the heat is transferred into the room.If The heat flux density of the cooling component is always positive,it indicates that the cold flow is transferred into the room.so the heat flux indicates the transmission direction of the heat flow.When the indoor load increases,the cooling envelope will reduce the indoor temperaturefluctuation to a certain extent by releasing more cold.