Study On The Process And Characteristics Of Building Load Formation In Large Space Under Radiant Floor Cooling

With the development of economy,more and more large space buildings begin to appear,such as terminal buildings,railway stations and so on.There are several shortcomings when the all-air conditioning system is applied to these buildings,such as unfriendly thermal comfort and large energy consumption,while the floor cooling system is free from these problems.It is more suitable for popularization and application in large space buildings with the characteristics,such as temperature and humidity independent control,low energy consumption,friendly thermal comfort and energy saving.It is based on the accurate calculation of the building load to promote the use of radiant floor cooling system in the large space buildings,and there is a big difference between the load formation principle of radiation cooling system and traditional all-air conditioning system.The existing harmonic response method and the cold load coefficient method can only be used for traditional convection air conditioning system,which are not applicable to the radiation cooling system.In this paper,energyplus software is used to simulate the load consumption of large space buildings,which plays an important role in the study of load calculation in the field of large space building radiation cooling system,and provides theoretical guidance for the design of cold radiation floor.In this paper,introduced the radiant floor cooling system and analyzed the heat conduction process of radiant floor.The background,development history and selected mathematical model of energyplus software are introduced,and then the floor radiating cooling system and the all-air conditioning system are built in Legacy OpenStudio plugin and energyplus software,the load is calculated using the heat balance method.Studied the load characteristics of the two air conditioning systems,and the main affecting factors to cooling load differences are analyzed at last.The main conclusions in this paper are as follows:(1)The peak cooling load of the radiant floor cooling system is 161.1W/m2,while the all-air conditioning system is 142.7W/ m2,and the maximum load difference is 11.4%.(2)The maximum cooling load difference between the all-air conditioning system and the radiant floor cooling system increases with the increase of the window-wall ratio of the outer envelope.The peak load of the radiant floor cooling system is larger than that of the all-air conditioning system,the maximum load difference is 11.6%.(3)The significant influencing factor of the load difference between the all-air conditioning system and the radiant floor cooling system is window-wall ratio of building.This is because when the window-wall ratio of building is large,the solar radiation in the room is more,the floor radiation cooling system can be directly removed part of the radiation heat,while the surface of the envelope in the all-air conditioning system absorbs solar radiation,and then releases into the room,which will form convection cooling load,but there is a delay in this process,so the load peak of the all-air conditioning system lags behind and the value is smaller.(4)The maximum cooling capacity of the radiation floor is 57.4W/m2 and the delay time of the concrete slab material is 3 to 4 hours.The floor can directly remove the solar radiation from the surface,so the floor radiation cooling capacity and direct radiation to the floor of the solar radiation is positively correlated.(5)Under the same conditions,the peak power consumption of the radiant floor cooling system is 22.4 kWh/m2,while the all-air conditioning system is 31.6kWh/m2.The total power consumption of the radiant floor cooling system is 86.3 kWh/m2,while the all-air conditioning system is 124.9 kWh/m2,compared to the all-air conditioning system,the radiant floor cooling system saves 30.9% power consumption,this is because the average temperature of the radiant floor cooling system is low,and it use high temperature cold water,which leads to the COP value of the air conditioning system is high,and reduces the power consumption;the specific heat capacity of water is greater than air,water flow is small,the energy consumption of the pump is reduced accordingly;the floor radiation cooling systems is combined with ventilation,which makes the air volume less than the whole air system,and reduces the energy consumption of the fan,so the power consumption of the floor radiation cooling system power consumption is smaller.In summary,the floor radiation cooling system is more energy-saving in large space building.