Study On The Quantitative Relationship Between Surface-side Cooling Load And Water-side Cooling Load Of TABS Cooling System

In the current strategic background of social sustainable development,radiant cooling system has become one of the preferred forms of air conditioning system for low energy consumption buildings and green buildings due to its characteristics of comfort,energy saving and environmental protection characteristics.It has urgent application prospects.However,due to the great difference between the terminal heat transfer mode and the traditional convection air conditioning system,some design theories of the traditional air conditioning system are not applicable to the radiant air conditioning system.The existing load calculation theory of air conditioning is mainly proposed for flow type air conditioning system.The existing load calculation methods,such as heat balance method(HBM),radiation time series method(RTSM),cooling load coefficient method and other calculation methods are used to calculate and determine the room cooling load.In engineering,room cooling load is also used as an important parameter for the selection of equipment at the end of air conditioning and the cold source side.As for the TABS System(Thermally Activated Building System,also known as concrete radiant cooling system),due to the thick concrete structure between the radiant cold surface and the water supply coil,the cooling capacity of the water supply coil(water side cooling load)and the cooling capacity of the radiant surface(surface side cooling load),That is,the room cooling load)affects each other but is different.In the traditional sense,the room cooling load calculated is the cooling capacity to be provided by the radiant cooling surface.The area of the radiant cooling surface and other parameters should be determined according to the room cooling load,while the selection of the equipment at the cold source side should be based on the water side cooling load.However,the existing research lacks the understanding of the quantitative relationship between the two kinds of loads and the method of determining the water side load from the surface side load.Based on the above research background,the heat storage time factor series method was proposed to quantify the relationship between water side load and surface side load in the TABS system.The heat storage time factor was studied and derived,and the heat storage time factor series of typical tubular structure was established,and the influencing factors of the heat storage time factor were analyzed.The main research contents and conclusions are as follows:Firstly,the heat storage time factor sequence method was proposed to quantify the transformation relationship between surface side load and water side load.The heat storage time factor sequence was derived by the transfer function method,and the calculation method of "heat storage time factor" was established.This method considers two conditions of continuous operation and intermittent operation.The water side cooling load can be calculated by surface side cooling load(room cooling load),and then the equipment selection of cold source side can be carried out.Then,the accuracy of the heat storage time factor sequence method established in this study is verified by experiments in the radiation-cooled climate chamber.The results show that the average relative errors of calculated values and experimental values are 2.97% and 4.48%respectively in continuous and intermittent operation,which proves the accuracy of the method.Then,12 groups of heat storage time factor sequences were calculated when the typical tube structure was applied to residential buildings and office buildings,and two working conditions of continuous and intermittent operation were considered.The heat storage time factor sequence of typical tubular structure can be directly applied to the calculation of water side load in engineering design.Under continuous working conditions,the time of peak water side load can be estimated by the heat storage time factor sequence.Finally,the influence of various influencing factors on the heat storage time factor is analyzed from three aspects: the heat storage characteristic index of the tube structure,the thermal physical property parameter of the concrete and the design parameter of the tube structure.Meanwhile,the sensitivity of the heat storage time factor to the design parameter of the tube structure is discussed,and the key parameters affecting the heat storage time factor are determined.The results show that the peak clipping and peak shifting of heat storage time factor are mainly affected by the volume heat capacity of the tube structure,and the thermal conductivity only affects the peak clipping effect.The influence of the design parameters of the tube structure on the heat storage time factor is discussed.When the peak value of the heat storage time factor is the output value,the sensitivity of the buried pipe depth,concrete thickness and pipe spacing is greater than 0.6,and the sensitivity of the water supply parameter is less than 0.35.When the variance of heat storage time factor is output,the sensitivity of buried pipe depth,concrete thickness and pipe spacing is greater than 1.5,and the sensitivity of water supply parameters is less than 1.It can be concluded that the heat storage time factor is mainly affected by the structure of the tube,and the influence of water supply parameters is low.The main influencing factors of heat storage time factor are buried pipe depth and concrete thickness.The research results of this paper will help improve the load calculation theory of the TABS system,improve the load calculation accuracy,reduce the unreasonable equipment selection caused by inaccurate load calculation,and provide theoretical guidance for the optimization design of the system.