| The building facade is the largest part of the building envelope and has a significant effect on the energy consumption of the building.The optical parameters of the building facade are parameters to evaluate the ability of the enclosure to absorb,reflect and transmit sunlight.Changing the optical parameters of the facade enclosure can effectively adjust the amount of absorption,reflection and transmission of sunlight,thus changing the net heat gain of the facade enclosure.However,different building envelope exterior finishes and envelope types have different exterior surface optical parameters,and the energy distribution of visible and infrared wavelength bands in solar energy changes with time and space,and the optimal optical parameters of the exterior surface of the envelope also change,therefore,studying the relationship between the optical parameters of the visible and infrared wavelength bands on the exterior surface of the fa?ade envelope and the building energy consumption can help the fa?ade envelope Therefore,the study of the relationship between the optical parameters of the visible and infrared wavelength bands of the facade envelope and the building energy consumption can contribute to the energy-saving renovation of the facade envelope and the energy-saving research of the solar spectrum adjustable envelope materials.In this paper,based on the meteorological conditions of typical days in summer and winter in Nanchang,Jiangxi,the heat transfer process of the south-facing envelope of residential buildings in this area was simulated numerically,and in order to obtain the relationship between the optical parameters of the south window and south wall surfaces and their temperature and heat gain,the D-optimal response surface method was used to optimize the heat transfer test design of the south window with different visible absorbance,visible transmittance,infrared absorbance and infrared transmittance of the exterior surface,and the 3~2-analysis factor test design method was used to optimize the heat transfer test design of the south wall with different visible absorbance and infrared absorbance of the exterior surface,and the following are the main results of this paper:(1)The surface temperature of the envelope is related to its heat transfer process and characteristics,so this paper investigates the effects of different external surface optical parameters on the surface temperature of the south exterior windows and the south exterior wall,respectively,and draws the following conclusions:(1)For the south-facing window,both the visible and infrared absorbance of the exterior surface are significant parameters that affect the temperature of its exterior and interior surfaces,compared to the visible and infrared transmittance of the exterior surface,which have essentially no effect on it.As the total southward solar radiation increases,the difference in the maximum surface temperature of the south exterior window caused by the different visible and infrared absorbance of the exterior surface becomes larger,compared with the south exterior window with zero visible and infrared absorbance of the exterior surface,the maximum temperature of the exterior and interior surfaces of the south exterior window with 1 visible and infrared absorbance of the exterior surface is about 1.3℃ and 1.1℃ higher in summer,respectively,while the maximum temperature of the exterior and interior surfaces of the south exterior window in winter is about 13℃ higher.In addition,with the change of visible and infrared absorbance of the exterior surface,the temperature difference between the exterior surface and the maximum temperature of the interior surface of the south exterior wall in summer varies very little,but in winter there is a more significant difference.(2)For the south facade,the visible absorption rate of the exterior surface has very little effect on the interior surface temperature of the south facade in summer,but the degree of effect on the interior surface temperature of the south facade in winter is comparable to the infrared absorption rate.Regardless of how the visible absorption rate and infrared absorption rate of the external surface change,the temperature of the external surface of the south facade is always higher than the internal surface temperature during the daytime in summer,and the heat is always transferred from the outside to the inside,but in winter,the temperature of the external surface of the south facade may be higher than the internal surface only when the sum of the visible and infrared absorption rates of the external surface is greater than 0.5.(2)The heat gain of the envelope has a direct relationship with the energy consumption of the building,so this paper analyzes the influence of different external surface optical parameters on the heat gain of the south window and the south facade,and the main conclusions obtained are as follows:(1)In summer,the visible transmittance of the exterior surface has the most significant effect on the heat gain of the south window,while in winter,the optical parameter that has the most significant effect on the heat gain of the south window is the infrared transmittance of the exterior surface.When the visible transmittance and infrared transmittance of the exterior surface are 1,the maximum instantaneous heat gain of the south window is about 289 W/m~2 and 175 W/m~2 in summer and winter,respectively.In contrast,the visible absorbance and infrared absorbance of the exterior surface have less influence on the heat gain of the south window,which indicates that the heat gain of the south window is mainly composed of the heat transmitted by solar radiation,and the heat gain from secondary heat transfer is smaller.(2)Whether in summer or winter,the influence of optical parameters on the heat gain of the south facade is smaller than its influence on the heat gain of the south window,and the maximum instantaneous heat gain of the south facade in summer can reach 21.62W/m~2 when the visible light and infrared absorption rate of the external surface are both 1,but it is less than one tenth of the maximum heat gain of the south window,therefore,regulating the heat gain of solar radiation through the external window will be a more effective way to save energy in buildings.Therefore,regulating the heat gain from solar radiation through external windows will be a more effective way to save energy in buildings.(3)Calculate the total net heat gain of the above two facade envelopes for the whole day under different optical parameters of the exterior surface,and use the regression analysis method to get the relationship models between the total net heat gain of the south window and the south facade for the whole day and the above optical parameters,and their correlation coefficients reach above 0.9.After validating the above models with external data,it can also be proved that all the above regression models have good accuracy and prediction. |
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