| The evaluation of the thermal performance of the building envelope is the premise of building energy-saving design,and the operation of the buildings will often have an impact on the thermal performance of the envelope.In the current energy-saving design standards,the evaluation of the thermal performance of the envelope structure is based on the indoor thermal environment model of continuous heating and air-conditioning operation.However,the actual mode of residence using is the intermittent mode,which is combined heating and air-conditioning and natural ventilation throughout the year.Therefore,this paper takes Chongqing as an example to analyze the thermal performance of different envelopes under different conditions by using simulations of different types of building envelopes under the year-round usage mode.The purpose is to estimate the thermal performance of the building envelope in engineering applications.In this paper,the heat transfer theory of the envelope is firstly combed,and the three main factors affecting the thermal performance of the envelope structure are determined: the structure type,the heat transfer coefficient and the thermal inertia index;Then select an independent room to measure the thermal performance of its external walls under different conditions,and evaluate the response relationship of the thermal parameters of the envelope to different climates,and analyze the energy saving potential of the external wall design under different conditions,and use the experimental data to verify the validity of the software;Finally,a residential building in Chongqing was selected to simulate the indoor temperature of typical households under the year-round usage model,which was used as the internal boundary conditions of the WUFI software,and then the different envelope structures were simulated respectively.There are following results:For the external wall structure,the internal thermal insulation wall is conducive to energy conservation,but the inside surface temperature of the external thermal insulation wall has a smaller amplitude.The effect of heat transfer coefficient on cooling energy consumption in summer is less than that of heating energy in winter.On the contrary,thermal inertia index has a greater impact on summer cooling energy consumption than winter heating energy consumption,but its effect is not as good as that of heat transfer coefficient.By increasing the thermal inertia of the wall,the annual energy saving rate of the internal wall insulation is 5.3%~12.5%,and the external insulation is usually lower than 10%.In addition,in the weather mainly based on intermittent ventilation,the thermal inertia index and the heat transfer coefficient of the external insulation wall have the same effect on the improvement of the indoor thermal environment.When the indoor comfort requirements are the same,the wall with a large heat transfer coefficient can increase the thermal inertia to compensate it,and vice versa;the thermal inertia index of the internal insulation wall will determine the heat transfer coefficient: When the thermal inertia is less than 3,the smaller the heat transfer coefficient,the lower the internal surface temperature is;when the thermal inertia is greater than 4,the greater the heat transfer coefficient,the lower the internal surface temperature is.For roofs,the variation of the minimum value of internal surface temperature in winter is consistent with that of the wall,but in the passive condition of winter,when the heat transfer coefficient of the roof is fixed,the minimum temperature of the internal surface increases first with the increase of the thermal inertia index of the roof,and then,it decreases.In the summer,under the same thermal parameters,the maximum temperature of the inner surface of the roof is significantly higher than that of the western wall.Therefore,in order to ensure the co-operation of the roof and the wall,the thermal performance of the roof is higher than that of the wall. |
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