Study On Thermal Performance Of Underground Cave Dwelling Under Thermal Charge-Discharge Performance Of Raw Soil Envelope

With the development of traditional aboveground building industry,its building energy consumption is also increasing.At the same time,the development and utilization of underground space has become an important direction of urban architecture development,so it is urgent to conduct research on underground architecture.At the same time,on the Loess Plateau of China,there exists a special kind of traditional underground architecture,which originated in the late Neanderthal Age-the underground cave dwelling.Its construction and operation energy consumption are lower than conventional above-ground buildings,but it can maintain a relatively comfortable and stable indoor thermal environment in extreme climate conditions.The experience of ecological design in excavation can provide reference for the sustainable design of modern underground buildings.To sum up,this paper supported by the National Natural Science Foundation project"Thermal Responsive Characteristics and Regenerative Design Evaluation of Raw Soil Construction in Western Henan"(Project No.51608486),takes a nearly centennial underground cave dwelling as the research object,and has carried out the following work:(1)A remote monitoring platform was built to carry out long-term monitoring on the thermal environment of a typical underground cave in Miaoshang Village,Shanxian County,Sanmenxia City,and a short-term field test was conducted on the thermal environment of the cave under the heating effect of the integrated Yaokang in the extreme cold climate in winter.The thermal characteristics of underground cave are analyzed throughout the year.The analysis shows that the indoor environment has a certain stability and is in a relatively comfortable temperature range compared with the drastic fluctuation of the outdoor environment under the natural operation state of the Yaokang.However,due to poor ventilation inside the Yaokang,the relative humidity is relatively high overall.The relative humidity exceeds 70%in 99.39%of the summer.Meanwhile,under the coupling action of the heating of the Yaokang and the good heat storage and release characteristics of the enclosure structure of the cave,the indoor air temperature is significantly increased and the stability is good,which improves the thermal comfort degree of the Yaokang to a certain extent.(2)In order to further explore the important role of facade in maintaining the stability of indoor thermal environment,based on the measured data,the thermal response mechanism of indoor and outdoor temperature waves on the facade of the cave was analyzed by using harmonic response method.The analysis shows that the hourly heat transfer of the facade can be decomposed into steady state heat transfer and additional heat transfer caused by internal and external disturbances respectively.Due to the additional heat transfer caused by thermal disturbance,the heat loss law of the facade is different from that of conventional buildings.The heat loss at night is lower than that in the daytime,which improves the stability of room temperature to some extent.In addition,the fluctuation range of convective heat flow on the inner wall of the facade is much greater than the heat transfer heat flow of the wall,the difference value is 599.01k J/m~2,that is,the heat stored by the wall,which is also the reflection of the heat transfer attenuation multiple of the heavy wall is much greater than the heat absorption attenuation multiple characteristic.(3)To provide the basis for optimization design,based on the thermal equilibrium theory,established the integrated heating furnace Yaokang sunken generates cave under the action of thermal process calculation model,through the measured data to validate the established model.The parameters of the Normalized average deviation NWBE(Normalized Mean Bias Error)and root Mean square Error CV(coefficient of variation of the root square Mean Bias Error)to evaluate the accuracy of the model,and analyze the cause of the error.(4)The thermal process model is used to solve the problem of high heat loss in the outer wall of the cave,and the measures of adding insulation layer and changing the wall structure are put forward,and the optimized thermal environment of the Yaokang is calculated and solved.The results show that the improvement of indoor thermal environment is not obvious when the insulation layer is added to the cave fa?ade.In addition,after the comparative analysis of indoor operating temperatures obtained under different Yaokang operation strategies,it is suggested that if conditions permit,intermittent combustion of Yaokang twice a day can reduce the amplitude of indoor air temperature and basically keep the room temperature above 10℃.The physical model of the sinking cave with Yaokang was established by using Airpak software to simulate the temperature and velocity fields of the Yaokang chamber under different space positions.The results of this study can provide theoretical basis and technical support for the green building design of rural residential buildings and the development and application of urban underground residential buildings.