The Research On The Effect Of Building Ground Structure Heat And Moisture Transfer On The Indoor Humidity Environment And Air-conditioning Load

It is often occurs the phenomenon that building ground surface wet accumulation.When the wet accumulation is serious,it may cause bacterial growth,and damage to the building structure.At present,the determination of the hygrothermal state of the building ground mostly ignores the heat and moisture transfer of the ground or using the insulation ground,while the wet state of the building ground floor is the combined effect of the underground wet components reaching the ground surface and the condensation of wet air on the cold ground surface.As a result,for the cities rich in shallow underground water,the phenomenon of ground wet accumulation is more serious,which affects the indoor humid environment and air conditioning load.Therefore,this paper analyzes the influence of ground heat and moisture coupling transfer process on indoor environment and air conditioning load through the combination of theoretical analysis and simulation methods,especially considering the influence of different shallow groundwater depths.In order to obtained the soil thermal boundary,the temperature distribution of the underground soil was calculated by two-dimensional soil heat and moisture transfer before the calculation of the building heat and humidity.The conclusions are as follows: In the hot and humid area(Wuhan),considering the moisture transfer,the ground structure desorb moisture under the water vapor pressure gradient during the air conditioning,and the latent heat exchange causes the surface temperature decreased.If the ground structure moisture transfer is not considered,the air conditioning cold load will be excessive estimated 21.7%,and the latent heat flux of the ground surface greatly increased,lead to the wet load greatly increased,and eventually lead to the total load of air condition increased;As for the hot and dry areas(Xi'an),the ground structure is in the moisture absorption zone in whole-day,and considering the moisture transfer,the temperature of the ground surface is slightly increased,but the change of the heat and moisture flux is not obvious;When considering the unground water,the shallower the groundwater,the larger the water content of the top layer of the ground structure,and its influence on the temperature and humidity of the indoor ground surface is more obvious,based on the condition of no groundwater,underground water at 5~0.5m depth,the ground temperature is reduced from 1.2%~ 6.5%,the relative humidity is increased from 2.0%~ 11.4%,the heat flux is increased 5.8~ 25.5 times,and the wet flux is increased from 13.7%~ 28.4%.It can be seen that if the influence of groundwater is not taken into account,the hot and humid areas will be overestimated when predicting the cold load of the house,resulting in energy waste and low wet load prediction,resulting in wet accumulation.Aiming at the problem of building ground floor moisture accumulation,two three preventive measures was studied: damp-proof insulated ground and overhead grounds.Then,the positive effects of the improved ground structure on the indoor environment and energy consumption control were analyzed.The conclusions are as follows: The optimum insulation thickness of the damp-proof insulation floor is 140 mm.Compared with the ordinary concrete floor,the relative humidity of the ground surface is reduced about 18.5%,and the water content is reduced about 49.5%,so the ground wet problem is controlled.For the air-conditioning load,the wet flux of the ground surface is reduced about 39.0%,which greatly reduces the wet load;But for the overhead layer,it is more significant,the relative humidity of the ground surface is reduced about 23.2%,the moisture content is reduced about 53.2%,and the wet flux is reduced about 37.9%,yet the overhead ground causes the outer boundary of the ground structure to be exchanged with the outdoor air,so that the ground temperature and humidity are close to the outdoors' data,so the heat flux through the ground is large,and the cooling load is increased.The above research obtained the effect of building ground structure heat and moisture transfer on the indoor humidity environment and air-conditioning load,that provided the basis for accurate calculation of indoor environment and load.Then,the research studied the ground wet prevention measures,effectively solving the problem of ground moisture accumulation.