Research And Application Of Numerical Calculation Model For Heat Transfer Coefficient Of Enclosure Structure In Sludge Composting Workshop

With the increase of people’s awareness of environmental protection,the utilization of sludge in urban sewage treatment plants has gradually become the focus of research.In the process of composting,the sludge releases a large amount of toxic pollutants such as heat and ammonia.The heat not only kills pathogenic bacteria in the sludge,but also reduces the amount of water in the sludge to 30%by evaporation.The following,in order to meet the requirements of organic fertilizer.The moisture in the sludge is emitted into the air in the form of water vapor,causing the entire composting plant to be in a state of high temperature and high humidity.In winter,when the inner surface temperature of the building envelope structure is lower than the dew point temperature of the surrounding air,condensation will occur on the wall surface.Indoor condensation will not only make the building envelope damp and mold,affecting the life of the building.When the condensation area is melted and dripping into the piled material,it will also affect the compost cycle and composting effect.The heat transfer coefficient of the envelope structure of the composting workshop will be studied.The selection of parameters in engineering design is of great significance.This paper takes the physical model of a sludge composting workshop in Zhengzhou City as the research object.Through the analysis of the indoor thermal and humid environment,the critical condensation of the wall and the heat transfer of the envelope,the building of the sludge compost workshop envelope structure is established.Thermal coefficient numerical calculation model.Based on the heat balance equation in the numerical calculation model and the internal and external surface heat transfer formulas of the wall,the internal surface temperature of the envelope of the compost workshop was calculated and the temperature of the interior surface of the roof was calculated using the DeST heat flow module.The results were compared and verified.The research results show that the numerical calculation model constructed in this paper can be applied to engineering design.According to the numerical calculation model of the heat transfer coefficient of the enclosure structure of the composting workshop,we studied the five major thermal zones in China’s climate:Shenyang in cold regions,Zhengzhou in cold regions,Hangzhou in hot summer and cold winter regions,and Guangzhou and mild regions in hot summer and warm winter regions.Kunming in the region.The heat transfer coefficient of the envelope structure of the sludge composting workshop in a typical city is the most unfavorable factor due to the fact that the roof is the enclosure with the largest heat loss in the sludge composting workshop.It is calculated on the premise that the roof does not form condensation.The maximum allowable heat transfer coefficients for composting roofs in Shenyang,Zhengzhou,Kunming,Hangzhou,and Guangzhou were:0.582 W/(m~2·K),0.823 W/(m~2·K),0.994 W/(m~2·K),0.998W/(m~2·K),1.142 W/(m~2·K).