Moisture Transport Of Envelop On Energy Consumption Effect Of Cold Storage

As one of an important facility for whole cold chain logistics for fruits and vegetables from harvesting and selling,the energy consumption of the cold storage during operation has always been a concern.The heat transfer through the enclosure is one of the important factors affecting the energy consumption of a cold storage.Morever,the wet migration process existing inside the enclosure will further increase the energy consumption of the cold storage.Therefore,it is significant to study the influence of the envelope wet transfer process on the energy saving operation of the cold storage.This paper takes a 100 t civil type apple cold storage of Shaanxi Provence for object.Using the method of theoretical analysis and numerical simulation to study the characteristics of the fluctuations of water vapor and liquid water in the envelope structure during the wet migration process over time,analyze the influence of the cold storage load and energy consumption.The main research work is as follows:(1)Theoretical analysis was carried out on the moisture transfer process in the envelope structure of the refrigerator.The structure and thickness of cold storage wall with different insulation material of the different climate zones under the representative cities were calculated by researching real cold storage and building thermal design code and construction general atlas.According to the relationship between material thermal conductivity coefficient and moisture content determined the heat transfer coefficient of stabilize value of interior insulation wall of contain moisture using different insulation materials,and obtained the variation range by comparing with the constant heat transfer coefficient values.(2)By establishing the wet migration model of the enclosing structure,using CHAMPS-BES to simulated the average volumetric moisture content of each material layer,wet stable moisture content and moisture stability time in the wall drying process of different insulation materials under the typical cities in different thermal zones.The simulation results show that the stable moisture content and average volume moisture content of each materials layer of the inside insulation wall are always smaller than external thermal insulation wall,while the wet stability time is opposite.The average volume moisture content and wet stable moisture content of wall and insulation layer are minimum in interior insulation wall when choosing PU as the insulation material.(3)Building model based on actual cold storage,using the EnergyPlus software to simulate the heat transfer rate of envelope structure,total heat transfer,the power consumption of refrigeration system and total power consumption of cold stores from different specific cities.By comparing data from the cases of different insulation materials and whether to take moisture migration into account,draw the conclusion that: the proportion of the heat flow of the enclosure structure to the total heat flow increases as the outdoor air temperature increases.In any case,the maximum and minimum values of the heat flow and the total heat flow of the envelope will increase,and the amplification will be more pronounced when there is a moisture migration.The exist of moisture migration will amplify the influence of heat transfer of envelope,which will further increase the power consumption of refrigeration system and total power consumption of cold stores.The power consumption of refrigeration system and total power consumption of different insulating materials will be at the same level without considering the influence moisture migration;the use of thermal insulation material as PU has the least impact on cooling power consumption and total power consumption,followed by XPS and EPS when considered the envelop moisture transport.