Study On The Heat And Moisture Transfer Principles Of Soil Fields Surrounding The Soil-Air Heat Exchanger In Solar Greenhouse

As a populous country,agriculture is always the key of social and economic development.Currently,the energy crisis intensified,natural disasters and environmental pollution aggravate,which caused wide social concern on the solar greenhouse heat and moisture regulator control system.Society is accepted that this system is reliable and can save energy.In this background,this research demonstrates the study of soil-air heat exchanger.Soil is the most important vector for saving and releasing heat of this heat exchange system,the distribution of heat and moisture will directly affect the operating effects of heat exchanger This article explores the heat coupling migration patterns during the unsaturated soil saving and releasing heat,when solar greenhouse soil-air exchange system in the process of running.As the interaction between temperature and humidity field in the soil,the temperature gradient will prompt the movement of moistur e in the soil.The movement of moisture will cause the change of temperature as the heat taken away.In order to solve this complex problem,by using the Fluent software,the author build the double driving model depending on the interaction of temperature and moisture in the unsaturated soil around horizon heat exchanger.This model is to simulate the dynamic distribution of temperature and moisture in the process during the unsaturated soil saving and releasing heat,which using temperature gradient and soil water potential as driving force of moisture migration.For intuitive to explore the effect of three-dimensional heat coupling migration during soil saving heat,the author simulates the temperature and moisture dynamic distribution of isotropic unsatur ated soil saving heat and analyzes the interaction of temperature and moisture.After analyzing,the author build the model of Agricultural soil moisture stratification in sunlight greenhouse,which breaking the recognition of isotropic soil and providing the analysis about the influence of heat exchange by moisture stratification.Finally,by comparing the model of heat moisture coupling migration with model of pure heat conduction,this research will find out the energy changing caused by Moisture migration.The results show that the distribution of temperature and humidity field are closely related.Under the effect of temperature gradient in soil,the moisture in the soil migrates along the opposite direction of temperature gradient,and accumulate to form wet peak in turn.Among isotropic soil,all points which have the same distance from the center of tube,appear the wet peak simultaneously.The higher the inside air temperature become,the more obvious the wet peak value is.In The anisotropy of layered soil,by Horizontal and vertical comparison,the distribution of temperature and moisture in the soil are obviously different.The difference of moisture volume percentage in the soil cause the change of thermophysical property in the soil.In the vertical direction,the distribution of moisture in the soil is more susceptible to be influenced by initial moisture layer,and under the function in the moisture gradient and temperature gradient obviously removed.Running soil-air heat exchanger under natural state,the effect of temperature and moisture by soil-temperature heat exchanger are less than 0.5 meters radius.And in the process of heat transfer,the change of soil temperature had obvious delayed effect.As with the increase of distance with heat exchange tube,the time delay effect of temperature change is more obvious.Also it shows that in the normal operation of the heat exchanger,in order to avoid mutual influence between tube,it need to guarantee the tube spacing is greater than 1 m.Compared with pure heat conduction model,the migration of the moisture in unsaturated soil will cause the transfer of heat,which makes soil acquire greater ability of saving and releasing heat.