Research On Heat Transfer Performance Of Vertical Ground Finned Heat Exchanger In Ground Source Heat Pump

In the social background of traditional energy sources dried up and environme nt a l pollution increasingly serious,with its abundant energy,high environmental benefits,energy saving,stable and reliable characteristics,ground source heat pump,the new technology for geothermal energy exploitation and utilization,is gradually attached great importance by all sectors of society.At present,ground source heat pump technology is in the high developing and promoting stage,the experts and scholars are constantly in-depth research on its innovat io n.From the aspect of changing U tube heat exchanger geometric structure,this article will design a new type of finned heat exchanger and study the heat transfer performance in the operation process,to improve the efficiency of the shallow geothermal energy development,it would have significant influence on saving systemic initial investment.In this thesis,starting with the research status at home and abroad,combining with the soil structure and its features,on the basis of introducing the thermal physical parameters of soil and the heat transfer process,the Gambit software was used for establishing the threedimensional heat transfer model of new type of heat exchanger with fin and without fin respectively,with discrete grids.The model size is same as the actual size.The Fluent software was used for simulating to calculate the change of soil temperature field around under the condition of unsteady heat exchanger,and to calculate the influence on heat transfer performance of heat exchanger,through changing the thermal physical parameter Settings,under the thermal seepage coupling.By comparing the two kinds of heat exchanger of outlet water temperature and the heat-exchange rate per depth,this article verify that the new type of heat exchanger with fin is superior on heat transfer performance.According to the results of simulation calculation under summer conditions,the heat transfer performance of heat exchanger with fin is better than the heat exchanger without fin under different seepage velocity,heat exchanger inlet velocity,edaphic porosity,edaphic thermal conductivity,edaphic specific heat capacity.Groundwater seepage not only remove the heat from heat exchanger by convection,but also weaken the hindering effect of heat transfer effectively under soil heat accumulation phenomena.Large seepage speed can take away the heat saving in the soil,faster and more effectively,that is advantageous to the heat transfer between heat exchanger and the surrounding soil.When seepage velocity is 30m/a,the smaller the porosity,the better the heat transfer between heat exchanger and soil.With the increase of inlet velocity,the total heat transfer between heat exchanger and soil improved to some extent,but export water temperature has increased.Meanwhile the circulating water pump will consume more energy.The greater the edaphic thermal conductivity or edaphic specific heat capacity,the better the heat transfer between heat exchanger and soil,but in the case of a large seepage velocity,the effect of improving the heat transfer performance of the heat exchanger by increasing the edaphic thermal conductivity or edaphic specific heat capacity is reduced.In this paper,the design of a single U-shaped ribbed finned tube,in order to achieve the purpose of enhanced heat transfer,saving the initial investment cost of the initial system.And its research and analysis under various working conditions provide a theoretical support for the optimization of the design of the ground source heat pump system,which is helpful to its application in practical engineering.