Experimental Study On Interfacial Heat Transfer In Porous Media With Pure Porous Media

In recent years,China aims to maintain a stable economic growth,and targets to reduce energy consumption per unit of GDP,meanwhile The 13 th five-year plan advocates the concept of green development,which means that our country pay more attention to the use of renewable energy,what is more the backward production capacity will be reduced further,and the enhancement of energy structure is going to take further step.Geothermal downhole heat exchanger is a geothermal energy utilization system which utilizes the natural convention of geothermal well water and heat exchanger to exchange heat.By comparing with groundwater source heat pump that extracts groundwater directly,it belongs to the closed circulation.This system provides heat to circulating working fluid(water)through suspended heat exchanger,which has the feature of taking heat only without any water.The process does not affect underground water level,groundwater environment,and protects geothermal resources affectively.It also eliminates the adverse effect of ground water recession and land subsidence.The circulating water in the heat exchanger tube is in a hermetic condition minimizing the issues of surface corrosion and impurity deposition.By comparing with ground heat exchanger,the geothermal downhole heat exchanger can extract heat energy more than two to three orders of magnitudes in the same well depth.Thus,when formation permeability in the geothermal region is in a preferable condition,by comparing with the current popular underground pipe heat exchanger system,the geothermal downhole heat exchanger is a better choice.Nowadays,because of heat exchange temperature difference,the strength of natural convection between water in the aquifer and water in well is the major factor that affects the heat transfer process composing of aquiclude,pure fluid in borehole and heat medium of heat exchanger.Ways to enhance the thermal output in downhole heat exchanger through intensifying heat convection is the main researching area in each nation.The heat transfer issue of geothermal downhole heat exchanger belongs to the areas of pure fluid in formation and porous media interface heat transfer problem.Now,we merely know the interacting effect of inland hot water and water in aquifers,and flow situation in the fluid is very complicated,so it is hard to get the general formula of utilizing heat transfer formula.The paper aims to build the stimulated experimental platform for geothermal underground heat exchanger to conduct the simulation experiment of geothermal underground heat exchanger system.It is the initial exploration of this system in the practical engineering,and will provide references to the future engineering design application.