Experiment And Simulation Research On Porous Medium Under Coupled Thermal Conduction And Groundwater Seepage Conditions

Because of its good energy saving and environmental protection,Soil source heat pump system belongs to effective technology which candevelop renewable shallow geothermal resources. But the buried tubeheat transfer performance of the quantitative calculation is difficult tofurther develop. According to the majority of buried pipe buried in looselayers, in this paper, The factors of effect the heat transfer performance,such as porous medium seepage or non-seepage, seepage velocity,variation of medium temperature, were studied, which was based on theexperiment of indoor physical model and combined numerical simulationtechnology. With coarse sand as a typical sample for the experimentalstudy, uses the experimental results to match with the value of simulationby COMSOL Multiphysics. Then use the physical model to simulatemedium sand, fine sand, silt and clay. The results show that:(1) Under the condition of dry sand and saturated sand withoutseepage, the temperature distribution of sand box is symmetrical for thecenter of heating rod, and the isotherms are a set of concentric circles centered on heating rods. In dry sand, the temperature variation havedifferent change rules with the different distances to heating rod, whenthe distance is0～5cm,5～10cm and10～20cm, the curve oftemperature is “logarithmic” type,“S” type, and “linear” typerespectively. The temperature variation in non-seepage is not obviouswith the change of distance, the amplitude of temperature variation is lessthan in dry sand.(2) Under the condition of seepage, the temperature distribution ofsand box is not centered on heating rod, the isotherms is a set of ellipses.With the increase of seepage and medium temperature, the influencedsphere of heating rods on the upstream is decrease, and the influencedsphere of heating rods on the downstream is increase.(3) According to the experimental results of the coarse sand, uses theexperimental results to match with the value of simulation by COMSOLMultiphysics, the results show that the maximum relative error was4.27%, the average relative error was1.55%between simulation andexperimental value, satisfy the accuracy requirements. The physicalmodel can be used simulation of different porous mediums.(4) By using physical model to study the heat transfer rules ofmedium sand, fine sand, silt and clay, shows that the heat transfer rules offour porous mediums is analogy. The clay and silt have a similar heattransfer performance, which is better than medium sand, and the heat exchange efficiency of medium sand is better than fine sand.