Numerical Simulation Study Of Performance Of Single U-tube Heat Exchanger In The Different Seepage Directions

Energy is the material foundation of the development of economy andsociety, which is integral to the survival of mankind and the development ofsociety. With the rapid development of global economy and the improvement ofhuman living standard, the problem of energy shortage is becoming more andmore prominent. Therefore, the sustainable development of energy has becomethe focus of attention of the society.As a kind of high efficient technology of renewable energy utilization,ground-coupled heat pump is more and more popular because of its advantage inenergy saving and sustainable development of environment, accordingly, theresearch and application about it have risen steadily.With the continuous development of computer technology, numerical simulation method has become an important mean to make research aboutground-coupled heat pump. In order to simplify the model, many scholars ignorethe influence of groundwater seepage, which is an important factor to theground-coupled heat pump. However, the groundwater seepage is the realexistence, and ignoring this factor will influence the assessment of the actualoperation of system. Through the existing study about groundwater seepage, wecan find that the groundwater seepage can enhance the heat exchange efficiencyof ground heat exchanger, and then improve the operation efficiency ofground-coupled heat pump, which is an advantage for ground-coupled heatpump system. Nevertheless, we can find that there is few existing research aboutthe influence of directions of groundwater seepage on the heat transferefficiency and the temperature field of the surrounding rock and soil. Therefore,this paper deals with the influence of the directions of groundwater seepage onthe ground-coupled heat pump system to explore the deficiencies of existingstudies and to provide certain reference for the engineering design.This paper firstly selected three directions of groundwater seepage todiscuss, namely the direction from the pipe of water supply to the pipe of waterreturn, the direction from the pipe of water return to the pipe of water supply,and the direction perpendicular to the plane of the axis of the pipe of watersupply and the pipe of water return. The influence of directions of groundwaterseepage on the temperature difference between inlet and outlet of U-tube of theground heat exchanger and the temperature field of the surrounding rock and soil were simulated by the FLUENT, which is a fluid calculation software, andthe simulation result was analyzed. Then, to deeply explore the influence of thedirections of groundwater seepage on the temperature difference between inletand outlet of U-tube of the ground heat exchanger, groundwater seepage angleof10℃,20℃,30℃,40℃,50℃,60℃,70℃,80℃were selected to simulate,and the simulation result was analyzed.The results show that the temperature difference between inlet and outlet ofU-tube not completely increase with the increasing of seepage velocity, whichhas the direct relationship with the direction of seepage. Meanwhile, theoptimum seepage velocity is not a constant, which changes with the change ofthe groundwater seepage angle. At the same time, when the direction ofgroundwater seepage is different, the thermal action radius in the same kind ofrock and soil is all different. Thus the direction of groundwater seepage is apredominant factor on the operation of ground-coupled heat pump. Meanwhile,the conclusions of this paper reveals the deficiency of alternative method ofequivalent pipe existing in the present numerical studies, illuminates theinfluence of groundwater seepage on the thermal efficiency of system andprovides a certain reference for practical engineering.