Research And Analysis Of Thermal Short Circuit Of Vertical Single U-shaped Buried Tube Heat Exchanger

In the contemporary world, energy shortage and environmental pollution has become one of the important problems of global sustainable development. With renewable ground heat source for the energy of the ground source heat pump technology,paid high attention by governments, universities and research institutes both at home and abroad, launching a lot of theoretical research and practical engineering applications.The design of buried tube heat exchanger is not only a focus in the study of ground source heat pump, but also the application foundation and the core theory of ground source heat pump air-conditioning system. How to reduce heat in the borehole drilled in the short circuit in the narrow and improve the performance of heat exchanger, the effect of the measure to restrain the hot short circuit is particularly important.Two aspects of heat exchanger: the heat exchanger heat transfer model and the circulating fluid turbulence model, are introduced, to make a theory for the study of ground heat exchanger. This paper introduces some relevant CFD numerical simulation softwares, using Gambit software to establish 3 d model of ground heat exchanger, using the Fluent software to simulate for numerical simulation. On the phenomenon of hot short circuit impact ground heat exchanger of three factors: the speed of the circulating fluid, buried depth of the pipe and run time were simulated respectively, by comparing the circulating fluid outlet water temperature, different temperature distribution in the depth of the heat exchanger nephogram and nearly export temperature difference and unit well depth in research and analysis on the quantity of heat of hot short circuit phenomenon. The following conclusion: tube flow velocity recommended value of 0.6 m/s, depth of buried pipes in the 80 m best, taken to shorten the time of the unit run continuously or intermittent operation strategy is more reasonable.Study the influence of different factors on the heat exchanger, found between the two pipe must be hot short-circuit phenomenon, and more close to the surface phenomenon more serious. This paper studies the two measures for suppression of the heat exchanger short-circuit phenomenon, namely in the perpendicular to the centerline between two tubes to add certain depth and thickness of insulation board or on the return pipe laying different depth and thickness of the insulation material. By comparing the adding of different depth and different depth and heat insulation board insulation and thermal insulation layer thickness of three different cases, qualitative research of hot short-circuit phenomenon, and based on the water temperature and the unit well depth of short-circuit phenomenon and heat exchanger heat exchanger heat transfer performance for quantitative analysis.When without adding any suppression measures, normal heat exchanger, circulating fluid out of the water temperature is 304.44 K, unit well depth in heat is 56.1 W/m: when adding heat shield inhibition measures, the best depth of 40 m point insulation board,lowest outlet temperature is 304.35 K, unit well depth in heat up to 57.5 W/m; When taking a certain depth and thickness of insulating layer, laying the best point for laying 10 m deep thermal insulation layer thickness of 4 mm, the lowest outlet temperature is 304.16 K, unit well depth in heat is 60.5 W/m. By comparing the unit well depth in heat,add heat shield between the two branch pipe unit well depth in the highest heat can increase 2.5%, the highest return pipe laying thermal insulation layer can increase of 7.8%.Through the research of buried tube heat exchanger thermal short-circuit phenomenon, and proposes two measures, provide theory support for improving the performance of heat exchangers, hope for a steady stream of heat pump technology promotion play a positive role, make the technology more energy conservation and environmental protection.