中浅层同轴套管式换热器的传热能力分析

Analysis of heat transfer capacity of double-pipe heat exchangers of medium-shallow layers

随着我国“双碳”战略目标的实施,地热能作为可持续开发利用的清洁能源也备受推崇。目前关于地热能开发利用的研究主要集中于浅层地热能和中深层地热能,对于中浅层地热能(200~500 m)研究较少,而利用中浅层地热能进行供暖与制冷也缺乏相关的工程案例和理论研究支持。本文基于河北省邯郸市某建筑物空调冷热源项目中施工的300 m地热井,开展了中浅层同轴套管式换热器的传热实验与理论分析研究。首先,对换热器的结构形式、施工工艺、换热特性等进行研究,根据建立的换热器开展了5种不同工况的现场传热测试,获取了相关的热物性参数;其次,通过分析中浅层地热能的特点,研究换热器换热内外不同的传热规律和循环方向,基于已有的浅层地埋管和中深层同轴管传热模型,创新性建立了针对中浅层套管式换热器冬夏两季的传热模型,通过相应的控制方程对传热模型进行模拟分析,并将模拟数据与实验数据进行了对比,校核了传热模型的准确性;最后,根据建立的传热模型对换热器进行了全年的模拟计算,获取了冬夏两季不同流量的进出口温差及换热量,岩土体温度横向、纵向的变化等参数,为进一步改进中浅层同轴套管式换热器结构以及室外埋管系统的设计与优化提供理论依据和技术指导。

With the implementation of China s“double carbon”strategic goal geothermal energy as a sustainable development and utilization of clean energy is also highly respected.At present,the researches on geothermal energy development and utilization mainly focus on shallow and middle-deep geothermal energy,few studies on middle-shallow geothermal energy(200-500 m).There is also a lack of engineering cases and theoretical research support for heating and cooling using middle-shallow geothermal energy.This paper based on a 300 m geothermal well constructed in a building air conditioning cold and heat source project in Handan City,Hebei Province,carrying out the heat transfer experiment and theoretical analysis of middle-shallow double-pipe heat exchanger.Firstly,the structure,construction technology and heat transfer characteristics of heat exchanger are studied,based on the established heat exchanger,carrying out the field heat transfer tests under five different conditions,obtaining the related thermal physical parameters.Secondly,analyzing the characteristics of middle-shallow geothermal energy,studying the heat transfer law and circulation direction of heat exchanger,based on the existing heat transfer models of shallow buried pipe and middle deep coaxial pipe,the heat transfer model for middle and shallow casing heat exchanger in winter and summer is innovatively established,simulation analysis of the heat transfer model is performed by the corresponding control equations,verifying the accuracy of the heat transfer model by comparing the simulated data with the experimental data.The last,based on the established heat transfer model,the geothermal well is simulated for the whole year,obtaining the parameters of inlet and outlet temperature difference and heat transfer at different flow rates in winter and summer,as well as the transverse and longitudinal changes of rock mass temperature,providing theoretical basis and technical guidance for further improving the structure of middle-shallow layers double-pipe heat exchanger and the design and optimization of outdoor buried tube system.