冷热负荷非平衡地区土壤源热泵土壤热失衡问题的研究

发布时间：2018-01-21 03:11

本文关键词： 土壤源热泵土壤热失衡管群换热辅助冷却复合系统实验研究　出处：《扬州大学》2014年硕士论文　论文类型：学位论文

【摘要】：土壤热失衡问题作为近些年土壤源热泵应用中所出现的亟待解决的难点及关键问题,已在一定程度上直接影响了其正确推广与健康发展。本文通过理论分析、数值模拟及实验相结合的研究方法,以控制地下土壤热平衡为目的,以供冷为主地区为例,分析了土壤源热泵在冷热负荷非平衡条件下,不同因素对地下换热区域土壤温度动态变化特征的影响及其控制措施,以期为土壤源热泵土壤热失衡的控制提供理论基础与技术支持。理论方面,本文建立了考虑地下水渗流的地下管群蓄热模型,采用MATLAB软件编写程序进行模拟,分析了放取热不平衡率、埋管间距、埋管布置形式、岩土类型及地下水渗流等因素对地埋管区土壤温度十年运行期变化规律的影响。结果表明：十年运行结束后,无地下水渗流时,地下埋管换热区域的土壤温度场沿轴线对称分布,且呈现出中心高外面低的分布状况；随放取热不平衡率的增大,埋管区域土壤温升率加大,土壤热失衡问题加剧；合理的埋管间距及采用条形或稀疏布置形式可减小埋管密集程度,有效控制土壤热失衡问题；对于需要强化热扩散的场合,宜采用热扩散率大的土壤以加快累积热量的扩散；此外,地下水渗流的存在可及时带走地下累积热量,从而可有效缓解或消除土壤热失衡问题。为了进一步平衡全年地埋管的累积取放热量,以从根本上控制土壤热失衡问题,本文提出采用外部辅助冷却散热控制的措施,并模拟分析了外部辅助冷却设备作用于混合系统中的时间和散热强度(即控制向地下排热的时间与量)对地下土壤温度十年运行期变化规律的影响。结果表明：随冷却塔辅助散热运停时间比的增大及散热率的增加,埋管区域土壤温升率降低,土壤热失衡问题得到减缓；合理的冷凝热回收时间及热回收率,可以完全满足土壤温度的及时恢复,缓解甚至消除土壤源热泵系统长期运行所造成土壤热失衡问题。实验方面,利用多功能复合型地源热泵实验台,展开了冷却塔—地埋管复合系统不同运行模式的实验研究,通过对地下埋管不同深度和半径方向土壤温度的采集以及4根地埋管与冷却塔进出口水温和流量的监测,分析得出了不同冷却塔辅助散热运行模式下地下换热区域土壤温度恢复特性。实验表明：带有外部辅助冷却塔的混合系统可以有效缓解土壤温度的急剧增加,降低地埋管的“热堆积”,提高土壤温度的恢复率。埋管半径方向的土壤传热有一定的延迟性,当运行时间小于24小时时,埋管热作用半径为0.5m。夜间电费低谷时开启冷却塔对地下埋管强制散热,有效提高了第二天埋管换热器的蓄热效果,这对于只需日间制冷的建筑是一种很好的选择模式。本文的研究工作为土壤源热泵土壤热平衡控制的进一步深入研究提供了理论依据与实验数据,为土壤源热泵的实际工程应用提供了参考。
[Abstract]:The problem of soil thermal imbalance as a difficult and key problem in the application of soil source heat pump in recent years has directly influenced its correct popularization and health development . In this paper , the influence of different factors on the dynamic change of soil temperature in the underground heat exchange region under the condition of non - equilibrium of cold and heat load is analyzed by theoretical analysis , numerical simulation and experiment . On the basis of theory , this paper establishes the underground pipe group heat storage model considering the groundwater seepage , and simulates the soil temperature field in the buried pipe area by using MATLAB software programming procedure . The results show that the soil temperature field in the heat exchange area of the underground pipe is distributed symmetrically along the axis when no groundwater seepage exists . The reasonable buried pipe spacing and the form of strip or sparse arrangement can reduce the diffusion of accumulated heat . In addition , the existence of groundwater seepage can take away the accumulated heat in the ground in time , so that the problem of thermal unbalance of the soil can be effectively alleviated or eliminated . In order to balance the accumulated heat of the buried pipes in the whole year , the effect of the external auxiliary cooling equipment on the change law of the operation period of the underground soil temperature ten years has been put forward . The results show that the temperature rise rate of the soil in the buried pipe area is decreased with the increase of the auxiliary heat dissipation transportation and stopping time ratio of the cooling tower and the heat dissipation rate . The reasonable condensation heat recovery time and the heat recovery rate can completely meet the timely restoration of the soil temperature , alleviate or even eliminate the problem of soil heat balance caused by the long - term operation of the soil source heat pump system . Experimental research on the different operating modes of the composite system of the cooling tower and the underground pipe is carried out by using the multifunctional compound ground source heat pump bench , and the characteristics of soil temperature recovery in the underground heat transfer area under the auxiliary heat dissipation operation mode of the different cooling towers are analyzed through the monitoring of the soil temperature in different depths and radius directions of the underground pipe and the monitoring of the water temperature and flow rate of the four buried pipes and the cooling tower . The experiment shows that the heat transfer of the buried pipe is 0.5m when the operation time is less than 24 hours . When the operation time is less than 24 hours , the heat storage effect of the second buried pipe heat exchanger is effectively improved , which is a good choice mode for buildings requiring only daytime cooling . The research work provides theoretical basis and experimental data for further research on the soil thermal balance control of the soil source heat pump , and provides a reference for practical engineering application of the soil source heat pump .

【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU83

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