共查询到19条相似文献,搜索用时 140 毫秒
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建立地埋管换热土壤热湿迁移过程的实验装置,对地源热泵间歇运行时不同进口流体温度及不同土壤体积含水率下土壤温湿度场的变化特性进行实验研究。实验结果表明∶间歇运行时,入口流体温度的升高会使土壤温度最大值升高,但不利于土壤温度的恢复,土壤体积含水率的增加在一定程度上有利于地下换热和土壤温度的恢复。系统开机后存在土壤温度上升的主上升区,此区温度增幅超过65%,关机后第18小时土壤温度基本恢复至初始温度;系统关停后在温湿度梯度的作用下会出现温度和含水率最大值后移的现象,热源对土壤温度和含水率的作用半径约为280和375 mm;开停比为1∶2时温湿度较1∶1能恢复得更低,合理设置停机时间有利于机组长期有效运行。 相似文献
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不同运行方式对地源热泵系统的长期稳定性有着重要作用。以西安地区为例,建立了双U型地埋管换热器三维传热模型,模拟了不同运行方式对单孔和群孔换热器换热特性的影响。研究结果表明:地源热泵管群系统应间歇运行,每天最大负荷工况下连续运行不超过8 h;年总供冷热量差值控制在10%内,以便土壤温度恢复;3年和10年土壤温差分别控制在1℃和3℃内,以保证地源热泵系统长期供能效果。 相似文献
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为了研究地埋管换热器在变负荷下连续运行与间歇运行的换热性能,基于有限长线热源渗流模型建立竖直地埋管钻孔外准三维非稳态传热模型,应用叠加原理计算钻孔群中钻孔壁温度场及地埋管内流体温度场。在存在地下水水平渗流的情况下,研究了变负荷连续运行模式下不同渗流速度、不同运行工况及不同钻孔位置对地埋管换热器的换热性能的影响。结果表明,在连续运行模式下,边缘位置的钻孔及较大的渗流速度能够增强地埋管换热器的换热性能;在间歇运行模式下,地埋管换热器的运行份额越小,其制冷效果越好,反之,制冷效果越差;在间歇运行工况下,土壤温度能在系统间歇期内得到一定程度的恢复,从而更好地提高地热能的利用率。 相似文献
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Yusuf Ali Kara 《国际能源研究杂志》2007,31(15):1504-1516
An experimental study is performed to determine the performance of a ground source heat pump (GSHP) system in the heating mode in the city of Erzurum, Turkey. The GSHP system using R‐134a as refrigerant has a single U‐tube ground heat exchanger (GHE) made of polyethylene pipe with a 16 mm inside diameter. The GHE was placed in a vertical borehole with 55 m depth and 203.2 mm diameter. The average coefficients of performance (COP) of the GSHP system and heat pump in heating mode are calculated as 2.09 and 2.57, respectively. The heat extraction rate per meter of the borehole is determined as 33.60 W m?1. Considering the current gas and electric prices in Erzurum city, the equivalent COP of the GSHP system should be 2.92 for the same energy cost comparing with natural gas. The virgin ground in Erzurum basin has high permeability and low thermal conductivity. In order to improve the thermal efficiency of GHE and thus improve COP of a GSHP in the basin, the borehole should be backfilled with sand as low‐cost backfill material and a 1 to 2 m thick surface plug of clay should be inserted. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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为了增强土壤源热泵系统地下埋管换热器的换热性能,通过CFD方法,探讨改用波纹管对地下换热所产生的影响,首次提出采用波纹管代替光管作为强化地下埋管换热器换热效率。 相似文献
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地源热泵是一种利用土壤所储藏的太阳能资源作为冷热源进行能量转换的供暖制冷空调系统,通过输入少量的高品位能源(如电力、机械功、燃气和液体燃料),实现热量从低温热源向高温热源的转移.以上海某小型别墅为对象,设计了一套家用地源热泵空调系统.首先计算了夏季冷负荷和冬季热负荷,然后根据冷、热负荷选择一套水源热泵机组(MWH080CR型机组)和相应的风机盘管,进行了室内水管环路系统、土壤热交换器和地板采暖的设计选型,最后对系统的能效比进行了计算.结果表明,该空调系统具有节能环保、稳定可靠、舒适耐用等优点. 相似文献
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A study on utilization of ground source energy for space heating using a nanofluid as a heat carrier
Ground source heat pump (GSHP) systems are well established as an energy-efficient space conditioning device. However, for better utilization of the ground source, improvement in GSHP performance is desirable, which limits the small temperature difference between the ground and the circulating fluid. In this study, efforts have been made to investigate the performance of a ground heat exchanger (GHX) with a nanofluid as a heat carrier. Mathematical modeling is performed for the closed-loop vertical U-tube GHX with six different (Al2O3, CuO, graphite, multiwalled carbon nanotube, graphene, and Cu) water-based nanofluids. The effect of different operating parameters on GHX length, fluid temperature, and pressure drop with nanofluids is determined. On the basis of the analytical results, it is found that the graphite particle-based nanofluid plays a prominent role to enhance the performance of the GHX as compared with other nanoparticles. The maximum enhancement in the increase in outlet fluid temperature and reduction in pipe length with graphite particle-based nanofluid are 68.3% and 63.3%, respectively, for an increase in temperature difference from 7°C to 15°C between the atmosphere and the ground. Also, with the graphite particle-based nanofluid and the increase in pipe diameter from 20 to 50 mm, the fluid outlet temperature increases up to 11.2%, and the requirement in GHX length reduces up to 55%. 相似文献
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A high-efficiency ground heat exchanger has been developed for use with ground-source heat pumps. The exchanger is made of copper tubing, shaped in the form of a spiral, which can be installed in a vertical borehole backfilled with sand. Thermal performance of a full-scale prototype indicated that this heat exchanger can achieve very high heat extraction rates if subfreezing operating temperatures are used. For most soil types cyclic freezing and thawing is not a problem; however, for the sensitive Leda clay in which the prototype tests were conducted, substantial settlement occurred after the first freeze-thaw cycle owing to initial collapse of the soil structure. 相似文献
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在冬冷夏热且夏季冷负荷远大于冬季热负荷的地区常采用带有冷却塔的复合式地源热泵系统,其控制策略存在极大的优化空间。文章提出了直接比较冷却塔和与土壤换热器相连的板式换热器的出口温度的控制方法,并通过人工神经网络预测板式换热器机组侧的出口水温来实现此控制方法。通过FLUENT软件建立复合式地源热泵系统动态数值模型,获取建立神经网络的数据,采用3层BP网络,建立了多个预测板式换热器机组侧出口温度的模型。研究结果表明,采用神经网络可以准确实现此预测,绝对误差不超过0.4℃。 相似文献