共查询到19条相似文献,搜索用时 187 毫秒
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本研究制备了新型癸酸-月桂酸/膨胀石墨复合相变材料并通过数值模拟研究了不同复合相变材料回填含量及不同运行模式下的地埋管换热器传热特性.复合相变材料中膨胀石墨与脂肪酸的最佳比例确定为10:100.本文提出了相变材料回填的地埋管传热模型并进行验证,研究了不同回填材料及运行模式下地埋管换热量,钻孔内液相比等参数的动态变化规律.数值模拟结果表明,U型地埋管系统的换热量随回填中相变材料含量的提高而提高,但温度恢复性能逐渐减弱.在相同的相变材料回填含量下,换热量随系统启停时间比的升高而升高,但平均能效比及恢复性能随启停比升高而降低.此外,高相变回填含量的换热系统不适宜在高启停比下长期运行. 相似文献
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平行流蒸发器是双排扁管布置的换热器,空气侧采用间断型扩展表面的波纹型百叶窗翅片,制冷剂侧采用小水力直径的非圆截面微通道多孔铝制扁管,本文选用适合于该微尺度强化换热结构的传热和压降关联式,对某一四流层布置的平行流蒸发器建立数学模型。并通过模拟计算不同翅片厚度对换热器换热性能的影响,发现在其他条件不变的情况下,制冷剂质量流量、换热量、制冷剂流动阻力和空气侧通风阻力都随翅片厚度的增加而增加,并且换热量,制冷剂流阻和通风阻力的增量百分比与制冷剂流量的增量很相近。 相似文献
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本文针对三套管蓄能型太阳能与空气源热泵集成系统建立了实验台,通过实验验证了这一新型系统在蓄冷模式下的运行特性。在蓄冷模式下,压缩机的蒸发压力和冷凝压力变化平缓,压缩比在3~3.6之间;系统换热效果良好,运行稳定。另外,实验还验证了三套管蓄能换热器作为蓄能装置的蓄能能力。在实验测得了冷凝热量和压缩机耗功的基础上,通过计算得到了蓄冷量,这一参数值与随后进行的取冷实验的取冷量之间可以满足能量守恒定律。在整个实验过程中,压缩机的COP在2.02~2.79之间,证明了三套管蓄能型太阳能与空气源热泵集成系统在蓄冷模式下可以安全、可靠地运行。 相似文献
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《建筑节能》2020,(1)
在所搭建的相变蓄能型地埋管换热器的数值模型和仿真模型实验台的基础上,考虑扬州地区地下土壤温度条件与相变材料经济性,夏季工况选用混合酸,冬季工况选用油酸。这两种相变材料分别以2∶8、4∶6、6∶4和8∶2的配比作为回填材料共同回填至钻孔内时,对比探究了相变回填材料配比在夏季和冬季工况下一天内运行10h以及夜间停机恢复14h对地埋管换热器蓄能传热特性影响。研究结果表明:混合酸和油酸两种相变材料的物性参数不同,当两者共同回填至钻孔内时,回填材料的综合热物性会发生变化;随着当季起作用的相变回填材料配比含量的增加,能够显著提升钻孔换热量,提升蓄热能力,缓解钻孔外土壤温度的冷热堆积问题,减小热影响范围;选择适合实际工程的配比需要参考实际建筑冷热负荷进行计算。 相似文献
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本文以能量守恒和质量守恒为基础建立了土壤耦合热泵U型埋管换热器三维非稳态模型,重点研究了回填材料导热率对U型埋管换热器换热性能的影响。结果表明:强化换热型回填材料可以大幅度提高钻井换热器的换热能力,钻井的换热能力随着回填材料导热率的增加而不断提高,但回填材料导热率并非越高越好,而是应该稍高于钻井周围岩土层的导热率。 相似文献
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对能量桩混凝土的材料配合比及桩周土温度场进行了试验和模拟研究,得出普通C30混凝土中掺入3%钢纤维同时用铁矿砂置换河砂,大大提高能量桩的换热效率;通过ABAQUS对桩周温度场进行模拟得出能量桩换热效率随桩周土体导热系数的增大而增强,当桩间距较小时两桩间热量传递会产生热干扰现象,随着桩间距的增加热干扰现象逐渐减弱,减弱的幅度随土体导热系数的提高而增加;相同桩间距下,热干扰现象在黏土层中较为严重,砂土次之,碎石土中热干扰影响较小。 相似文献
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The technical feasibility of an innovative solar collector is studied in this paper. A phase change material (paraffin) is
used in the solar collector to store solar energy. This type of system combines both collection and storage of thermal energy
into a single unit. The major advantages of the phase change stores are their large heat storage capacity and isothermal behavior
during the melting and solidifying processes. A negative aspect of paraffin is its low thermal conductivity which increases
the melting and solidifying time for paraffin energy storage. In this paper, new aluminum foams infiltrated with paraffin
are presented. It presents a two dimensional model describing the melting and solidifying processes of paraffin while accounting
for both phase change heat transfer and natural convection. Apparent heat capacity method was used to simulate the melting
and solidifying processes of paraffin. The simulation results show that the motion of the hot liquid paraffin plays an important
role in increasing the heat transfer between paraffin and top surface of solar collector. The shape profile of the pure paraffin
solid-liquid interface is determined by the synergistic relationship between its temperature and velocity field. Though aluminum
foams impregnated with paraffin will limit motion of the hot liquid paraffin, the heat transfer ability is greatly improved.
The distributions of the temperature in the paraffin with aluminum foams are more homogeneous compared with that of the paraffin
without aluminum foams. Thus, use of aluminum foams infused with paraffin improves heat transfer and enhances paraffin’s melting
and solidifying rates. 相似文献
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为了研究强化相变蓄热器的换热情况,搭建了矩形腔体内填充泡沫金属/石蜡的实验台,在恒壁温条件下,进行了泡沫金属/石蜡复合相变材料的融化蓄热实验.根据实验数据绘制了不同加热温度下石蜡内部温度随时间变化曲线,分析了腔体内自然对流对温度分布的影响、传热温差对蓄热时间的影响.结果表明,泡沫金属的高导热性能强化了石蜡在腔体内的融化... 相似文献
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韩成 《建筑热能通风空调》2020,39(3):12-15
毛细管换热器表面敷设的装饰层材料对辐射顶板表面温度和热流密度有较大的影响,本文提出材料热阻的概念,通过模拟得出材料热阻值,再进行拟合得出装饰层导热系数和材料热阻的函数曲线图,通过实验验证模拟的准确性。结果表明基于材料热阻的工程预估具有较为精确的实际应用价值。 相似文献
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The aim of the present work is to study numerically 2-D steady state coupled heat transfer by conduction, free convection
and infra-red radiation through two honeycomb walls separated by a vertical air layer. Airflow in both holes and separating
air layer is laminar. The limiting vertical sides of the double honeycomb wall are assumed to be isothermal but at different
temperatures while the upper and lower horizontal surfaces of the structure are insulated. The FVM method and the SIMPLE algorithm
are used to solve numerically the equations of conservation of mass, momentum and energy in both air filled cavities and solid
partitions. It is found that the global heat flux across the entire wall varies almost linearly with the difference between
the outside and the inside temperatures. Based on this linear thermal behaviour, appropriate overall heat exchange coefficients
are derived. These coefficients can be used easily in practice to predict the global heat transfer across the studied honeycomb
walls without solving the detailed and complex equations that govern the different heat transfer mechanisms. Effect of the
thermal conductivity of the construction material on the overall heat transfer through double honeycomb walls is studied. 相似文献
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针对螺旋地埋管嵌岩能源桩传热,提出一种新的计算模型,可考虑基岩温度、大气-地面对流换热、桩顶处绝热处理、流体速度和流体热量损耗对其传热影响。首先求解土体温度自由场;接着考虑桩体运行时系统传热相互作用的影响,得到桩体温度场;然后将土体温度场问题转化为一系列未知系数求解;最后通过边界条件得到土体附加温度场。分析表明:在桩顶和桩底两倍桩径范围内,土的附加温度变化幅度最大;桩土传热系数对能源桩传热性能影响最大,减小桩土传热系数可显著提高能源桩传热性能;流体导热系数及流速对桩的传热效果影响不可忽略;土的导热系数及大气-地面对流传热系数对其传热性能影响很小。 相似文献