共查询到18条相似文献,搜索用时 187 毫秒
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蓄热式换热器是高温有机化合物废气氧化器的核心部件之一。提出了一种带有赤藓糖醇相变材料的翅片缩放管式蓄热体,并用数值模拟的方法对蓄热体蓄放热过程的热工特性进行研究,分析了翅片厚度对蓄热体传热性能的影响。模拟结果表明:翅片缩放管(翅片厚2 mm )在蓄/放热阶段的传热速率分别比光管缩放管高13%和9%,一定条件下适度增加翅片厚度有助于提高蓄热体的蓄放热性能。所得结论为今后翅片缩放管相变蓄热体的优化设计提供了理论依据。 相似文献
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设计了基于圆柱形相变蓄热单元的相变蓄热装置,通过循环实验对蓄热装置的运行特性进行分析,研究了装置的蓄热影响因素。研究结果表明;在等质量相变材料(Phase Change Material,PCM)时,相变单元数量对装置蓄热速率的影响较大;蓄热单元布置间距对装置蓄热速率的影响较小;当增大换热流体(Heat Transfer Fluid,HTF)的流量时,装置总蓄热时间分别缩短了14.5%和29%;提高换热流体入口温度时,不仅增加了蓄热装置的总蓄热量,并且总体蓄热时间分别缩短了10.6%和16.5%。 相似文献
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肋板式相变蓄热器蓄热性能的试验研究 总被引:1,自引:0,他引:1
采用萘作为蓄热材料,对其在新型铝制肋板式相变蓄热器中的储、放热过程即内部萘的熔化和凝固过程进行了试验研究,改变了供、取热流体参数,测定了储、放热过程的时间,分析了热流体的入口温度与流量对蓄热器储、放热过程的影响.结果表明,新型肋板式相变蓄热器极好地发挥了换热元件的作用,热流体的入口温度与流量对储、放热速率有重要的影响. 相似文献
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姬长发李生金陈柳李品利 《流体机械》2015,(12):50-54
通过自行建立的试验台,对封装优态盐同心套管式相变储冷单元的蓄冷、释冷特性进行试验研究。主要研究了制冷剂的蒸发温度对蓄冷特性的影响及载冷剂的温度和流量对释冷特性的影响。结果表明,制冷剂的蒸发温度对蓄冷的影响较大,制冷剂的蒸发温度越低,结冰越快,结冰率越大,达到同样的结冰率需要的时间也越短;载冷剂的进口温度对释冷过程的影响较大,相比之下载冷剂的流量对蓄冷和释冷过程的影响要小。在试验条件下,蓄冷时较合理的制冷剂蒸发温度和载冷剂流量分别为1℃和0.241m3/h,释冷过程较合适的载冷剂进口温度和载冷剂流量分别为10℃和0.283m3/h。 相似文献
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为了提高蓄热装置内蓄热球的蓄热效率,该文设计了一种表面有螺旋凹槽的蓄热球,用ICEM CFD建立了三维模型并进行网格划分,在fluent中分别仿真了一种基于凹槽蓄热球和光滑蓄热球的相变储热水箱在初始温度308 K、入口流速0.1 m/s、入口温度363K和初始温度308 K、入口流速0.15 m/s、入口温度363 K两种工况下的蓄热过程,得到了蓄热过程中相变材料(PCM)温度和液相率随时间的变化曲线以及液相率的分布云图,截取了蓄热过程中某一时刻的水流速度矢量图.研究结果得出:与光滑蓄热球相比,螺旋凹槽蓄热球的凹槽结构既增加了PCM与热媒体的热交换面积,又增强了蓄热箱内的对流传热,提高了换热效率,避免了热量的流失.对整个蓄热箱而言,大大减少了蓄热时间,提高了蓄热箱的蓄热效率. 相似文献
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Jesumathy Stella P. Udayakumar M. Suresh S. 《Journal of Mechanical Science and Technology》2012,26(3):959-965
An energy storage system has been designed to study the heat transfer characteristics of paraffin wax during melting and solidification
processes in a vertical annulus energy storage system. In the experimental study, three important issues are focused. The
first one is temperature distribution in the phase change material (PCM) during the phase change processes. The second one
is the thermal characteristics of the paraffin wax, which includes total melting and total solidification times, the nature
of heat transfer phenomena in melted and solidified PCM and the effect of Reynolds number as inlet heat transfer fluid (HTF)
conditions on the heat transfer parameters. The final one is to calculate heat transfer coefficient and effectiveness during
solidification process. The experimental results proved that the PCM melts and solidifies congruently, and the melting front
moved from the top to the bottom of the PCM container whereas the solidification front moved from bottom to the top along
the axial distances in the PCM container. Experiment has been performed for different water flow rates at constant inlet temperature
of heat transfer fluid for recovery and use of heat. Time-based variations of the temperature distributions were explained
from the results of observations of melting and solidification curves. Charging and discharging processes were carried out.
Heat transfer characteristics were studied. 相似文献
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The isothermal characteristics of a rectangular parallelepiped sodium heat pipe were investigated for high-temperature applications.
The heat pipes was made of stainless steel of which the dimension was 140 m(L) ×95m(W) ×46m(H) and the thickness of the container
was 5 mm. Both inner surfaces of evaporator and condenser were covered with screen meshes to help spread the liquid state
working fluid. To provide additional path for the working fluid, a lattice structure covered with screen mesh wick was inserted
in the heat pipe. The bottom surface of the heat pipe was heated by an electric heater and the top surface was cooled by circulating
coolant. The concern in this study was to enhance the temperature uniformity at the bottom surface of the heat pipe while
an uneven heat source up to 900 W was in contact. The temperature distribution over the bottom surface was monitored at more
than twenty six locations. It was found that the operating performance of the sodium heat pipe was critically affected by
the inner wall temperature of the condenser region where the working fluid may be changed to a solid phase unless the temperature
was higher than its melting point. The maximum temperature difference across the bottom surface was observed to be 114°C for 850 W thermal load and 100°C coolant inlet temperature. The effects of fill charge ratio, coolant inlet temperature and operating temperature on thermal
performance of heat pipe were analyzed and discussed. 相似文献
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Jongmin Choi Jongug Jeon Yongchan Kim 《Journal of Mechanical Science and Technology》2008,22(3):575-582
Optimum control of the PCB surface temperature is very important in achieving high performance and operational reliability
of telecommunication equipment with high power density and thermal density. In this study, the performance of a liquid cooling
unit with MPCM slurries (called as “MPCM cooled unit”) was tested and analyzed. In addition, its performance was compared
with that of an air cooled unit and a water cooled unit. The maximum surface temperature and the index of uniform temperature
distribution (IUTD) were introduced to analyze cooling performance. The surface temperature in the unit rack of telecommunication
equipment can be controlled properly by using an MPCM cooled unit instead of an air cooled unit. The maximum surface temperature
and IUTD of the MPCM cooled unit at the inlet temperature of 19°C were lower than those at inlet temperatures of 25°C and
27°C due to the increases of heat capacity and heat transfer rate. The heat capacity of the MPCM cooled unit increased significantly
with the increase of mass flow rate due to high specific heat of MPCM particles with latent heat transfer rate. The cooling
performance of the MPCM cooled unit was superior to that of the water cooled unit. 相似文献
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建立单面加热垂直矩形窄通道流动沸腾换热试验装置,针对截面250mm×3.5mm的窄缝通道,对水流动沸腾换热特性进行试验研究。通过试验分析可知:(1)随着干度的增加,局部换热系数先增加后减小,有一个最大值,此时处于饱和核沸腾区域,其蒸汽干度也接近于0,同时也接近于沸腾起始点。相应地流体从单相流-泡状-块状流-搅拌-环状流转变。(2)在流动沸腾换热中,热流密度对核态沸腾换热有明显影响,而对流动沸腾液膜蒸发的影响甚小,所以可以认为由热流密度的变化而引起的换热变化,主要表现在核态沸腾。(3)入口温度的变化对单相流动的换热系数有影响,而沸腾换热系数与流型及汽泡的产生及扰动有极大关系,入口温度对流动沸腾局部换热系数基本没有影响。 相似文献
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相变储热有着密度高、体积小、质量轻,蓄放热过程中温度波动小等优点,在太阳能热利用、工业余热回收、采暖及空调等领域有着较为广泛的应用。本文利用相变储热试验平台模拟储热器的工作原理,对储热器不工作状态下内部和外部温度进行监测,发现相变储热器在非稳态散热时具有比较明显的凝固放热现象,而且通过顶面的热损失严重;对储热器热损失进行了分类,对储热器热损失系数这一关键数据进行探讨;最后,在试验和理论分析基础上提出增大上部保温层厚度、加强进出口部位的保温、减小管径和增加阀门可减小储热器通过顶面的热损失。 相似文献