热管式相变蓄热换热器储/放能过程中传热特性的实验研究

将热管作为换热元件应用于相变蓄热系统中,研制了一套热管式相变蓄热换热器。采用石蜡作为蓄热材料,对其储、放能过程即内部石蜡的融化与凝固过程进行了实验研究。测定了储、放能过程中不同时刻换热器内石蜡的温度分布; 改变供、取热流体参数,分析了供/取热流体的入口温度与流量对换热器储/放能过程的影响;分析了储、放能过程中能量随时间的变化情况。结果表明,热管在本换热器内极好地发挥了换热元件的作用,换热器运行状况良好,各项功能均能较好地实现。     

分离式热管蒸发段充冷过程性能研究

建立了分离式热管蒸发段充冷过程的数理模型,分析了在不同热管介质入口温度下热管蒸发段管外冰层厚度、热管介质出口温度、热管外蓄冷介质温度、单位时间蓄冷量以及总蓄冷量随时间的变化关系,研究结果表明,在热管蒸发段长度和管径一定的情况下,降低热管介质入口温度可以提高热管蒸发段单位时间蓄冷量、减小热管充冷时间。     

Enhancement of charging and discharging rates in a latent heat storage system by use of PCM with different melting temperatures

A latent heat storage module with rapid charging and discharging rates has been developed. The heat storage module consisted of horizontal cylindrical capsules filled with three types of PCM with different melting temperatures. A numerical model has been developed to predict the transient behavior of the heat storage module. Both the experimental and numerical results showed some improvements in charging and discharging rates by use of a “three-type” PCM     

Thermal control of electronic equipment by heat pipes

In the frame of the BRITE-EURAM european programme (KHIEPCOOL project), a literature survey on the main heat pipe and micro heat pipe technologies developed for thermal control of electronic equipment has been carried out. The conventional heat pipes are cylindrical, flat or bellow tubes, using wicks or axial grooves as capillary structures. In the field of micro heat pipes, three and four corner tubes have been developed. The pipes are mounted on single chips, in-line chip arrays or integrated into the component interconnection substrate. The best performances were achieved with Plesch's axially grooved flat miniature heat pipe [1], which is able to transfer a heat flux of about 60 W·cm⁻². Theoretical models have shown that the performance of micro heat pipe arrays increase with increasing tube diameter, decreasing tube length and increasing heat pipe density. The heat pipe technologies are classified and compared according to their geometry and location in the system. A list of about 150 references, classified according to their subjects, is presented.     

组合式热管换热器在热泵系统中的试验研究

采用组合式热管换热器作为生活浊水余热热泵热水器的热管蒸发器,并在试验台上进行了不同污水进口温度和不同污水流量的可视化试验,通过分析试验结果,发现组合式热管上升管和下降管的温差很大的现象,这与热管特性相矛盾。采用理论分析和实验相结合的方法,研究了热管中产生温差的原因。它主要是由于下降管压力损失较大,使热管工质在热管蒸发器中的滞留引起。     

分离式螺旋热管蓄冰过程动态特性模拟

在提出分离式螺旋热管蓄冷空调系统的基础上,建立了螺旋热管蒸发段蓄冰过程的理论模型,分析了单位时间内管外结冰厚度、管外冰层厚度、蓄冰率、单位时间蓄冷量以及系统总蓄冷量随时间的变化关系,并对三种不同管径的螺旋热管的蓄冰特性进行了分析研究,研究结果表明在螺旋热管曲率半径相同的条件下,增大管径可以提高系统的单位时间蓄冷量。     

新型平板热管式太阳能集热技术

利用二维微通道阵列平板热管,提出了全新平板式太阳能集热技术及其热水系统,测试了平板微热管基本性能,将其应用于平板太阳能热水器,研制成功了新型平板热管式太阳能热水器,测试了热水器性能,其逐时最高效率为87.82%,日平均效率高达65.98%,且不受时域和地域限制,并具有成本低、抗冻、承压、紧凑、轻巧、不结垢等优点,整体性能优越,应用前景极其广阔。     

分离式螺旋热管管外融冰放冷特性分析

在提出分离式螺旋热管蓄冷空调系统的基础上,建立了螺旋热管管外融冰放冷过程的理论模型;分析了蓄冷桶内融冰量及放冷量随时间的变化关系。研究结果表明,在蓄冷桶进口水温一定的情况下,外融冰的循环水流量越大,其融冰放冷过程就越快;在外融冰循环水流量一定的情况下,放冷过程随蓄冷桶进口水温的升高而加快。     

Empirical Study of an Air-to-Air Heat Pipe Heat Exchanger in Tropical Climates

Abstract

This article presents the empirical study of a heat pipe heat exchanger that was directly experiencing the ambient tropical air in its evaporator section. The performance of the heat pipe heat exchanger was monitored during two weeks of operation to determine the performance curves. The temperature of return air was controlled at about 22°C as the representative temperature of inside air, and a face velocity of 2 m/s on the heat pipe heat exchanger coil was established for this purpose. It was found that for the present investigation, the heat pipe heat exchanger can pay for itself in 1.5 years.     

纳米流体在热管中应用的研究进展

随着纳米流体用于换热器的强化换热,纳米流体热管换热器的研究逐步扩展到各个领域,从航天到化工,从电子到能源。纳米流体热管由于表面温度低,较高的传热系数和较小的热阻,受到了广泛的关注。文中总结了纳米流体热管国内外的最新研究进展。     

Experimental and numerical analysis of cylindrical turbulators in a double pipe heat exchanger under turbulent flow conditions

In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor.     

Second law optimization of a latent heat storage system with PCMS having different melting points

The exergy efficiency, as well as the charging and discharging rates, in a latent heat storage system can be improved by use of the PCMs having different melting points. The melting point distribution of the PCMs has substantial effects on the exergy efficiency. The optimum melting point distribution of the PCMs has been estimated from numerical simulations and also from simple equations. The fast charging or discharging rate leads to high exergy efficiency.     

新型沟槽道微热管散热性能实验研究

微热管以其效率高、响应快且无能耗,在高功率集成微电子散热方面应用广泛。针对电子器件的小型化、高能耗发展趋势,本文提出一种新型沟槽道微热管结构,对该沟槽道微热管进行稳态和瞬态热性能实验研究,研究了风速、角度、加热功率等因素对该新型热管的热性能影响规律。结果表明,该微热管在整个散热器传热上起主导作用,性能比达到0.88,冷凝端温差为0.8℃,具有良好的均温性,该微热管加热功率为140 W,空气流速1.5 m/s时,换热系数可达2 359 W/(m^2·℃),热阻为0.27℃/W;高功率状态下可保持良好的热扩散性能,有效避免微热管的热应力集中,有望高效解决集成电子器件的散热问题。     

翅片长度对纵向翅片扁管换热器换热性能的影响

纵向翅片扁管换热器是一种新型换热器。气体沿扁管轴向方向流动,与管内介质的流动路径平行,可强化传热,减少气侧阻力,不易积灰结垢,维护方便。利用数值模拟方法,以纵向翅片扁管换热器为研究对象,分析翅片长度对换热性能的影响,对换热器的翅片长度进行优化。研究表明,不同进口风速对应不同的有效纵向翅片长度。随着进口风速的增大,翅片的有效长度越大。     

列管式换热器强化传热研究及发展

简述了列管式换热器强化传热技术的进展及发展方向,管程强化传热采用螺纹管、横纹管、波纹管、缩放管、管内插入物、三维内肋管、翘片管等传热元件,壳程强化传热采用板式支撑、折流插式支撑、空心环支撑、管子自支撑等管束支撑结构。指出了列管式换热器研究中存在的不足。指出了今后的发展方向,为列管式换热器的研究和应用提供理论参考。     

基于管排组合的热管换热器温度分布的研究

建立了热管废热锅炉的换热器模型,研究了在各种管排组合方案下的分离式热管换热器的工质温度分布、管壁温度分布、烟气温度分布及热回收量等,结果表明,调整管排组合是解决工质温度过高和低温腐蚀问题的一种有效方法.     

微矩形槽平板热管的设计制造及性能分析

目前微槽平板热管成为热管研究和开发的重点。文中简要介绍了平板热管的设计要点及制造工艺,并通过实验,对设计制作的平板热管进行了性能测试。得出如下结论:该平板热管具有良好的启动特性和工作特性;在设计中要注意工质与管壳材料的相容性;制作时要严格控制清洗、检漏、充装等关键工序以保证制作质量。     

气液双热源耦合换热器性能研究

设计了一种由管翅式换热器和套管式换热器耦合而成的气液双源耦合式换热器,该换热器可以实现一种介质同时与气态热源和液态热源进行同步耦合换热.对该换热器进行了详细的介绍,并对其耦合换热特性及该换热器在耦合热源热泵空调中应用时的制热工况进行了的性能测试.研究结果证明,使用该气液双热源耦合式换热器的耦合热源热泵空调系统,气液双热...     

球形堆积床蓄冷空调系统实验性能研究

文中对球形堆积床蓄冷空调系统的蓄冷和放冷特性进行实验研究。在实验过程中,测量堆积床内流体温度、蓄冷时蒸发器进出口温度、放冷时换热器进出口温度以及室内机组进风和出风温度。通过测量的数据,得出蓄冷和放冷过程中的蓄冷、放冷速率和蓄冷、放冷量随时间的变化。在放冷时,出风温度稳定在16℃。因此,该系统可以用于空调系统的蓄冷和放冷过程,既有利于电力负荷"移峰填谷",又能满足室内温度调节的需求。     

分离式螺旋热管在蓄冷系统的换热特性分析

阐述了分离式螺旋热管的换热特性,并提出了将螺旋热管应用于蓄冷系统的新方案。建立了分离式螺旋热管的换热模型,分析了热流密度、充液率以及几何尺寸对螺旋热管管内换热的影响,为螺旋热管结构的优化以及在蓄冷系统的应用提供了理论依据。