平流层电子设备温度数值模拟

分析了平流层电子设备内外部热环境,考虑平流层大气对流、设备内部自然对流、太阳直射辐射、大气辐射、地面反射太阳辐射、地球红外辐射以及设备自身辐射等因素的基础上,建立了计算电子设备温度分布特征的对流、辐射耦合模型,模拟了其在不同功率、不同对流换热、不同环境条件下的温度分布。结果表明:对于平流层电子设备散热,对流换热和辐射换热都会影响电子设备的温度分布,尽管由于平流层大气压力低、对流换热弱,但对流换热量占到散热总量的60%以上,是散热的主要方式。因此,在平流层电子设备热设计时,可以优先考虑采取开孔等强化对流散热方法来控制设备的温度。最后,开展了平流层模拟环境的实验验证,典型工况实验值与计算值吻合较好,验证了计算模型的正确性。对平流层电子设备热设计有重要的指导意义。     

太阳能直供毛细管末端辐射供暖系统的实验研究

描述太阳能直供毛细管末端辐射供暖系统,并通过实验对室内热环境进行分析,结果表明晴天工况时,毛细管壁面温度响应较快,全天实验房间平均温度比非采暖房间平均温度高4.5℃左右,关闭太阳能集热循环泵3h后,单位面积毛细管供热功率仍能基本满足实验房间的平均采暖热负荷.全天室内热舒适性较好,温度基本达到设计计算要求.实验结果为天津地区低能耗建筑应用此套系统的可行性提供了参考.     

三维填充床内换热及热回流机理研究

利用计算流体力学（CFD）对顺序排列多孔介质小球的三维填充床进行数值模拟。研究填充床内位置及空气流速变化对温度分布、努塞尔数影响,并对多孔介质小球的热回流特性进行分析,揭示填充床内传热机理。结果表明：相比于气-固两相交替存在处,与小球相切处的热的非平衡性更强。最高温度上游的换热强度与下游相比更强烈;当流速增加时,上游的对流换热作用增强,下游变化不大。在热回流过程中,在入口区域对流换热占主导地位,导热和辐射换热作用较弱;在主流场区域,导热占主导地位,其次是辐射换热,对流换热作用最弱。     

极端热湿气候区建筑外壁面总换热系数研究

统计中国不同气候区主要代表城市冬、夏季室外平均风速及逐时降雨情况,采用理论研究和数据统计相结合的方法,分析对流、辐射和蒸发换热系数的理论计算方法,进而计算各城市外壁面总换热系数。结果表明:极端热湿气候区风速远大于内陆地区且壁面潮湿概率可达0.042;中国北方地区及南方部分风速特别小、壁面潮湿概率相对较小的城市,总换热系数可按规范忽略蒸发换热,但南方风速大、降雨多或风速相对较小、降雨特别频繁的城市,则需要计算蒸发换热部分。极端热湿气候区建筑夏季潮湿外壁面总换热系数经计算可达39.0 W/(m~2·K),远高于规范值。     

考虑建筑房间内导热辐射与自然对流耦合时外围护结构对对流换热的影响

对具有导热和表面辐射换热相互耦合的建筑房间内的自然对流进行了数值研究。计算采用层流模型,为SIMPLE算法,QUICK差分格式。计算结果表明,辐射参与换热对流动将产生显著影响,会使房间内形成二次涡流。在自然对流的房间内,辐射换热比对流换热更占主导地位。当具有外围护结构时,导热效应使总对流换热有所增长(曲线的初始部分),但当导热系数比超过一定值时(kr≥10),再增加固体的导热性能,对房间内的流动和换热的影响就不明显了。从数值上证实了在实际建筑环境中,只要外围护结构的厚度达到一定数值就可达到隔热保温的要求。再增加厚度并不会得到更好的效果。     

考虑水—汽两相流增压锅炉近炉对流蒸发管的换热分析

考虑近炉对流蒸发管内的水—汽两相流动,依据传热学原理,计算管内工质在不同温度不同流速下的对流换热系数。进一步考虑管外高温烟气的辐射对流换热、管外火焰的辐射换热和管内水—汽两相流的对流换热,采用有限元方法计算近炉对流蒸发管在紧急启动下的瞬态温度场;与实际温度场对比,吻合良好。提出的考虑水—汽两相流动确定对流换热系数的方法及温度场分析结果有一定参考价值。     

辐射通道一维稳态温度场数值模拟

为得到辐射对流通道中的温度分布,依据能量守恒原理,建立了辐射、对流非线性边界条件下圆形管壁与管内空气的传热数学模型,提出了管壁温度、管内冷却空气温度一维稳态换热有限差分求解方法,其中辐射换热计算采用基于辐射传递系数的蒙特卡罗法。分析了相关参数对辐射通道温度分布的影响,所研究的参数包括辐射器表面温度、管道长度与半径比、管内冷却空气流速等。计算结果表明：辐射器表面温度是影响辐射通道最高温度的主要因素。此方法可为辐射通道精细的热工特性计算提供温度场数据。     

基于热管置入式墙体的室内热环境研究

以墙体传热实验数据为依据,利用数值模拟技术定量研究应用于南外墙的热管置入式墙体(WIHP)在供暖季对天津地区低能耗居住建筑室内热环境和热舒适的影响。结果表明:热管置入式墙体在其工作时能改善低能耗居住建筑的室内热环境和人体热舒适;相较于未安装热管置入式墙体的对比建筑,模拟建筑室内空气温度和平均辐射温度在热管工作时平均提高1.1℃,预测平均热感觉指标相较于对比建筑提高32.54%。     

采暖建筑外表面热流及换热系数现场测试研究

建筑表面换热系数是建筑热工与节能及暖通空调领域的重要基础计算参数。为研究实际建筑表面热流与换热系数的波动趋势,为换热系数的取值和边界条件的设置提供合理的实测依据,采用一种新型超薄热流传感器,利用直接热平衡法,实测了西安采暖季期间的某办公建筑外墙,获取了外表面的辐射、对流及总热流,对流与辐射换热系数的变化曲线。结果表明,测试期间外表面辐射与对流换热系数分别在2.19～11.32 W/(m~2·K)和0.15～6.58 W/(m~2·K)之间变化;总热流中辐射热流平均占比80%;城市中心低风速区域,对流换热系数值较小,其取值需重新考虑;对风速较低的自然风,给出对流换热系数分别与风速和湍流度的关系式,发现对流换热系数与湍流度相关性更好;对于重质围护结构,换热系数取值带来的误差较小;而对于传热系数较大的轻质围护结构,取固定值可能会产生较大的误差。     

基于非接触测量的圆柱相界面对流传热系数计算方法研究

为发挥非接触测量实验方法在相变对流换热研究中的优点,充分考虑显热传热在整个相变传热中的作用,以长圆柱对流融化过程为研究对象,建立圆柱内部导热控制方程及定解条件,采用三次多项式热平衡积分方法进行近似求解,构建基于非接触测量的圆柱相界面对流换热系数计算方法。建立水流顺掠冰柱实验台,通过对实验例题的分析与讨论得到结论如下:圆柱相界面对流换热系数与相界面位置、圆柱半径融化速率、融化时间、圆柱初始温度及圆柱中心温度等参数有关,该计算方法能够较好的反映出显热变化对于对流换热系数的影响;相界面位置是影响对流换热系数计算准确性的主要因素,提高其测量准确性是减小计算误差的主要努力方向。     

基于计算机仿真的低温地板辐射采暖系统的节能性分析

介绍了基于空间热网模型的采暖系统的计算机仿真程序，并运用该程序对低温地板辐射采暖和对流采暖两种系统进行计算机仿真，通过对一个采暖日内两种采暖方式下房间的采暖负荷、室内平均空气温度和维护结构内表面温度的动态分析和比较，证明了在维持房间相同热舒适度的情况下，低温地板辐射采暖系统的采暖负荷比对流采暖系统的采暖负荷小，具有节能性。     

室内低温热水地板辐射供暖系统的节能分析

本文阐述了低温热水地板辐射采暖分户热计量系统是一种易控、易调、节能的采暖系统,讨论了地板辐射供暖方式与其他方式在房间内人体热舒适方面的差异,并通过对其综合节能效果的考察,分析了地板辐射供暖系统不稳定供暖过程的数学模型,用数值计算的方法分析了间歇供暖条件下,达到室内要求温度所需的预热量与预热时间的关系。     

Thermal performance and energy saving investigation in a modified baseboard radiator and compare it with conventional heating systems—Experimental and CFD approach

In the present work, thermal performance of a new modified baseboard radiator is investigated experimentally based on the European Standard EN-442. Temperature distribution and thermal comfort conditions of the floor heating system and panel radiator is compared with the present system numerically. To validation of the simulation results, a comparison has been made between the simulation and the experimental obtained results. Comparison shows that there is a good agreement between them. The heat output rate of the new system increased about 46.06% compared with conventional baseboard radiant model and also the baseboard heating system is capable of providing better thermal comfort conditions than two other systems. Energy consumption in three systems is investigated experimentally by smart temperature control mechanism. Results show that energy consumption in the baseboard radiant is 83.03% and 55.96% lower than floor heating system and panel radiator, respectively.     

Energy efficiency and indoor thermal perception: a comparative study between radiant panel and portable convective heaters

This study investigates experimentally the thermal perception of indoor environment for evaluating the ability of radiant panel heaters to produce thermal comfort for space occupants as well as the energy consumption in comparison with conventional portable natural convective heaters. The thermal perception results show that, compared with conventional convection heater, a radiantly heated office room maintains a lower ambient air temperature while providing equal levels of thermal perception on the thermal dummy head as the convective heater and saves up to 39.1% of the energy consumption per day. However, for human subjects’ vote experiments, the results show that for an environmentally controlled test room at outdoor environment temperatures of 0°C and 5°C, using two radiant panel heaters with a total capacity of 580 W leads to a better comfort sensation than the conventional portable natural convective heater with a 670 W capacity, with an energy saving of about 13.4%. In addition, for an outdoor environment temperature of 10°C, using one radiant panel heater with a capacity of 290 W leads to a better comfort sensation than the conventional convection heater with a 670 W capacity, with an energy saving of about 56.7%. From the analytical results, it is found that distributing the radiant panel heater inside the office room, one on the wall facing the window and the other on the wall close to the window, provides the best operative temperature distribution within the room.     

Performance evaluation of a radiant floor cooling system integrated with dehumidified ventilation

The radiant floor cooling system can be used as an alternative to all-air cooling systems, using the existing Ondol system (a radiant floor heating system) in Korea to save energy and maintain indoor thermal comfort. Unfortunately, a radiant floor cooling system may cause condensation on the floor surface under hot and humid conditions during the cooling season. In addition, the radiant floor system does not respond quickly to internal load changes due to the thermal storage effect of the concrete mass, which is usually present in radiant floor cooling systems.This study proposes a radiant floor cooling system integrated with dehumidified ventilation, which cools and dehumidifies the outdoor air entering through the cooling coil in the ventilator by lowering the dew-point temperature to prevent condensation on the floor surface. Furthermore, outdoor reset control was used to modulate the temperature of chilled water supplied to the radiant floor, and indoor temperature feedback control was then used to respond to the internal load changes.To evaluate the performance of the radiant floor cooling system integrated with dehumidified ventilation, both a physical experiment in a laboratory setting and TRNSYS simulation for an apartment in Korea have been conducted. As a result, it was found that the proposed system was not only able to solve the problem of condensation on a floor surface but also to control the indoor thermal environment within the acceptable range of comfort. Furthermore, the proposed system improved the responsiveness to internal load changes.     

低温热水地板辐射与低温电热地膜辐射供热方式的特性分析

主要对低温热水地板辐射与低温电热地膜辐射供热方式进行分析。分析了低温热水地板辐射与低温电热地膜辐射两种供热系统的节能特性及其适应性;两种供热系统存在的问题及及其在集中供热中的应用发展前景。     

地板辐射采暖和风机盘管采暖室内热环境及能耗比较

对地板辐射和风机盘管两种采暖方式进行了实验研究和理论分析，提出了围护结构临界热阻临的概念，推导出了两个采暖系统的热舒适性随围护结构热阻和冷风渗透量波动的变化关系。实验验证了地板辐射采暖既改善了室内热环境又显示较好的节能效果。     

浅析火炕与低温地面辐射供暖住宅的生态节能性

调查表明火炕仍然是我国北方小城镇和农村住宅中最重要、最有效的供暖设施;新建的城市住宅中低温地面辐射供暖逐渐普及,其原因在于辐射供暖具有供热均匀、热舒适性好、散热体蓄热性强、节能明显等优点。文中对比普通的暖气供暖,分析了住宅中火炕与低温地面辐射供暖的独特优势,各自的适用场合。最后提出了推广应用火炕与低温地面辐射供暖的建议,以及对火炕的改进建议。     

低温地板辐射采暖构造层传热模拟

本文针对以哈尔滨为代表的寒冷地区的低温热水地板辐射供暖系统的传热特点和铺设方式，建立了构造层内传热过程的数学模型，分析了低温热水地板辐射供暖系统的热工性能，确定了构造层内温度分布、地板表面温度分布、单位面积散热量等设计指标与管间距、水温、表面材料之间的定量关系。     

Passive solar radiant system,SIRASOL. Physical–mathematical modeling and sensitivity analysis

When using passive solar heating systems, it is necessary to have available an Equator-facing facade on which to install them. Rooms without such a facade are not the best option for conventional passive solar heating systems. SIRASOL is a passive solar radiant system that captures solar energy and is to be installed in the ceiling of the room. This room must not necessarily have an Equator-facing facade. Solar energy heats up a metal sheet, which is the radiant panel, which transfers heat by long-wave radiation to the room below it. This paper presents a mathematical model and a sensitivity analysis. The mathematical model was used to analyze radiant panel temperature, radiant mean temperature, operative temperature and panel surface area. Results of the sensitivity study showed that when solar radiation rises (from 200 to 800 W) panel temperature increases from 36 °C to 92 °C, whereas variations in outside and inside air temperature have a negligible impact on the panel temperature. Thus, the use of SIRASOL is possible in locations with clear skies. Moreover, from panel temperature values we calculated mean radiant temperature and thereby the room’s operative temperature, which is proportional to the radiant panel area. When this area is 50% of the room’s floor area, operative temperature grows 3.1 °C higher than inside air temperature when solar radiation is 500 W/m². The analysis shows that a thermal asymmetry appears only when SIRASOL’s surface area to floor area ratio is higher than 32%.