共查询到17条相似文献,搜索用时 250 毫秒
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全玻璃真空管太阳热水器数值模拟研究 总被引:2,自引:0,他引:2
基于FLUENT软件及TECPLOT软件,通过对均匀加热条件下的全玻璃真空管太阳热水器内流场及温度场的数值模拟,研究了热水器的对流换热与传质过程;分析了集热管倾角、真空管双面受热对热水器内流场及温度场的影响和真空管与水箱连接处、垂直等温面上的流体速度、温度分布。结果表明,在真空管与水箱连接处出现随机的涡流和真空管内出现分段的小环流,对传热传质过程不利,特别是对于带反射板的双面受热的集热器,应采取措施确保管内对流换热流动的有序性。建议加装导流板,并初步探讨了导流板的长度,确立了最佳板长模拟结构,为后续的理论研究与试验打下基础。 相似文献
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文章建立了三维非稳态的全玻璃真空管太阳热水器的数值模型,分析了夜间散热时,该热水器内的流动和传热特征,并且在夜间同一工况下,模拟研究了贮热水箱保温材料的导热系数、保温厚度,以及真空管涂层的发射率对贮热水箱温度、真空管温度和该热水器夜间热损失的影响。分析结果表明:随着散热过程的持续进行,全玻璃真空管太阳热水器内温度分层情况越来越明显,内部流体的流速越来越小,真空管内静滞区域自下往上逐渐扩大;当贮热水箱保温材料的导热系数由0.035 W/(m·℃)减小至0.020 W/(m·℃)时,该热水器的夜间热损失减少了8.5%;当贮热水箱保温厚度由50 mm增加至60 mm时,该热水器的夜间热损失减少了5.0%;当真空管涂层的发射率由0.06减小至0.05时,该热水器的夜间热损失减少了4.0%。 相似文献
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<正>太阳能热水器具有安装使用方便灵活、节能效果明显等优点,目前普及较广的是全玻璃真空管式太阳能热水器。水箱式的结构决定了其不可避免地会产生水垢,为了防止水垢进入真空集热管内,实际生产中大多数厂家都将真空管伸入水箱内10~20cm不等。在寒冷的冬季,采用这种结构的太阳能热水器由于室外管路上冻,水箱内水位达不到集热管伸入的水位,长时间以后,造成集热管收集的热量无法与 相似文献
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近几年 ,太阳能热水器以其安全、经济、适用、无污染 ,逐渐被城乡居民所接受。随着太阳能热水器用户的逐年增多 ,由此而引发的问题也逐年增多 ,如果能充分认识太阳能热水器运行规律 ,正确地操作、使用 ,不仅可以大大延长其使用寿命 ,而且可以起到事半功倍的效果。下面简要介绍几种全玻璃真空管太阳能热水器的使用技巧和常见故障排除。一、使用技巧1、科学地安排上水时间和上水量全玻璃真空管式太阳能热水器忌空晒后上水 ,否则容易造成真空管暴裂。福建地区最佳的上水时间为早上七点钟之前 ,经过一夜的冷却和散热 ,此时真空管内壁温度最低 ,… 相似文献
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对一种新型简化CPC(非追踪式复合抛物线聚光板)式全真空玻璃集热管太阳能高温空气集热系统的传热过程进行了理论分析和数值模拟计算,通过实验数据对该传热模型进行了验证分析。该系统由多个集热单元组成,每个集热单元包括一个简化CPC集热板,一根全真空玻璃集热管,在玻璃集热管内安装一个U形铜管。流动空气在各级U形铜管内被逐级加热。计算研究表明:系统空气最大出口温度可达到200℃,系统平均集热效率达到0.3以上,整个系统表现了良好的高温集热特性。同时,计算也表明当系统工质流量增加时,只要系统增加更多的集热管以增加系统总功率即可满足工质温度达到200℃的设计要求。研究提出的新型简化CPC式全真空玻璃集热管太阳能高温空气集热系统是一种有工业实用前途的太阳能集热器;研究提出的传热模型模拟效果也可以满足一般性工程计算需求。 相似文献
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对夹层换热器的传热效率和总传热系数以及带夹层换热器平板型太阳能热水器的热性能进行测试与分析,对比分析三种热水器的平均日效率和平均热损系数。测试结果表明,夹层换热器的换热效率都在85%以上,一天中的平均总传热系数(UA)hx为88.16 W/K;带夹层换热器的平板太阳能热水器的平均日效率为49.8%,低于普通平板太阳能热水器的平均日效率(53.4%),但要高于全玻璃真空管太阳能热水器的平均日效率(48.7%)。 相似文献
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全玻璃真空管空气集热器管内流动与换热的数值模拟 总被引:2,自引:0,他引:2
目前,对于太阳能集热器的数值模拟大多是基于一维、非稳态的简化模型之上。该文采用三维数学及物理模型对插管提热系统的流动与换热情况进行了数值模拟。并对模拟结果进行了实验验证。 相似文献
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为了实现太阳能热水器和建筑的结合,设计了一种分体式全玻璃真空管太阳能热水器。它由集热器、室内储水箱、上升管和下降管组成,其集热器的每根真空管内有一个分水管,分水管通过集箱内的集管与下降管相连。与已有的太阳能热水器相比,其分水管把真空管内的冷、热水流道分开,减少了冷热水流相互干扰,提高了热水器效率,同时实现了分体式太阳能热水器系统的自然循环。实验表明,带内集管的分体式太阳能热水器比不带内集管的分体式太阳能热水器有更高的效率。 相似文献
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Numerical and Experimental Investigation on Heat Transfer Performance of a Solar Single Storage Tank
《热科学学报(英文版)》2021,(5)
The single-tank latent heat thermal energy storage(LHTES) of solar energy mainly consists of two modules: the first one is the phase change material(PCM) module heated by solar energy; the second is a module of heat transfer between melted PCM and the user's low-temperature water. This paper mainly focuses on the former one. To investigate the heat transfer performance of the paraffin-based solar single storage tank and find a more suitable experimental configuration, as basic research work, we established a single-tank thermal storage platform and then conducted a numerical simulation on the heat transfer process with Fluent. The result of numerical simulation shows that the test situation was basically reflected and the data agreed well with the experiment results. The numerical simulation analysis is accurate and the method is reliable. To obtain the heat transfer performance of paraffin in a single tank and strengthen heat transfer, the aspect ratio, the melting temperature of paraffin, and the heating power of the electric heater were analyzed based on simulation. The results show that the heat transfer gets more uniform when the aspect ratio is lower. This results in an increase in the liquid fraction of 61.83% to 76.47% one hour after heating when the aspect ratio of the tank reduced from 2.8 to 1.1. The higher the melting temperature of paraffin, the longer it takes for PCM to reach a stable state. And the curvature of liquid heating is greater than that of solid heating at the bottom layer. Under the constant total work, the heating power has little effect on the heat transfer performance of the paraffin. This study will provide some reference value for the optimization design of single-tank LHTES systems in the future. 相似文献
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Performance analysis on a novel micro‐channel heat pipe evacuated tube solar collector‐incorporated thermoelectric generation
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In China, because of the emergence of a large number of high‐rise buildings, the solar hot water heater system often uses the balcony wall‐mounted method for installation. The thermoelectric energy converter is proposed as one of the possible technologies to incorporate solar water heater to produce electricity for building application. In this paper, the conceptual development and theoretical analysis of a novel micro‐channel heat pipe evacuated tube solar collector‐incorporated thermoelectric generation are all proposed. The new system takes into account many advantages, including the high heat transfer, low convective heat loss, and low contact thermal resistance. The exergy analysis method based on the second law of thermodynamics is also introduced to evaluate the performance of this system. The results show that a novel micro‐channel heat pipe evacuated tube solar collector‐incorporated thermoelectric generation has a high thermal performance with addition of electricity production. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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利用fluent软件中的太阳载荷模型对真空管家用太阳热水器进行了三维数值模拟计算,分析了30°、45°、60°倾角下真空管热水器内的流场和温度场随加热时间的变化及传热和流动过程。结果表明,真空管热水器在加热期间,在真空管管口的上壁面出现温度最大值,水箱内真空管管口以下水的温度相对于管口以上的温度分层很明显,水箱内真空管管口以上的热水温度几乎相同,说明水箱内管口以上的水进行了充分混合;对于30°和45°倾角的系统,随着加热时间的增加,水箱内管口以下的水温与管口以上的水温从10 K增加到30 K,以45°倾角为例,当考虑了水箱内管口以下的冷水区时,随着加热时间的增加,真空管与水箱内的温差从0.73 K增大到1.13 K,仅考虑水箱内均匀分布的三点时,随着加热时间的增加,真空管与水箱内的温差从0.15 K减小到了0.03 K;随着系统倾角从30°增加到60°,水箱内管口以下的冷水区域在逐渐减小。因此,为了减小水箱底部的冷水区,插入水箱内的真空管应尽可能短。 相似文献
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Jeong Tai Kim Hyun Tae Ahn Hyunjoo Han Hyung Taek Kim Wongee Chun 《International Communications in Heat and Mass Transfer》2007
A numerical investigation has been carried out for a solar system, which consists of all-glass (double skin) solar vacuum tubes. Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is filled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. Results show good agreement when compared with other experimental data demonstrating the reliability of the present model. The one-dimensional numerical model could be used efficiently in designing all-glass solar collector tubes with different geometrical parameters other than those considered in the present analysis. 相似文献