毛细管换热器在养殖水体温度调节中的应用

本文从传热学的基本原理出发,利用毛细管换热器的传热过程热量计算公式,探讨了不同毛细管长度、管间距及流量下的毛细管换热效果,为毛细管换热器在养殖水体温度调节提供参考。结果表明,管内介质流量和管长的增加,皆会增大毛细管换热量;管间距的增大伴随着换热面积的减小,换热效果降低。同时,根据毛细管换热的特点及海水温度和管内介质温度变化可知,进口温度与海水的温差越大,换热越明显。     

倾角对环状热管蒸发器性能的影响

针对生产过程中低品位能量回收,设计了带有环状管蒸发器的不锈钢水工质重力型分离式热管,环状管由31.6 mm管径内管热水加热,环空间隙为15.0 mm,可视化地研究了26 kPa蒸发压力,0~90 °倾斜角度下多个充注率环状管蒸发器的壁温特性。结果表明：该类热管的环状管蒸发器运行时存在一高温区,随倾角增加而扩大;环状管内蒸发侧平均表面换热系数随倾角增大先增后减、再增大,与沸腾流型随角度发生转变有密切关联;与一些相似文献进行了对比,发现环状管蒸发器与普通重力型热管在换热性能均在10~20 °倾角达到极大值,而环状管蒸发器则在90 °时达到了另一极大值。     

单/双U形地埋管换热器传热特性模拟研究

为了研究不同因素对单/双U形地埋管换热器传热特性的影响,建立单U形和双U形地埋管换热器传热物理数学模型,分析流体进口流速、流体进口温度、回填材料和土壤竖向温度梯度对地埋管周围土壤温度分布规律和单位管长换热量的影响。结果表明：地埋管周围土壤温度随流速的增加而增加且双U形大于单U形,对径向距离大于1 m的土壤基本无影响;双U形地埋管换热器的单位管长换热量大于单U形,双U形地埋管换热器的热短路现象更严重;增加流体进口温度时,土壤温度、单位管长换热量均增加,但热作用范围基本不受影响;回填材料为砾砂时的土壤温度增加幅度大于黏土,单位管长换热量大于黏土,但增加比例小于回填材料为黏土时的情况;土壤竖向温度梯度越大,土壤温度和单位管长换热量波动幅度越剧烈,且双U形的波动幅度大于单U形;钻井深度和土壤竖向温度梯度较大时,地埋管不宜采用U形管作为换热器。研究结果对单/双U形地埋管换热器的设计及地源热泵系统的运行提供参考。     

低气压环境下开缝翅片管换热器换热性能研究

利用低气压环境模拟装置对开缝翅片管换热器在不同气压下的换热性能进行实验研究.研究结果表明:随着气压不断降低,换热器周围空气密度逐渐降低,换热器空气侧换热系数以及显热换热量逐渐降低,而空气含湿量随着气压降低逐渐升高,导致潜热换热量逐渐增加;当气压降至0.058 MPa以下时,换热器空气侧潜热换热量占主要部分,当气压为0.04 MPa时,换热器换热能力与常压下相比下降了36.63%.     

太阳能相变蓄热复合土壤源热泵系统的研究

叙述了以太阳能相变蓄热装置蓄热,且与蒸发器进口处换热的辅助热泵系统,用20号蓄热专用石蜡,通过板式换热器与蒸发器进水管进行热量传递的实验。指出,利用太阳能集热器在白天升高蒸发器侧的温度提高热泵效率,利用储存在蓄热装置中的热量夜晚可对蒸发器的进水增温,以此实现太阳能相变蓄热装置与复合土壤源热泵系统的良好结合,提高整个系统的供热效率。     

海水源空调用盘管换热节能效果分析

为了研究海水源空调用盘管换热器节能效果,采用现场实验的方法对盘管单位管长换热量进行测定.基于实验测试值,结合工程实例,对海水源空调系统冷却水采用盘管换热器获取方式和传统冷却塔在节能、经济和环境方面进行对比.研究结果表明,管内流速越大换热量越大,在流速为0.7 m/s时,PE32的换热管单位管长换热量为27.2 W/m.此外,夏季采用盘管与海水换热制备冷却水的海水源空调系统经济性和环境效益明显.     

相关参数对增强型冷却塔换热性能影响的研究

以增强型冷却塔为研究对象,通过数值模拟的方法,对其在不同环境温度、湿度及不同换热器布置下的换热性能进行计算与分析,得到不同条件下空气流量和换热量的分布。研究表明:系统换热量随空气湿度增加小幅度增加,而随温度的增加却有较大幅度的下降;在换热面积一定且换热器均匀分组条件下,如换热器间隙有填塞物,换热量随着覆盖率的增加而减小;若换热器间隙无填塞物,换热量随着覆盖率的增加而增加至覆盖率为93%达到最大值,随后减小。最优换热器布置为:覆盖率93%,换热器分组均匀且尽量细分,间隙内无填塞物。     

非能动余热排出系统C型管换热器数值模拟

为保证在事故工况下非能动余热排除系统有效导出余热,对其主要设备PRHR热交换器进行换热特性研究,建立了非能动余热排出系统C型管换热器的内外耦合传热分析模型,采用一维均相流模型计算管内冷凝换热与CFD程序分析水池空间的自然对流。研究进口质量流量、进口流体含气率、管倾角和水箱温度对C型管换热器换热特性的影响。结果表明:C型管换热器入口倾斜段管内始终为饱和的两相流体,在竖直段与出口倾斜段,管内流体温度逐渐下降;管内压力、流体焓值和换热系数沿管长逐渐降低;大约在冷凝70 s后,管内流体参数趋于稳定;管壁温度在入口倾斜段迅速下降,在竖直段和出口段趋于平缓。增大进口质量流量与进口流体含气率,流体温度、流体焓以及管内外换热系数增加,并且沿流动方向受两者的影响逐渐减小;若管倾斜角度增大20°,出口倾斜段管内流体温度下降约3℃;当水箱温度升高10℃,汽泡生成与脱离速度加快,水箱内部换热增强,入口倾斜段外壁温升高2℃左右,出口倾斜段外壁温大约升高0.2℃。CFD模拟结果展示出水箱内汽泡大部分聚集在C型管上部并逐渐向上流动,致使热流体向上运动,冷流体向下流动,形成自然循环。     

板式相变储能换热器流动与换热性能实验研究

为了探究板式相变储能换热器在不同工作状态下的流动与换热性能,以及不同工况下的损失。通过实验研究换热流体的流速、温度以及板式相变储能的摆放位置对相变储能换热器出口温度、换热功率以及效率的影响。实验结果表明,在相变材料融化结束前,进口流体流速高、温度低时,出口流体温度高,进口流体流速低、温度高时,出口流体温度低;当相变材料融化结束后,进口流体流速高、温度低时,出口流体温度低,进口流体流速低、温度高时,出口流体温度高。换热流体温度高、流速低时,效率低;换热流体温度低、流速高时,效率高。相变储能换热器的摆放位置对换热器的流动与换热性能只产生微弱的影响。     

重力热管内部相变及传热传质过程的数值模拟

重力热管内部包含复杂的两相流动以及相变传热过程,传统理论分析及实验手段不能直观给出其内部流动、相变、热质传递的详细信息。采用VOF(volume of fluid)多相流模型对重力热管内气液两相流动及传热进行模拟,捕捉到蒸发段气泡产生、合并、长大、上升,以及冷凝段壁面附近液滴形成、合并、下滑、汇集到液池的全过程,得到的壁温分布与实验测量值对比体现良好一致性,表明数值模拟的正确性。同时,以热阻、传热量和热效率为评价标准,研究不同充液率和倾斜角度下对重力热管运行性能的影响。结果表明:在所研究的参数范围内,随着充液率的增加,热阻逐渐减小,冷凝段传热量逐渐增大。且工质初始充注量充满蒸发段时热管性能较好;倾角对热阻的影响不明显,冷凝段传热量和热效率均随倾角增加而增长。     

显热储热材料的制备及性能研究

采用水泥作为材料的胶凝剂,添加热容、热导率大的物质作为骨料来制备混凝土储热材料。研究表明:当铝酸盐水泥含量为10%时,材料的抗压、抗折强度能满足工业需求;材料的比热容随温度的升高先增大,在500℃时达到最大,后随着温度的升高反而降低;材料的热导率随着石墨粉含量的增加几乎成直线上升,当石墨含量为5%时材料的热导率大于1.7W/(m·K)。     

On the steady‐state modelling of a two‐stage evaporator system

We develop and validate against experimental measurements a steady‐state two‐stage flooded refrigerant evaporator model for a heat pump drying system. A prototype two‐stage heat pump dryer test facility was designed, built and instrumented to provide the required measurements for the validation of the model. Repeatability and data quality tests were conducted to evaluate the accuracy of measurements. Experimental data could be reproduced to within ±6.5 per cent of replicated air and refrigerant side measurements for the same evaporator's air inlet conditions while the discrepancy of energy balance at the air‐side and refrigerant‐side was observed to be within ±8.9 per cent. The two‐stage evaporator model predicted the air‐side total heat and latent heat transfer of the two‐stage evaporator to within (?6.3 per cent, 7.6 per cent) and (?11.5 per cent, 9.5 per cent), respectively. On the refrigerant‐side, the model enabled the calculation of the degree of superheat to within (?10.6 per cent, 1.7 per cent). The model has shown that there is significant improvement in the heat recovered from a two‐stage evaporator system compared to a single evaporator system. In addition, the model demonstrated that the improvement in total heat recovery could be as high as 40 per cent over its base‐value when the latent to total load at the two‐stage evaporator is increased. Copyright © 2001 John Wiley & Sons, Ltd.     

间歇式热处理炉传热计算与分析

建立了台车式热处理炉炉膛传热数学模型和辐射换热器工作模型,分析了换热器的传热特性（空气预热温度、壁温、传热系数）随炉况的变化。结果表明,辐射换热器的传热特性随炉子的升温及保温过程变化而波动很大,因而对炉子的热工性能产生了影响。     

Quantification of the European industrial heat demand by branch and temperature level

We present the first comprehensive estimate of the final energy demand for heat in all EU28 member states for the reference year 2012, differentiated by temperature levels, comparing two different approaches. Two different calculation approaches based on different data sets yielded estimates of the total final energy demand for heat in the EU28 of 8150 PJ and 8518 PJ in 2012, respectively. Approach 1 distinguishes between three different process heat (PH) temperature levels and results in final energy demand for heat <100°C: 2077 PJ, 100–400°C: 2214 PJ and >400°C: 3859 PJ. The second approach distinguishes between low temperature space heat and hot water (<100°C: 1161 PJ) and four different PH temperature levels with a resulting energy demand of <100°C: 1027 PJ, 100–500°C: 1785 PJ, 500–1000°C: 1679 PJ and >1000°C: 2865 PJ. The high share of high‐temperature heat illustrates the limits to the potential decarbonisation of industrial thermal processes with renewable energy sources such as (non‐concentrating) solar thermal, geothermal or environmental heat. Therefore specific information on required temperature levels is of the essence. This, in turn, points out the relevance of renewable electricity and synthetic fuels based on renewable power for a significant reduction of CO₂ emissions from the industry sector in Europe. Considering current data quality, it is recommended to develop a consistent, comprehensive methodology to significantly improve the data basis on industrial heat demand. Copyright © 2015 John Wiley & Sons, Ltd.     

Heat pump dryer Part 1: Simulation of the models

Heat pump dryer is a complex system because of the interaction of heat and mass transfer of the working fluids. Since the system cannot be completely close, ambient conditions (temperature and humidity) influence the performance of the system. To investigate the performance of the heat pump dryer thoroughly, simulation models of heat pump dryer components have been developed. The finite-difference method was employed in the simulation to examine the state of the working fluids and heat and mass transfer. The simulation of each component can be used to construct different system configurations the results of which are reported in Part 2.     

国内分离式热管概况与热环研究的小结及展望

本文对我国分离式热管技术的研究进行了简要概况,针对工程中热源在上,冷源在下及冷热源相距较远时的热量传递问题,在分析了一般分离式热管及“水回路”等技术的基础上,对一种新型分离式热管－泵或风机驱动的动力型分离式热管（简称热环）的研究进行了小结和展望。     

地源热泵竖直埋管的有限长线热源模型

对地热换热器竖直埋管的非稳态传热模型进行了分析讨论。采用虚拟热源和格林函数法给出了半无限大介质中有限长线热源产生的非稳态温度场的解析解表达式。与稳态温度场的解进行比较,讨论了温度场达到名义上的“稳态”所需的时间,同时对于达到稳态时的温度场也进行了分析,指出了现行教科书中关于该问题的错误,提出了稳态时两个地热换热器孔壁代表性温度的定义,并对两者进行了比较,进而给出了可供工程应用的简化计算公式,并对两者进行了比较,进而给出了可供工程应用的简化计算公式。基于以上分析,进一步讨论了全年冷热负荷不平衡对地热换热器长期性能的影响。     

Augmentation of heat transfer through passive techniques

The thermal performance of energy preservation systems is greatly improved by increasing miniaturization and boosting. These are imaginative (or Promethean) techniques to enhance heat transfer. Enhancement methods of heat transfer draw great attention in front of the industrial sector because of their ability to provide energy savings and raise the economic efficiency of thermal systems. Three techniques these methods are categorized; those are active, passive, and compound. Different types of components are used in passive methods because of the transfer/working fluid flow path to the enhancement of the heat transfer rate. In this article, the subject of the review was the passive heat transfer enhancement methods including inserts (conical strips, winglets, twisted tapes, baffles), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), extended surfaces (fins) and nanofluids (mono and hybrid nanofluid). Recent passive heat transfer enhancement techniques are studied in this article as they are cost-effective and reliable, and also comparably passive methods do not need any extra power to promote the energy conversion systems' thermal efficiency than active methods. In the passive approaches, various components are applied to the heat transfer/working fluid flow path to improve the heat transfer rate. The passive heat transfer enhancement methods studied in this article include inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluid). From the pioneers' research work, it is clear that a lower twist ratio and lower pitch, lesser winglet angles can provide more heat transfer rate and a little bit more friction factor. In the case of nanofluids, a little bit of pumping power is enhanced. Finally, heat transfer enhancement is compared with the thermal performance factor, which is more than unity.     

Field test of a novel combined system of a high-efficiency heating/cooling heat pump and a clathrate cool storage unit

The Research Laboratory of Kyushu Electric Power Co., Inc. (KEPCO) installed a novel system in March 1992 which is a combination of a super heat pump with about twice the performance of a conventional one and a compact chemical storage-type clathrate cool storage unit. A field test was implemented by integrating these units into an actual air-conditioning system. As a result of the test, system performance was determined and the effectiveness of the system was confirmed. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(6): 410–418, 1997     

城市住宅及企业集中供热浅析

随着住宅商品化进程的进一步加快 ,以及供热商品化意识的普及 ,人们对集中供热提出了更高的要求 ,在利用其它手段诸如空调、电暖气等设施取暖的同时对集中供热进行开发