Effect of the Arrangement of a New-Type of Turbulator Inserts on Heat Pipe Exchanger Performances

This research tests the effect of introducing turbulators of a new type into a circular tube heat exchanger under a constant and uniform longitudinal heatflux condition.A 45 mm diameter copper tube with a length of 1,350 mm is utilized with a solid disk being inserted inside the tube,which consists of three sections,each one containing two slots.The slot is cut at a 45 degree angle toward the inner tube surface,which results in diverging theflow toward the inner hot tube surface in order to enhance the heat transfer process.Air is considered as the workingfluid with Prandtl number 0.71.The Reynolds number spans the interval from 6,000–13,500,which indicates that the consideredflow is turbulent.The heat exchanger performance is studied and analyzed in terms of average Nusselt number.The experimental results show that the Nusselt number value is directly proportional to the increase of the Reynolds number,and the number of turbulators inserts.With the use of three novel turbulators,the heat transfer was about 3.15 times higher than that in the smooth tube and the friction factor was about 1.11.

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

This work contributes to the improvement of energy-saving in air conditioning systems. The objective is to apply the thermal efficiency of heat exchangers for localized determination of the thermal performance of heat exchangers with individually finned heat pipes. The fundamental parameters used for performance analysis were the number of fins per heat pipe, the number of heat pipes, the inlet temperatures, and the flow rates of hot and cold fluids. The heat exchanger under analysis uses Freon 404A as a working fluid in an air conditioning system for cooling in the Evaporator and energy recovery in the Condenser. The theoretical model is localized and applied individually to the Evaporator, Condenser, and heat exchanger regions. The results obtained through the simulation are compared with experimental results that use a global approach for the heat exchanger. The thermal quantities obtained through the theoretical model in the mentioned regions are air velocity, Nusselt number, thermal effectiveness, heat transfer rate, and outlet temperature. The comparisons made with global experimental results are in excellent agreement, demonstrating that the localized theoretical approach developed is consistent and can be used as a comprehensive analysis tool for heat exchangers using heat pipes.

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

This work contributes to the improvement of energy-saving in air conditioning systems. The objective is to apply the thermal efficiency of heat exchangers for localized determination of the thermal performance of heat exchangers with individually finned heat pipes. The fundamental parameters used for performance analysis were the number of fins per heat pipe, the number of heat pipes, the inlet temperatures, and the flow rates of hot and cold fluids. The heat exchanger under analysis uses Freon 404A as a working fluid in an air conditioning system for cooling in the Evaporator and energy recovery in the Condenser. The theoretical model is localized and applied individually to the Evaporator, Condenser, and heat exchanger regions. The results obtained through the simulation are compared with experimental results that use a global approach for the heat exchanger. The thermal quantities obtained through the theoretical model in the mentioned regions are air velocity, Nusselt number, thermal effectiveness, heat transfer rate, and outlet temperature. The comparisons made with global experimental results are in excellent agreement, demonstrating that the localized theoretical approach developed is consistent and can be used as a comprehensive analysis tool for heat exchangers using heat pipes.

Numerical Simulation and Optimization of a Mid-Temperature Heat Pipe Exchanger

In this paper,we take the mid-temperature gravity heat pipe exchanger as the research object,simulate the fluid flow field,temperature field and the working state of heat pipe in the heat exchanger by Fluent software.The effects of different operating parameters and fin parameters on the heat transfer performance of heat exchangers are studied.The results show that the heat transfer performance of the mid-temperature gravity heat pipe exchanger is the best when the fin spacing is between 5 mm and 6 mm,the height of the heat pipe is between 12 mm and 13 mm,and the inlet velocity of the fluid is between 2.5 m/s to 3 m/s.

Research on Performance of Ground-Source Heat Pump Double U Underground Pipe Heat Exchange

This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.

Heat Transport Study of the Laminar Heat Pipe Heat Exchanger

The purpose of this experiment is to analyze the performance of the Laminar Heat Pipe Heat Exchanger. The test samples were divided two groups, one is the metal corrugated sheet with heat pipe, and the other is the metal corrugated sheet only. By dipping these two group samples into hot water and to see the thermal image by Infrared thermal imager. The results shown the temperature risen of the sheet with heat pipe was faster than that of the sheet without heat pipe. In addition, the bigger of the temperature difference between hot water temperature and ambient temperature, the quicker of the temperature risen for the metal corrugated sheet, and the temperature of the metal corrugated sheet were homogenous as well. For example, when the water temperature is 30℃, ambient temperature is 20℃, the metal corrugated sheet with heat pipe rise rapidly to 26℃ within 1 minute, while the metal corrugated sheet without heat pipe rise to 22℃ only, this temperature difference would be more obvious with the increasing of the hot water temperature. When the hot water temperature is up to 40℃, the metal corrugated sheet with heat pipe rise rapidly to 31℃ within 1 minute, while the metal corrugated sheet without het pipe is still rise up to 22℃ only. When the hot water temperature is up to 50℃, The metal corrugated sheet with heat pipe rise rapidly to 33℃ within 1 minute, while the sheet without heat pipe still keep at 22℃, the results shown the heat pipe affect the temperature rising speed is obvious, and it also implying heat pipe is a very important parameter for the heat transfer rate of the Laminar Heat Pipe Heat Exchanger.

Optimal design of the separate type heat pipe heat exchanger

Separate type heat pipe heat exchangers are often used for large-scale heat exchanging. The arrangement of such a heat exchanger conveniently allows heat input to and output from the heat exchanger at remote locations. The traditional method of designing an ordinary HPHE (heat pipe heat exchanger) is commonly applied in the separate type exchanger design, but the calculations have to be carried out separately, which makes it very complicated. In this work, the ε-NTU (effectiveness-Number of Transfer Units) method was applied for optimization analysis of single- or multi-level separate type heat pipe heat exchangers. An optimizing formula for single-level separate type heat pipe heat exchangers was obtained. The optimizing principles of effec- tiveness-NTU and heat transfer rate by the equal distribution method for multi-level separate type heat pipe heat exchanger are presented. The design of separate type heat pipe heat exchangers by the optimizing method is more convenient and faster than by the traditional method.

Development of Submersible Corrugated Pipe Sewage Heat Exchanger

Based on the characteristics of heat transfer for corrugated pipe,a method of calculating and design on the submersible corrugated pipe sewage heat exchanger was put forward theoretically and experimentally.The actual movement parameters of air-conditioning system used in this heat exchanger were measured.The experimental result shows that the quantity of heat transfer of the corrugated pipe sewage heat exchanger can satisfy the building's load with the average coefficient of performance 4.55.At the same time,the quantity of heat transfer of the corrugated pipe sewage heat exchanger was compared with that of the other nonmetallic sewage heat exchangers(i.e.,the plastic-Al pipe sewage heat exchanger and PP-R pipe sewage heat exchanger)experimentally.It is found out that the effect of heat transfer for submersible corrugated pipe sewage heat exchanger is superior to those of the plastic-Al pipe and the PP-R pipe.The quantity of heat transfer per mile of corrugated pipe sewage heat exchanger is 5.2 times as much as that of the plastic-Al pipe,and it is 8.1 times as much as that of PP-R pipe.

The Current Situation of the Study on Twisted Tape Inserts in Pipe Exchangers

热转移改进包括热 exchangers，空调，和制冷系统在许多应用程序被使用；因此许多研究人员在热转移改进上进行了试验性、数字的研究并且开发了各种各样的技术和方法。作为一种被动的热转移技术，扭曲了磁带广泛地为他们他们容易被建立的费用积蓄，更低的维护要求和事实在各种各样的工业被使用。这篇论文介绍扭曲的磁带的热转移改进的原则并且考察一些研究人员在最近的年里在这种技术上做的试验性的工作。不同地修改的扭曲的磁带插入广泛地被研究并且过去常为热 exchangers 提高热转移效率。扭曲的磁带处于低 Re 条件并且在方形的试管更好表现。然而，他们能也引起更高的压力落下。如果他们能在传统的热 exchangers 被使用，扭曲的磁带有大潜在、深刻的含意。除这以外，在 Nusselt 数字和磨擦因素之间的一些关联在这篇论文被介绍。

Experimental study on heat exchange of several types of exchangers

Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.

Heat transfer performance of fresh-air handing device using earth energy

In order to reduce the fresh-air handing energy consumption,a fresh-air handing device using earth energy was presented. The major part is a double pipe soil-air heat exchanger. Its performance was tested in summer and winter. The results show that while the volume of the treated fresh-air is 125 m3/h,in summer,at the outlet of the device,the air temperature is 21.5-24.0 ℃,the air humidity ratio is about 17 g/kg,the greatest temperature drop is about 9 ℃ ,and the largest dehydration quantity is about 6 g/kg. In winter,at the outlet of the device,the air temperature is 15-17 ℃,the air humidity ratio is about 11 g/kg,the largest temperature rise is about 11 ℃,and the largest humidification quantity is about 6 g/kg. Therefore,the application of this new fresh-air handing device can take full advantage of the natural energy,thus effectively reduce the traditional energy consumption for fresh-air handing.

太阳能-埋管换热器增温填埋垃圾技术的性能研究

填埋垃圾的厌氧发酵需要较高的温度,由于中国北方地区冬季的气温低,垃圾填埋场的厌氧发酵速度较慢。为解决这一问题,提出太阳能-埋管换热器增温填埋垃圾技术,建立垃圾填埋体及其周边区域的3D物理模型,采用试验和数值模拟的方法,对垃圾填埋体内部的增温效果和传热性能进行了研究,并对试验结果和数值模拟结果进行了相互对比验证。研究结果表明:埋管密集处垃圾填埋体的温度变化显著,热量向上传递多于向下传递;在晴天白天,埋管换热量呈现先升高后降低的变化趋势;2021年9月23日—12月21日,垃圾填埋体的日平均温度的平均值为36.3℃,增温加热期内,垃圾填埋体传热系数的平均值为32.5 W/(m^(2)·K);随着埋管内水流量在0.4~1.0 m^(3)/h内增加,垃圾填埋体的日平均温度和单位体积换热功率均逐渐增加,且增加趋势逐渐平缓,埋管内水流量增加至1.0 m^(3)/h时,模拟得到的垃圾填埋体日平均温度为37.0℃,单位体积换热功率为52.9 W/m^(3)。

深层埋管换热技术研究热点与发展趋势分析

为动态分析深层埋管换热领域研究热点与前沿发展趋势,运用可视化知识图谱分析软件,将近23年CNKI和WOS数据库中与深层埋管研究相关的学术性文献作为数据源,分别从发文量、国际核心机构和关键词等进行文献计量与内容分析,解析该领域的研究热点和前沿分析。研究结果表明:2000年以来深层埋管研究领域的文献发文量逐步上升,核心作者及机构之间的合作仅为单线或团队内部之间,跨机构之间较少;研究热点和趋势具有阶段性特征,不同阶段的研究重点不同。随着地热能+、“双碳”目标和“十四五”可再生能源发展规划等一系列战略决策及清洁能源高效利用理念的提出,深层埋管换热领域的研究热点更聚焦于交叉学科的渗透和技术方法的创新,国内深层埋管换热技术未来的发展趋势表现为开采技术突破、换热器类型及材质方面的创新与探索、研究方法优化和外扩中深层地热、综合效益评价等新的研究方向,国外则侧重于换热性能、热泵系统、深层埋管换热器和数值模拟等方向。相关数据可为深层埋管换热技术相关学者的研究工作提供借鉴。

竖进平出型地埋管群换热器结构与控制优化

【目的】为提高浅层地热能利用效率,亟须对影响地源热泵系统性能的地埋管换热器结构和控制开展优化设计。【方法】建立了一种竖进平出型地埋管群换热器模型,研究其换热系统性能,探究其最佳结构及运行方式。【结果】管群布置横纵比越低,单位面积换热量越大,横纵比超过0.15后对系统影响较小;换热器间距越小,土壤利用率越高,但热短路损失越大;双列双出型埋管每延米换热量相较于双列单出型结构提升7%以上;负荷较大工况下叉排布置结构的换热效果更好;整个夏季优化结构的平均出口温度下降2.28℃,换热器周围土壤温度下降1℃以上;实际运行过程中应优先考虑采用流速随负荷变化控制模式。【结论】研究结果可为地源热泵换热器的设计、制造提供理论依据。

土壤源热泵地埋管侧水系统优化运行研究

本文基于江苏无锡某典型厂房土壤源热泵空调项目的实测数据,以地源侧系统总能耗最低为目标,构建设备模型对地源水泵运行工况进行优化,并与两种传统控制策略的运行效果进行对比,据此提出进一步的优化建议。结果表明:基于负荷的优化控制策略,其节能效果要明显优于定频控制策略,冬夏季典型测试日平均节能率分别为28.33%和13.27%,相比于5℃温差变频策略节能了3.61%和2.21%。适当增大地埋管的埋管深度或管径,可以进一步提升该优化控制策略的节能效果。传统的定温差控制策略在负荷率大于60%时,可在5℃基础上将温差增加1~5℃以提升节能效果。

中深层地热地埋管管群换热性能模拟和布置优化

在中深层地热地埋管(DBHE)供热技术应用中,主要使用多个地埋管构成管群为建筑供暖。为了研究中深层同轴地埋管管群换热性能,本文基于西安市西咸新区典型地质分布,构建了中深层同轴地埋管管群数值模型,研究了不同间距、不同分布下各地埋管换热器间热交互作用以及长期取热期水温衰减规律。结果表明,多井集群供暖过程中周围岩土所形成的“冷堆积”现象是导致地埋管集群供暖能力逐年下降的主要原因;当地埋管间距从5m增至25m,平均出口水温和取热功率分别提升3.86%和11.5%;在西咸新区典型地质条件分布下,地埋管间间距应保持在15m以上;本文提出的四种管群分布中,地埋管呈直线分布时各地埋管出口水温和取热功率衰减最小,其中心地埋管出口水温仅衰减5.74%。在工程设计中,中深层地埋管管群应尽可能直线排布,避免重叠排布。

碳封存超临界CO_(2)螺旋管换热器传热规律

在“双碳”目标背景下,探索CO_(2)高效地质封存和高能利用途径,是CO_(2)减排研究的热点问题。基于CO_(2)多相态变化特性以及能源利用方面表现出的安全环保及成本优势,提出一种新型碳封存超临界CO_(2)螺旋管换热器,并建立了数值仿真模型,以5℃条件下CO_(2)为对象,设计水作为载热流体的换热方案,研究了螺旋换热器在不同水温作用下对CO_(2)的温度、压力及其热应力耦合变化规律。结果表明:随着水热流体温度的增加,CO_(2)的升温速率与水温成正比,CO_(2)输出温度与水热流体温度呈正相关变化;与CO_(2)传热效率相比,受CO_(2)相变吸热影响导致水热流体传热效率较慢,水热流体传热与温度变化成正比;初始水温升高,CO_(2)相变速度明显增加,流量对CO_(2)相变吸热影响较大,水热流体的体积流量与CO_(2)温度变化呈负相关;受CO_(2)升温吸热影响,水热流体的耗散温度与CO_(2)吸热温度成正比;当管径和入口压力恒定情况下,100℃的水热流体与CO_(2)进行换热可以较好地满足CO_(2)相变吸热的要求。试验验证了水热流体螺旋管换热器的有效性和便捷性,研究为超临界CO_(2)螺旋式换热器的设计提供了依据。

陕北地区中深层同轴地埋管取热性能影响因素分析及优化

中深层同轴地埋管地热供热技术在我国北方城镇供热领域兴起并广泛应用。陕北地区地热资源丰富,但地温梯度略低且岩土热物性参数特性不同,地质参数影响中深层同轴地埋管的取热性能。采用OpenGeoSys开源数值模拟平台建立三维中深层同轴地埋管耦合地层传热计算模型,并基于陕北地区典型地质参数,研究不同设计参数对中深层同轴地埋管取热性能的影响及全生命周期技术经济性,优选出地热工程最佳工艺参数。结果表明,中深层同轴地埋管的外管径与埋深增大均能提升取热能力。相较于外管径,埋深对取热能力的提升效果更为显著,埋深从2 500 m增加到3 500 m,取热量增加了77.3%。依据工程实践,当外管外径×厚度大于177.80 mm×9.19 mm时所对应的平均能源成本因其钻井成本陡增而增大。在给定工况参数下,推荐中深层同轴地埋管的最佳外管外径×厚度为177.80 mm×9.19 mm,埋深为3 200 m,此时平均能源成本为0.524元/(kW·h),经济效益最优。

地埋管换热系统改造项目关键技术节点施工工艺研究

天津某管业公司建筑原采用常压燃气热水锅炉供热和分体式空调供冷,现拟以浅层地热能为基础能源对原供热制冷系统进行改造,施工前首先通过现场岩土热响应试验、地下管线探测等查明施工场地岩土体结构和换热能力,掌握地下综合管线的分布,并对建筑单位冷热负荷指标校正。重点阐述地埋管换热系统施工过程的关键技术节点,即竖直换热孔钻进、下管、回填及水平管线连接等,为类似改造项目提供参考。