Achieving Cooler Soil as an Effective Heat Sink for Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia Tropical Climate

This research is intended to explore the capacity of Malaysia soil in becoming a more effective heat sink for the application of Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia. EAHE Cooling Technology consists of buried pipes underground where the ambient air is channeled through from the pipe inlet and produces cooler air at its outlet. Within the buried pipes, heat exchange process occurs between the air and the soil that surrounding the pipe. This building cooling technology has been applied in many countries, mostly in temperate or hot and arid climate where the diurnal temperature is large. However, minimal resources were found on the study of EAHE application to buildings in Malaysia, hence there is room to develop. A parametric study on EAHE cooling application in Malaysia was done through field experiment and concluded that among many parameters affecting the technology performance, the soil temperature which surrounded the pipe was the most influential factor. The study recommended to further reduce the soil temperature to achieve a cooler outlet temperature. In response to that, this research conducted a parametric study of soil temperature under three different soil surface conditions: bare, shaded with timber pallettes and insulated with used tyres at 1.0 m and 1.5 m underground. The data was logged for a month and the result has shown significant reduction in the soil temperature underground below the shaded and insulated soil surface as compared to below bare soil surface condition. The insulated soil surface produced the best result where the soil temperature was reduced up to 26.9°C. The main contribution of this paper is to highlight that the soil surface treatment can be used to reduce solar heat gain within the soil underground and thus improving the performance of EAHE Cooling Technology particularly for the application in Malaysia tropical climate.

Experimental Study on Ice Slurry Refrigeration System with Pre-Cooling Heat Exchanger

In the present study, the ice slurry refrigeration system with pre-cooling heat exchanger (ISSH) is studied experimentally to achieve the system performance, ice crystal formation time and the temperature of ice crystal formation. The operating parameters considered in this paper include the concentration of salt solution, suction pressure, discharge pressure and Energy Efficiency Ratio (EER). The result shows that the temperature of critical time of ice crystal formation decreases with the increasing concentration of salt solution and that the ice crystal formation time increases with the increasing concentration of salt solution. In the same concentration of salt solution, the ice crystal formation temperature of ISSH is lower than that of basic ice slurry refrigeration system (BISS), and the ice crystal formation time of ISSH is shorter than that of BISS. On the whole, the EER of ice slurry refrigeration system with pre-cooling heat exchanger is higher than that of basic ice slurry refrigeration system.

Potential reduction in water consumption of greenhouse evaporative coolers in arid areas via earth-tube heat exchangers

This study aimed to explore the potential of developing a novel cooling system combining a greenhouse and an earth-tube heat exchanger(ETHE).In this system,greenhouse air is circulated through the underneath soil mass to use the deep-soil cooling effect.This was achieved through the following steps.First,soil temperature profile inside and outside the cultivated greenhouse was monitored for almost one year to study the possibility of using deep-soil coldness for cooling the greenhouse air.Second,a prototype ETHE was built to practically investigate the potential reduction in air temperature as the air flows inside the deep earth pipes.Third,a prototype greenhouse was erected to study the ETHE concept.Results from the first experiment revealed that soil temperature at a soil depth of 2.5 m inside the greenhouse offers good conditions to bury the ETHE.The soil temperature at this soil depth was below the maximum temperature(32℃)that most greenhouse crops can withstand.Results from the prototype ETHE showed a slight reduction in air temperature as it passed through the pipes.From the prototype of the integrated greenhouse and ETHE system,reduction in air temperature was observed as the air passed through the ETHE pipes.At night,the air was heated up across the ETHE pipes,indicating that the ETHE was working as a heater.We concluded from this study that greenhouses in arid climates can be cooled using the ETHE concept which would save a large amount of water that would otherwise be consumed in the evaporative coolers.Further investigations are highly encouraged.

Numerical simulation of heat transfer and flow of cooling air in triangular wavy fin channels

Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfer coefficient and pressure drop are displayed with variable structural parameters of fins and inlet velocities of cooling air.Within the range of simulation,TWFC has the best comprehensive performance when inlet velocity vin=4-10 m/s.Compared with those of straight fins,the simulation results reveal that the triangular wavy fin channels are of higher heat transfer performances especially with the fin structural parameters of fin-height Fh=9.0 mm,fin-pitch Fp=2.5-3.0 mm,fin-wavelength λ=14.0-17.5 mm and fin-wave-amplitude A=1.0-1.2 mm.The correlations of both heat transfer factor and friction factor are presented,and the deviations from the experimental measurements are within 20%.

Energy Efficient Air Conditioning System Using Geothermal Cooling-Solar Heating in Gujarat, India

It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.

Improved Efficiency of Heat Exchange Using KELEA Activated Water

An environmental force termed KELEA (kinetic energy limiting electrostatic attraction) is postulated to reduce the strength of intermolecular (hydrogen) bonding of water molecules, resulting in increased kinetic activity of the water. While regular water does not directly absorb KELEA from the environment, various dipolar compounds with separated electrical charges can seemingly act as a primary antenna for KELEA, with secondary transfer of energy into nearby water. Moreover, once sufficiently activated, the separated electrical charges in activated water can apparently function as a receiver for KELEA, leading to further activation of the water and also to the activation of added water. Prior publications have addressed the agricultural and potential clinical benefits of using KELEA activated water. This article is intended as the first in a series of papers describing useful industrial applications of KELEA activated water. The focus of the present paper is on the improved efficiency of industrial water heating and cooling systems by using KELEA activated water provided by pelleted, ground and heated volcanic rock as supplied by Kiko Technology.

Analysis of Ejector Cooling Flow

Now there were different aspects of heat exchangers of ejectors who could work in broad range of speed regulation characteristics, and with the different cores and auxiliary substance flows. For affirming of estimated performances the bench had been project, allowing to change speed regulation characteristics of a main stream and to regulate metering characteristics of an auxiliary fluid flow. For affirming of estimated performances of a heat exchanger of an ejector the imitative bench and with a view of accident prevention had been project, cooled air and the prepare water actuation mediums. The bench had been positioned in an insulated cooled room. For putting off gauging the multifunctional measuring complex of TESTO 400, was taken the temperature a surrounding medium, and a water rate does regulate by us. The high speed photo cameras were applied to bracing of formation of drips. Strain-gauge balances apply to determination of mass of water on the shield. The air flow was shape, and moving in an ejector heat exchanger by means of the axial multiple-speed fan. The purpose of projection of a heat interchanger of an ejector is maintaining of airspeeds by means of the ventilator in the mixing chamber 10 to 80 meters per second. The temperature of given air was a stationary value, equal to -20℃. Temperature of injection water was varying from 4 to 20℃.

Distribution optimization of circulating water in air-cooled heat exchangers for a typical indirect dry cooling system on the basis of entransy dissipation

The flow and heat transfer of air-cooled heat exchangers play important roles in the performance of indirect dry cooling systems in power plants,so it is of benefit to the design and operation of a typical indirect dry cooling system to optimize the thermo-flow characteristics of air-cooled heat exchangers.The entransy dissipation method is applied to the performance optimization of air-cooled heat exchangers in this paper.Two irreversible heat transfer processes in air-cooled heat exchangers,the heat transfer between circulating water and cooling air and the mixing of circulating water,are taken into account and analyzed by means of the entransy dissipation method.The total entransy dissipation rate,which connects the geometrical parameters of air-cooled heat exchanger sectors and the heat capacity rates of the fluids to the heat flow rate in every sector,is obtained.Based on the mathematical relation and the conditional extremum method,an optimization equation group is derived,by which the air-cooled heat exchanger with known air-side parameters is optimized,showing that the entransy dissipation based optimization approach can contribute to the distribution optimization of circulating water in air-cooled heat exchangers of a typical indirect dry cooling system.

Cooling performance of earth-to-air heat exchangers applied to a poultry barn in semi-desert areas of south Iraq

Earth-to-air heat exchangers(EAHE)can reduce the energy consumption required for heating and cooling of buildings.The composition and the thermal characteristics of the soil influence the heat exchange capacity,and the soil moisture can furthermore affect thermal performance of EAHE.The aim of this study was to compare the thermal performance of EAHE in dry and artificially wetted soil.Tests were carried out in the Basra Province(Iraq),in a semi-desert area.Two experimental EAHE were built in a poultry barn and tested from June 2013 to September 2013.The pipe exchangers were buried at 2 m deep.One heat exchanger operated in dry soil(DE),while the other one operated in artificially wetted soil(WE).In the WE system,a drip tubing placed 10 cm above the air pipe wetted the soil around the exchanger.Air temperatures at the inlet and at the outlet of both the exchangers as well as soil temperature at 2 m deep were continuously monitored.The experimental results confirmed that wetting the soil around EAHE improves the general heat exchange efficiency.The coefficient of cooling performance(COP)of the earth-to-air heat exchangers system was evaluated on the basis of the ratio between the heat removed from the air or added to the air and the energy input.During the day,with an average COP of 6.41,the WE system cooled the air more than the DE system,which reported a value of 5.07.On average,in the hottest hours of the day,the outlet temperature of the WE was 37.35℃ while in the DE it was 38.91℃.Moreover,during the nighttime,the WE system warmed the air more than the DE system.

Flow Structure and Heat Exchange Analysis in Internal Cooling Channel of Gas Turbine Blade

This paper presents the study of the flow structure and heat transfer,and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade.The investigations focus on heat transfer and aerodynamic measurements in the channel,which is an accurate representation of the configuration used in aeroengines.Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models.It is important to note that real engine passages do not have perfect rectangular cross sections,but include coiner fillet,ribs with fillet radii and special orientation.Therefore,this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

WHR （Waste Heat Technology） Method in Tri-generation Model

This paper is focused on description of cool production in using WHR （Waste Heat Technology） Technology-a new method of centralized production of heat by using the waste heat from generated exhaust gas, which has been in 2009 developed and operated by companies HELORO s.r.o, and COMTHERM s.r.o.

车用燃料电池散热性能实验研究

质子交换膜燃料电池(PEMFC)作为能效转换率高、清洁可靠的发电装置,在交通、储能、航天及军事等领域有着广泛应用。为了解决质子交换膜燃料电池散热密度高、发热量大、散热效率低等突出问题,本文针对散热量为15 kW的质子交换膜燃料电池,设计并搭建了一套具有四种不同流程换热器的车用燃料电池散热系统实验台。分别使用两相冷却工质HFE-7100和乙二醇水溶液作为冷却工质,探究了在35℃的高温环境中,两种工质在不同流程换热器和不同工质流量下的散热性能和系统能效比(Energy Efficiency Rating, EER)。结果表明,在相同的流程下,采用HFE-7100两相散热方式相对于采用乙二醇水溶液液冷散热方式散热量提升率在81.2%~98.8%之间,系统EER提升率在68.2%~88.6%之间。且在4种不同流程下,3流程的系统散热效果和节能效果最佳,两相工质HFE-7100散热量和系统EER分别达到14.4 kW和20.5 kW/kW,液冷工质乙二醇水溶液散热量和系统EER分别达到7.7 kW和12.1 kW/kW。冷却工质流量为4 L/min时,系统节能效果较好,其两相和液冷散热系统EER分别能达到20.9 kW/kW和10.5 kW/kW。

强化换热管冷却壁传热分析及结构优化

强化冷却水管的换热,对提高冷却壁的传热性能、延长冷却壁使用寿命有重要意义。利用Fluent数值模拟研究了丁胞管、螺纹管、扭曲椭圆管3种强化换热管对冷却壁换热性能的影响,并对强化换热管结构参数进行了优化,建议丁胞管结构参数设定如下:丁胞纵向间距为40 mm,径向丁胞数为4,丁胞半径为2 mm;螺纹管结构参数设定肋条数为4,肋高为1 mm,肋宽为5~7 mm,导程为25~40 mm;扭曲椭圆管结构参数设定导程不大于100 mm,短长轴之比取0.4~0.6。对比分析实验结果表明:螺纹管和扭曲椭圆管对冷却壁强化换热效果较好,丁胞管较差,扭曲椭圆管可以在水管压力损失较小下实现较好的强化换热效果。

还原磁化焙烧竖炉冷却系统研究

某氧化铁矿石属于难选铁矿石,磁化焙烧工艺是处理此类铁矿石最有效的方法之一。竖炉磁化焙烧工艺加工成本相对较高,其中竖炉冷却系统是竖炉加工成本的重要组成部分,通过对竖炉冷却系统冷却水速、水箱梁水垢、水箱梁冷却水量等方面的研究,探索高效、节能的竖炉冷却系统.

基于浸没式液冷的锂电池热管理研究进展

电池热管理系统对电动汽车的安全性至关重要。随着电池能量密度和放电功率的提高,传统散热方案已无法满足当前电池散热的要求。浸没式液冷电池热管理系统作为电动汽车动力电池组和动力系统的高效热管理解决方案之一,正受到越来越多的关注。本文综述了目前锂离子电池浸没式液冷技术,包括单相浸没式液冷和两相浸没式液冷;探讨了冷却液种类、排布方式、流速、压力等因素对系统性能的影响及浸没式液冷效率的评价方法。同时,分析了目前浸没式液冷技术在电池热管理中的行业趋势。最后,对于浸没式液冷在锂电池热管理中的应用进行了展望,为开发更高功率、更安全和更持久的电动汽车提供参考。

环境风影响下换流变压器空冷换热系统换热能力衰减特性研究

为实现换流变压器冷却系统换热容量的合理设计并保障其安全稳定运行,研究了环境风影响下换流变压器空冷换热系统换热能力的衰减特性。针对北方某换流站换流变压器,采用基于空冷换热系统大尺度热量传递与换热器翅片管束小尺度换热计算相耦合的方法,建立了包含空冷换热器、风机、防火墙、环境风等多种因素在内的三维传热流动数值分析模型。研究了环境风向及风速对空冷换热系统换热能力的负面影响机制,获得了真实环境条件下换热能力的衰减特性。结果表明:正前方风向下,换热器进风体积流量随风速增加而显著减小、进气温度略有下降,导致不同风速下换热效率维持在66.01%~66.75%之间;侧方风向下,迎风侧防火墙阻碍了气流运动,导致换热效率随风速增加在55.98%~83.13%之间变化,其中环境风速为6 m/s时换热效率最低;正后方风向下,与风机出流方向相同的环境风引起换热器附近更加剧烈的热风回流,导致换热效率随风速增加,在50.96%~91.46%之间变化,其中环境风速9 m/s时换热效率最低。研究结果可为换流变压器空冷换热系统换热容量的设计提供一定的参考。

天然气水合物泥浆制冷传热效率优化实验的设计与实践

冻土天然气水合物在钻探取心过程中极易因为温度升高而发生分解,因此需采用泥浆制冷系统将钻井泥浆的温度控制在0℃以下,抑制水合物的分解。换热器是泥浆制冷系统的核心设备,选择合适的换热器结构是获得低温泥浆的关键。该文通过室内实验研究3种换热器结构的换热效果,以泥浆出口最低温度、进出口温差以及换热功率3个关键参数作为指标,评价3种换热器的换热效果。结果显示螺旋折流板换热器能够获得最低的泥浆出口温度为-2.1℃,进出口温差达到4.1℃,具有良好的换热效果。最后针对换热器关键工艺参数及泥浆制冷系统关键设备的选型提出了指导性意见。

核电站蒸汽发生器传热管电磁超声导波自动化检测系统设计

蒸汽发生器传热管作为高温气冷堆核电站一回路压力边界的关键部件,承担着热交换及辐射屏障的重要作用,其结构完整性严重影响核电安全运行。针对该类特殊结构传热管的在役检查难题,设计了专用的电磁超声导波自动化检测系统,研制了内置单点检测式的磁场增强型电磁超声导波探头,开发了采用模块化组件的五轴联动多自由度自动运载装置,提出了基于机器视觉的管孔动态定位方法,建立了蒸汽发生器全尺寸模拟体试验平台并开展了定位精度测试与缺陷检测试验。试验结果表明所设计的自动化检测系统可实现任意位置目标管孔的高精度定位及自动行走,可识别模拟体上异种钢焊缝处与距离检测端约60 m处的刻槽缺陷,有效检测范围覆盖传热管全长,有望为高温气冷堆核电站蒸汽发生器特殊结构传热管的质量健康评价提供技术支撑。

急冷系统运行问题与优化措施探讨

某石化80万t·a^(-1)乙烯装置采用美国S&W公司专利技术,前脱丙烷前加氢,设计年操作时间为8000 h,装置的操作弹性60%~110%。介绍了急冷系统中的裂解汽油干点过高、稀释蒸汽发生器频繁泄漏以及急冷水一级冷却器泄漏的问题,通过数据建模、压力和p H值分析、扫描电子显微镜分析、金相分析等手段找出其导致问题产生的原因,并提出了调整急冷油塔侧线采出量、增加pH值APC调节系统、增加工艺水甲苯萃取装置、外管壁渗硼工艺处理、对换热器设置阳极保护等技术建议以解决这些问题,来提高急冷系统的稳定性和长期运行性。

双层动车复合式冷却系统散热与噪声控制的优化研究

高速双层动车由于其内部空间紧凑以及元件的高功率化,冷却系统存在整体散热性能较差、噪声污染严重的问题。为此,通过冷却系统空气流场的数值模拟与试验研究,对其散热性能和噪声控制进行了优化。参照常用的冷却系统空气流道结构,基于双层动车复合式冷却系统的技术参数要求,对其尺寸进行了初步设计计算。分别采用多孔介质模型和多参考系(MRF)对复合式冷却系统换热器的芯体结构与旋风过滤器进行简化,并对其空气侧流场进行数值模拟。研究结果表明:风机入口处存在局部涡流,导致流体进入通风机的角度混乱,影响风机有效做功,在工作环境下系统风量(2.96 m^(3)/s)远小于设计值(3.35 m^(3)/s);同时局部涡流产生较大的气动噪声。此外,换热器入口的风速分布不均匀,导致系统冷却能力不足。针对上述问题,对空气流道结构进行了优化。调整了进、出口消声器的3个流道的流通面积,并在过渡段设置“喇叭型”导流结构来改善换热器进口处风速的均匀性;在冷却系统进、出口增加弧线型消声器能进一步降低噪声。结果表明:空气流道结构优化后水侧散热功率从33.18 kW增加到41.55 kW,油侧散热功率从157.82 kW增加到173.82 kW,系统加权平均噪声值从74.95 dB(A)降低到72.21 dB(A)。本研究可为类似工程项目冷却系统的优化设计提供参考,有助于改善乘坐体验和车辆运行的经济性。