板壳式换热器板片流动与传热性能的数值模拟

针对板壳式换热器的人字形板片建立了单流道物理模型,并利用数值模拟软件分析了其重要结构参数波纹夹角的变化引起的模型流场、速度场和温度场的变化情况,以及对其传热性能的影响。结果显示:换热板片波纹夹角的变化使得流体的流动状态发生了变化,随着波纹夹角的增大,流体的流态由十字交叉流逐渐转变为曲折流。随着波纹角度的增大,流体的扰动程度加强,湍流程度提高,与此同时,努塞尔数和传热因子增大,传热性能增强。模拟结果表明波纹夹角对板壳式换热器流动和传热性能具有较大的影响,可以成为板壳式换热器优化设计的一个重要方向。     

SCR脱硝反应器内烟气与氨均混的数值模拟

为了改善选择性催化还原(SCR)脱硝反应器内烟气与氨气的混合效果,提出3种导流板布置方案,应用数值模拟方法分析了导流板布置方式对SCR反应器内烟气流场与氨浓度分布的影响.分析结果表明:不同的导流板布置方式对烟气与氨气混合效果具有重要影响,采用3块导流板不均匀布置的方案具有最佳的混合效果.     

电厂温排水累积影响数值模拟研究

基于正交曲线网格,采用有限体积法建立了天然河道平面二维温排水数学模型,利用实测的电厂温排水资料验证了模型,并以长江下游镇扬河段世业洲汊道段为例,计算了考虑拟建的句容电厂单独运行和与上下游电厂同时运行两种工况下温排水影响。结果表明,三电厂同时运行影响范围明显大于单个电厂,0.1～0.3℃温升线相互贯通;拟建句容电厂1℃温升线扩散长度与宽度均增大约5%,取水口最大温升增加0.2℃,为电厂环境影响评价和水资源论证提供了科学依据。     

太阳能空气集热器吸热板结构优化及其数值模拟

文章提出了一种新型抛物线型吸热板结构的太阳能空气集热器,建立其数学模型和物理模型,运用ANSYS数值模拟软件,对不同入口流速和倾角下集热器内空气换热特性进行数值模拟。结果表明:随着流速的增加,3种吸热板集热器瞬时效率逐渐增加;随着倾角的增加,集热器瞬时效率先增加后减小,在倾角30°时最大;对比传统平板和三角波纹吸热板结构,抛物线型空气集热器具有较高的瞬时效率和较小的压损。     

火电厂温排水余氯浓度扩散三维数值模拟

通过三维模型方程垂向积分,将三维问题转化为类似二堆问题求解,构建了长江宜都河段的三维水流及余氯浓度扩散三维模型,预测分析了宜都电厂温排水中余氯的浓度分布及影响范围,为排水口附近水域生态环境保护提供依据.     

环保型大面积均温加热太阳能热处理炉

说明了在热处理生产中需节能和保护环境的重要性和迫切性;介绍了环保型大面积均温加热太阳能热处理炉聚光系统的创新结构;论证了只有是大面积均温加热才有利于金属的热处理;列举了太阳能热处理1号炉的基本数据并指出了使用1号炉进行热处理实验的良好效果。     

混合集箱结构优化数值模拟

本文采用数值模拟方法分析集箱管接头的排布情况对介质混合过程的影响,研究表明,集箱管接头的合理排布可以提高介质的混合均匀性和流畅性。     

叉排板束换热器传热特性数值研究

为提高换热器的传热性能,设计了叉排板束换热器,利用Fluent软件中的RNG k-ε模型数值研究了叉排板束的传热特性。分析了叉排板束排数对于整体Nu的影响以及板束的局部传热特性,比较了不同横纵比对整体Nu的影响,并给出不同Re下叉排板束的Nu经验公式。实验结果表明：叉排板束整体传热性能随板排数的增多而增强,当达到一定排数后传热性能趋于稳定,不同Re下趋于稳定的排数不同,当Re=4.3×105时进入稳定阶段需13排,当Re=4.3×103时进入稳定阶段仅需7排;叉排板束局部传热性能在各板排中先增大后减小,在第2~4排局部Nu达到峰值,板的局部传热性能在两个直角处以及撞击点位置大大增强;板束在横纵比为5时传热性能最佳,横纵比大于或小于5时,传热性能均会减弱;给出Re在1~500,500~1 000,1 000~200 000范围内板束整体Nu拟合公式,当Re>30 000时,与叉排圆管束相比,叉排板束传热性能提高25%     

水冷板式换热器结构参数对换热性能影响规律的数值模拟

基于流体计算软件FLUENT,针对水冷板式换热器构建了三维的物理模型,选择标准k-ε湍流模型,模拟了实际换热过程,并与实验结果进行比较,两者结果基本吻合。对换热器内部结构参数进行了优化研究,发现在压降允许的范围内,通过适当减小槽道截面的水力直径可以提高换热效率和热源面的温度均匀性。     

光伏光热系统导热流道传热性能的数值模拟

对光伏光热系统实体模型进行简化处理,并建立了包含单条流道、带翅片的单条流道、单侧排列两条流道的三种型式导热流道的物理模型。以20℃蒸馏水为流动工质,借助FLU-ENT分别对三种不同型式的导热流道的传热性能展开数值模拟研究,分析了导热流道的出口平均温度和壁面导热速率。     

Thermal performance of flat vapor chamber heat spreader

Experiments were performed to examine the spreading thermal resistance of centrally positioned heat sources and the thermal performance of a water charged, gravity assisted flat vapor chamber to be used for electronic cooling. Parametric studies including different heat fluxes and operating temperatures were conducted, and the effect of the relevant parameters on the cooling performance in terms of the spreading resistance was presented and discussed. The present vapor chamber heat spreader showed a heat removal capacity of 220 W/cm² with a thermal spreading resistance of 0.2 °C/W.     

Thermal performance of plate-fin vapor chamber heat sinks

Since vapor chambers exhibit excellent thermal performance, they are suited to use as bases of heat sinks. This work experimentally studies the thermal performance of plate-fin vapor chamber heat sinks using infrared thermography. The effects of the width, height and number of fins and of the Reynolds number on the thermal performance are considered. Experimental data are compared with corresponding data for conventional aluminum heat sinks. The results show that generated heat is transferred more uniformly to the base plate by a vapor chamber heat sink than by a similar aluminum heat sink. Therefore, the maximum temperature is effectively reduced. The overall thermal resistance of the vapor chamber heat sink declines as the Reynolds number increases, but the strength of the effect falls. The effect of the fin dimensions on the thermal performance is stronger at a lower Reynolds number. At a low Reynolds number, a suitable number of fins must be chosen to ensure favorable thermal performance of the vapor chamber heat sink. However, at a high Reynolds number, the thermal performance improves as the fin number increases.     

Heat transfer characteristics of high heat flux vapor chamber

To meet the challenge of heat spreading in electronic products, highly efficient high heat flux heat transfer vapor chambers have been manufactured and their heat transfer characteristics have been studied by a fast test system. A solid copper block with the same shape as the vapor chamber is used to compare the performance of the vapor chamber. The result shows that, it will take about 5 min to achieve a steady state in the fast test system. The heat transfer characteristics of the vapor chamber are more superior to those of the copper block. In this paper, total thermal resistance of the test system is used to evaluate the heat transfer characteristics of the vapor chamber, because it has already been used to consider both the spreading thermal resistance and the flatness of the vapor chamber.     

Heat transfer characteristics of high heat flux vapor chamber

To meet the challenge of heat spreading in electronic products, highly efficient high heat flux heat transfer vapor chambers have been manufactured and their heat transfer characteristics have been studied by a fast test system. A solid copper block with the same shape as the vapor chamber is used to compare the performance of the vapor chamber. The result shows that, it will take about 5min to achieve a steady state in the fast test system. The heat transfer characteristics of the vapor chamber are more superior to those of the copper block. In this paper, total thermal resistance of the test system is used to evaluate the heat transfer characteristics of the vapor chamber, because it has already been used to consider both the spreading thermal resistance and the flatness of the vapor chamber.     

Effects of shield on thermal-fluid performance of vapor chamber heat sink

This work investigates the effects of a shield on the thermal and hydraulic characteristics of plate-fin vapor chamber heat sinks under cross flow cooling. The surface temperature distributions of the vapor chamber heat sinks are measured using infrared thermography. The thermal-fluid performance of vapor chamber heat sinks with a shield is determined by varying the fin width, the fin height, the fin number and the Reynolds number. The experimental data thus obtained are compared with those without a shield.Experimental results indicate that the maximum surface temperature of the vapor chamber heat sink is effectively reduced by adding the shield, which forces more cooling fluid into the inter-fin channel to exchange heat with the heat sink. However, using the shield increases the pressure drop across the heat sink. The experimental data also show that the enhancement of the heat transfer increases with the Reynolds number, but the improvement declines as the Reynolds number increases. When the pumping power and heat transfer are simultaneously considered, vapor chamber heat sinks with thinner, higher or more fins exhibit better thermal-hydraulic performance.     

Experimental study on heat transfer performance of pulsating heat pipe with refrigerants

The effects of different refrigerants on heat transfer performance of pulsating heat pipe(PHP) are investigated experimentally.The working temperature of pulsating heat pipe is kept in the range of 20℃-50℃.The startup time of the pulsating heat pipe with refrigerants can be shorter than 4 min,when heating power is in the range of 10W-100W.The startup time decreases with heating power.Thermal resistances of PHP with filling ratio 20.55% were obviously larger than those with other filling ratios.Thermal resistance of the PHP with R134a is much smaller than that with R404A and R600a.It indicates that the heat transfer ability of R134a is better.In addition,a correlation to predict thermal resistance of PHP with refrigerants was suggested.     

弯曲微热管阵列传热性能的实验研究

微热管阵列是一种导热能力较强的元件,具有接触面积大、热输运能力强和承压能力强的特点。将750 mm长的微热管阵列分别弯曲成"L"形和"乙"字形,测试其在热源温度为45℃条件下的响应时间及轴向均温性,并与平直微热管阵列对比,分析弯曲对微热管阵列传热性能的影响。结果表明:弯曲会使微热管阵列响应时间滞后,"L"形、"乙"字形1号和"乙"字形2号微热管阵列响应时间约为120 s,较平直微热管阵列滞后80 s;弯曲微热管阵列两端温差随弯道数的增加而增大,随弯曲角度的增大而增大,"L"形和"乙"字形1号微热管阵列蒸发段与冷凝段温差分别为0.76℃、1.61℃,较平直微热管阵列大11.76%、106.41%;"乙"字形2号微热管阵列两端温差为1.70℃,比"乙"字形1号微热管阵列两端温差大10.84%。     

垂直地埋管换热器的换热性能

为研究土壤源热泵垂直地埋管换热器的换热特性,对长沙地区一套土壤源热泵系统进行了夏季及冬季工况连续运行的实验,实时采集U型管进出口的水温、流量以及地温等数据。通过对所采集的实验数据进行处理分析,对比了不同工况、不同埋管形式、不同埋深条件下的地埋管换热器进出口温差及单位井深换热量,结果表明,无论是夏季工况还是冬季工况,双U型管的单位井深换热量比单U型管高25%～30%。     

微通道内流动沸腾特性研究

对国内外微通道流动和换热的研究实验作了总结,阐述了影响微通道换热系数的因素,如热流密度、过热度和干度等.对去离子水在内径为0.65 mm、长为102 mm的圆形管道内流动沸腾换热进行了实验研究,得到了局部换热系数随干度的变化关系,进而根据换热系数的变化趋势讨论了饱和流动沸腾区微通道内主导的换热机制.结果表明:从换热系数随干度的变化关系很难判定主导的换热机制;将实验数据与已发表的预测关联式进行了比较,发现大多关联式都失效,说明基于常规理论的模型不再适用于微通道.     

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%.