CFD方法与间接蒸发冷却换热器的三维数值模拟

采用计算流体力学(CFD)和数值传热学方法,对间接蒸发冷却器内流体流动与热质交换过程进行简化和假设,建立了换热器内三维层流流动与传热的数学物理模型。采用交错网格离散化非线性控制方程组,编制了三维simple算法程序。对间接蒸发冷却器内的流场、温度场及浓度场进行数值模拟研究,得到换热器内的流体流动状态和热流分布,并分析了通道宽度变化对换热器内流体流动与换热的影响。     

板式间接蒸发冷却器热工特性的实验研究

对自行研制设计的间接蒸发冷却换热试件开展了实验,研究了影响换热器换热性能的因素。结果表明：板式间接蒸发冷却器换热效率随二次空气入口的速度升高、一次空气入口的温度、二次空气入口的湿球温度升高而变大,随一次空气入口的速度变大而变小。实验结果对于深入认识间接蒸发冷却器的换热机理及开展换热器的优化设计有着很大的指导意义。     

板管式间接蒸发冷却换热器的设计分析

介绍一种结构具有代表性的间接蒸发冷却换热器——板管式间接蒸发冷却换热器,并从芯体结构、材料的选择、芯体的换热计算和各功能部件的设计计算等方面进行详细设计分析。     

间接蒸发冷却板式换热器的(火用)效率分析

在考虑壁面两侧空气温度实际变化的前提下,对间接蒸发冷却传热过程中影响yong效率的主要因素,如一次空气进口温度、一、二次空气流速之比,二次空气相对湿度,一、二次通道宽度之比以及壁面润湿率进行了分析研究,为实际换热器设计提供理论依据。     

间接蒸发传热过程特性分析

本文在考虑壁面两侧流体温度实际变化的前提下,对间接蒸发过程中的主要影响因素,如流体温度、流体速度、流体相对湿度、壁面湿润率以及流道宽度进行了分析研究。     

间接蒸发冷却技术的应用研究与现状

由于我国各地区气候条件不同,蒸发冷却的应用方式也有些不同.通过对直接蒸发冷却和间接蒸发冷却技术原理的分析,提供了分析研究的结果.着重介绍间接蒸发冷却技术在我国的应用研究与现状.     

压气机进气用雾化式蒸发冷却器实验研究

从实验角度对压气机进气用蒸发式冷却器进行了。探讨了含有水滴的空气的湿度测量方法。针对不同的常温蒸发加湿方案,研究了不同喷水量对蒸发冷却效果产生的影响。对于不同形式的雾化喷嘴在不同的喷射方向下对蒸发冷却效果所产生的影响进行了实验分析。     

蒸发冷却空调技术在住宅建筑中的研究进展

介绍蒸发冷却空调技术在住宅领域的研究进展。主要包括:直接蒸发冷却空调技术在住宅建筑的应用、间接蒸发冷却在住宅建筑的应用以及蒸发冷却与其他技术相结合在住宅建筑领域的应用几个部分。参考国内外相关文献及其专利,得出蒸发冷却空调技术在部分地区住宅领域应用效果较好的结论,特别是将蒸发冷却空调技术与其他技术相结合的应用过程中,这项技术能够提高整个机组的运行能效比,使机组运行更加节能、环保。在广阔的农村住宅领域以及"干空气能"丰富的部分地区,蒸发冷却空调技术值得被大力推广。     

不同蒸发冷却装置工作的影响因素及对比

采用CFD模拟了2种蒸发冷却装置,讨论了一次空气入口温度和喷淋水温度对蒸发冷却装置效率的影响。通过模拟一、二次空气出口处的温度分布,水蒸气相分布以及装置内整个通道的温度分布,得到影响2个蒸发冷却装置的传热性能的变化规律。同时,比较2个蒸发冷却装置的传热性能,给出了一种确定蒸发冷却装置性能的方法。对于管式蒸发冷却装置,选择管径为5 mm和10 mm,管间距为5 mm和10 mm的装置进行模拟。对于板式蒸发冷却,取板长度为500 mm和1 000 mm,并且板宽度为6 mm,8 mm和10 mm用于模拟。通过模拟得到装置尺寸对蒸发冷却效率的影响。     

降膜蒸发冷却复合传热传质研究

建立了描述叉流式降膜蒸发传热传质过程的数学模型,对气相微分中利用积分法求解,导出确定气液界面温湿度的数学表达式。计算与实验结果对比基本一致。对叉流式降膜蒸发冷却进行深入分析表明,该冷却手段可使处理空气的最低温度接近或达到空气的湿泡温度,得到叉流式蒸发冷却脱身人气流温湿度分布曲面及气液界面温度分布曲面,表明典型工况下,叉流直接蒸发冷却器可使处理空气温度１０℃左右。     

Performance evaluation and comparison of multistage indirect evaporative cooling systems in two operation modes

The evaporative cooling technique is an efficient approach for cooling application. This study aims to establish a performance evaluation method to advance the appropriate design for multistage indirect evaporative cooling systems. A mathematical formulation has been developed for the indirect evaporative cooler (IEC). After the validation, the mathematical model was used to analyze the evaluation criteria by considering the simultaneous influence of the cooling effectiveness, the pressure drop, and the cooling capacity of the multistage IEC operating in two modes. The Mode-1 IEC is a conventional counterflow unit, while the Mode-2 IEC employs a regenerative M-cycle arrangement. The IECs are operated in a tandem arrangement. The multistage system is capable of improving the cooling performance and reducing the outlet air temperature. In addition, the multistage system displays a higher pressure drop resulting in a lager consumption of fan power. The analysis of performance evaluation criteria indicates that the appropriate maximum stage is suggested to be three-stage and two-stage for the Mode-1 and the Mode-2 IEC, respectively.     

间接空冷机组空冷塔塔群内空气流动及传热性能研究

由于具有巨大的节水优势,间接空冷机组在我国富煤少水区域得到广泛应用。研究环境风对间接空冷系统的影响机理对指导电厂运行具有重要意义。以某电厂间接空冷机组为基础,构建水平布置散热器的空冷塔群物理和数学模型,通过数值模拟方法分析环境风对塔内空气流场及空冷散热器换热性能的影响。结果表明:环境风对空冷系统塔内空气流场影响较大,进而影响空冷散热器的散热性能。随着风速的增加,空冷塔的换热性能不断恶化。在临界风速时额定负荷下,下游空冷塔换热量比上游空冷塔减少2.5%。     

蓄冷平板相变换热器凝固传热特性研究

本文建立了蓄冷平板相变换热器中蓄冷平板单体凝固过程变化规律的数理模型,并用一种简便方法求解了凝固过程非稳态移动界面传热问题,获得了有关传热速率,界面移动,载冷剂出口温度的变化规律,讨论了蓄冷平板相变换热器的传热特性。     

波纹板式换热器传热与流动特性分析

通过数值模拟的方式,对一种用于低粘度流体的波纹板式换热器的传热特性和阻力性能进行分析,以控制变量法分析了流体速度对传热特性及阻力性能的影响;搭建了板式换热器测试平台,验证了数值模拟结果的正确性和可行性;用等速法拟合了Nu-Re与Eu-Re的相关准则式,并采用JF因子评价换热器综合性能。结果表明：模拟结果与实验结果相比误差在10%以内;当流体流速小于1.0 m/s时,换热器传热系数和压降随着流速的增大而增大,但综合换热性能逐渐变差,在此流速范围内,总传热系数随冷流体进口温度升高而增大。     

Enhancement in Evaporative Effectiveness of an Evaporative Tubular Heat Dissipator Using Experimental Design Approach

An experimental investigation of evaporative effectiveness and mass transfer coefficient on a bundle of tubes of an evaporative tubular heat dissipator is presented. Based on the experiments, correlations of evaporative effectiveness and mass transfer coefficient are derived using multiple regression analysis. A statistical model is developed to correlate the operating variables using design of experiment approach by selecting central composite design of a response surface methodology. Results shown in this article indicate that as the cooling film flow rate increases, evaporative effectiveness and mass transfer coefficient increases provided that the air flow rate is constant which is flowing from underneath the tubes of the evaporative tubular heat dissipator. Derived correlations are helpful in improvement of the design of heat transfer devices and many other engineering applications. Consideration of relative humidity of upstreaming air as one of the operating variables leads to the contribution to heat and mass transfer study of evaporative tubular heat dissipators in the present investigation.     

多斜孔气膜冷却传热特性数值研究

对三种不同结构的多斜孔气膜冷却结构进行了数值研究。多斜孔均为叉排结构,斜孔与平板表面夹角均为30,°重点研究了不同相邻孔间距与孔径比Pm/dm(3.0～5.0)和不同吹风比M(0.5～1.5)对热侧壁面绝热温比和换热系数的影响规律。     

Heat and mass transfer model of a Ground Heat Exchanger: theoretical development

A new approach to the simulation of a horizontal type Ground Heat Exchanger is proposed resulting in a better accuracy and at the same time a reduced computational effort. These results come from the concentration of the computational effort at the locations with the largest temperature and moisture gradients, i.e. the pipe–soil interface. The model takes into account heat and moisture transfer in the soil allowing for more accurate predictions of the soil thermal response to the heat fluxes induced by the GHE operation. This in turn allows for a more accurate prediction of the soil temperature field and the circulating fluid temperature profile. A comparison of the results obtained by using the implicit and explicit methods of solving the set of governing equations is discussed. The implicit method requires partial linearization of the heat and mass transfer equations but results in a considerably shorter simulation time. The explicit formulation allows for the solution of the fully nonlinear set of heat and mass transfer equations at the expense of increased simulation time. The following analysis shows that the difference between the solutions obtained using these two methods is minimal, thus favouring the implicit formulation. Copyright © 1999 John Wiley & Sons, Ltd.     

家用蒸发冷却中央空调的应用研究

针对现有三种技术路线的家用中央空调缺点。结合国情,提出了利用蒸发冷却技术和变风量技术实施分室控制的家用蒸发冷却变风量中央空调的方案。