水平圆管外溴化锂水溶液降膜吸收过程的数值分析

提出了一种改进的水平圆管外降膜吸收过程的传热传质耦合的吸收模型及其相应的数值解法。模型申首次考虑了液膜中径向速度及稀释热对吸收过程的影响。计算表明径向速度对吸收过程有强烈影响,忽略径向速度的影响对预测液膜中温度和浓度的分布带来较大误差。     

采用预冷却绝热吸收的溴化锂吸收式制冷循环的研究

基于将吸收器中溴化锂溶液的传热与传质过程相互分离的预冷却绝热吸收的溴化锂吸收式制冷循环,建立预冷却绝热吸收过程的热力学模型,对溴化锂溶液采用预冷却双效并联循环进行吸收过程的热力计算,并与传统双效并联循环进行比较,分析了预冷却器特性参数对预冷却绝热吸收过程及溴化锂吸收式制冷机组性能的影响及吸收器运行参数对预冷却绝热吸收过程的影响。     

竖直板翅通道降膜吸收的运行特性

针对溴化锂水溶液沿竖直板翅通道降膜吸收水蒸气的过程,建立了开式系统、间歇式运行的实验台。应用VisualC ＋语言编制了软件,实现了实验数据的计算机自动采集、处理、计算和汇总。针对影响降膜吸收传热传质的因素进行了相应的实验研究,从而验证了实际降膜吸收过程中的溴化锂水溶液浓度的应用范围。     

吸收器二元溶液两相流动总体性能分析

对发生在吸收器内的二元溶液两相流动传热传质过程进行了深入细致的描述。结合实际运行情况,将流动过程划分为3个区域,给出了不同区域的控制微分方程,建立了溶液滴状降膜吸收模型。基于Matlab平台进行求解,分析了水平管束式吸收器溶液温度、浓度的变化以及不同结构参数及运行工况下,溶液质量流量、润湿率WR、蒸发温度等变量对吸收器蒸气吸收能力、吸收器热负荷及蒸发器制冷量的影响。所得结果对于吸收器等热力部件的结构计算具有一定的参考作用。     

垂直管外溴化锂溶液降膜吸收的传热传质模型研究

通过对溴化锂吸收式制冷机中垂直管外降膜吸收过程特点的分析，建立了吸收过程中传热传质相互耦合的数学物理模型，并在此基础上，进一步提出了溶液多次布液降膜吸收的模型；并对吸收过程中液膜流动、传热传质进行了分析，得出的结论可以为吸收器的设计和实际运行的优化提供一定的理论指导。     

溴化锂绝热、增压双效吸收式制冷循环

吸收器是溴化锂吸收式制冷循环中最大的部件,传统吸收器换热面积占机组的40%左右,采用传热传质分离吸收器,其传热面积不到传统吸收器的30%,大大改善了吸收器的传热效果.本文在传热传质分离双效吸收式制冷循环的基础上,增加了一台增压器以提高绝热吸收器压力,强化循环传质能力.根据模拟结果,补偿了少量电功的增压系统,可以有效降低循环总传热面积;通过降低循环溶液浓度,还可以达到降低循环驱动热源温度的目的,且循环热力系数与增压前基本相当.     

冷却水进出方式及溶液再循环倍率对溴化锂吸收器吸收性能的影响

根据溴化锂吸收式制冷机吸收器中传热传质的物理模型和数学模型，通过计算分析了吸收器的布置方式和溶液再循环倍率对其吸收性能的影响，认为在所计算的三种布置方式中，以冷却水下进上出方式的总吸收效果最好，出液浓度和温度最低；计算结果还表明，溶液再循环倍率越大，吸收器的吸收性能越差，所以在满足喷淋密度的情况下应尽可能地减小溶液再循环倍率。     

溶液喷淋密度对溴化锂降膜吸收器吸收效果的影响

本文分析了溴化锂吸收式制冷机降膜吸收器的吸收过程,建立了溶液吸收冷剂蒸汽过程的数学物理模型,并且获得了数值解。同时分析了喷淋密度对液膜流速、液膜厚度、传热Nusselt数以及溶液出口温度、出口浓度和吸收量等的影响。结果表明,喷淋密度Γ并非越大越好,当Γ=200kg/m·h时,吸收器的吸收效果最佳。最后,通过实验验证了模型的正确性。     

板式膜反转降膜吸收器的设计研究

建立并求解了板式膜反转降膜吸收过程的数学模型。通过计算比较了不同反转次数和分段位置降膜吸收过程的吸收效果,确立了最佳反转次数和分段位置。这项设计研究可作为板式膜反转降膜吸收器设计的理论依据,并为今后这类传热传质设备的工程设计、开发和应用提供一定的理论参考。     

基于电磁力反馈的浓度测量系统设计

降膜溶液浓度的快速准确测量对传热传质的特性分析具有重大意义.基于电磁力矩反馈平衡的原理设计了一种新型的数字式溶液浓度测量系统,通过该系统实现降膜后溶液浓度自动测量.     

叶片前缘气膜冷却数值模拟

为了研究叶片前缘区域的换热特性,采用非结构化网格和realizable紊流模型,求解三维N-S方程,对前缘带有一排冷气孔的涡轮叶片进行了换热特性的数值模拟.分析了不同动量比,湍流度,孔间距及径向角下冷气射流的运动规律,换热分布以及冷效分布特点.结果表明,当动量比Ⅰ大于1时,在相同孔型下,动量比越高,冷效越大.在相同动量比下,孔间距越小,冷效越大.但动量比,孔间距及径向角对换热系数影响不大.当湍流度增加时,换热系数增加而冷效降低.沿展向,气膜孔中心区域冷效较高,两孔之间区域较低;而换热系数则相反,气膜孔中心区域换热系数较小,两孔之间区域较大.     

Cooling characteristics on the forced convection of an array of flat-form electronic components in channel flow

Present study is concerned with forced convective heat transfer of the channel flow with line arrays of heated electronic components mounted on a printed circuit board. For the assessment of thermal performance in channel flows, three separate variables are used:channel spacing, row number of the component, and inlet air velocity. The thermal characteristics of a component due to own power and upstream air heated by components were studied. The experimental results were compared with those of numerical solution for various conditions: surface temperature of the components, adiabatic temperature rise, and heat transfer coefficient. The experimental results agree well with the numerical solutions. The study shows that the adiabatic heat transfer coefficient is significantly affected by the inlet velocity in channel flow and less dependent on the channel spacing and row number, except for the case ofH/B=3.3. While reviewing the previous literatures, it is found that a little difference in the correlation between Nu and Re is due to the different geometric ratio of the packaged components.     

Measurement of mass flow rate and evaluation of heat transfer coefficient for high-pressure pneumatic components during charge and discharge processes

Both the mass flow rate and heat transfer characteristics are significant factors to the flow behavior of the high-pressure air; however, they are not easy to be obtained by analytical model during discharge and charge processes. In this paper, the mass flow rate characteristics of high-pressure pneumatic components (HPPC) are measured by a compounding approach; two components under test with the same geometry and dimension are needed to be connected in series. Both the effective cross-section area and critical pressure ratio of HPPC are determined accurately, and only the pressure variation and the steady-state temperature of air in the chamber are utilized. The compared results between experimental and simulation data show that the accuracy of the measured effective cross-section area and critical pressure ratio of the HPPC is high when the sonic and adiabatic releasing time is less than 2 s. And then, a new combined method of calculating the heat transfer coefficient during discharging and charging processes for the high-pressure air is proposed. The computational fluid dynamics (CFD) method is used to illustrate the intensity of heat exchange between the high-pressure air inside the chamber and outer atmosphere. The dynamic flow behavior is analyzed based on the tested flow rate characteristics of HPPC, mixed heat transfer theory and numerical results. The results show that the heat-transfer coefficient during charge process is much greater than discharge process, and the forced convection heat exchange happened owing to the strong “air agitation” during the charge process. The experimental results also validate that the proposed method of calculating the transient heat transfer coefficient is more reasonable to describe the heat transfer behavior. The findings may also have general implication in the development of the design and analysis of the high-pressure pneumatic system.     

斜盘式空气压缩机压缩与膨胀热力过程的数值分析

根据斜盘式空气压缩机的运动特性和变质量系统热力学的基本原理,建立了斜盘式空气压缩机伴有气体泄漏和不稳定传热耦合作用影响的气体压缩与膨胀热力过程的数学模型,采用四阶龙格库塔法对其进行求解,得到了斜盘式空气压缩机工作过程中气体质量、压力与温度随主轴转角的变化曲线,并分别分析了气体泄漏、不稳定传热及其耦合作用对气体压缩与膨胀过程的影响,为斜盘式空气压缩机的设计与应用提供了参考。     

垂直管内TFE/NMP降膜吸收热质传递数值模拟

通过对垂直管内溶液降膜吸收过程特点的分析，建立了垂直管内TFE/NMP降膜吸收过程中热，质传递物理和数学模型，充分考虑了吸收液膜膜厚的变化，以及横向对流项对液膜内流，质传递和气液界面处热量流率及质量流率的影响。采用适当有限差分法对数学模型进行数值求解，得出温度，浓度分布及界面质量，热量流率等参数，通过对算例计算结果的分析，得到一些相关结论。     

涡旋压缩机工作过程模拟及传热分析

根据涡旋压缩机的运转规律,得到了绝热状态涡旋压缩机非定常流动的数值模拟计算方法;对涡旋压缩机理论计算模型进行网格无关性验证、动网格重构验证,保证其数值模拟计算结果的准确性.得到了涡旋压缩机工作过程的压力场、温度场、速度场分布规律,得到其工作过程曲线与各工作腔的泄漏规律,并与理论绝热过程进行对比,验证了所采用的数值模拟计算方法的正确可行性.进而探究考虑流热耦合传热的涡旋压缩机工作过程的数值模拟计算方法,提出通过合理地设置壁面热力条件参数实现涡旋压缩机达到热力平衡状态的数值模拟计算方法.     

基于耦合传热的圆锥液体静压轴承热态性能分析

针对圆锥液体静压轴承的发热问题,利用CFX软件建立了轴承系统耦合传热模型。首先分析了网格数量对计算精度的影响,然后求解获得了轴承的温度场分布和热量传递情况,最后分析了不同参数对轴承热态性能的影响规律。结果表明,采用CFX软件计算圆锥液体静压轴承耦合传热问题是可行的,与绝热假设下的计算方法相比,耦合传热有效地反映了真实的传热情况;圆锥液体静压轴承的端泄散热占总散热量的大部分,轴颈散热能力最弱,在不同的转速和进油压力下,各个方向上的散热比率发生变化。     

Optimum design of vaporizer fin with Liquefied Natural Gas by numerical analysis

Generally, the temperature drop under 0°C on vaporizer surface creates frozen dews. This problem seems to increase as the time progress and humidity rises. In addition, the frozen dews create frost deposition. Consequently, heat transfer on vaporizer decreases because frost deposition causes adiabatic condition. Therefore, it is very important to solve this problem. This paper aims to study of the optimum design of used vaporizer at local LNG station. In this paper, experimental results were compared with numerical results. Geometries of numerical and experimental vaporizers were identical. Studied parameters of vaporizer are angle between two fins (Φ) and fin thickness (TH_F). Numerical analysis results were presented through the correlations between the ice layer thickness (TH_ICE) on the vaporizer surface to the temperature distribution of inside vaporizer (T_IN), fin thickness (TH_F), and angle between two fins (Φ). Numerical result shows good agreement with experimental outcome. Finally, the correlations for optimum design of vaporizer are proposed on this paper.