采用扩展温度振荡法测量超临界CO_2管内对流换热特性

提出了考虑小通道内流体温度变化时测量管内对流换热系数的扩展温度振荡法模型，该法可用于测量各种光滑表面通道内流动的局部对流换热系数。实测了典型压力温度条件下2mm内径不锈钢圆管内超临界CO2对流换热系数。     

紧凑式换热器表面瞬变测试的敏感性分析和数值模拟

提出了一种考虑纵向导热效应的紧凑式换热器表面平均传热系数瞬变测试方法.根据出口流体温度变化的实测数据,用Levenberg-Marquardt非线性曲线拟合,同时对理论模型中的纵向导热参数λl和进口流体温度变化时间常数τ ,以及传热单元数Ntu进行参数估计.敏感性分析和具有测量噪声的数值模拟实验表明,待求的反映换热面传热性能的Ntu参数估计值具有良好的精度.     

板式相变储能换热器流动与换热性能实验研究

为了探究板式相变储能换热器在不同工作状态下的流动与换热性能,以及不同工况下的损失。通过实验研究换热流体的流速、温度以及板式相变储能的摆放位置对相变储能换热器出口温度、换热功率以及效率的影响。实验结果表明,在相变材料融化结束前,进口流体流速高、温度低时,出口流体温度高,进口流体流速低、温度高时,出口流体温度低;当相变材料融化结束后,进口流体流速高、温度低时,出口流体温度低,进口流体流速低、温度高时,出口流体温度高。换热流体温度高、流速低时,效率低;换热流体温度低、流速高时,效率高。相变储能换热器的摆放位置对换热器的流动与换热性能只产生微弱的影响。     

纳米流体稳定性及其导热性能研究

为了探究影响纳米流体稳定性和导热系数的因素,采用一步法和两步法分别制备了SiO_2-EG/DW(50∶50)纳米流体和SiO_2-EG纳米流体,探讨团聚体等效直径对纳米流体稳定性的影响。基于瞬态热线法的原理,测量一步法纳米流体的导热系数,分析温度和纳米颗粒质量分数对其导热系数的影响。结果表明:相比一步法制备的纳米流体,两步法纳米流体内团聚体的沉降速度增加了10~3倍,团聚体等效直径对纳米流体稳定性具有关键性的影响。纳米流体导热系数与温度和纳米颗粒质量分数呈线性正相关,纳米流体质量分数为15%时,80℃的样品导热系数相比40℃时提高了5.2%;60℃时,质量分数6%的纳米流体导热系数相比基液提高了6.4%;质量分数增加到15%时,导热系数相比基液提高了15.8%。     

中高温导热油基SiO2纳米流体比热容实验研究

实验采用两步法制备了6种不同类型导热油基SiO₂纳米流体样本，使用Zeta电位法进行了稳定性检验。采用高温流体比热容测试系统，对6种不同类型导热油基SiO₂纳米流体的比热容在30～290℃的中高温区间进行了测量。结果表明：实验温度升高，导热油基SiO₂纳米流体的比热容也会随之升高。在30～240℃,比热容与质量分数成正相关，240℃之后，纳米颗粒由于聚合沉降，比热容的相对增大率不再上升。加入纳米颗粒粒径分别为15 nm和30 nm时，前者比热容比后者比热容有明显增大，而基液对纳米流体比热容影响较小。     

采用扩展温度振荡法测量超临界CO2管内对流换热特性

提出了考虑小通道内流体温度变化时测量管内对流换热系数的扩展温度振荡法模型,该法可用于测量各种光滑表面通道内流动的局部对流换热系数.实测了典型压力温度条件下2mm内径不锈钢圆管内超临界CO     

大治地热田使用流体流动电位法进行热储监测（Reservoir Monitoring of the Onuma Geothermal Field Using Fluid Flow Tomography，水永秀树、青野哲雄、田中俊昭、佐佐木纯一、牛岛惠辅、日本地热学会志，Vol.26，No．3（2004），251-271）

流体流动电位法是改进的流动电电位法，可用作热储监测的方法。此方法是4维电位法。为了把通过测量地下电阻引起的人工电位和地下流体流动引起的流动电位，而得到的地下流体流动瞬时状况可视化。此方法可用于干热岩工程水力破碎期间，和定期检查地热电站时监测流体的流动状况。     

喷嘴临界截面直径对喷射器性能影响实验研究

依据索科洛夫等学者提出的经验公式对喷射器进行优化设计,搭建了用于测量喷射器性能的实验台,以CO2为工质,分别研究当工作流体压力在8.0~9.6MPa、引射流体压力在2.4~2.8MPa以及工作流体温度在70~90℃时,喷嘴临界截面直径对喷射系数的变化规律。实验结果表明：当喷射器背压为3.9MPa、工作流体温度为90℃、引射流体压力为2.4MPa、工作流体压力在8.0~9.6MPa时,喷射器的喷射系数随喷嘴临界截面直径的增大而减小；当喷射器背压为3.9MPa、工作流体温度为90℃、工作流体压力为10.0MPa、引射流体压力在2.4~2.8MPa时,喷射器的喷射系数也随喷嘴临界截面直径的增大而减小；且喷射系数理论值与实验值吻合度较好,误差在±3.75%范围内。当喷射器工作流体压力为10.0MPa、引射流体压力为2.7MPa、喷射器背压为3.9MPa、工作流体温度在70~90℃时,喷射系数随着喷嘴临界截面直径的增大而逐渐减小。另外，在保持喷射器的基本工作参数不变时，工作流体压力及引射流体压力的提高对喷射器喷射系数均有提升作用。     

基于TiN-EG纳米流体的直接吸收式太阳集热系统性能实验研究

采用两步法制备稳定性较好的TiN-EG纳米流体。对该流体进行辐射特性实验研究,测量纳米流体的半球透射率及反射率,计算得出其吸收率参数,并计算纳米流体对太阳辐射的吸收率。进行光学性能分析后,筛选出合适质量分数的纳米流体,通过自搭建的直接吸收式太阳集热系统,分流量对其性能进行验证,加入菲涅耳透镜聚光使流体出口温度达到中温水平。结果表明,太阳辐照度是系统温升直接影响因素,温度变化响应时间短;且太阳辐照度变化不大时,流体出口温升随着流量的降低而大幅攀升。同时系统连续运行5 h无异常,说明系统的稳定性及数据之可靠性。     

发动机凸轮升程光顺时不同方法的应用

简要介绍了曲线光顺时的圆率法，回弹法及磨光法。比较了不同光顺方法对发动机配气凸轮升程曲线拟合的影响。给出了凸轮升程用圆率法和隔点差分比较法进行预光顺，用回弹法和磨光法进行精光顺后构造凸轮型线的计算实例。     

较大规模换热器网络的一种综合优化方法

基于分级超结构换热器网络模型的特点，改进了计算温度分布的通用解方法，以遗传算法和模拟退火算法为主，以瞎子爬山优化算法以及一些特殊优化策略为辅，设计了相应的计算程序，它需要的计算机内存要比现有的其他方法小。实例证明，该方法可成功地应用于较大规模的换热器网络的优化，并得到比现有各种方法更优的结果。     

基于夹点技术的航煤加氢换热网络优化

针对某航煤加氢装置现行换热网络夹点温差不合理导致能耗较大的现状,利用夹点技术对该装置换热网络进行分析、优化。在该装置实际工况下的夹点温差附近选取相应的夹点温差,计算出不同夹点温差对应换热网络的年总费用,得出年总费用最小的夹点温差,即最优夹点温差。在最优夹点温差的基础上生成新的换热网络,结果表明,节能效果显著。     

Computational and statistical analysis on the U-tube heat exchanger with different passes configuration: Taguchi method

In the present study, the passive technique of heat transfer in which single pass and double passes are included in a simple U-tube heat exchanger is analyzed. The computational fluid dynamics (CFD)-based parametric analysis is carried out to optimize the parameters affecting the temperature drop and heat transfer achieved from the U-tube heat exchanger. ANSYS Fluentv20 is used for the CFD analysis, and the RNG k-ɛ model and energy equation were considered to define the turbulence and heat transfer phenomena. The Taguchi method is used to formulate the experimental work and analyze the working parameters of the U-tube heat exchanger, such as hot and cold mass flow rate and hoRenew Energyt inlet temperature and cold inlet temperature. For the U-tube heat exchanger, four operating parameters are considered at four different levels in the Taguchi method. The best combination of parameters for achieving a maximum temperature drop is A₄B₁C₂D₃, and it is A₃B₄C₁D₂ in case of heat transfer. A U-tube single-pass heat exchanger is more effective as compared with other U-tube heat exchangers (zero- and double-pass). Experimental results are provided to validate the suitability of the purpose of the approach.     

Efficiency of Vertical Geothermal Heat Exchangers in the Ground Source Heat Pump System

Taking the fluid temperature distribution along the borehole depth into account, a new quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchangers. On this basis the efficiency of the borehole has been defined and its analytical expression derived. Comparison with the previous two-dimensional model shows that the quasi-three-dimensional model is more rational and more accurate to depict the practical feature of the conduction of geothermal heat exchanger, and the efficiency notion can be easily used to determine the inlet and outlet temperature of the circulating fluid inside the heat exchanger.     

A New Method for Analyzing Heat Exchangers- Matching of Temperature Field

In heat exchangers, the magnitude of Nu of each duct is influenced by the temperature field, since the ratio of heat capacity rate will influence the matching status of the temperature field between contacting ducts, the total heat transfer coefficient is related with the ratio of heat capacity rate. Considering this relationship, a new method for analyzing heat exchanger is proposed - matching of temperature field. First, for a single duct with the temperature field varying exponentially along the flow direction, its Nu is calculated. Then under the hypothesis that the thermal resistance of the wall is negligible, the matching condition was set like this: both the temperature and heat flux are equal for the hot and cold fluids at the wall, so the matching relationship of parameter that describes the temperature field of the hot and cold fluids, was obtained. Finally the relationship between the total Nu and the ratio of heat capacity rate along with the ratio of inherent thermal resistance is obtained. Compared with traditional analyzing methods, the temperature matching method can be used to get the total heat transfer coefficient directly, and also be used for optimization of heat exchanger design. For a parallel flow, the optimal ratio of heat capacity rate is reciprocal to the ratio of inherent thermal resistance, and for a counter flow, the optimal ratio of heat capacity rate is zero or infinity.     

Economic optimization of shell and tube heat exchanger based on constructal theory

In this paper, the new approach of constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger.     

The condition requiring conjugate numerical method in study of heat transfer characteristics of tube bank fin heat exchanger

The overall heat transfer performance of a tube bank fin heat exchanger is very important for engineering applications. Developing a fin pattern with good heat transfer performance for tube bank fin heat exchanger needs more our intensive effort. There are two methods to obtain the heat transfer performances of a fin pattern, i.e., one is experimental method, and the other is numerical method. If numerical method is used, the thermal boundary condition on the fin surfaces is necessary. Generally, there are two ways to treat the thermal boundary, i.e., one is to treat fin surface with uniform temperature, and the other is to use a conjugate numerical method. The former is very easy to be applied in numerical method, but the latter needs more numerical effort. This paper reports the condition under which whether a conjugate numerical method or a numerical method just specifying uniform temperature thermal boundary condition should be used. It is found that such condition is the fin efficiency. When the fin efficiency is less than 0.8, a conjugate numerical method must be used. Otherwise, the numerical results obtained by applying an uniform temperature thermal boundary condition on the fin surfaces has only slightly differences with the results obtained by a conjugate numerical method. The reported results will provide a criterion for the researchers to choose a suitable numerical method in finding a fin pattern more efficiently and reliably.     

深层地埋管换热器换热性能模拟及稳定性研究

以深层地源热泵地埋管换热器为研究对象,对其换热特性进行数值模拟和实验研究。建立考虑轴向地温梯度的深层地埋管换热器传热模型并进行模拟计算,通过示范工程现场测试数据验证该模型的正确性。对深层地埋管换热器换热的性能稳定性进行研究,发现深层地埋管换热器连续长期运行及间歇长期运行下换热性能基本稳定。当按不同运停比运行时,岩土温度恢复效果良好。研究结果表明深层地源热泵有较好的换热性能及运行稳定性,为深层地热能的开发利用提供了新思路。     

结构参数对电厂翅片管散热器动态特性的影响

散热器经常处于变化的工作条件中,研究散热器的动态特性有助于改善间接空冷系统的安全和经济运行,而散热器的结构参数会影响其动态特性。根据能量守恒建立了散热器空气、管壁和循环水的热平衡偏微分方程,采用改进欧拉法对偏微分方程组进行求解。以迎面风速阶跃变化为典型工况,研究了换热面积、换热系数和工质体积对散热器动态特性的影响。结果如下:当空气侧换热面积增加时,散热器换热量增大,两个稳态之间的空气出口温度差值不变,循环水出口温度差值增加,空气侧响应时间增加,循环水侧响应时间不变。当循环水侧换热面积增加时,散热器换热量增大,两个稳态之间的空气和循环水出口温度差值不变,空气侧和循环水侧的响应时间也不变。换热系数变化时,散热器动态过程的变化规律与换热面积变化时类似。空气侧工质体积变化对散热器动态特性没有影响。循环水侧工质体积增大会使得动态响应时间变长。     

多股流换热器动态过程场协同分析

建立了多股流板翅式换热器动态数学模型,通过换热器入口温度及流量阶跃的改变,模拟过渡过程中温度场的动态响应,利用温差场均匀性因子对多股流换热器过渡过程动态特性进行了评价,通过分析内部温度场与速度场的协同关系,揭示温差场在动态过程中的变化特征.将温差场均匀性因子与过渡时间结合,建立了自组织能力系数,并对多股流换热器控制品质进行了分析.多股流换热器在流量阶跃时,温差场均匀性因子平缓迁移,而温度阶跃时变化剧烈且存有极值.多股流换热器自组织系数越大,越易达到新的热平衡.