An Investigation of the Thermal Stresses Induced in a Thin-Film Thermoelectric Cooler

This work aims at investigating the thermal stresses induced within a four-layered thin-film thermoelectric cooler. The one-dimensional (1D) temperature and thermal-stress distributions are firstly analyzed under the consideration of Joule heating, the conduction heat transfer as well as Thomson heating. Followed are two-dimensional (2D) calculations of the thermal stresses with the commercial software ANSYS. The validity of the 1D analytical model is then examined by a comparison of its predicted thermal stresses with the numerical ones obtained from the 2D model. In the 2D model, the thermoelectric element becomes curved due to the shrinkage and the fixed boundary conditions. The latter also causes huge values and rapid changes of thermal stresses near the ends. In the middle portion of the thermoelectric element where the thermal effect dominates, the thermal stresses predicted by the 1D model are not much different from those computed from the 2D model. Quantitative differences arise from the fact that the 1D model does not count the stresses induced by the non-zero Poisson's ratios. In addition, the normal-stress distributions are pretty uniform across the layer thickness (the variation is less than 1MPa within each layer in the worst case). These results verify the possibility of using the 1D model for a preliminary estimate of the thermal stresses induced within the layered thin-film thermoelectric element. The 1D model nonetheless fails to capture the behaviors near the ends of the thermoelectric element.     

热电制冷的热力学机理分析研究

把热电制冷的机理与一般相变制冷的机理作比较，分析热电制冷过程的热力学原理。由分析结果得知，在理想工作条件下，电流通过半导体材料进行制冷时，同时存在的帕尔帖效应、汤姆逊效应和傅立叶效应三种效应共同耦合作用的制冷效果可以分解为电子循环与两种不可逆效应的叠加。其中的作用力是二种材料的电子化学势，最大的影响因素是二种不可逆热效应。     

Cooling Performance of the Endwall Vertical Hole Considering the Interaction between Cooling Jet and Leading-Edge Horseshoe Vortex

Interaction between the coolant and the secondary flow plays an important role in endwall cooling performance. For the leading-edge region, oncoming main flow inside the boundary layer impinges onto the vane leading edge and turns into the horseshoe vortex. Horseshoe vortex entrains coolant off the surface, thus posing severe challenges to the cooling design there. Based on analyses on the leading-edge vortex formation mechanism, a new kind of endwall film cooling design, vertical hole upstream ...     

NACT滚筒冷渣机工业性能研究

报道第一台NACT(新型灰渣冷却技术)滚筒冷渣机的工业试验结果。工业测试显示,锅炉满负荷运行时NACT滚筒冷渣机的表观传热系数大于95 W/(m~2·K),几乎是现有滚筒冷渣机产品传热系数的2倍。该装置采用扬料板组织灰渣运动,设置迎合抛洒灰渣的对流受热面,将主导热阻由灰渣接触热阻转变为灰渣对流冲刷热阻,大幅度提高了总传热系数。工业测试结果显示:滚筒转速对NACT滚筒冷渣机性能影响巨大。随着滚筒转速提高,灰渣处理量直线升高,但不同转速下的排渣温度升高速率不同;滚筒转速增加,表观传热系数升高,有利于传热过程。增加滚筒对流传热份额,延长灰渣在滚筒内停留时间,是滚筒设计的关键。     

滚筒式冷渣器冷却水系统改造

为提高焦作某电厂滚筒冷渣器冷却水系统安全和经济性,对冷渣器冷却水系统长期运行状况进行了分析研究,提出冷渣器冷却水系统的能源回收利用改造方案,并据此对冷渣器的冷却系统进行了改造。改造后系统的运行结果表明,该系统改造不仅解决了冷渣器超温问题,降低了冷渣器的故障率,而且具有显著的节能效益和环境效益。系统的改造成功的实现了排渣余热回收利用,提高了机组的安全经济性。     

考虑透平冷却的再热燃气轮机联合循环热力性能参数影响

燃气轮机再热被认为可以提高效率和比功。本文基于准一维透平连续膨胀冷却模型和底循环简明估算模型对再热燃气轮机联合循环进行热力性能研究,以GT-26燃气轮机为基准分析了循环总压比、燃烧室出口温度、再热压力等关键参数对联合循环热力性能的影响特性,并与无再热燃气轮机的联合循环性能进行了比较。研究表明:不同燃烧室出口温度下的再热燃气轮机联合循环效率最大值对应的循环总压比相差不大;不同燃烧室出口温度和循环总压比下,联合循环效率对应的最佳高压透平膨胀比不同。当燃烧室出口温度为1683 K时,在各自的效率最佳压比下,再热燃气轮机联合循环比无再热燃气轮机的联合循环效率提高了1.34个百分点,同时比功提高了33.2%。     

汽轮发电机定子冷却水冷却器的技术改造

原有冷却器在运行中存在出力不足和工质泄漏两个方面的问题,经分析研究,找出了存在问题的原因,并提出了解决措施,研制开发了新型全逆流管壳式冷却器。     

Achieving Better Super-cooling in a Two-Stage Transient Thermoelectric Device with Constraint-Free Pulse Current by Multi-Objective Optimization

As a promising energy conversion technology,transient thermoelectric device has potential applications in temperature control and refrigeration.The performance ...     

Numerical Study and Optimization of a Combined Thermoelectric Assisted Indirect Evaporative Cooling System

This paper numerically investigates the performance of a novel combined cross-regenerative cross flow(C-RC) thermoelectric assisted indirect evaporative cooling(TIEC) system.This C-RC TIEC system combines the indirect evaporative cooling and thermoelectric cooling technologies.A heat and mass transfer model is developed to perform the performance analysis and optimization of this novel system.Performance comparison between the novel C-RC TIEC system and a regenerative cross flow TIEC system is c...     

基于有限元的某柴油机冷却水冷却器强度分析

某柴油机内部产生的热量除热辐射外全部都在冷却水冷却器进行热交换,其可靠性关系着整个柴油机的运行安全。针对某柴油机冷却水冷却器在实际使用过程中,由于采用不恰当的预紧力矩出现的压板断裂问题,利用有限元软件、三维建模软件及载荷分析理论,开展预紧力矩及承受载荷对其结构强度的影响分析,得出冷却水冷却器安装使用时所能承受的最大力矩及最佳安装方式。经过现场试验验证,解决了某柴油机冷却水冷却器压板断裂、密封失效和淡水泄漏故障。     

柴油机EGR冷却器综合性能分析及改进

利用ANSYS软件对某款EGR冷却器的流场、温度场及热负荷进行数值模拟,并通过试验验证其合理性与准确性。通过对柴油机工作过程进行一维建模,得到EGR冷却器的冷却效率的提高对柴油机工作过程具有重要意义的结果。最后通过改变冷却管的结构,并用数值模拟的方法对其分析;结果表明,结构改进使冷却器的冷却效率提升了5.36%,这对以后EGR冷却器开发研制提供了一定的参考。     

Effect of Convection Heat Transfer on Performance of Waste Heat Thermoelectric Generator

Efficiency of energy conversion processes can be improved if waste heat is converted to electricity. A thermoelectric generator (TEG) can directly convert waste heat to electricity. The TEG typically suffers from low efficiency due to various reasons, such as ohmic heating, surface-to-surrounding convection losses, and unfavorable material properties. In this work, the effect of surface-to-surrounding convection heat transfer losses on the performance of TEG is studied analytically and numerically. A one-dimensional (1-D) analytical model is developed that includes surface convection, conduction, ohmic heating, and Peltier, Seebeck, and Thomson effects with top and bottom surfaces of TEG exposed to convective boundary conditions. Using the analytical solutions, different performance parameters (e.g., heat input, power output, and efficiency) are calculated and expressed graphically as functions of thermal source and sink temperatures and convection heat transfer coefficient. Finally, a two-dimensional (2-D) mathematical model is solved numerically to observe qualitative results of thermal and electric fields inside the TEG. For all calculations, temperature-dependent thermal/electric properties are considered. Increase in thermal source temperature results in an increase in the power output with adiabatic side wall conditions. A change in boundary condition to convection heat transfer from adiabatic boundary has a large impact on thermal efficiency.     

冷却塔冷却性能的评价模型

冷却塔是汽轮发电机组重要的冷端设备之一，其运行性能对电站的经济和安全运行有重要的影响。通过建立自然通风冷却塔出水温度和冷却性能的计算模型，为冷却塔的经济运行提供依据，并且还可以为冷却塔的检修和改造提供指导。     

在南京铁路南站地区实施热电冷三联供的探讨

简要介绍了热电冷三联供优越性和存在的经营风险,分析了在南京铁路南站地区实施热电冷三联供项目的必要性和优越性,提出了实施项目需要的政策支持。对该地区实现热电冷三联供项目有一定的引导性。     

Effect of Inlet Window Deflectors on the Performance of a Natural-Draft Cooling Tower Subjected to Crosswinds

The effect of inlet window deflectors on the performance of a natural draft cooling tower subjected to a crosswind was studied numerically. Three patterns of the inlet window deflectors with different setting angles (62, 72, and 82 degrees) were tested under various crosswind velocities. The assumption of heat and mass transfer equivalence was adopted for simulation. A numerical model was developed and verified by comparison with experimental data. The simulations show that the 72-degree inlet window deflectors are efficient in a wide range of crosswind velocities. The effect of the number of deflectors was also investigated and the link between the velocity profile and the critical wind velocity was clarified. It was shown that the use of deflectors in the inlet window increases the thermal efficiency of a cooling tower up to 8.6% at wind velocities greater than 2 m/s and does not exhibit any effect at the wind velocities close to critical wind velocity. The investigation may be helpful in optimal design of natural draft and “hybrid” cooling towers.     

Development of an Oil Gallery Cooling Model for Internal Combustion Engines Considering the Cocktail Shaker Effect

An internal combustion engine oil gallery cooling model was developed, which can predict average heat transfer coefficients by considering the cocktail shaker effect due to the reciprocal motion of the engine piston. The model prediction showed good agreement with available experimental data. Using the gallery cooling model and a computational fluid dynamics code which was developed to predict the combustion process, the influence of various oil cooling methods was studied numerically. Comparing the peak temperature of air cooling and oil jet-with-gallery cooling cases, the difference of the piston surface temperature was predicted to be as much as 300 K.     

Performance Optimization of Irreversible Air Heat Pumps Considering Size Effect

Considering the size of an irreversible air heat pump (AHP), heating load density (HLD) is taken as thermodynamic optimization objective by using finite-time thermodynamics. Based on an irreversible AHP with infinite reservoir thermal-capacitance rate model, the expression of HLD of AHP is put forward. The HLD optimization processes are studied analytically and numerically, which consist of two aspects: (1) to choose pressure ratio; (2) to distribute heat-exchanger inventory. Heat reservoir temperatures, heat transfer performance of heat exchangers as well as irreversibility during compression and expansion processes are important factors influencing on the performance of an irreversible AHP, which are characterized with temperature ratio, heat exchanger inventory as well as isentropic efficiencies, respectively. Those impacts of parameters on the maximum HLD are thoroughly studied. The research results show that HLD optimization can make the size of the AHP system smaller and improve the compactness of system.     

FORGO型电站空冷器冷却单元气压试验泄露分析

简要介绍了冷却单元的结构、组装与压力试验工艺、压力试验的泄漏分析等。     

一种用于船舶烟气冷却的喷雾螺旋管冷却器的传热特性研究

船舶使用的主动降噪设备需要连接到排烟支管,但高温烟气会缩短设备的使用寿命。为了降低烟气温度,建立了冷却器喷雾冷却的数值模型对支管冷却器的运行工况进行优化,通过数值模拟分析喷射压差与喷雾半角对冷态以及热态性能的影响。结果表明：最佳喷雾半角为60°,喷射压差为1.5 MPa时,冷却器性能最佳;采用液滴蒸发效率与逃逸质量分析冷却器内液滴的流动特性,根据模拟结果进行二次回归式拟合,喷雾压差和喷射半角与蒸发效率相关系数分别为0.19和0.56,其相对于逃逸质量的相关系数为0.25和0.72,喷嘴工作参数应选取较高的喷雾半角和较低的喷射压差。     

核电厂汽轮机滑油冷却器新结构性能研究

为了克服传统弓形折流板管壳式滑油冷却器的固有缺点,提出了双层连续螺旋折流板管壳式滑油冷却器.采用Realizable k-ε湍流模型结合标准壁面函数的方法,对比分析了弓形折流板管壳式以及单、双层连续螺旋折流板管壳式滑油冷却器的壳侧流线分布及传热和阻力性能.结果表明:与弓形折流板相比,连续螺旋折流板壳侧不存在流动死区,壳侧传热系数有所增大,压降有所降低,综合性能显著提高;双层连续螺旋折流板的壳侧传热系数介于弓形折流板和单层连续螺旋折流板之间,压降最低,综合性能与单层连续螺旋折流板相当.