对流换热场协同理论的新视角

从能量方程出发，对过增元教授提出的对流换热场协同理论公式变形，得到另一种形式的速度场和温度场的协同关系。研究表明，除物性外对流的换热强度主要取决于与温度和速度积的散度，并通过例子对其进行了探讨。     

节能建筑外窗传热系数现场测量的简易方法

鉴于窗户传热系数现场测量复杂,本文提出一种简易方法供讨论,其关键是利用热流计测量窗户表面换热系数,利用红外热像仪测量窗户表面平均温度,并用实例说明该方法简便可行.     

Heat Transfer Characteristics of Nanofluids in an Acoustic Cavitation Field

Heat transfer characteristics of nanofluids in an acoustic cavitation field have been investigated experimentally. The effects of acoustical parameters, nanofluids concentration, and fluid subcooling on heat transfer are determined in detail. Results show that acoustic cavitation and nanometer particles have a profound influence on single-phase convection and boiling heat transfer of a horizontal circular copper tube. The former is mainly ascribed to the impingement and disturbance of cavitation bubbles and anticipatory activation of smaller vapor embryos within the cavities, while the latter is caused by roughness modification of the tube surface. The above mechanisms are given based on the Schlieren photographs and optical observation. Acoustic cavitation has been shown to be a good way to reduce or eliminate boiling hysteresis.     

磁场作用下纳米磁流体热管传热速率的研究

提出了一种利用外加磁场来强化纳米磁流体真空热管传热的实验研究方法,设计和建立了纳米磁流体真空热管传热测试实验台,并在不同种类、不同强度的外加磁场作用下分别对纳米磁流体真空热管的传热速率进行了实验研究.结果表明：纳米磁流体热管在各种外界条件下都优于磁流体热管和水工质热管;各种磁场都能强化纳米磁流体热管的传热,其中静态直流磁场作用下纳米磁流体真空热管的传热速率提高最大.     

有机热载体锅炉盘管内流场的分析

为了分析有机热载体锅炉盘管内杂质对流场的影响,使用数值模拟方法对不同特征尺寸的杂质在不同流速和温度下的局部流动状况进行了分析。分析结果表明:杂质对特征尺寸内局部流场影响明显,降低使用温度并不能保证盘管安全运行,配备高目数过滤网能有效改善局部流场。     

基于场协同理论的超声波对强化换热影响

本研究分别对圆管、波节管和横纹管在Fluent软件中进行数值模拟,模拟了3种管型在紊流工况下的换热效果并对数值模拟所得到的结果用场协同的理论分析。结果表明:从场协同理论得出加入超声波会增强场的协同程度,增强换热管的换热效果;圆管、波节管、横纹管的场协同数则随着雷诺数的增加而减小;而努塞尔数和表面传热系数随着雷诺数的增加而增加,综合性能系数随着雷诺数的增加而增加,而效能评价系数会随着雷诺数的增加而减小。     

圆形换热板片传热及流动性能对比计算研究

整理了几种与研究结构相关的换热器的传热系数与压降计算公式,如:螺旋板式、伞板式、弯管式,并针对新型圆形换热板片进行了传热和压降的计算研究及其对比分析,得出了板片的主要设计参数对流动与传热的影响规律,所做工作对新型圆形板片式换热器的优化设计有重要的参考价值。     

The Heat Transfer Family of Kyushu University

Kyushu University has been one of the most active universities in heat transfer research, especially in the field of boiling and condensation. The heat transfer research in Kyushu University was initiated by Prof. K. Yamagata about 75 years ago. He brought up a number of heat transfer professors including Prof. K. Nishikawa and his successors, and his group has been called the “Heat Transfer Family.” The present article introduces its history and the current status of heat transfer research in Kyushu University.     

纳米流体传热强化技术

主要汇总了国内外纳米流体传热强化技术的研究成果,对纳米流体传热强化技术的国内外研究发展状况进行了综述;针对纳米流体的物性参数及流动情况,分析了纳米流体的强化传热机理;并具体阐述了纳米流体的主要物性参数——导热系数和粘度的影响因素;叙述了纳米流体的在各个领域中的应用并对其未来进行了展望。     

考虑凝结换热的汽轮机高中压外缸温度场分析

以某机组的冷态启动为例,在考虑凝结换热的基础上,用大型有限元分析软件ANSYS10．0对其高中压外缸进行了瞬态温度场分析,为以后的强度计算和寿命评估打下了基础。     

A Study of Bubble Behavior and Boiling Heat Transfer Enhancement under Electric Field

The effect of a D.C. electric field on nucleate boiling heat transfer for refrigerants, R11, R113, and FC72, was investigated experimentally in a single-tube shell/tube heat exchanger by using the temperature control method of wall superheat. Also the behavior of bubble under nonuniform electric field produced by wire electrodes was studied by numerical calculation. For R11, the electrohydrodynamic (EHD) enhancement for boiling heat transfer was observed for all ranges of wall superheat tested. However, the enhancement in boiling heat transfer disappeared if the wall superheat exceeded 13°C for R113, and no electric field effect on the boiling heat transfer was observed for FC72. An application of approximately 5 kV was enough to eliminate the boiling hysteresis for R11 and R113. Numerical study of the electric field in a single medium has hinted that the bubbles are forced away from the heating surface and toward the electrostatic stagnation point by the dielectrophoretic force. Such modified bubble motion turns out to promote the boiling heat transfer if one uses proper electrode configuration.     

重力对微槽平板热管传热性能的影响

系统地研究了重力对微槽平板热管传热性能的影响,分析了工作温度、冷却方式和倾角等影响因素。通过对比实验发现重力对热管的轴向液膜分布影响非常明显,在周向只在大充液率时有明显的影响,从而使得倾角较大地影响了热管的传热能力。研究表明深槽平板热管具有优良的传热性能,在微电子器件冷却等微小空间散热方面有着良好的应用前景。     

Investigation of the Heat Transfer Characteristics

In the present study a numerical investigation of the heat transfer in an annular combustion chamber of a typical industrial gas turbine was done using a Galerkin-based finite-element solution of the problem. Results were obtained for three basic cases: constant flux incident on the entire combustion segment, constant flux in three quadrants of the chamber and a different magnitude constant flux in the other quadrant, and different magnitude fluxes on the upstream and downstream portions of the chamber. The chamber Biot numbers, dimensionless heat flux, and dimensionless structural wall and thermal barrier coating thicknesses were found to have a crucial effect on the chamber temperature distribution. It was shown that changing the magnitude of the heat flux in a single quadrant prominently alters the temperatures throughout the wall in this area, leading to exceedingly steep temperature gradients. It was also found that any step decrease in downstream incident flux leads to a sharp drop in temperatures at the interface of the thermal barrier coating and the combustion gases.     

应用流场协同理论的多纵向涡强化换热管

应用流场协同理论研发了两种多纵向涡强化换热管———不连续双斜向内肋管和交叉缩放椭圆管,分析了其强化换热的物理机制。数值模拟和实验结果表明,当Re=500-2300 时,与考虑进口段效应的圆形截面管(L D=300)相比,不连续双斜向内肋管的换热增强250%~650%,阻力增加120% 300%;交叉缩放椭圆管Nu 可提高200%~500%,沿程阻力增加100%~350%;当Re=2300~5×104 时,与圆管相比,不连续双斜向内肋管换热可增强110%~240%,阻力增加120%~240%;交叉缩放椭圆管换热可增强35%~170%,阻力增加130%~160%。两种新型强化换热管具有优良的换热性能,可广泛应用于电力、石化、建筑供热等行业。图7参10     

考虑辐射换热计算的汽缸温度场分析

在考虑内外缸间辐射换热计算的基础上,用有限元方法分析了某机组中压内缸、高压内缸、高中压外缸的温度场;考虑了内外缸间水蒸汽对辐射换热计算的影响。分析过程包括了汽缸温度场分析简化模型的建立,计算对流换热系数和等效的辐射换热系数,迭代分析温度场。以某机组为例,其中压内缸内表面沿轴向长度平均温度为528.8℃,考虑辐射换热计算后为524.6℃,减少了4.2℃;中压内缸外表面沿轴向长度平均温度为514.6℃,考虑辐射换热后为502.2℃,减少了12.4℃;增加的径向温度差为8.2℃。计算结果表明了考虑辐射换热计算的必要性。     

Heat Transfer Studies of a Heat Pipe

The present investigation reports a theoretical and experimental study of a wire screen heat pipe, the evaporator section of which is subjected to forced convective heating and the condenser section to natural convective cooling in air. The theoretical study deals with the development of an analytical model based on thermal resistance network approach. The model computes thermal resistances at the external surface of the evaporator and condenser as well as inside the heat pipe. A test rig has been developed to evaluate the thermal performance of the heat pipe. The effects of operating parameters (i.e., tilt angle of the heat pipe and heating fluid inlet temperature at the evaporator) have been experimentally studied. Experimental results have been used to compare the analytical model. The heat transfer coefficients predicted by the model at the external surface of the evaporator and condenser are reasonably in agreement with experimental results.