阵列射流冲击冷却流场与温度场的数值模拟

采用数值模拟方法对冲击冷却的流动和传热过程进行了三维数值研究。特别研究了在冲击孔叉排方式下,相邻孔间距、冲击距离以及射流入口雷诺数对冲击表面冷却流动传热特性的影响规律。     

透平冷却空气系统和冷却空气量研究

介绍了燃气轮机的叶片冷却技术,并对燃气轮机各级冷却空气分布进行分析。在假设等熵效率η和混合效率ηε的基础上,根据透平工作原理,建立了一个能够求解出合理空气量的方程。最后针对燃气进出口焓值和冷却空气对焓值变化的影响求解出适当的空气量分配,这为研究燃气轮机二次空气系统提供了理论依据,同时也为透平部件的寿命评估提供了边界条件。     

Self-Convectional Three-Dimensional Integrated Circuit Cooling System using Micro Flat Heat Pipe for Portable Devices

A self-convectional three-dimensional integrated circuit (3D IC) cooling system using micro flat heat pipes (MFHP) was proposed and the electrothermal behavior of the proposed structure was modeled by an equivalent circuit for simulation. Experimental measurements using the fabricated evaluation board for the 3D IC cooling system demonstrated that the temperature of the chip under test drops about 42°C due to the MFHP on the chip in steady state. The cooling performance of the proposed system is satisfactory for use as a 3D IC cooling system for mobile applications. We have applied the proposed system to the central processing unit cooler of a commercial laptop personal computer (PC). The volume of an air cooling system with conventional heat pipes for a laptop PC is about 40 times larger than that of the proposed system. However, the cooling performance of the proposed system is comparable to the original air cooler in the laptop PC both for horizontal and for vertical operation of the MFHP. The main advantage of the proposed cooler is that it is a slim, noiseless system that operates without additional cooling power consumption. The experimental results for vertical and horizontal operation of the MFHP demonstrate the possibility of the proposed self-convection MFHP architecture as a solution for the cooling system of 3D ICs that is suitable for portable devices.     

基于热管阵列锂电池组喷雾冷却实验研究

为了解决传统空气冷却系统散热效率不足的问题,通过实验方法将喷雾蒸发过程与强制空气冷却相结合,强化电池热管理系统的散热效率。建立了基于热管阵列/喷雾冷却复合结构的电池组散热系统,对比了不同冷却措施的散热性能,研究了入口风速、喷雾频率及喷雾占空比对系统散热性能的影响规律。结果表明：复合温控结构在1 C倍率下可完全抑制电池组升温,在3 C倍率下可将电池组平均温度维持在41℃左右;采用10 s喷雾周期进行冷却可将电池组平均温度降低2℃,喷雾频率的增加可显著降低电池温度波动。     

扰流空心翅片式微流道液冷板流动换热特性研究

液冷板冷却技术是解决高功率芯片热管理问题最有前途的技术之一,带翅片结构的液冷板具有低流阻、低热阻的优势,因而受到广泛关注。目前翅片结构多以实心为主,空心交错翅片对液冷板散热能力和压降等冷却特性的影响尚未得到系统的研究。对此,设计了空心交错翅片液冷板,采用数值模拟的方法研究进口温度和流量对液冷板流动换热特性的影响。模拟结果表明,空心翅片式液冷板具有良好的散热性能,随着进口温度的升高,液冷板温度不均匀性逐渐降低,但降低趋势有所减缓,而流量的增大对降低平均热阻有显著的作用,当进口流量超过1.2 L/min时,液冷板的平均热阻可低于0.04℃/W;然而,流量的增大也提高了流动阻力,当流量增大至1.7 L/min时,流体出口区域形成涡旋,产生回流区,不利于液冷板的散热效果,且流动阻力增大。     

横流对振荡射流冲击冷却特性影响的数值研究

为了分析横流条件下振荡射流冲击靶面的换热特性,采用数值计算方法研究了横向排列和纵向排列方式下振荡射流冲击靶面的冷却性能,并对纵向排列下的射流振荡器进行了排布角度修正.结果 表明:横流对冲击换热的作用主要受到两方面影响,即冲击点附近的马蹄涡和冲击点向后偏移程度;对于靶面上的冲击核心区,总体上纵向排列的高换热区域后移程度小...     

Studies on Three-Dimensional Mixed Convection with Surface Radiation in a Rectangular Channel with Discrete Heat Sources

The flow behavior and heat transfer characteristics of conjugate heat transfer under mixed convection for a three-dimensional laminar flow in a rectangular channel with six protruding heat sources, mounted on the lower wall of the channel, have been studied numerically and experimentally. At higher temperatures, radiation plays an important role. This work reports the effect of radiation on conjugate mixed convection heat transfer. Air is taken as a cooling medium and is considered to be radiatively non-participating medium. The parameters considered for the study are positions (streamwise and spansise) of the heat sources, Reynolds number, emissivity of the heat sources, and the thermal conductivity of a printed circuit board (PCB) having constant fluid properties with the Prandtl number being 0.707. The Boussinesq approximation has been used. Commercial software ANSYS Fluent has been used for numerical analysis, and experiments have been carried out in a small-sized wind tunnel. The ranges of Reynolds number, emissivity, and thermal conductivity of PCB are 115–690 (corresponding inlet velocity of 0.25–1.5), 0–0.9, and 0.038–1.4 W/mK, respectively. Results indicate that the radiative heat transfer is significant at lower Reynolds number and lower thermal conductivity of PCB. The streamwise spacing of heat sources has larger influence compared to the spanwise spacing.     

基于CFD的活塞振荡冷却的流动与传热仿真研究

由于柴油机热负荷不断提高,必须要对活塞进行有效冷却。应用计算流体动力学(CFD)方法对活塞的振荡冷却瞬态传热进行了仿真分析,得到了不同转速下冷却油腔的机油填充率以及壁面换热系数等随曲轴转角的变化规律。研究结果表明,随着发动机转速的提高,冷却油腔内的机油填充率下降,但是壁面换热系数却有所提高;机油的振荡冲击对冷却油腔顶部和底部的强化换热明显高于侧壁。此结果可为活塞有限元分析提供热边界条件,在活塞概念设计阶段为活塞的优化设计提供依据。     

车用内燃机冷却系的流动与传热仿真

本提出了车用内燃机冷却系的流动与传热仿真方法。采用一维的方法研究了车用内燃机冷却系的流动问题；采用集总参数法研究了车用内燃机冷却系的传热问题；将车用内燃机冷却系的流动问题与传热问题耦合起来作为一个系统，进行整体研究，建立了内燃机冷却系的流动与传热问题的整体模型。编制了计算程序。对某型坦克内燃机冷却系的流动与传热进行了实例计算，仿真结果与试验值符合较好。     

六缸柴油机冷却系统流动与传热的数值模拟研究

冷却水的流动与传热直接影响柴油机的冷却效率、高温零件的热负荷、整机的热量分配和能量利用。在冷却系统传热计算时，利用流固耦合的方法，较为准确地确定了缸体水套的传热边界条件。采用CFD商用软件STAR—CD对直列六缸柴油机的冷却系统的流动与传热进行三维数值模拟，给出了整机冷却水套内冷却液的流场、换热系数及压力场分布，为柴油机冷却水腔的优化设计提供了理论依据。     

Electrohydrodynamic Induced Flow and Heat Transfer in Vertical Channel with Fin Array Attached

Electrohydrodynamic heat transfer enhancement of natural convection inside the finned vertical channels is investigated via a computational fluid dynamics technique. The interactions between electric field, flow field, and temperature field are numerically determined. Flow and heat transfer enhancements are significantly influenced at low Rayleigh number. The effect of electrode arrangement and number of electrodes to the average velocity and Nusselt number are expressed. An optimum inclined angle of the channel is recommended. Relation between the number of fins and fin length to the augmented flow and heat transfer is also analyzed.     

某中速柴油机冷却液流动及流固耦合传热计算分析

为获得直观的流场和温度场数据,对某16缸中速柴油机建立了完整的冷却水三维模型,采用FLUENT流体计算软件对其进行了绝热CFD计算分析,得到了冷却水流速、压力等数据。考虑到各缸冷却水套为并列排布方式,各缸之间相对独立,建立了单缸的缸盖-缸套-冷却水耦合传热模型,对其进行了缸盖-缸套-冷却水耦合传热仿真,获得了各部件比较精确直观的温度场分布。结果表明:仿真结果与实测数据吻合较好,从而为柴油机冷却水套的优化设计提供了依据。     

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%。     

Numerical Investigation of Confined Multiple-Jet Impingement Cooling Over A Flat Plate at Different Crossflow Orientaions

This study investigates the fluid flow and heat transfer characteristics of round jet arrays impinging orthogonally on a flat-plate with confined walls at different crossflow orientations. A computational fluid dynamic technique based on a control volume method is used to compute the detailed Nusselt number distributions on the flat plate. This is achieved by solving the steady-state three-dimensional incompressible Reynolds-averaged Navier-Stoke's equations. The Reynolds stress turbulence quantities are determined by a realizable κ-ε turbulence model with an enhancement near-wall treatment. Numerical computations are performed for two types of arrangements in round jet arrays, both inline and staggered, and three different crossflow directions, parallel, hybrid, and counter. The jet Reynolds numbers ranging from 2,440 to 14,640 and three different jet-to-plate spacing ratios (Zn/d_j) of 1, 3, and 6 are investigated in this study. Results show that the flow exit crossflow direction would significantly affect the developing jet flow fields and Nusselt number distributions on the target flat-plate. Area-averaged Nusselt number increases with an increase of jet Reynolds number. Of all the cases tested, the highest average Nusselt numbers were obtained for the case with inline jets and hybrid crossflow orientation. The thermal performance of impingement multiple jets is enhanced when the value of Zn/d_j decreases from 6 to 3. Results show that further reducing the value of Zn/d_j to 1 creates a significant nonuniform distribution in local Nusselt number over the target plate regardless of the crossflow orientations. This study also provides a correlation of the area-averaged Nusselt number with the jet Reynolds number for both inline and staggered jet arrays.     

单一地板辐射供冷空调方式适用区域的划分

叙述了不加置换通风等其他空气处理方式单一地板辐射供冷空调系统的局限性和可行性以及结合中国各主要城市逐时气象参数,对普通住宅建筑,划分了单一地板辐射供冷空调方式的适用区域。     

Study of Heat Transfer Distribution in a Channel with Inclined Target Surface Cooled by a Single Array of Staggered Impinging Jets

An experimental investigation has been carried out to study the heat transfer characteristics in a channel with a heated target surface inclined at an angle, cooled by a single array of staggered impinging jets. The work encompasses the effect of three feed channel aspect ratios (5, 7, 9) and three exit outflow orientations (coincident with the entry flow, opposed to the entry flow, and both), and three Reynolds numbers (9400, 14,400, 18,800) on heat transfer. Results show that increasing the Reynolds number increases the heat transfer on the inclined target surface. The outflow orientations affect significantly the local heat transfer charactracistrics, through influencing the jet flow together with the crossflow in the impingement channel. The outflow orientation coincident with the entry flow and the outflow from both sides show better averaged Nusselt number values compared to outflow orientation opposed to the entry flow. The inclined surface affects the local Nusselt number distribution especially for the outflow orientation opposing the entry flow at the narrow region of the impingement channel. In general, the feed channel aspect ratio does not affect the Nusselt number distribution, except for outflow coincident with the entry flow. The local Nusselt number for aspect ratio 9 has been found to be greater than the Nusselt number for aspect ratio 5 by 11%. Additionally, for a given jet-orifice plate with staggered holes, the heat transfer is almost the same throughout the target surface for the outflow exiting in both directions.     

低温热源喷射式冷电联产系统经济性分析

建立了低温热源喷射式冷电联产系统热力学模型,提出以换热器的总面积与输出有效能之比值Rap以及膨胀机入口比体积与输出有效能之比值Rvp为目标函数,对系统的经济性进行了分析,并对所选5种有机工质进行比较筛选.结果表明:在电冷比r=0.5的情况下,存在最佳冷凝温度tc=30℃左右和最佳制冷蒸发温度te=8℃左右,且有机工质R600为最优工作工质;低温热源喷射式冷电联产系统适宜电冷比较低的场合.     

逆流-叉流板式全热空气热交换器换热效率的实验研究

全热空气-空气热交换器是能量回收的有效装置。本文在双房间环境的试验平台上,对逆流-叉流板式全热交换器在冬季标准工况和非标准工况下进行了实验测试,结果表明,在冬季标准工况下,其全热效率可达70％。风量、温度差、湿度差均对换热效率有影响,换热效率随风量增加而降低,随温度差和湿度差的增大而增大。根据试验结果,整理得到了换热效率的经验计算公式。     

Numerical Study on Flow and Cooling Characteristics for Supersonic Film Cooling

With the booming performances of the gas turbine engine, the turbine vane of the gas turbine engine experiences more extreme thermal environment with supersonic flows. The film cooling applied in the supersonic flow condition has essential difference from that used in the subsonic flow condition in the flow characteristics and cooling effectiveness. This article focused on the film cooling of two parallel flows (primary flow and coolant flow) with supersonic or subsonic velocity, respectively. The results show that: on the condition of supersonic primary flow and subsonic coolant flow, the coolant flow with lower momentum is sheared and dragged by the higher momentum primary flow because of the viscous property of fluid． At the meantime, the thermal and momentum of the primary flow transfers into the coolant flow rapidly． It causes the great damage of the film coverage, and the decrease of the cooling effectiveness dramatically． In contrast, on the condition of supersonic primary flow and supersonic coolant flow, the film coverage of the supersonic coolant flow can last further far than that of the subsonic coolant flow on the same blowing ratio． The turbulence kinetic energy seems to be depressed by the shorten of velocity difference of two supersonic flow. Therefore, the cooling effectiveness is enhanced by 45% for the supersonic primary and coolant flow.     

燃气透平叶片尾缘内部冷却通道流动与换热特性研究

针对更为接近于真实叶片尾缘段的楔形内部冷却通道的流动与换热特性开展了数值研究,分析了不同冷却工质应用在楔形冷却通道中的性能表现以及不同扰流柱结构、柱肋组合冷却结构对尾缘内部冷却通道中的热力特性的影响.研究表明:区别于矩形内部冷却通道,楔形通道中壁面传热系数沿流动方向呈现逐渐升高的趋势;冷却工质对换热性能影响明显,蒸汽的...