平板和叉排散热器的综合换热性能分析及结构优化

本文引用无量纲品质因数F,分别对平板和叉排散热器的换热性能进行了综合分析。研究了空气流动速度、肋片排列方式以及几何尺寸对散热器综合换热性能的影响,并且以最小化F为目标函数优化了散热器。计算所得的数据有利于散热器结构的设计与改进。     

对排凸胞换热管内传热分析及多目标优化

在湍流状态下对对排排列的凸胞换热管的传热及流动特性进行了数值模拟,讨论了凸胞排数对换热性能的影响,分析了强化换热机理;以换热性能Nu、阻力系数f及综合换热性能PEC指数为目标函数,利用多目标遗传算法对凸胞换热管的深度H、半径R及节距P进行优化。结果表明:凸胞附近的湍流强度明显高于光滑管,且2排凸胞数的换热管综合换热性能更优;在所研究的范围内,结合响应面分析发现,结构参数对目标函数的敏感性表现为H﹥R﹥P;维持Re=13136,优化结构与初始结构相比,换热性能至少提高75%,阻力系数减少14.5%。     

独立微网风电机组谐波特性多目标优化分析

针对分布式永磁风电机组在独立微网中的谐波恶化问题,文章对不同匹配方式的风电机组开展谐波测试。选择电流谐波畸变率(THDi)和电压谐波畸变率(THDu)综合评价独立微网谐波,采用博弈策略改进多目标优化,提出基于权重分析法的微网谐波评价方案。结果表明:选择合适的机组类型以及调节机组叶尖速比可有效降低微网谐波;基于权重分析法赋予各评价指标权重系数,借助多目标优化法求解微网中发电侧谐波极小分布区域。提出微网谐波评价的精确分析和可行性评价方法,为优化独立微网电能质量奠定基础。     

压缩空气储能系统分析及多目标优化

为解决压缩空气储能系统热力学性能与经济学性能相互制约的问题,本文同时考虑热力学性能与经济学性能对系统进行优化.首先建立了系统的热力学模型和经济学模型,研究了关键节点参数对系统性能的影响规律,在此基础上以热力学评价指标能量效率和经济性评价指标单位能量成本为目标函数对系统进行多目标优化.研究结果表明:增大膨胀比、提高透平入口温度能够提高系统效率、降低发电成本;系统最佳运行工况条件下,能量效率可达55.12％,单位能量成本为396.60$/kW.     

双向扭曲管传热与流阻特性及其多目标优化

以水为工质,对双向扭曲管湍流状态下传热与流阻特性进行数值计算和准确性实验验证,分析了其强化换热机理及截面尺寸a与导程S对其传热流阻的影响,并在其基础上对双向扭曲管结构参数进行多目标优化以及努塞尔数和阻力系数的关系式拟合。结果表明:相同工况下,双向扭曲管的综合换热性能优于光管和扭曲管,在Re小于20 000时具有较好的强化效果,且高出扭曲管3.92%;流体旋转流动的方向周期性改变,进一步强化了对流传热;当a增加到一定程度,管内的湍流程度不再增加;相同Re下,η、Nu和f对导程S的变化反应较灵敏。在Re=2 300～20 000、介质为水时,拟合关系式具有较高的准确性,且通过优化得到了结构的最优组合。     

虚拟电厂负荷多目标优化调度策略分析

在新能源日益被各国重视的背景下,虚拟电厂的重要性日益凸显,在虚拟电厂的支持下能够大规模地集合分散的分布式能源、用户负荷,在整合多方资源的情况下提升供电系统的稳定性,解决能源入网问题。为此,本文就虚拟电厂及负荷侧和发电侧的多目标优化调度问题进行探究。     

考虑随机特性的分布式电源多目标优化配置

针对分布式电源优化配置研究中存在的优化目标单一和忽略源荷侧随机特性问题,应用机会约束规划方法建立计及源荷侧随机特性的多目标优化配置模型,该模型以投资效益、电压指标和有功网损为优化目标,通过效仿细菌在觅食过程中的趋化思想,将种群多样性信息反馈机制引入粒子群算法寻优过程中,以动态调整粒子速度更新策略,结合多目标优化理论,提出一种改进的多目标粒子群算法求解优化配置模型。PGE-69系统仿真结果表明,分布式电源合理优化配置能有效提高投资效益和系统运行水平;系统薄弱节点的电压水平满足机会约束要求;分析不同负荷水平下的优化配置结果,可为后续负荷不断增长情况下的优化配置研究提供借鉴。     

汽油机动力性能试验设计与多目标优化研究

针对某高速汽油机中低转速工况下动力性能较差的实际问题,分别建立发动机一维模型和三维模型,计算分析导致汽油机在中低转速工况下动力性能差的原因并确定优化参数。在此基础上利用试验设计方法（design of experiment, DOE）分析了多影响因素共同作用对发动机动力性能的影响,随后采用遗传算法对原发动机动力性能进行多目标优化。优化结果显示汽油机在目标转速工况下的转矩和功率都有10%以上的提升,在中低转速工况下的动力性能得到较大提升。最后根据优化结果试制样机并进行台架试验,结果显示在5 000 r/min转速工况下,样机的转矩和功率分别提升29.7%和28.1%,样机相较于原机在中低转速工况下动力性能有较大提升,解决了原发动机在中低转速工况下动力性能较差的实际工程问题。     

Hymod模型参数敏感性分析和多目标优化

以汉江上游向家坪水文站以上流域为研究对象,通过对集总式模型Hymod的参数敏感性分析和多目标参数优化,分析了Hymod模型5个主要参数的敏感性特征,体现了该模型描述降雨径流过程特点的全面性,采用多目标遗传优化算法(NSGA-Ⅱ)对模型参数作多目标自动参数优化.结果表明,Hymod模型能较好地描述流域降雨径流过程特征,并能通过参数自动优化得到最优参数并取得理想的验证效果.     

新型钢制散热器翅片管的传热分析及优化

通过试验测得了翅片管的温度分布 ,得出这种新型散热器翅片管的自然对流换热规律。通过对试验数据的分析整理得到了肋壁平均换热系数的经验公式。分析了翅高比、翅片夹角对平均换热系数、平均辐射换热系数的影响。以金属热强度最大为目标函数 ,采用解多变量最优化问题的坐标轮换法得出了该形式翅片管的最佳结构尺寸。     

Numerical study on natural convection heat dissipation of flared fin heat sink for high concentrating photovoltaic module cooling

High operating temperature of solar cell in high concentrating photovoltaic system reduces its electrical power efficiency and lifetime. Therefore, it is urgent to find an efficient cooling method to manage the temperature of solar cells. In this paper, we presented a structure and established a three-dimensional numerical model of flared heat sink to investigate the performance with different structural parameters. The simulation results reveal that the thermal resistance gradually decreases and tends to be constant as the increase in non-dimensional fin length. In addition, the thermal resistance of flared fin heat sink decreases with the increase in fin number to a certain value and then increases. The value of thermal resistance is minimum when the fin number of flared fin heat sink reaches to 13.     

Investigating the effect of various fin geometries on the thermal performance of a heat sink under natural convection

Experimentally investigates heat dissipation by different longitudinal fins fitted to a cylindrical heat sink under natural convection conditions. Five aluminum fin configurations at base temperatures (70°C, 85°C, 100°C, and 115°C) were studied. The first fin was plain (fin1), while second fin had a triangular edge (fin2). The rest fins have the same triangular edge but with six 1cm circular perforations near the edge (fin3). While the perforations in fin4 were in the middle longitudinal fin length. The last fin (fin5) had twelve 0.5 cm circular perforations distributed into two columns. The measurements were validated with theoretical correlation with an acceptable deviation. The results showed that fin2, fin3, fin4, and fin5 dissipate more heat by 2.4%, 8.7%, 11.4%, and 5% than the flat fin with 9.8%, 11.85%, 11.85%, and 10.82% weight reduction, respectively. The heat transfer coefficient enhanced by 7.98%, 16.81%, 12.35%, and 5.44% for fin5, fin4, fin3, and fin2, respectively. Large circular perforation was more effective to dissipate heat especially when located near the heat source as in fin4 which gives the best heat dissipation with more weight reduction. The proposed fins efficiency were greater than 92%.     

Study on heat transfer characteristics of reservoir embedded loop heat pipe (Influence of condenser cooling method on heat transfer characteristics)

As heat generation in satellites increases, securing sufficient radiator panel area is an important problem. Deployable radiators, whose radiator panels are deployed post‐launch in space to increase the effective radiator panel area of the satellite, is becoming an important thermal control technology. A reservoir embedded loop heat pipe (RELHP) is applied to the deployable radiator for a thermal transport device. This paper presents the heat transport dynamic characteristics of a RELHP using a radiant cooling condenser and liquid forced convection cooling condenser by an experimental study. It was found that heat leak into the liquid line, flexible line, and reservoir increases the length of the sub‐cooling region in the condenser. In the case of the radiant cooling condenser, the sub‐cooling region length is shorter than that of a liquid forced convection cooling condenser. Furthermore, vapor temperature is mainly decided by the radiation capacity of the radiator panel, because liquid temperature returned into the evaporator rises with an increase in radiator panel temperature. In addition, time length from start‐up until steady state is greater than the liquid forced convection cooling condenser case, because the radiator panel has a large heat capacity. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20229     

The heat transfer and pressure drop characteristics of the finned tube banks in forced convection (effects of fin height on heat transfer characteristics)

In recent years the requirement for the reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. For example, in the power generation field, as thermal power generation occupies 60% of the power generation demand, considerable improvement of thermal efficiency is required. This paper describes the heat transfer characteristics of finned tube banks used for the heat exchanger in thermal power generation that were clarified by testing serrated finned tube banks with different fin heights for improved higher heat transfer and conventional spiral finned tube banks with different fin height. Then an equation to predict the heat transfer coefficient which is necessary for the design of the heat exchanger was proposed. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 194–208, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20111     

Heat transfer characteristics of a reservoir embedded loop heat pipe (Heat transfer characteristics of a deployable radiator for use on the ETS‐VIII satellite while in orbit)

As heat generation in satellites increases, ensuring that they are provided with sufficient radiator panel area is an important problem. Deployable radiators, with radiator panels that are deployed post‐launch in space to increase the satellite's effective radiator panel area of the satellite, are becoming an important thermal control technology. A reservoir embedded loop heat pipe (RELHP) is used in deployable radiators as a heat transport device. A deployable radiator of this type was mounted on the ETS‐VIII satellite, which was launched on December 18, 2006 and injected into a geostationary orbit. The satellite is still operating without any significant issues over two years later. This paper investigates the heat transport characteristics of an RELHP system used in a deployable radiator in a geostationary orbital environment. This system can be successfully started up in a micro gravity environment. We also found that the sub‐cooling region is shorter in a micro gravity environment than in a terrestrial gravity environment, because there is less heat leakage into the reservoir in a micro gravity environment. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20346     

Heat transfer and pressure drop characteristics of finned tube banks in forced convection (comparison of the heat transfer characteristics between spiral fin and serrated fin)

In recent years the requirements for the reduction of energy consumption have been increasing to solve the problems of global warming and the shortage of petroleum resources. For example in the power generation field, as thermal power generation occupied 60% of the power generation demand, an improvement in thermal efficiency is greatly needed. This paper describes the clarification of heat transfer characteristics of finned tube banks used for a heat exchanger in thermal power generation by testing serrated finned tubes banks for a heat transfer improvement and conventional spiral finned tube banks under the same test conditions. The equations to predict the heat transfer coefficient necessary to design the heat exchanger are proposed. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(2): 120–133, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20043     

A numerical study of natural convection heat transfer in a composed thermal diode

The effects of inclination on the steady natural convection local heat transfer characteristics in an air-filled enclosure, which is composed of rectangular and parallelogrammic portions, are studied numerically. In this investigation, two geometrical aspect ratios are introduced: one for a parallelogrammic portion of an enclosure, the other for a rectangular one. The governing equations for a two-dimensional, laminar, natural convection process in an enclosure are discretized by the control volume approach which ensures the conservative characteristics to be satisfied in the calculation domain, and then solved by a modified SIMPLE algorithm. The momentum and energy equations are coupled through the buoyancy term. Computations are carried out for Prandtl number Pr = 1 and Rayleigh number Ra = 2.7 × 10⁸. In order to obtain a greater understanding of the flow and heat transfer behaviors, flow patterns with streamlines and isotherms at different inclination angles are shown. Also, the effects of numbers of installed guide vanes in a composed enclosure are studied to consider the enhancement of heat transfer of the inner diode. © 1999 Scripta Technica, Heat Trans Asian Res, 28(7): 573–582, 1999     

The heat transfer and pressure drop characteristics of finned tube banks in forced convection (effects of fin height on pressure drop characteristics)

In recent years the requirement for the reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. For example, in the power generation field, as thermal power generation occupied 60% of the power generation demand, considerable improvement of the thermal efficiency is required. This paper describes the pressure drop characteristics of finned tube banks used for heat exchangers in thermal power generation that were clarified by testing serrated finned tube banks with different fin heights for improved heat transfer and conventional spiral finned tube banks with different fin heights, and an equation to predict pressure drop which is necessary for the heat exchanger design is proposed. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 179–193, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20112     

Experimental study of heat transfer of buried finned pipe for ground source heat pump applications

Ground heat exchangers have vital importance for ground source heat pump applications. Various configurations tried to improve heat transfer in the soil. A new kind of aluminium finned pipe buried in the soil for this aim. In order to compare effectiveness of the Al finned pipe over the traditional PPRC pipe an experimental study carried out. The experimental GSHP system was installed at Y?ld?z Technical University Davupasa Campus on 800 m² surface area with no special surface cover. Temperature data were collected using thermocouples buried in soil horizontally and vertically at various distances from the pipe center and at the inlet and the outlet of the ground heat exchanger. Experimental results were compared with results from analytical study. To compare effectiveness of the Al finned pipe and PPRC pipe a new parameter defined as transferred amount of heat per unit mass of working fluid per unit time for this aim. It is found that Al finned pipe has higher heat transfer values than the traditional PPRC pipe.