不同工质沟槽式微热管传热性能实验研究

为了研究工质对沟槽式微热管传热性能的影响,通过试验对不同充液率下,不同工质对沟槽式微热管的温差、热阻与极限功率等性能的影响进行研究.结果表明:充液率对丙酮热管的温差变化影响较大,在相同情况下,丙酮热管需要更高的充液率.乙醇热管的温差性能较差,但充液率小的乙醇热管其热阻较小.水热管的极限功率最高,且在100%的充液率时,有着最为良好的传热性能,较另两种工质更适合用于高功率场合.该研究对实际生产和应用中的工质选择有着重要的参考意义.     

微沟槽热管拉削成形工艺及其传热性能研究

提出一种热管内表面微沟槽拉削成形方法,利用多齿拉刀在铜管内表面的挤压作用加工出具有连续翅结构的微沟槽,并通过实验研究了微沟槽热管的启动性能、等温性能以及不同倾角下传热功率.结果表明:拉削成形微沟槽热管在约(15～20)s内实现启动,具有快速热响应能力;热管还具有良好的等温性能,蒸发段和冷凝段的温差较小;热管内真空度对热管传热性能有很大的影响;热管在重力辅助条件下传热功率最大,水平放置时次之,反重力状态下传热功率最差.     

微沟槽热管旋压成形及其传热性能研究

对管内微沟槽高速充液旋压成形工艺和传热性能进行了实验研究,研究了加工工艺参数包括拉管速度和旋压钢球数量对微沟槽成形的影响,并测试微沟槽热管的启动性能和极限功率等。同时分析了沟槽横截表面形貌。实验研究表明,随着拉管速度越大,微沟槽槽高逐渐减小;旋压球数量越多,沟槽质量更好;微沟槽热管的启动性能和均温性能良好。     

水基Fe_3O_4磁性液体脉动热管传热性能实验研究

针对磁性液体脉动热管传热性能及其影响因素问题,在风洞试验台上,采用电加热方式对13种水基Fe_3O_4磁性液体脉动热管及1根水工质脉动热管传热性能进行了试验研究。测量了磁性液体工质质量浓度(1. 5%,3%,4. 5%,9%,12%)、热管冷热段长度比(12∶14,14∶12,16. 5∶9. 5)、充液率(30%,50%,70%)、结构形式(等高,渐高,高低结构)、外磁场强度及作用角度,随电加热功率变化下的脉动热管传热性能,对脉动热管性能影响规律进行了对比分析与归纳。研究结果表明:4. 5%磁性液体质量浓度,50%充液率,冷热段长度比为14∶12,8弯头等高结构且在无外加磁场下的脉动热管传热性能最优;热阻最小值较水工质脉动热管降低了85%,并且热传导系数较紫铜导热系数提高了340倍。     

微沟槽热管充液旋压成形实验研究

对微沟槽热管充液旋压成形工艺进行了研究,通过试验对影响充液旋压成形加工的三种关键性因素进行了研究与分析.结果表明,在影响充液旋压加工沟槽式热管的三种因素中,旋压当量直径和刀具与滚珠间相对位置主要影响热管内微沟槽形状和尺寸大小,如槽深、槽宽和深宽比;刀具与滚珠间相对位置和拉伸速度影响充液旋压加工过程中铜管是否被拉断;拉伸速度对热管表面粗糙度影响很大.     

重力热管两相传热特性影响参数的数值研究

重力热管以其极佳的传热能力广泛应用于工程领域，而对于单根热管传热性能的提升则能够更好地提高换热设备的效率。本文通过数值模拟方法，分析了重力热管参数变化对其传热特性的影响。结果表明：VOF (Volume of Fluid)模型能够捕捉重力热管内部的蒸发冷凝现象；热管热阻随着充液率或加热功率的增大而减小；在一定范围内，热管热阻随热管内径增大而减小，随冷凝段长度增大而先增大后减小，但冷凝段长度过小会导致气液循环效果变差，因此，在实际设计中应考虑热管传热极限及安全长度比，保证热管的安全运行。     

采用微通道蒸发器的分离式热管空调传热性能的试验研究

设计了一套采用微通道换热器作为蒸发器的分离式热管空调,并试验研究了充液率、室内外温差和风机风量等因素对其传热性能的影响。试验结果表明:充液率过大过小均会影响系统的传热性能,其最佳充液率为120%左右;室内外温差越大分离式热管空调传热效果越好,空调传热量在室内外温差为20℃时比室内外温差为8℃时增加了228%;当风机风量低于2000m3/h时,传热量和EER随着风量的增加而增大,当风机风量超过2000m3/h时,增加风量对传热量的影响减小,而EER开始呈现下降趋势。     

加工沟槽式微热管的微型多齿刀具研究

分别采用GCr15和W18Cr4V微型多齿刀具,利用充液高速钢球旋压技术加工微型圆热管内壁的轴向微沟槽,进行了刀具性能实验,介绍了多齿刀具的齿型对微沟槽形状的影响及刀具位置对沟槽壁面结构和沟槽走向的影响,分析了刀具的磨损和破损特征。实验结果表明:GCr15刀具在加工热管内壁微沟槽时,刀具的失效形式主要是断齿与压溃,且刀具寿命短;W18Cr4V高速钢刀具在加工圆热管内壁微沟槽时,刀具的失效形式主要表现为磨损,但磨损量很小,刀具寿命长。     

横管蒸发纵管冷凝式热管充液量、倾角对传热的影响

通过搭建试验台对横管蒸发纵管冷凝式热管进行试验研究,分析该型热管在不同充液量和不同的倾角的情况下传热性能的变化。经分析发现,充液量和倾角两个因素都对该型热管的传热性能有很大影响。当倾角变化时,其热阻随倾角增加而不断增加且存在临界角。倾角在到达临界角之前热阻上升缓慢,倾角大于临界角后其热阻急剧增大。当充液量变化时,随充液量增大热管热阻先减小后增大;且在60%充液量时热阻最小,传热性能最佳。     

微热管的灌注抽真空制造技术

微热管是高热流密度光电芯片领域广泛应用的高效热传导元件,抽真空和灌注是其性能的重要影响工序。通过分析目前微热管制造工艺中常用的抽真空灌注技术,提出灌注抽真空微热管制造技术;分析该技术的工作原理和二次除气理论,建立工质额外充液量、微热管工作死区、二次除气集气段长度等数学模型;对比分析抽真空灌注与灌注抽真空两种制造技术的特点;搭建微热管性能测试平台,对采用灌注抽真空技术制造的铜—水沟槽式微热管进行性能测试;对比研究引入额外充液量前后,灌注抽真空技术制造的微热管传热性能的差异,发现引入额外充液量后,微热管性能提高了12倍。试验结果表明灌注抽真空技术可以很好地满足微热管的制造需求。     

利用吸收式热泵回收工业废热的探讨

吸收式热泵是一种利用热驱动的节能设备,在节约和充分利用能源方面具有显著的作用,具有很高的可推广性。阐述了吸收热泵的工作原理,对其技术情况作了分析,并对其节能和环保方面的应用作了介绍。     

热管换热器在烟气余热回收中的应用

介绍了热管技术，并分析了其传热机理。热管换热器具有许多独特的优点，已经获得了广泛的工业应用，应用主要集中在中低温余热资源回收利用方面，应完善高温热管，以拓宽热管换热器在高温余热资源中的应用。     

Enhancement of the critical heat flux by using heat spreader

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the critical heat flux. In this experimental study, we tried to enhance the critical heat flux by increasing the nucleate boiling area in the heat spreader (Conductive Immersion Cooling Module). Heat flux of 2 MW/m² was successfully removed at the heat source temperature below 78°C in FC-72. Some modified boiling curves at high heat flux were obtained from these modules. Also, the concept of conduction path length is very important in enhancing the critical heat flux by increasing the heat spreader surface area where nucleate boiling occurs.     

Experimental study on heat transfer characteristics of water-spray-bed heat exchanger

An experimental study was conducted on a water-spray-bed heat exchanger to investigate the heat transfer characteristics. A laboratory-scale test rig was built and its heat transfer characteristics were investigated with respect to various design and operation parameters such as the water spray flow rate, exhaust gas flow rate and number of tube rows. It was found that the implementation of the water spray increased the heat transfer rate to about 1.3 - 2.2 times that of a heat exchanger without water spray, although with a slight increase in the pressure loss. It was thus confirmed that the water spray was effective for enhancing condensing heat recovery from an exhaust gas.

     

Laser heat treatment

This paper reviews recent developments in the application of high power lasers to materials processing technology. The use of fine beams of laser energy to modify the surface properties of metallic materials is described in detail with specific emphasis on transformation hardening, surface alloying, and laser glazing. The successful exploitation of this new technology points to a significant potential for manufacturing industry to develop wear resistant surfaces using these laser systems     

无机传热技术及其工业应用

无机传热技术具有钢-水热管技术的优点，并解决了钢-水热管应用温度范围窄、常用工质热管易爆管和使用寿命短的缺陷。用该技术制造的空气预热器、余热锅炉等设备已成功地应用于石油行业，用于回收余热或进行工艺加热，并取得了良好的社会效益。     

Topological design of heat dissipating structure with forced convective heat transfer

This paper discusses the use of the topology optimization formulation for designing a heat dissipating structure that utilizes forced convective heat transfer. In addition to forced convection, there is also natural convection due to natural buoyancy forces induced by local heating inside fluid. In the present study, the temperature distribution due to forced convection, neglecting buoyancy and viscous dissipation inside fluid, was simulated and optimized. In order to analyze the heat transfer equation with forced convective heat loss and the Navier-Stokes equation, a common sequential computational procedure for this thermo/hydraulic characteristic was implemented. For topology optimization, four material properties were interpolated with respect to spatially defined density design variables: the inverse permeability in the Navier-Stokes equation, the conductivity, density, and the specific heat capacity of the heat transfer equation. From numerical examples, it was found that the balance between the conduction and convection of fluid is of central importance to the design of heat dissipating structures.     

An analytical solution to heat conduction with a moving heat source

This paper deals with an analytical solution to heat conduction in the medium subjected to a moving heat source. It evaluates the temperature distribution around a rectangular shape source moving at a constant speed along the axis of a bar. The transient temperature field from a moving heat source was analyzed using a Fourier series procedure. The most interesting result of the theory, is the derivation of a single formula capable of predicting the cooling time and cooling rate with a fairly good accuracy for ranges of temperature. Because of the passage of the heat source, the rise of temperature produced at a given near the source, tends to rapidly become constant. Several sample problems are discussed and illustrated, and comparisons with numerical approaches where these can also be used made. The results show that these solutions are in good agreement with the numerical results.     

提高KZL4-13型锅炉发热量减少热损失

对老式KZL4-13型锅炉的辅机和内拱结构进行改造，提高了锅炉热效率，加强对供热系统管理，增加了企业效益。     

An experimental investigation on heat transfer performance of pulsating heat pipe

Journal of Mechanical Science and Technology - Heat input and inclination angle are essential factors influencing heat transfer performance of a pulsating heat pipe (PHP). The heat transfer...