微沟槽热管传热性能实验研究

为研究充液率、真空度和长度对热管传热性能的影响作用,利用基于虚拟仪器技术的热管传热性能测试平台对直径6mm的微梯形沟槽热管在不同充液率、不同真空度以及不同长度等条件下进行实验测试.实验表明:微沟槽热管的最佳充液率在(75～100)%之间.热管内必须具备足够低的真空度,且充液率需根据真空度的不同适当调整.热管长度缩短可以提高其传热性能,但长度较短时,需适当提高充液率.     

薄带表面微沟槽多齿犁削成形装置的设计

设计了一种薄带表面微沟槽多齿犁削成形装置,通过牵引机构和张紧机构将薄带预张紧,牵引下轮带动薄带前进过程中利用上下两把多齿犁削刀具在其表面加工出多条平行的微沟槽,加工过程中并不产生切屑,微沟槽两侧形成波纹状的翻边结构.微沟槽多齿犁削成形方法可以实现快速加工,并且降低加工成本,有利于微通道薄片在层叠式微反应器中的推广应用.     

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.     

微矩形沟槽热管传热极限模型和实验研究

对微矩形沟槽热管的传热极限进行数学建模,并通过实验讨论分析热管工质物性群数NI、几何结构群数Ge和重力比数Hg三者对其传热极限的影响作用.研究表明,Qc与Ge和Hg呈近似指数增长变化,而与NI成线性增长关系.热管运行于较高温度、合理的几何结构和有效利用重力的辅助作用,可明显提高热管的传热能力,同时也证明了该传热极限模型的正确性.     

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。     

平板铝热管微沟槽吸液芯的制备及毛细性能研究

采用犁切-挤压(P-E)和表面化学加工相结合的方法制备出一种新型的铝沟槽吸液芯结构,通过毛细上升红外测试方法对其毛细性能进行测试表征,研究不同的CuCl_2溶液浓度和浸泡时间对吸液芯结构毛细性能的影响。研究结果表明,化学加工后的铝沟槽吸液芯的毛细性能显著提高,其最大毛细上升高度可达49.3 mm,相比于未经化学加工的犁切沟槽,其毛细上升高度提高约79.3%;当CuCl_2溶液浓度超过1mol/L时,浸泡时间和溶液浓度对铝沟槽吸液芯的毛细压力影响较小。该方法能够简单、有效的提高铝沟槽吸液芯的毛细性能,为平板铝热管吸液芯的制备提供了一种新手段。     

沟槽式微热管缩径工艺研究及装置开发

分析了沟槽式微热管的缩径工艺,通过实验研究分析对比了模具挤压、钢球旋压和径向锻造这三种方法对微热管缩径质量的影响,并在此基础上设计出了符合沟槽式微热管缩径工艺要求的高效缩径装置.     

沟槽式微热管封口机构设计

研究了沟槽式微热管制造过程中的封口工艺.微热管封口压力曲线由专用压力机测定,然后通过分析压力位移曲线图来选择合适的封口压力,并根据压力大小设计一种简易的增力机构,联合Pro/E和ADAMS软件对机构进行建模仿真,结果表明,所设计的封口机构在较小的压力输入下能获得期望的钳口压力.     

内齿圈一次拉削成型大拉刀的设计制造技术及应用

给出大拉刀的结构设计方案,小径定心并以渐成式和同廓式相结合,并对参数进行优化,均衡拉削力,粗、精刀套均采用可换套筒式的装配结构.     

沟槽式微热管弯曲变形特性研究

沟槽式微热管具有良好的导热能力,是解决微电子高热流密度问题的关键元件之一.在实际应用中,微热管常需进行弯曲加工以配合安装需求,弯曲变形对热管性能会产生不良影响.针对微热管弯曲变形过程建立了受力模型,并进行了相应的弯曲实验和分析,结果表明弯曲半径对弯管变形程度影响显著,弯曲半径越小,变形量越大;经过去应力退火的热管有利于提高弯管质量;弯曲角度对弯管变形影响甚小.     

Study of the heat transfer performance of gravity heat pipes based on lattice Boltzmann surface modification

Journal of Mechanical Science and Technology - Surface modification is an important means to improve boiling heat transfer. Based on the research of surface wettability, this paper briefly...     

Prediction of heat transfer process in helical milling

This paper represented a three-dimensional heat transfer model which describes the temperature distribution with the time variation in solid with conduction-convection boundary during the helical milling process. On the basis of the kinematic mechanisms of helical milling, two types of heat sources were presented; one was the first heat source (FTHS) resulting from the peripheral cutting edge, and the other one was the second heat source (STHS) resulting from the bottom cutting edge. Both effects of the FTHS and the STHS on the temperature distribution of the workpiece were investigated. The FTHS was defined as one semicircle which acted on a helical path; the STHS was defined as one straight line and the movements of which consisted of three ways: rotating around the axis of the tool, turning around the center of the hole, and moving along the axial direction. In order to accurately study the heat transfer model, a stationary coordinate established in the hole and a moving coordinate established in the heat source were developed. The transformation of coordinates and the trajectory of the moving coordinate had been illustrated. Under the two coordinates, a nonhomogeneous partial differential equation (PDE) containing heat source term was derived and was solved using the Green function approach. The heat source term was depicted using the Dirac delta function. A series of experimental tails for Ti-6Al-4V were organized. The experimental results agreed well with the data calculated using the model. The effects of different cutting parameters on the temperature rise were also investigated.     

Investigation of the effects of geometrical parameters on heat transfer from buried finned pipes

Heat transfer from finned pipes buried in the soil has been investigated using experimental, analytical and numerical techniques. The experimental setup consists of a ground source heat pump system and two separate ground heat exchangers. Constant surface temperature approach based on Carslaw and Jaeger’s theory study was used for calculating the heat transfer from the pipes analytically. The problem was modeled and solved using a CFD program numerically. Effects of the fin number, fin length and simulation time on the heat transfer rate have been investigated and compared with bare tube. A modified analytical formula was also proposed for finned pipes in this study.     

紫铜管钎焊工艺

对紫铜管钎焊进行了工艺试验 ,用国产焊材代替进口焊材 ,在工程上取得了良好的效果。     

Equivalent thermal conductivity of heat pipes

In precision machining, the machining error from thermal distortion carries a high proportion of the total errors. If a precision machining tool can transfer heat fast, the thermal distortion will be reduced and the machining precision will be improved. A heat pipe working based on phase transitions of the inner working liquid transfers heat with high efficiency and is widely applied in spaceflight and chemical industries. In mechanics, applications of heat pipes are correspondingly less. When a heat pipe is applied to a hydrostatic motorized spindle, the thermal distortion cannot be solved during the heat transfer process because thermal conductivity or equivalent thermal conductivity should be provided first for special application in mechanics. An equivalent thermal conductivity model based on equivalent thermal resistances is established. Performance tests for a screen wick pipe, gravity pipe, and rotation heat pipe are done to validate the efficiency of the equivalent thermal conductivity model. The proposed model provides a calculation method for the thermal distortion analysis of heat pipes applied in the motorized spindle.     

An improved correlation to predict the heat transfer in pulsating heat pipes over increased range of fluid-filling ratios and operating inclinations

Journal of Mechanical Science and Technology - Previous correlations that have been used to predict the heat transfer performance of pulsating heat pipes (PHPs) offer limited thermal predictions...     

Three-dimensional fin-tube expansion process to achieve high heat transfer efficiency in heat exchangers

A novel manufacturing process for expanding the tubes of fin-tube type heat exchangers using a three-dimensional (3D) spiral expanding ball fabricated via metal additive manufacturing was proposed for the manufacture of highly efficient heat exchangers. To improve the heat transfer efficiency of fin-tube type heat exchangers, fine grooves are generally formed inside a tube to increase the heat transfer area. However, the height of a groove is commonly reduced when a tube is expanded for tightening with fins. To address this issue, a 3D expanding ball with spiral grooves was first developed and used in the expansion process. In conventional tube expansion, the height reduction of grooves is approximately 10.3 %. However, we demonstrated that it was dramatically improved, reaching approximately 1.7 %, when the proposed process with a 3D expanding ball was applied. We believe that this approach can be used in practical industries to manufacture highly efficient fin-tube heat exchangers.

     

逆流冷凝塔热泵系统热质交换过程数值模拟研究

冷凝塔作为冷凝式热泵系统的重要组成部分,其热质交换过程对于降低能耗及热泵系统设计具有重要意义.以逆流冷凝塔热泵系统形式为基础,通过建立冷凝塔内热质交换过程的数学模型,推导出热质交换过程的通用计算方程组,并以贵阳地区的气象参数为参考,对不同工况下塔内热质交换情况进行模拟计算及具体分析.研究结果表明,不同入口空气参数对溶液...