Investigation of a heat pipe cooling system in high-efficiency grinding

The high grinding temperature is one of the problems restricting on the further development of high-efficiency grinding due to the workpiece burnout and excessive wheel wear. An original method about enhancing heat transfer in the contact zone based on heat pipe technology is put forward to reduce the grinding temperature in this paper. Drawing on the structure of rotation heat pipe, one heat pipe cooling system, heat pipe grinding wheel (HPGW) applied to high-efficiency grinding, is developed and its heat transfer principle is illustrated. Besides, the cooling effect in the contact zone using HPGW is simulated through a three-dimensional heat transfer model in grinding, and the influence of different parameters of the wheel speed, cooling condition, and heat flux input on the grinding temperature is analyzed. Eventually, preliminary grinding experiments with HPGW were carried out to verify the cooling effect by comparing with non-HPGW in grinding of 0.45 wt.% C steel and titanium alloy Ti-6A1-6V. Results show that using HPGW can significantly reduce the grinding temperature and prevent the burnout.     

半导体制冷系统热端散热试验研究

分别对TEC1-12704和TEC1-12706两种型号半导体制冷片的热端进行了散热器有热管散热与散热器无热管散热的试验装置设计,同时设计了分离电流输入两级制冷散热器有热管散热的试验装置,并分析了热端散热工况对冷端温度的影响.试验结果显示:散热器有热管散热可强化热端散热,半导体制冷片冷端温度与散热器散热能力有关,在有限...     

Investigation of heat partition in dry turning assisted by heat pipe cooling

Dissipation of the cutting heat through the cutting tool assisted by the heat pipe is a new cooling method in metal cutting. However, as an important indicator to evaluate the cooling performance, the heat partition in the cutting process for the heat pipe cutter has not been reported in the previous publications. This investigation is concerned with the estimation of the amount of heat flowing into the heat pipe cutter and that dissipated by the heat pipe. The aim is to characterize the heat partition of the heat pipe cutter and thus evaluate its cooling performance. Experimental results are presented of temperature measurements at the accessible positions on the cutter during orthogonal cutting. With these measured temperatures, the finite different methods and an inverse procedure are utilized to solve the heat flux loaded on the tool–chip interface and the amount of heat flowing into each part of the heat pipe cutter. It is shown that the installation of the heat pipe increases the heat flowing into the tool; however, much greater amount of heat can be dissipated by the heat pipe; this results in the reduction of the temperature at tool–chip interface.     

An investigation of a heat pipe cooling system for use in turning on a lathe

A novel proposal is presented in this paper for reducing the thermal inaccuracy of turning on a lathe by removing the portion of the heat generated during the cutting process which is transferred to the carbide cutting insert by installing a heat pipe in the toolholder. The ability of the heat pipe to affect the temperature of the carbide cutting insert and the elongation of the toolholder is inferred from the response of thermocouples and strain gauges mounted on the toolholder to the heat generated during various cutting conditions. The results of the experimental investigation have proved the feasibility of the concept and recommendations have been made for continuing the research and improving the performance of the system.     

Active mode-locking in semiconductor lasers

This paper presents the results of experimental studies of active mode-locking in an external-cavity semiconductor laser. Two methods of obtaining active mode-locking regimes have been studied: by modulation from an external generator with a frequency close to the intermode frequency of the external laser cavity and by laser current modulation at the frequency of intermode beats of the external laser cavity through an amplification feedback loop. In the first case, a stability of intermode beats of 10^-14 is experimentally achieved, and in the second case, it is shown that semiconductor laser current modulation by an amplified intermode beat signal from the output of a photodetector provides a stable mode-locking regime also with mode frequency tuning, i.e., a mode-locking regime involving intermode frequency tuning with optical cavity tuning. The effects that accompany mode locking, in particular, the pulling effect and the stability of the mode-locking regime, and possibility of obtaining highly stable intermode beats by suppressing the amplitude noise component in the modulating signal have been studied. A phenomenological study of the pulling and phase locking of the intermode frequency is attempted.     

Investigation of tool-chip interface temperature in dry turning assisted by heat pipe cooling

Aiming to effectively remove the cutting heat in machining process, the cutting tool with heat pipe cooling has been developed in recent years; however, there were few reports on the quantitative investigation of temperature at the tool-chip interface of this tool. In this work, a heat pipe cooling system was used to decrease the temperature of the cutter. The temperature at defined locations of the cutter in the dry turning of an AISI-1045 steel was obtained by the cutting test. The finite difference solution and an inverse procedure were used to determine the tool-chip interface temperature. It was found that with the increase of cutting speed, the tool-chip interface temperature and effective heat flux of the cutter will increase. The tool-chip interface temperature could be reduced by the heat pipe cooling. The temperature reduction was more obvious in higher cutting speed.     

翅片热板散热器的传热研究

在已设计的翅片热板散热器基础上进行了传热性能实验,对于充装不同工质、工质充装量、翅片热板散热器的工作方式等因素都进行了较深入的传热测试,分析这些因素对翅片热板散热器传热性能的影响.同时对翅片热板散热器的瞬态和稳态传热性能也进行了实验测试,分析了瞬态、稳态表面温度变化曲线,并进行了传热性能比较分析,讨论了工质充装量、倾斜角度等对翅片热板散热器传热性能的影响.     

Investigation of dry machining with embedded heat pipe cooling by finite element analysis and experiments

This paper investigates the performance of a cutting tool embedded with a heat pipe on reducing cutting temperature and wear in machining. The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as the tool life in machining. A new embedded heat pipe technology has been developed to effectively remove the heat generated at the tool–chip interface in machining, thereby, reducing tool wear and prolonging tool life. In particular, the technique can effectively minimize pollution and contamination of the environment caused by cutting fluids, and the health problems of skin exposure and particulate inhalation in manufacturing. The ANSYS finite element analysis simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining. Temperature measurements at several locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. Experiments were carried out to characterize the temperature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The performance of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color, chip color, and the chip radius of curvature.     

数据中心用热管空调系统研究进展

针对回路热管机房空调在数据中心冷却中的适用性问题,总结了数据中心用回路热管空调系统最新研究进展,对比分析了重力型、气相动力型和液相动力型3种回路热管机房空调系统,并介绍了3种回路热管自然冷却与蒸气压缩主动制冷相结合的一体式机房空调系统的构成方式与运行性能,结果表明3种回路热管在不同的应用场景下都具有良好的节能效果:从驱...     

1470nm大功率半导体激光溶脂仪控制系统设计

为了实现大功率激光溶脂仪安全、稳定的输出,设计了1 470nm大功率半导体激光溶脂的控制系统。对该控制系统所采用的驱动模块、温控模块、主控模块和人机交互模块等进行了研究。首先,采用FPGA实现恒流源的数字控制,功率反馈闭环实现恒功率控制,以提供1 470nm大功率激光器和弱激光红光指示的驱动,单片机负责实现RS232的协议解析。采用数字模拟PID混合控制,根据NTC的反馈对TEC进行驱动实现激光器温度控制。设计了基于ARM Cortex-M3架构的STM32F系列微处理器主控模块和人机交互模块,实现了相关数据的输出显示与存储、触摸屏驱动及响应以及各接口控制。最后,利用MDK平台编写控制软件并对整机控制系统进行联调和测试。实验结果表明:整机输出功率与设置功率的偏差小于2%,安全性能符合国家医用电气安全通用标准的要求。该系统能够满足1 470nm大功率半导体激光溶脂仪的稳定可靠、安全性高、抗干扰能力强等要求。     

Experimental study on nanofludic heat pipe hot chuck plate in semiconductor wafer baking process

The temperature uniformity on a heat pipe hot chuck (HPHC) during semiconductor wafer processing has been an important factor to critical dimension (300 mm) uniformity as the feature size of semiconductors decreases and productivity density increases due to the new process of nano size special manufacturing technology. To design the present heat pipe hot chuck system, which has enhanced temperature uniformity for the wafer process, the heat distribution of the system was analyzed experimentally with various working fluids such as water, TiO₂, ATO, ITO, Al₂O₃, and Ag-nanofluids and 8 cell structures. Unlike the conventional solid state chuck, the present heat pipe hot chuck system consists of a heat pipe containing specially charged working fluid. Various working fluids have been tested to find best temperature uniformity feature on the top surface of hot chuck. TiO₂-nanofluid was used and tested as the working fluid of the heat pipe hot chuck system in this paper. The temperature uniformity of upper surface was sustained in the range of ±1°C. A nano-porous layer was observed on the surface with the good result of surface temperature uniformity compared with distilled water.     

Development of hybrid loop heat pipe using pump assistance for cooling application on high heat flux device

Loop heat pipe (LHP) is an effective two-phase heat transfer device that utilizes evaporation and condensation of a working fluid. LHP is widely used in a passive cooling system, highly reliable and a very high thermal conductive device. However, extreme power density can cause dry-out in the evaporator section of LHP and might hinder the performance of the cooling system. The purpose of this research is to design and manufacture a new prototype of LHP by modifying the conventional LHP. The modification was performed by adding a diaphragm pump, called hybrid loop heat pipe (HLHP). The experimental results show that the installation of pumps in the modified LHP was able to prevent the occurrence of a dry out and reduce the operating temperature. Under a constant conductance mode, the pump was activated for 20 minutes and succeded in forcing the system to a new stable condition with a significant temperature drop. These results indicate that HLHP is very promising as a two-phase cooling system that can be proposed for devices that produce high heat flux.

     

Characteristics of cooling water fouling in a heat exchange system

This study investigated the efficiency of the physical water treatment method in preventing and controlling fouling accumulation on heat transfer surfaces in a laboratory heat exchange system with tap and artificial water. To investigate the fouling characteristics, an experimental test facility with a plate type heat exchange system was newly built, where cooling and hot water moved in opposite directions forming a counter-flow heat exchanger. The obtained fouling resistances were used to analyze the effects of the physical water treatment on fouling mitigation. Furthermore, the surface tension and pH values of water were also measured. This study compared the fouling characteristics of cooling water in the heat exchange system with and without the mitigation methods for various inlet velocities. In the presence of the electrode devices with a velocity of 0.5m/s, the fouling resistance was reduced by 79% compared to that in the absence of electrode devices.     

Heat transfer of a sustainable personal garment cooling system

Journal of Mechanical Science and Technology - This paper provides examines sustainable personal cooling systems. The impact of micro-fan configuration and inflow airspeed was tested. First, three...     

Intensified heat transfer in pipe with tall baffles

A model of the heat transfer in pipe with tall baffles is proposed, in conditions of intensified heat transfer. The model takes account of various factors for a broad range of Prandtl numbers and Reynolds numbers.     

Use of 13CO2 in high-power pulsed TEA lasers

The use of 13CO2 in carbon dioxide lasers enhances the available spectral range very significantly but is prohibitively expensive if gas flow through the laser is required. A TEA CO2 laser equipped with a gas recirculation system is described. This reduces gas costs to negligible levels even for expensive isotopic mixtures.     

半导体激光器的最新进展及其应用现状

简述了半导体激光器的现状,详细介绍了半导体激光器在激光雷达、激光测距、激光引信、激光制导跟踪、激光瞄准和告警、激光模拟、激光通信和光纤通信、光纤陀螺以及国民经济等各个领域中的应用.     

热管单管性能测试系统开发

针对现有的热管检测过程中通常采用人工摇动以辨别声音的方式,其存在效率低、准确性差等缺点,研制开发了一套重力热管单管性能测试系统。该系统以高精度环形槽作为热管的加热源,采用非接触式的红外测温技术,以流水作业的方式测量管壁温度,实现了热管传热性能的自动判别。通过阐述热管工作原理,建立了一个测试系统模型;根据整个系统结构设计开发了PLC控制器程序,在.Net开发平台下运用面向对象的设计方法开发了相应的测控软件;在此基础上该系统还引入了抗干扰技术等稳定性设计的方法,以克服外界因素的干扰,保证了整个系统的可靠性;最后,对测试结果进行了分析比较。研究结果表明,该测试系统具有测量效率高、测量数据准确、运行稳定可靠等优点。     

对焊钻杆热处理系统自动化改造

介绍了一个焊钻杆热处理智能控制系统。该系统对热处理的升温保温全过程实现闭环控制,温度检测采用固定式红外测温仪,控制算法采用β-GPC,使温度在基本无超调的情况下控制精度达到1％以内。     

微热管红外测温系统的设计

根据集成发光二极管(LED)的微热管尺寸小、温升快、温度梯度变化剧烈等特点,搭建了非接触式红外测温系统,以实现对其不同特征区域的温度测量。对该系统的信号采集与转换、误差分析与补偿、测温特性指标、以及微热管的热性能进行了研究。该系统通过LabVIEW编程软件实现红外传感器的电信号采集与温度转换;将不同温度的加热块作为等温体参考,对比热电偶与红外测温结果完成静态和动态测温特性分析,进而通过环境温度补偿方法修正LED辐射热引起的传感器漂移误差;最后基于线性拟合法完成传感器的校准。利用该测试系统在不同热负载下测试了微热管的热性能。结果显示:测温系统的准确度、重复性及线性度分别为1.2~1.5℃、1%和0.2%;时间常数T和响应时间t0.05分别约为15ms和30ms。该红外非接触测温系统能够减小传感元件对被测温度场的影响,具有测温精度高和热惰性小的特点,为微热管热性能评估提供了新的测量方法。