Theoretical and Experimental Investigation of Flexural Vibration Transfer Properties of High-Pressure Periodic Pipe

According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.

Energy Transfer Mechanism and Probability Analysis of Submarine Pipe Laterally Impacted by Dropped Objects

Energy transfer ratio is the basic-factor affecting the level of pipe damage during the impact between dropped object and submarine pipe. For the purpose of studying energy transfer and damage mechanism of submarine pipe impacted by dropped objects, series of experiments are designed and carried out. The effective yield strength is deduced to make the quasi-static analysis more reliable, and the normal distribution of energy transfer ratio caused by lateral impact on pipes is presented by statistic analysis of experimental results based on the effective yield strength, which provides experimental and theoretical basis for the risk analysis of submarine pipe system impacted by dropped objects. Failure strains of pipe material are confirmed by comparing experimental results with finite element simulation. In addition, impact contact area and impact time are proved to be the major influence factors of energy transfer by sensitivity analysis of the finite element simulation.

Maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick

A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model.Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.

Analysis of Vibration of the Euler-Bernoulli Pipe Conveying Fluid by Dynamic Stiffness Method and Transfer Matrix

The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fluid, the element dynamic stiffness is established. The vibration characteristic of the single-span pipe is analyzed under two kinds of boundary conditions. The results compared with the literature, which has a good consistency. Based on this method, natural frequency and the critical speed of the two types of multi-span pipe are deserved. This paper shows that the dynamic stiffness method and transfer matrix is an effective method to deal with the vibration problem of pipe conveying fluid.

STUDIES ON HEAT TRANSFER OF FLUID OSCILLATED WITHIN PIPES

This paper is a brief summarization of research achievements about enhanced heat transfer of a fluid oscillated within pipes. Analytical solutions, numerical results and dimensional analyses are summarized and compared with experimental data in the paper. Also, the mechanism of enhanced heat transfer is discussed. It is considered that increase in the effective area of heat conduction and increase in temperature gradient are the main reasons of enhanced heat transfer.

Experimental Analysis of Heat Transfer Behavior inside Heat Pipe Integrated with Cooling Plates

This work used experimental methods to study heat transfer behavior inside a heat pipe and found that heat transfer behavior inside the heat pipe was changed due to its integration with cooling plates. This change caused the heat pipe to have copper-like heat transfer behavior. Experimental performances first built a CPU simulator with maximum heat power 300 W in accordance with the ASTM standard as heat source and measured temperature distribution by using infrared thermography and thermocouple thermometer. Observation of heat transfer behavior inside heat pipe influenced by its integration with cooling plates used color schlieren technique. A commercial CPU heat pipe cooler was also used as reference object in this work. Integration of the heat pipe with cooling plates causes the heat pipe to have the copper-like heat transfer behavior. The results indicate that rebuilding the bare heat pipe’s heat transfer behavior is the best solution for improving cooling efficiency of the heat pipe cooler.

Simulation of Heat Transfer in a Tubular Pipe Using Different Twisted Tape Inserts

This paper performs a simulation study of the heat transfer phenomena in a tubular U-loop pipe. We have investigated the enhancement of heat transfer with mass flow in a pipe without insert, with full length and short length twisted tape inserts. The length of the pipe is approximately 2436.80 mm long with 29 mm inner and 33 mm outer diameter respectively. A constant heat flux is taken which generated the boundary layer of the pipe close to the flowing fluid around the boundary. The simulations are considered for the stationary and the time dependent module for 35 seconds with different length of inserts. The comparisons are made among the results. We observed that the transfer of heat is enhanced significantly with the increase of the length of inserts inside the computational domain. We also found that, full length twisted tape inserts are more effective than comparing with the short length inserts and without insert.

Thermal performance of heat pipe with different micro-groove structures

Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heat pipe with groove wick structure. The results show that these micro heat pipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.

低频导波检测技术在输油场站应用的效果分析

本文主要是对低频导波检测技术原理和应用进行分析,进而选取本次最优开挖验证点,通过MsS长距离超声导波检测仪在姬塬外输总站管网腐蚀检测过程中的应用效果分析,判断其应用效果具有哪些局限性和优缺点,为后续输油场站常规检测工作提供参考依据。

飞秒激光选区微织构AlN超浸润平板热管

目的为了提升AlN基板的散热性能,研究嵌入式一体化AlN平板热管的激光加工方法。方法通过飞秒激光微织构技术结合热处理工艺制备出AlN亲疏水组合表面,并组装嵌入式一体化平板热管,测试其传热性能。通过三维表面轮廓仪、SEM、EDS和XPS分别分析表面的三维轮廓、形貌、元素含量和化学成分,研究表面亲、疏水的形成机理。结果楔形亲疏组合AlN平板热管的启动时间、启动温度均最低,相较于全超亲水样品,启动时间降低了14.9%,启动温度降低了6.0%。楔形亲疏组合热管的热阻最低,热流密度最高。相较于全亲水热管,热阻降低了33%,热流密度提升了2%。结论AlN陶瓷表面经过激光织构会产生AlOx(多价铝氧化物),具有较高的表面能,呈超亲水状态。热处理能使表面充分氧化,降低表面能,呈超疏水状态。嵌入一体化AlN平板热管的设计和无化学激光选区微织构方法,为电子陶瓷基板的散热提供了一种新思路。

特斯拉阀通道结构毛细芯对环路热管启动性能的影响

受制于3D打印技术的制造精度,其制备的可用毛细芯孔径约为300μm。基于该毛细芯的环路热管(loop heat pipe,LHP)启动初期会产生蒸汽反向穿透毛细芯的现象,造成严重的热泄漏,对LHP的启动性能产生极大的消极影响。为了解决这个问题,本文开创性地将具有单向流动特性的特斯拉阀结构引入3D打印毛细芯中,设计制备了孔径为300μm的特斯拉阀通道结构毛细芯,并与相同孔径的圆柱直通孔毛细芯分别进行了渗透率以及在不同低功率(20W、40W、60W)下启动性能的对比。结果表明:3D打印特斯拉阀毛细芯具有明显的单向流动特征。其渗透率在流动方向上存在明显的差异,正向流动渗透率大于反向流动的渗透率;特斯拉阀毛细芯在不同功率下均能有效抑制蒸汽穿透,实现更快的启动;随着启动功率的增加,LHP的启动速度更快,特斯拉阀毛细芯对蒸汽穿透的抑制效果更明显,启动性能更好。

脉动热管太阳能集热器传热性能实验研究

以真空玻璃管为载体、石蜡为相变储热材料、脉动热管和铜管为传热元件,对比分析了充液率φ=50.0%的脉动热管太阳能集热器与铜管太阳能集热器在相同辐照度下的集热性能。研究结果表明,当辐照度大于0 W/m^(2)时,脉动热管太阳能集热器相比于铜管太阳能集热器管壁温度提高了40℃;相较于铜管太阳能集热器,热源温度越高,脉动热管太阳能集热器吸热能力越强,传热效果越好;在相同的辐照度下,相比于铜管太阳能集热器,脉动热管太阳能集热器内的石蜡达到熔点的时间缩短了13%;脉动热管太阳能集热器输出的热量比铜管太阳能集热器高0.5 kJ,随着辐照度的增强,热量差值将会更大;脉动热管蒸发段和冷凝段壁面与其相接触的传热工质会形成一种准平衡态,蒸发段与冷凝段的传热能力呈反比关系,当蒸发段传热能力下降时,冷凝段传热能力上升,保证了集热器的稳定运行。

Experimental Studies on Thermal Performance of a Pulsating Heat Pipe with Methanol/DI Water

The effect of working fluid on the start-up and thermal performance in terms of thermal resistance and heat transfer coefficient of a pulsating heat pipe have been studied in the present paper. Methanol and de-ionized water has been selected as the working fluid. The minimum startup power for DI water was obtained at 50% filling ratio and for methanol at 40%. The optimum filling ratio in terms of minimum startup power and minimum thermal resistance was 50% for DI water and 40% for methanol. The minimum thermal resistances for DI water and methanol were observed at vertical orientation. The evaporator side heat transfer coefficient for water was slightly more, while the condenser side heat transfer coefficient was appreciably more than that of methanol. Studies were also conducted for start-up time and temperature at different orientations and it was found that the PHP charged with methanol worked efficiently at all orientations.

波纹结构液氮脉动热管传热传质特性研究

低温热管换热器是天然气液化系统中的关键装置,液氮脉动热管作为其核心器件具有体积小、换热效率高等特性,可有效克服系统冻堵及设备紧凑等问题,然而开展相应实验难度较大,因此通过数值模拟方法研究其内部传热传质规律具有重要意义。首先,文章通过UDF(User-Defined Functions)编写自适应相变模型,研究了典型液氮脉动热管的传热传质特性。随后,在冷凝段优化设计了波纹结构,结合相态分布与轴线温度方差值,对比分析了充液率为50%情况三种液氮脉动热管传热传质特性,结2果表明5 mm波纹结构热管两侧方差值为51.49 K与99.22 K2,工质循环速率较快且轴线温度分布均匀。最后,研究了充液率分别为30%、50%与70%情况下5 mm波纹结构的脉动热管的传热性能。结合相态、温度及轴线温度分布分析得出充液率过高或过低均会导致热管内部产生液塞,充液率较高时,轴线温度均匀分布,热管充液率为70%时,综合性能最佳。

超深井控温钻井隔热涂层参数影响机制研究

为揭示隔热涂层对超深井井筒温度场的影响规律,针对隔热涂层与钻杆的导热特点,采用传热热阻形式计算钻杆的综合传热系数,构建了考虑钻杆内隔热涂层影响的超深井井筒–地层瞬态传热模型,并采用有限差分法对模型进行离散,利用高斯–赛德尔算法进行迭代求解。通过理论分析和现场数据验证了模型的准确性。研究发现,钻杆内隔热涂层的导热系数对井底循环温度影响显著,随着导热系数减小,井筒环空温度迅速降低,出口温度升高;隔热涂层的厚度和长度对井筒温度也有重要影响,隔热涂层厚度越大,井底循环温度越低。这些发现为超深井钻井过程中井筒温度的调控和隔热钻杆参数的优选提供了重要理论依据。

不同土质条件下土壤蓄热特性的数值模拟研究

选取严寒地区、寒冷地区、夏热冬冷地区典型地源热泵作为研究对象,建立地埋管及周围土壤的物理模型,根据不同地域的地质条件,为土壤区域设置不同的热物性参数及分层数,对整个蓄热季的地埋管及周围土壤的换热情况进行数值模拟,探究地质条件对地源热泵换热特性及土壤蓄热量的影响。结果表明,由于所选各地区土壤热物性参数及分层数不同,整个蓄热季后土壤蓄热量差异较大,严寒地区、寒冷地区、夏热冬冷地区土壤蓄热量分别为949.251 MJ、1 031.122 MJ和709.225 MJ。受土壤各层热物性参数差异影响,同一地区各层土壤的热量传递半径及升温速率也存在较大不同。粉质粘土层热量传递半径大,中粗砂与淤泥质粘土层温度提升快。此外,在整个蓄热季中,受土壤热容增大影响,蓄热效率呈现出下降趋势,在实际运行过程中应采用间歇蓄热,提升蓄热效率。

Numerical Study of Thermal Performance of a Capillary Evaporator in a Loop Heat Pipe with Liquid-Saturated Wick

Heat transfer of a capillary evaporator in a loop heat pipe was analyzed through 3D numerical simulations to study the effects of the thermal conductivity of the wick, the contact area between the casing and the wick, and the subcooling in the compensation chamber (CC) on the thermal performance of the evaporator. A pore network model with a distribution of pore radii was used to simulate liquid flow in the porous structure of the wick. To obtain high accuracy, fine meshes were used at the boundaries among the casing, the wick, and the grooves. Distributions of temperature, pressure, and mass flow rate were compared for polytetra-fluoroethylene (PTFE) and stainless steel wicks. The thermal conductivity of the wick and the contact area between the casing and the wick significantly impacted thermal performance of the evaporator heat-transfer coefficient and the heat leak to the CC. The 3D analysis provided highly accurate values for the heat leak;in some cases, the heat leaks of PTFE and stainless steel wicks showed little differences. In general, the heat flux is concentrated at the boundaries between the casing, the wick, and the grooves;therefore, thermal performance can be optimized by increasing the length of the boundary.

Experimental Investigation on the Effection of Flow Regulator in a Multiple Evaporators/Condensers Loop Heat Pipe with Plastic Porous Structure

Multiple loop heat pipes which have two evaporators and two condensers in one loop are a kind of active heat transfer device. Since they have two evaporators and two condensers, the operating mode also becomes multiple. This work discusses the cases that multiple loop heat pipes were operated with one condenser at high temperature and the other at low temperature. To avoid the high temperature returning liquid and keep the multiple loop heat pipes work properly, the flow regulator which was made of polyethylene was designed, fabricated and applied in this test. The effect of flow regulator was confirmed and analyzed. In the test that large temperature difference existed between two sinks, it can be found according to the result that the flow regulator worked effectively and prevented the high temperature vapor to enter the inlet of common liquid line, which can keep the evaporators and returning liquid to operate at low temperature. With the increment of heat loads and the temperature difference between two sinks, the pressure difference between two condensers became larger and larger. When the pressure difference was larger than the flow regulator’s capillary force, the flow regulator could not work properly because the high temperature vapor began to flow through the flow regulator. According to the test data, the flow regulator can work properly within the sinks’ temperature 0°C/60°C and the two evaporators’ heat load 30/30 W.

高温钠热管启动传热振荡及热疲劳安全分析

高温热管的启动是复杂的相变及流动过程,若发生传热振荡将造成温度波动,进而影响热管堆运行安全。本文通过实验及仿真方法研究高温钠热管在启动过程中的传热振荡现象及热疲劳后果。在竖直工况中,不同输入热流密度将引起钠蒸发速率变化,呈现不同振荡特征;热流密度提升时振幅下降,周期缩短;振荡发生时,若输入功率骤降,波形将从锯齿状转变为梯形状;在水平工况中,传热振荡被明显抑制。热管在堆内发生传热振荡时,应力风险区为热管蒸发段内壁中部;异相振荡时相较同相振荡工况应力均值升高,振幅下降,疲劳损伤减轻;当安全因子K低于1.4时热管不存在疲劳失效风险,K达1.4以上后损伤逐渐显著;其中同相工况疲劳损伤最严重,K=1.6时管壁材料疲劳寿命已降低至3.29年。本研究对高温钠热管传热振荡的机理分析及完善热管可靠性评估具有重要意义。

基于电池冷却用新型脉动热管性能的实验研究

提出一种电池冷却用C形脉动热管(pulsating heat pipe,PHP),具有较好的散热性和包裹特性。选择甲醇、丙酮、去离子水、乙醇和甲醇-丙酮混合物为PHP工质,实验研究了不同加热功率和充液率(filling rate,FR)工况下PHP的性能。结果表明,FR过高或过低均不利于C形PHP稳定运行,实际应用中需综合考虑热阻、传热极限等指标,选取合适的FR。实验研究范围内,C形PHP最佳FR在45%左右。综合考虑蒸发温度与热阻,甲醇-丙酮混合物C形PHP具备更好的性能,能够满足第二代Mirai电池冷却需求,可将其表面温度控制在84℃以下,允许的电池最大体积功率密度为6 kW/L。依据应用场合选择工质和布置方式后,PHP能保证受控对象的安全运行。相关结论为电池热控制系统设计提供了重要的参考和借鉴。