In this work, the heat transfer characteristics of a multi-turn pulsating heat pipe in three commonly used vertical arrangements in space are investigated using infrared thermography. The influence of the local channel structure on the overall pulsating heat pipe operation is revealed by means of temperature oscillations. The temperature distribution of the condenser section was investigated to verify the trend of working fluid flow at different inclination angles and the effect of different inclination angles on the start-up characteristics. Influenced by gravity and heating mode, there is a symmetry in the working fluid flow mode for a certain heat input load at an inclination of 0 degrees (bottom heating), and the symmetrical flow tendency is not broken until the heat input load is increased to 160 W. The flow tendency remains uninterrupted until the heat input load is increased to 160 W. When the inclination angle reaches 90 degrees, the working fluid facilitates unimpeded directional circulation. Conversely, at an inclination of 180 degrees, counteracting gravity, fluid flow becomes substantially hindered. At a 0 degrees inclination, where the system is horizontal, fluid reflux is observed within the communication pipe, accompanied by a slight increase in heat transfer resistance. However, the PHP system exhibits a substantial temperature overshoot. With the maximum thermal resistance reaching 0.34 degrees C/W, heat transfer efficiency is compromised during the startup and unstable oscillatory phases, especially when the inclination angle is set at 180 degrees. Conversely, at an inclination of 90 degrees, the working fluid achieves a circulating state at minimal heat power input and temperature thresholds, thereby reducing temperature overshoot to less than 1 degrees C. Hence, for this study, a 90 degrees inclination angle is shown to provide enhanced thermal stability and superior heat transfer characteristics.

In this work, the unstable wetting characteristics and transition of wetting stage on 2 mu m ceramic membrane tube with experimental time is reported by LBM simulation and observation experiment. The observing analysis of wetting behavior on membrane wall surface is condcuted by high-speed camera in 1000 fps. During the wetting process, contact angle, droplet width and thickness versus time is researched by analyzing wetting interface profile by S-C LB model and wetting experiment, and transition among wetting stages including contacting stage, spreading stage and permeating stage is highlighted. Variation of wetting characteristics on membrane surface are summarized along with nonuniform thermal performance by investigating convective heat-transfer coefficient and membrane temperature with experimental time. The influences of wetting characteristics on permeating behavior is researched experimentally. It is found that heat-transfer deterioration phenomenon on membrane surface may appear due to fluctuation of thermal resistance caused by continuous permeating stage during the multi-level condensation porcess. Additionally, the relationship between evaporating behavior and water-uptake ability is introduced to illustrate the fluctuation mechanism experimentally and numerically. This work provides experimental and theoretical insights into optimizing wetting characteristic and water-recovery performance on micro-porous ceramic membrane.

Pulsating heat pipe (PHP) are extensively utilized in waste heat recovery systems due to their superior heat transfer efficiency. This study compares a copper asymmetric structure pulsating heat pipe (AS-PHP) with an inner diameter of 3 mm to a traditional symmetric structure pulsating heat pipe (SS-PHP). Both configurations employ a liquid filling ratio of 45 % and utilize air-cooled heat dissipation methods. The comparison encompasses starting performance, heat transfer characteristics, and wavelet analysis. The findings indicate that the ASPHP commences oscillation at 26 degrees C, which is 3 degrees C lower than the SS-PHP. Additionally, the AS-PHP exhibits rapid start-up, reduced thermal resistance, enhanced thermal conductivity, and minimal temperature differences between its ends, consistently maintaining a temperature differential of approximately 5 degrees C. This facilitates efficient low-temperature differential heat transfer. As the heat source temperature increases, the AS-PHP demonstrates continuous high-frequency oscillations with higher energy peaks, with an oscillation frequency 0.2 Hz greater than that of the SS-PHP. During oscillations, unlike the SS-PHP, the central and peripheral tubes of the AS-PHP maintain a consistent relationship.

In the context of international education competition in the new era, graduate education in clean energy majors shoulders the mission of cultivating high-level innovative talents with both morality and talent. As the first person responsible for graduate education, graduate supervisors are the key to promoting the development of the clean energy discipline and cultivating high-quality professional talents. Therefore, it is necessary to strengthen the role of supervisors in fostering moral character and talent. This paper aims to systematically construct a team of mentors from five dimensions: selection criteria, training system, management mechanism, school enterprise cooperation, and international exchange. The goal is to optimize the selection and appointment management, clarify the responsibilities of mentors, strengthen the interaction between mentors and auxiliary students, and enhance the ability to educate students. Efforts will be made to build a team of mentors with rational beliefs, moral character, solid knowledge, and a compassionate heart.

The flat-plate pulsating heat pipe (FP-PHP) offers several advantages, including a simple structure, low cost, high reliability, and effective heat transfer performance. These attributes contribute to its widespread use in the heat dissipation of various electronic devices. The operation of a FP-PHP involves a complex process of phase change heat transfer. To gain a clearer understanding of how the working fluid behaves within the FP-PHP, this paper presents a visualization experiment focused on FP-PHP with rectangular cross-section channels. The experiment primarily examines the start-up and heat transfer characteristics of the FP-PHP under different heating powers and inclination angles. Additionally, it analyzes the vapor-liquid two-phase flow patterns within the pipe under various operating conditions. Experimental results indicate that as heating power increases, the flow pattern in the evaporation section of the FP-PHP changes from a plug-shaped flow to a local annular flow, and subsequently from a local annular flow to a global annular flow. Higher heating power results in a shorter start-up time and a higher start-up temperature for the FP-PHP. The heat transfer characteristics are optimal when the inclination angle is at 90?. At this angle, with a heating power of 120 W, the thermal resistance of the FP-PHP measures only 0.51?C/W.

In this paper, an experimental study is presented to investigate the start-up and quasi-steady operation characteristics of a loop pulsating heat pipe (LPHP). The effects of the localized start-up of the LPHP, along with the communication pipe, on the overall start-up process are analyzed, considering the temperature oscillations. In this regard, the temperature oscillations of each channel during the quasi-steady operation are analyzed to characterize and highlight the effects of different LPHP structural parts on the process. The results showed that there is a localized start-up process when employing the side-heating arrangement. Under this arrangement, the start-up time and average temperature at start-up are significantly reduced compared to the three other arrangements. Overall, using a side-heating arrangement, along with the periodic temperature oscillations in the quasi-steady state stage and the multiple quasi-steady state phenomena makes the LPHP withstand higher heat input loads.

The pulsating heat pipe (PHP) is an efficient passive heat transfer device that offers an effective solution for thermal management in proton exchange membrane fuel cells (PEMFCs). However, conventional single-side channel PHPs face significant challenges in PEMFC thermal management, including integration limitations, high start-up temperatures, and insufficient working fluid oscillation intensity. This study proposes an optimized configuration for PEMFC thermal management based on its structural characteristics: a large-scale parallel pulsating heat pipe (P-PHP) with bilaterally symmetric channels. The aim is to improve the thermal performance of PEMFCs. Results show that, in the x-axis orientation, the P-PHP exhibits remarkable adaptability to low heat input, achieving a rapid start-up time of just 205 s, while maintaining a temperature control threshold as low as 51.08 degrees C. The P-PHP also excels in fluid oscillation under low heat input conditions, making it well-suited for heat-sensitive scenarios. Furthermore, it demonstrates excellent heat transfer performance, with a 40 % decrease in thermal resistance in the x-axis orientation compared to other orientations. These results offer valuable insights and new solutions for optimizing PEMFC thermal management, thereby contributing to the advancement of fuel cell technology commercialization.

The Pulsating Heat Pipe (PHP), lauded for its efficacy in heat transfer, is distinguished by its uncomplicated architecture, economical production, diminutive form, and robust adaptability to environmental conditions. This study delineates the design of an asymmetric PHP heat transfer apparatus, achieved through the alteration of select conduit lengths within the comprehensive circulation system. The thermal transfer efficacy of this apparatus was empirically scrutinized under dual dissipation modalities: natural and forced convection. It was observed that the asymmetric PHP, when devoid of oscillatory activity, maintained a heat source temperature of 25∘C, whereas the temperature escalated to 26∘C upon the initiation of pipe vibration. Under the regime of forced convection, the asymmetric PHP demonstrated expedited activation, reduced initiation temperature, and heightened oscillatory behavior compared to its natural convection counterpart, thereby facilitating the phase change condensation within the condensation segment and ensuring efficient, sustained heat dissipation. Consequently, this bolstered the PHP’s heat transfer capabilities. The thermal resistance exhibited a declining trajectory under both dissipation strategies, with forced convection consistently yielding lower thermal resistance than natural convection. Nonetheless, the decrement in thermal resistance was gradual near the critical startup juncture and throughout the initiation phase. The PHP’s equivalent thermal conductivity displayed an upward trend in tandem with the escalation of the heat source’s temperature under both dissipation methods. Despite the superior heat transfer performance at elevated heat source temperatures, the efficiency of natural convection dissipation remained suboptimal, necessitating the application of forced convection to the condensation segment to further enhance the PHP’s thermal transfer proficiency and the overall device performance.

An innovative pulsating hot plate rib is introduced in this paper to increase the average heat transfer temperature difference between conventional fins of LED heat sinks and air and enhance the heat dissipation performance of the heat sink. The heat transfer performance of the pulsating hot plate rib in different inclination angles and heating power is systematically investigated through experiments. An electric heating plate was used as the heat source at the root of the pulsating hot plate rib, and deionized water was used as the working fluid of the pulsating hot plate with a liquid filling rate of 75 %. The results of the experimental study show that the pulsating hot plate exhibits good temperature uniformity when the inclination angle is less than 90 degrees, and the best temperature uniformity is obtained at a 45 degrees inclination angle. At low heating power, the average temperature difference between the rib root and the rib end of the pulsating hot plate is not over 3.58 degrees C. In addition, the equivalent thermal conductivity (K-eff) of the ribs of the pulsating heat sink increases gradually with the increase of heating power. The maximum equivalent thermal conductivity (2627.02 W/(m center dot degrees C)) of the pulsating heat plate is achieved when the inclination angle is 45 degrees and the heating power is 30 W, which is about 161 times the thermal conductivity of the traditional steel heat sink. The analysis of experimental data shows that the pulsating heat plate fins through phase change heat transfer have significant potential and advantages in improving the average temperature difference between the heat dissipation fins of the LED heat sink and the air.

The objective of this research is to experimentally evaluate the specific impact of a collaborative heat sink composed of gravity heat pipes (GHP) and pulsating heat pipes (PHP) on the thermal efficiency of LED light sources. The heat sink developed in this experiment is designed to improve the thermal management system, ensuring that LED operate within a safe temperature range, which is crucial as the performance of LED is directly affected by their junction temperature. An HPPHP collaborative heat sink was employed in the experiment, where PHP served as heat dissipating fins to enhance its thermal performance, while HP handles the majority of the heat transfer tasks. The results showed that under forced convection conditions, the HP-PHP collaborative heat sink can increase the maximum thermal power capacity of LED to 192 W. The HP-PHP collaborative heat sink can reduce the substrate's temperature to below 70.5 degrees C in passive mode when the LED input power does not exceed 96 W. Additional experimental results show that the minimum thermal resistance of the collaborative heat sink is 0.19 K/W under natural-convection conditions, under forced convection conditions, this value drops to 0.15 K/W, which still lower than the non-collaborative heat sink. These results demonstrate that the contact thermal resistance between HP and PHP significantly enhances the thermal performance of the collaborative heat sink. Therefore, this collaborative type of heat sink is an effective method for cooling high power LED.

PHPs (pulsating heat pipes) are widely used as an efficient heat transfer element in equipment thermal management and waste heat recovery due to their flexibility. The purpose of this study was to design a heat transfer device that utilizes an asymmetric pulsating heat pipe structure by adjusting the lengths of selected pipes within the entire circulation pipeline. In the experiment, a constant temperature water bath was used as the heat source, with heat dissipated in the condensing section via natural convection. An infrared thermal imager was used to record the temperature of the condensing section, and the local wall temperature distribution was measured in different channels of the condensing section. Based on an in-depth analysis of the wavelet frequency, the following research conclusions are drawn: Firstly, as the heat source temperature increases, the start-up time of the pulsating heat pipe is shortened, the operating state changes from start–stop–start to stable and continuous oscillation, and the oscillation mode changes from high amplitude and low frequency to low amplitude and high frequency. These changes are especially pronounced when the heat source temperature is 80 °C, which is when the thermal resistance reaches its lowest value of 0.0074 K/W, and the equivalent thermal conductivity reaches its highest value of 666.29 W/(m·K). Secondly, the flow and oscillation of the working fluid can be effectively promoted by appropriately shortening the length of the condensing section of the pulsating heat pipes or the heat transfer distance between the evaporation and condensing sections. Third, under a low-temperature heat source, the oscillation frequency of each channel of a pulsating heat pipe is found to be low based on wavelet analysis. However, as the heat source temperature increases, the energy content of the temperature signal of the working fluid in each channel changes from a low- to a high-frequency value, gradually converging to the same characteristic frequency. At this point, the working fluid in the pipes no longer flows randomly in multiple directions but rather in a single direction. Finally, we determined that the maximum oscillation frequency of working fluid in a PHP is around 0.7 HZ when using the water bath heating method.

Pulsating heat pipes (PHPs) are widely used in the heat dissipation of electronic components, waste heat recovery, solar energy utilization, etc., relying on the pulsating flow of the work material in the pipe and the heat transfer by phase change, and they have the advantages of high heat-transfer efficiency, simple structure, and low cost. In this paper, an experimental method is used to adjust the length of local pipes in the PHP structure, so that the PHP forms a high- and low-staggered asymmetric structure, and to study the effects of different liquid charging rates and heat-source temperatures on the vibration, startup, and operation of the PHP in the asymmetric structure. We found the following: it is difficult to start up and operate the workpiece at 10%, 68%, and 80% liquid charging rates; the effect of the oscillating impact is worse; the temperature difference between the evaporation section of the pulsating heat pipe and condensation section is larger; and the temperature difference between the evaporation section and condensation section is larger. The temperature difference between the evaporation section and condensation section of the pulsating heat pipe is large, the temperature difference is between 10~25 °C, and it is difficult to achieve a small temperature difference in heat transfer. When the liquid charging rate is 30% and 50%, the pulsating heat pipe oscillates better; the pulsation frequency is relatively high; and the temperature difference between the end of the cold and hot sections is small, the temperature difference is between 3 and 7 °C, and the performance of heat transfer is better. However, when the liquid charging rate is 30% and the heat source is 70 °C, the thermal resistance is increased to 0.016 K/W, and the equivalent thermal conductivity is reduced. When the performance of heat transfer is changed to 0.016 K/W and the equivalent thermal conductivity is reduced, the coefficient decreases, and the heat-transfer performance becomes weaker.

Heat-transfer deterioration is a thermal phenomenon existing one or multiple wall temperature fluctuation along the flowing direction on porous heat-transfer surface. Effects of condensate film on deterioration phenomenon for non-condensation heat-transfer process has been reported in the literature, but for condensation process is seldom proposed and specifically researched. Here, the condensation heat and mass-transfer characteristics on micro-porous ceramic membrane module is investigated experimentally and numerically, with absolute humidity of artificial flue gas, inlet temperature of cooling water, volume flux of cooling water covered the ranges of 0.6375-0.6845 kg/m(3), 294.4-297.2 K, 0.32-0.41 m(3)/s, respectively. Sudden temperature fluctuation and collapsing water-recovery efficiency are observed nearby 1/3 region of the ceramic membrane module, which corresponds to the fact that remaining condensate film induces large thermal resistance because of the low thermal conductivity of the gas-like phase, and causes fluctuation of temperature gradient (i.e. condensation heat-transfer deterioration) on membrane surface. It is found that, condensation-regime transition range decreases to 0.763-0.781 at 1/3 region of membrane module, which results in a more remarkable permeation hysteresis effect and a more dominant capillary condensation process. The present findings of this paper are helpful to optimize the design parameters and operation conditions of micro-porous ceramic membrane modules.

Proton exchange membrane fuel cell (PEMFC), as a new power generation method with high efficiency, cleanness and no pollution, has broad development prospects, but it’s thermal management problems need to be solved urgently. This paper uses ANSYS Fluent software, based on the VOF model and PHMPC model, uses the unsteady state method to simulate PEMFC without pulsating heat pipe and PEMFC with pulsating heat pipe, respectively, to study the temperature distribution law inside PEMPC. The results show that the temperature at PEMFC channel is the highest, about 68°C. Compared with PEMPC without pulsating heat pipe, it is found that the temperature of PEMPC channel decreases by about 12°C. Therefore, the pulsating heat pipe can reduce the internal working temperature of PEMFC. The simulation results can provide a theoretical basis for future experiments.

The structure and inclination angle of a pulsating heat pipe are critical factors influencing the heat transfer performance and operation mode. In this work, a single-layer double-row pulsating heat pipe is designed, and the start-up and heat transfer characteristics of pulsating heat pipe at limit angles (0?, 90?, and 180?) are experimentally investigated. Also, the operation mode and heat transfer characteristics are studied through infrared imager and temperature profiles. The study highlighted that the pulsating heat pipe has excellent operation characteristics in the limit angle. When the inclination angle is 0?, the double-row structure improves the start-up performance and at 90? inclination, the pulsating heat pipe starts the fastest, and the heat transfer resistance keeps the smallest in the whole test. When the inclination angle is 180?, the pulsating heat pipe has the best thermal sensitivity but weak working fluid-flow capacity during operation.

The temperature rise of solar cells will reduce the service life and efficiency, so cooling technology is very necessary, this paper summarized a variety of solar cell cooling technology, the main cooling technologies of the solar cell, cooling technologies divided into traditional cooling (air cooling, liquid cooling) and the new cooling technology (heat pipe cooling, Liquid immersion cooling, jet impingement cooling, microchannels cooling, etc.), this paper summarized the research related to various scholars solar cell cooling system, introduced various technical advantages and disadvantages; the temperature of fuel cell was simulated by numerical simulation method, and it was found that the cooling technology was very important for the stability of cell, the conclusion is also applicable to fuel cell.

热负荷与倾斜角是影响脉动热管传热性能的重要因素.在热负荷与倾斜角度相耦合的工况下对脉动热的传热性能进行分析.实验采用热电偶测温的方法,得到脉动热管在热负荷与倾斜角相耦合工况下的温度分布规律.实验表明:在相同功率下,倾斜角度为0°时脉动热管工作效率最高,倾斜角度为180°时脉动热管工作效率最低.当倾斜角度不变时,随着热负荷的增加脉动热管振荡周期减小,振荡逐渐趋于稳定.倾斜角度小于90°时,传热热阻随倾斜角变化不明显;当倾斜角大于90°时,随着倾斜角的增大传热热阻增加.

Herein, a horizontal CPU cooler with a pulsating heat pipe for cooling desktop computer was developed. In the experiment, an electric heating block was used to heat a copper plate to simulate the heating process of CPU. The cooling system consists of a cooling fan and a pulsating heat pipe cooler. The influence of cooling wind speed and heat load on heat transfer performance, start-up performance, and temperature uniformity of the pulsating heat pipe cooler was analyzed by controlling variable method. The wind speed was set to be 0 m/s, 0.1 m/s, 0.3 m/s, 0.5 m/s, and 0.7 m/s, respectively. The contour plots were used to analyze the uniformity of temperature distribution due to cooler. The results show that the start-up of the pulsating heat pipe led to a decrease in temperature of CPU. As the cooling wind speed increased, the start-up time of the pulsating heat pipe dropped, the start-up temperature dropped, and its stability was also improved. The operation at different cooling wind speeds also changed the start-up mode of the pulsating heat pipe. The start-up performance was best at cooling wind speed of 0.3 m/s. The contour plot for temperature showed that the temperature distribution of the pulsating heat pipe cooler became more uniform with increased cooling wind speeds. There was excellent temperature uniformity at the cooling wind speeds of 0.3 m/s and 0.7 m/s. When the cooling wind speed was 0.7 m/s, the minimum average thermal resistance was 0.51 K/W.

Pulsating heat pipe(PHP) has many advantages, such as small volume, simple structure, low cost, good heat transfer performance, it have great potential in the application of refrigeration, aerospace, waste heat recovery and low - grade energy utilization. Based on the analysis of a large number of research results at home and abroad, the application status of pulsating heat pipe technology is summarized in this paper, which can provide scientific guidance for the design, operation and large-scale application of pulsating heat pipe.