Journal articles: 'LHP Wick'

1

Htoo, Kyaw Zin, Phuoc Hien Huynh, Keishi Kariya, and Akio Miyara. "Experimental Study on Thermal Performance of a Loop Heat Pipe with Different Working Wick Materials." Energies 14, no. 9 (April 25, 2021): 2453. http://dx.doi.org/10.3390/en14092453.

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In loop heat pipes (LHPs), wick materials and their structures are important in achieving continuous heat transfer with a favorable distribution of the working fluid. This article introduces the characteristics of loop heat pipes with different wicks: (i) sintered stainless steel and (ii) ceramic. The evaporator has a flat-rectangular assembly under gravity-assisted conditions. Water was used as a working fluid, and the performance of the LHP was analyzed in terms of temperatures at different locations of the LHP and thermal resistance. As to the results, a stable operation can be maintained in the range of 50 to 520 W for the LHP with the stainless-steel wick, matching the desired limited temperature for electronics of 85 °C at the heater surface at 350 W (129.6 kW·m−2). Results using the ceramic wick showed that a heater surface temperature of below 85 °C could be obtained when operating at 54 W (20 kW·m−2).

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Asmara, Dimas Panji, Mukhsinun Hadi Kusuma, Giarno Giarno, and Darwin Rio Budi Syaka. "STUDI EKSPERIMEN PENGARUH WICK PIPA KAPILER PADA MODEL LOOP HEAT PIPE." SIGMA EPSILON - Buletin Ilmiah Teknologi Keselamatan Reaktor Nuklir 25, no. 2 (November 28, 2021): 74. http://dx.doi.org/10.17146/sigma.2021.25.2.6365.

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Kecelakaan yang terjadi pada Pembangkait Listrik Tenaga Nuklir Fukushhima Dai – Ichi memacu para periset di bidang keselamatan nuklir untuk menggunakan sistem pendingin pasif dalam rangka meningkatkan keselamatan termal isntalasi nuklir. Salah satu teknologi sistem pendingin pasif yang potensial untuk diterapkan adalah Loop Heat Pipe (LHP) karena memiliki kemampuan pembuangan kalor yang baik. Tujuan penelitian ini adalah untuk mengetahui pengaruh performa wick berupa pipa kapiler dalam rangka meningkatkan unjuk kerja termal dan distribusi suhu pada LHP. Metode eksperimen dilakukan dengan mengoperasikan LHP menggunakan wick. LHP dioperasikan dengan memvariasikan suhu air panas sebagai beban kalor di evaporator pada 35˚C, 45˚C, 55˚C dan 65˚C. Pendinginan pengambilan panas di bagian condenser dilakukan dengan mengaliri udara pada laju aliran udara 2 m/s. Sebelum dioperasikan, model LHP sebelum dioperasikan divakum hingga memiliki tekanan awal -74 cm Hg, dan diberikan fluida kerja air demineral dengan filliing ratio 200 %. Hasil eksperimen didapatkan suhu pada bagian adiabatic dengan wick lebih rendah dibandingkan pada bagian adiabatik tanpa wick. kesimpulan dari penelitian ini membuktikan bahwa penggunaan wick pada LHP dapat berfungsi dengan baik untuk menahan uap tidak naik ke bagian condenser dan sebagai jalur fluida hasil kondensasi untuk kembali ke evaporator.

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Putra, Nandy, Wayan Nata Septiadi, Rosari Saleh, Rardi Artono Koestoer, and Suhendro Purbo Prakoso. "The Effect of CuO-Water Nanofluid and Biomaterial Wick on Loop Heat Pipe Performance." Advanced Materials Research 875-877 (February 2014): 356–61. http://dx.doi.org/10.4028/www.scientific.net/amr.875-877.356.

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The determinants of heat pipe performances are its wick and working fluid, instead of controlled by the material, dimension, and the shape of heat pipe. This study aimed to determine the effect of using nanofluid on the performance of Loop heat pipes (LHP) with CuO-water nanofluid that using biomaterials wick. LHP was made of 8 mm diameter copper pipe, with the diameter of evaporator and the condenser was 20 mm respectively and the length of the heat pipe was 100 mm. The wick was made of biomaterials Collaria Tabulate and the working fluid was CuO-water nanofluids where the CuO nanoparticles were synthesized by sol-gel method. The characteristic of the Tabulate Collaria biomaterial as a wick in LHP was also investigated in this experiment. The results of the experiments showed that the temperature differences between the evaporator and condenser sections with the biomaterial wick and CuO-water nanofluid were less than those using pure water. These results make the biomaterial (Collar) and nanofluids are attractive both as wick and working fluid in LHP technology. Keywords: loop heat pipe, wick, biomaterial, nanofluid.

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Lin, Bingyao, Rongjian Xie, and Leren Tao. "Study of the heat transfer performance of a loop heat pipe with aluminum wick." Thermal Science, no. 00 (2021): 248. http://dx.doi.org/10.2298/tsci200904248l.

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This study used aluminum (Al) powder as a raw material to fabricate a wick for loop heat pipes (LHPs) by the powder metallurgy method and took advantage of the excellent corrosion resistance, low density and low cost of Al. The average pore diameter, porosity and permeability of the Al wicks were 9 ?m, 47.65%, and 2.1?10-13 m-2, respectively. Then, to verify the feasibility of the Al wick, it was installed into a LHP to test the heat transfer performance. The experimental results showed that the LHP could transport a heating load of 130 W with a thermal resistance of 0.04 KW-1 under horizontal condition. A steady-state LHP mathematical model was developed, and the numerical results were compared with the experimental data. The results show that the model data are consistent with the experimental data, which means that Al wicks are suitable for use in the case of a high heating load and light weight.

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5

Nemec, Patrik, Martin Smitka, and Milan Malcho. "Heat Removal from Bipolar Transistor by Loop Heat Pipe with Nickel and Copper Porous Structures." Scientific World Journal 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/724740.

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Loop heat pipes (LHPs) are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements’ influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT) have been made.

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Szymanski, Pawel, Dariusz Mikielewicz, and Sasan Fooladpanjeh. "Current Trends in Wick Structure Construction in Loop Heat Pipes Applications: A Review." Materials 15, no. 16 (August 21, 2022): 5765. http://dx.doi.org/10.3390/ma15165765.

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Thermal control systems have been introduced as an important part of electronic devices, enabling thermal management of their electronic components. Loop heat pipe (LHP) is a passive two-phase heat transfer device with significant potential for numerous applications, such as aerospace applications, high-power LEDs, and solar central receivers. Its advantages are high heat transfer capability, low thermal resistance, long-distance heat transfer, and compact structure. The essential role of wick structures on the performance of LHPs has already been highlighted, but no comprehensive review is available that deals with different parameters such as LHP design and wick size, which are largely decisive and effective in achieving a practical level of thermal transmission governed by wick structures. To rely on this necessity, this article summarizes, analyzes, and classifies advancements in the design and fabrication of wick structures. The main conclusion to be drawn after careful monitoring and weighing of the related literature is that LHPs with composites and additively manufactured wicks show a higher heat transfer coefficient than other conventional structures. Indeed, future works should be focused on the design of more structurally efficient wicks, which may allow us to optimize materials and geometrical parameters of wick structure for higher heat transfer through LHPs.

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7

Wu, Shen Chun, Chuo Jeng Huang, and Jhih Huang Gao. "Effect of Filling Powder Volume Rate in Wick Manufactured for Loop Heat Pipes." Advanced Materials Research 488-489 (March 2012): 321–27. http://dx.doi.org/10.4028/www.scientific.net/amr.488-489.321.

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This investigation studies the effect on pressure of the filling volume rate in a manufactured nickel powder capillary structure (wick) for a loop heat pipe (LHP). The filling volume ratio is an index of pressure from 1 to 1.3 to investigate the influence on filling weights of the internal parameters of a wick (permeability, effective pore radius and porosity) and heat transfer performance for LHP. The wick is manufactured, based on the standard and non-pressurized filling weights in the manufactured wick mold. The conversion of a pressure change to a weight change used to investigate the relationship between the change in filling volume of pressure to the internal parameters of the wick and the heat transfer performance. As the filling volume rate increases, the capacity of the wick increases, but an excessive filling volume rate makes the wick too dense, affecting its permeability and heat transfer performance in LHP. An experimental test demonstrates that the permeability and heat transfer performance are optimal at a filling volume ratio of 1.2.

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Blauciak, Krzysztof, Pawel Szymanski, and Dariusz Mikielewicz. "The Influence of Loop Heat Pipe Evaporator Porous Structure Parameters and Charge on Its Effectiveness for Ethanol and Water as Working Fluids." Materials 14, no. 22 (November 19, 2021): 7029. http://dx.doi.org/10.3390/ma14227029.

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This paper presents the results of experiments carried out on a specially designed experimental rig designed for the study of capillary pressure generated in the Loop Heat Pipe (LHP) evaporator. The commercially available porous structure made of sintered stainless steel constitutes the wick. Three different geometries of the porous wicks were tested, featuring the pore radius of 1, 3 and 7 µm. Ethanol and water as two different working fluids were tested at three different evaporator temperatures and three different installation charges. The paper firstly presents distributions of generated pressure in the LHP, indicating that the capillary pressure difference is generated in the porous structure. When installing with a wick that has a pore size of 1 μm and water as a working fluid, the pressure difference can reach up to 2.5 kPa at the installation charge of 65 mL. When installing with a wick that has a pore size of 1 μm and ethanol as a working fluid, the pressure difference can reach up to 2.1 kPa at the installation charge of 65 mL. The integral characteristics of the LHP were developed, namely, the mass flow rate vs. applied heat flux for both fluids. The results show that water offers larger pressure differences for developing the capillary pressure effect in the installation in comparison to ethanol. Additionally, this research presents the feasibility of manufacturing inexpensive LHPs with filter medium as a wick material and its influence on the LHP’s thermal performance.

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Cai, Bing, Weizhong Deng, Tong Wu, Tingting Wang, Zhengyuan Ma, Wei Liu, Lei Ma, and Zhichun Liu. "Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics." Processes 9, no. 8 (July 30, 2021): 1332. http://dx.doi.org/10.3390/pr9081332.

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A pouring silicate wick was manufactured to explore the influence of process and physical properties on the production and performance of loop heat pipes (LHP). This paper theoretically analyzed the advantages of pouring porous wick and introduced the technology of pouring silicate directly on evaporator. Based on this, the heat transfer performance of copper-methanol LHP system with pouring porous wick was tested under different positions. The results showed that with the input of multiple heat sources, the LHP could start up and maintain a stable temperature from 40 W to 160 W. When the vapor grooves were located above the compensation chamber, it was difficult to start up positively. By adding gravity assistance, the system could obtain more stable liquid supply and vapor flow, so as to realize start up. In the variable heat load test, the LHP showed good adaptability to the change of heat load. The thermal resistance of the system decreased with the increase of heat load. The thermal resistance of the evaporator almost unchanged and was always lower than 0.05 °C/W, which indicated that the pouring porous wick in the evaporator had good heat load matching.

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Wu, Shen Chun, Shih Syuan Yan, Chen Yu Chung, and Shen Jwu Su. "The Study of PTFE Wicks Application to Loop Heat Pipes with Flat Evaporator." Applied Mechanics and Materials 775 (July 2015): 54–58. http://dx.doi.org/10.4028/www.scientific.net/amm.775.54.

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This study investigates the application of PTFE wicks to flat-plate loop heat pipes (FLHPs). PTFE’s low heat transfer coefficient effectively prevents heat-leakage, which is a problem with using metal wicks, lowering the operating temperature and pressure. This paper uses PTFE particles to form wicks, and the effect of PTFE on flat-plate LHP performance is investigated. Experimental results shows that the highest heat load reached was 100W, with lowest thermal resistance of 0.61°C/W, and heat flux of about 10W/cm2, For the wick properties, the wick had an effective pore radius of the wick was around 9.2μm, porosity of 47%, and permeability of 1.0 x 10-12m2. Compared to the highest heat flux reported in literature thus far for PTFE flat-plate LHPs, the heat flux in this study was enhanced by around 50%.

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11

Zheng, Suzheng, Binyao Lin, Chenyang Zhao, Xue Zhou, Nanxi Li, and Deping Dong. "Numerical Investigation with Experimental Validation of Heat and Mass Transfer during Evaporation in the Porous Wick within a Loop Heat Pipe." Energies 16, no. 5 (February 21, 2023): 2088. http://dx.doi.org/10.3390/en16052088.

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The heat transfer performance of the evaporator significantly affects the heat transfer capacity of the loop heat pipe (LHP). The vapor blanket can be formed once the vapor penetrates the wick especially at high heat flux, resulting in an unsaturated state of the wick and deteriorating the evaporator performance. It is crucial to understand the liquid–vapor behavior for enhancing the LHP performance by investigating the fundamental heat and mass transfer in the wick with phase-change. However, previous modeling studies only considered a single-phase flow or complete saturation in the wick, and the capillary effect on the fluid states was rarely taken into account. The present work developed two mathematical models based on the assumptions of saturated and unsaturated wicks. The fluid states were analyzed at the liquid–vapor interface under the consideration of the capillary effect, and a pore-scale evaporation model was applied to study the phase change behavior and interfacial heat and mass transfer. The relative permeability was introduced to describe the two-phase flow in the porous wick, and the capillary force was modeled as a function of the local saturation in the two-phase region. The temperature results calculated by the models were compared with the experimental results, and the assumption that the vapor penetration leads to deterioration of evaporator performance at high heat flux was validated. Vapor blanket thickness can be estimated through the saturation profile, which provides a simple and effective method. It was also found that the capillary number ω was the key factor affecting the thickness of the vapor blanket. The greater the ω, the faster the vapor blanket thickness increases.

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12

Wu, Shen Chun, Jhih Huang Gao, Zih Yan Huang, Dawn Wang, Cho Jeng Huang, Hsih Shing Li, Sheng Jwu Su, and Ya Wei Lee. "Effect of Increasing Wick Evaporation Area on Heat Transfer Performance for Loop Heat Pipes." Advanced Materials Research 711 (June 2013): 223–28. http://dx.doi.org/10.4028/www.scientific.net/amr.711.223.

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This study investigates the effects of increasing the evaporating area of wick in a loop heat pipe (LHP). This work attempts to improve the performance of the loop heat pipe by increasing the number of grooves and thereby the surface area of the wick. The number of grooves is increased from eight to twelve. Experimental results show that increasing the number of grooves not only increases the surface area of the wick but also enhances LHP performance. When the evaporating surface area increases by 50%, which corresponds to increasing the number of grooves from eight to twelve, the heat transfer capacity increases from 310W to 470W and the thermal resistance is reduced from 0.21°C/W to 0.17°C/W. According to preliminary measurements, increasing the number of grooves in the loop heat pipe is highly promising for improving the heat transfer performance.

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13

Zhang, Xian Feng, and Shuang Feng Wang. "Experimental Investigation of Heat Transfer Performance of a Miniature Loop Heat Pipe with Flat Evaporator." Applied Mechanics and Materials 71-78 (July 2011): 3806–9. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.3806.

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The present work experimentally investigated the operating characteristics of a miniature loop heat pipe (LHP) under different power cycle. The miniature LHP with flat evaporator of 8mm thick is made of copper. The evaporator with sintered copper power wick is in series structure with compensation chamber. Water is working fluid. It is found that the LHP can start up at heat load of 15W with temperature oscillation and the maximum heat load is 160W with Rl=0.068°C/W. The LHP operates unstably under low heat load. The oscillating frequency of temperature rises with heat load increased. The operating performance of the LHP is affected by the power cycle.

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Wang, Yiwei, Jiwen Cen, Fangming Jiang, Wenjiong Cao, and Jian Guo. "LHP heat transfer performance: A comparison study about sintered copper powder wick and copper mesh wick." Applied Thermal Engineering 92 (January 2016): 104–10. http://dx.doi.org/10.1016/j.applthermaleng.2015.08.109.

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Berti, Lucas Freitas, Paulo Henrique Dias dos Santos, Carlos Renato Rambo, Dachamir Hotza, and Edson Bazzo. "Steady State Thermal Behaviour of Ceramic Wick Structure for Application in Two Phase Heat Transfer Devices." Advanced Materials Research 1082 (December 2014): 302–8. http://dx.doi.org/10.4028/www.scientific.net/amr.1082.302.

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This work reports on results from two phase heat transfer devices assembled with ceramic capillary structure. It is firstly presented the manufacturing of the ceramic wick structures and afterwards the characterization of the morphological-and fluid-dynamical properties of these ceramic wick structures. As closing results, it is presented the thermal behaviour of two different two phase heat transfer devices, i.e. a Capillary Pumped Loop and a Loop Heat Pipe. The properties of the ceramic wick structure are within the desirable range for a correct functioning of these devices, e.g. porosity, pore size and permeability constants ranging from 40 to 60%, from 5 to 30μm and from 10-10 to 10-13m2, respectively. The thermal behaviour tests of the heat transfer devices used power heat load input in range from 10 to 20W and for all devices the evaporator temperature reached steady state condition. Thus, as a result, it can be claimed these ceramic wick structures as successful alternative for assembling capillary evaporator of CPL and LHP.

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Huynh, Hien Phuoc, Htoo Zin Kyaw, Keishi Kariya, and Akio Miyara. "Experimental Study on Thermal Performance of Loop Heat Pipe with Flat-Rectangular Evaporator Under Gravity Assisted Condition." EPI International Journal of Engineering 1, no. 2 (November 20, 2018): 40–46. http://dx.doi.org/10.25042/epi-ije.082018.06.

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In company with extreme developments of electronic devices, there are some unavoidable challenges to the conventional cooling methods such as high heat dissipation, limitation of cooling space, reliable operation as well as saving energy consumption. Therefore, the necessity of studying on new or how to improve the existing technologies is undoubted. Among various methodologies, the loop heat pipe (LHP) whose operation principle base on phase changing process, can be considered as one of the potential solutions of modern electronics cooling. This paper introduces the experimental investigation on the thermal performance of a flat-rectangular evaporator LHP with sintered stainless-steel wick when functioning under gravity assisted condition. Working fluid of this LHP was water. The present LHP could maintain stable operation in the range of heating power from 50 W to 520 W and keep the temperature on the heater’s top surface at 85oC, commonly recommended as the limitation temperature of electronics, when heating power reaches value 350 W (129.6 kW/m2). Besides, when turning the heater off, it took about 15 minutes for the LHP to cool the heating block from 102oC to 37oC. In addition, an assumption of the boiling heat transfer is introduced in this paper to explain the performance of evaporator at different heat flux conditions of the experiment.

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Wang, Dezhi, Xiaoying Wang, Pan Zhou, Zhuangzhi Wu, Bohua Duan, and Chao Wang. "Influence of packing density on performance of porous wick for LHP." Powder Technology 258 (May 2014): 6–10. http://dx.doi.org/10.1016/j.powtec.2014.03.004.

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Yang, Yang, Zhu Kai, Wang Yabo, Wei Jie, and Sarula Chen. "Experimental analysis of a Vapour-Liquid Separated Flat Loop Heat Pipe Evaporator System." MATEC Web of Conferences 307 (2020): 01055. http://dx.doi.org/10.1051/matecconf/202030701055.

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In this paper, a unique operation mechanism of loop heat pipe (LHP) was proposed. To test the performance of LHP under this new mechanism, a visual flat LHP evaporator prototype and an open experimental system were designed and assembled, and start-up experiment and variable heat load experiment were done respectively to obtain the actual operation characteristics, such as the evaporator thermal resistance (Re), total thermal resistance (Rt), start-up time and temperature of base plate. The proposed LHP had better overall performance during the start-up tests when He value of EC was set to 0.5mm, and its corresponding Re and Rt value were 0.035 K/W and 0.451 K/W when the heating power was 208w. Meanwhile, as per the heat load applied to the base plate, the whole variable heat load experiment could be divided into three distinct stages: low heat load stage, efficiency operation stage and dry-out stage. Moreover, the results also showed that the circulation driven head formed inside of the EC played an important role in promoting the operation performance, especially when the wick, the vapour-liquid interface and the bottom of the evaporator arrived at a reasonable situation.

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Szymanski, Pawel, Richard Law, Ryan MᶜGlen, and David Reay. "Recent Advances in Loop Heat Pipes with Flat Evaporator." Entropy 23, no. 11 (October 20, 2021): 1374. http://dx.doi.org/10.3390/e23111374.

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The focus of this review is to present the current advances in Loop Heat Pipes (LHP) with flat evaporators, which address the current challenges to the wide implementation of the technology. A recent advance in LHP is the design of flat-shaped evaporators, which is better suited to the geometry of discretely mounted electronics components (microprocessors) and therefore negate the need for an additional transfer surface (saddle) between component and evaporator. However, various challenges exist in the implementation of flat-evaporator, including (1) deformation of the evaporator due to high internal pressure and uneven stress distribution in the non-circular casing; (2) heat leak from evaporator heating zone and sidewall into the compensation chamber; (3) poor performance at start-up; (4) reverse flow through the wick; or (5) difficulties in sealing, and hence frequent leakage. This paper presents and reviews state-of-the-art LHP technologies; this includes an (a) review of novel manufacturing methods; (b) LHP evaporator designs; (c) working fluids; and (d) construction materials. The work presents solutions that are used to develop or improve the LHP construction, overall thermal performance, heat transfer distance, start-up time (especially at low heat loads), manufacturing cost, weight, possibilities of miniaturization and how they affect the solution on the above-presented problems and challenges in flat shape LHP development to take advantage in the passive cooling systems for electronic devices in multiple applications.

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Lu, Pan, Teng Gao, Quanwang Chen, and Xiaohan Ren. "Energy Saving Thermal Management of Space Remote Sensor and Validation." Energies 16, no. 2 (January 12, 2023): 864. http://dx.doi.org/10.3390/en16020864.

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An energy-efficient thermal control management method for space remote sensors using optical, mechanical, electrical, and thermal integration is proposed. The satellite power resources are insufficient, so an energy-efficient loop heat pipe (LHP) is designed for six intermittently operating detectors. The charge-coupled device (CCD) has a total heat generation of 72 W and operates for 8 min per orbital cycle. The LHP includes a capillary pump, six cold plates, and two radiators. The working fluid of the LHP is high-purity ammonia and the material of the wick is ceramic. The drive power on the capillary pump evaporator automatically switches between 30 W and 90 W depending on the operating mode of the remote sensor, resulting in an average power saving of about 58.2% compared to a conventional LHP. For the optical structure, a three-stage insulation technology was developed to save heater power and improve temperature stability. A transient numerical simulation model of the LHP was developed to study the vapor–liquid zone of two radiators under the condition of rapid power change. Vacuum thermal tests were conducted and the test data agreed well with the numerical simulation results. The in-orbit temperature data showed that the temperature fluctuations of the optical structure and CCD were less than ±0.2 °C and ±0.8 °C, respectively.

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Wu, Shen Chun, Kuei Chi Lo, Jia Ruei Chen, Chen Yu Chung, Weie Jhih Lin, and Shen Jwu Su. "Effect of Sintering Temperature Curve in Wick Manufactured for Loop Heat Pipe with Flat Evaporator." Applied Mechanics and Materials 595 (July 2014): 24–29. http://dx.doi.org/10.4028/www.scientific.net/amm.595.24.

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This paper specifically addresses the effect of the sintering temperature curve in manufacturing nickel powder capillary structure (wick) for a loop heat pipe (LHP) with flat evaporator. The sintering temperature curve is composed of three regions: a region of increasing temperature, a region of constant temperature, and a region of decreasing temperature. The most important region is the increasing temperature region, as the rate of temperature increase directly affects the performance of the wick.When the slope of the region of increasing temperature is 0.8 (equivalent to 8 OC/min), the structure of the manufactured wick is complete, with the best heat transfer performance result. Experimental resultsshowed that the optimal heat transfer performance is 160W, the minimal total thermal resistance is approximately 0.43OC/W, and the heat flux is 17W/cm2; the optimal wick manufactured has an effective pore radius of 5.2 μm, a permeability of 5.9×10-13m2, and a porosity of 64%.

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Zhu, Kai, Xueqiang Li, Hailong Li, Xiaoqing Chen, and Yabo Wang. "Optimization of A Loop Heat Pipe (LHP) with Wick Separated from Heating Surface." Energy Procedia 158 (February 2019): 2409–16. http://dx.doi.org/10.1016/j.egypro.2019.01.293.

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23

Jung, Eui Guk, and Joon Hong Boo. "A Novel Analytical Modeling of a Loop Heat Pipe Employing Thin-Film Theory: Part II—Experimental Validation." Energies 12, no. 12 (June 22, 2019): 2403. http://dx.doi.org/10.3390/en12122403.

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Part I of this study introduced a mathematical model capable of predicting the steady-state performance of a loop heat pipe (LHP) with enhanced rationality and accuracy. Additionally, investigation of the effect of design parameters on the LHP thermal performance was also reported in Part I. The objective of Part II is to experimentally verify the utility of the steady-state analytical model proposed in Part I. To this end, an experimental device comprising a flat-evaporator LHP (FLHP) was designed and fabricated. Methanol was used as the working fluid, and stainless steel as the wall and tubing-system material. The capillary structure in the evaporator was made of polypropylene wick of porosity 47%. To provide vapor removal passages, axial grooves with inverted trapezoidal cross-section were machined at the inner wall of the flat evaporator. Both the evaporator and condenser components measure 40 × 50 mm (W × L). The inner diameters of the tubes constituting the liquid- and vapor-transport lines measure 2 mm and 4 mm, respectively, and the lengths of these lines are 0.5 m. The maximum input thermal load was 90 W in the horizontal alignment with a coolant temperature of 10 °C. Validity of the said steady-state analysis model was verified for both the flat and cylindrical evaporator LHP (CLHP) models in the light of experimental results. The observed difference in temperature values between the proposed model and experiment was less than 4% based on the absolute temperature. Correspondingly, a maximum error of 6% was observed with regard to thermal resistance. The proposed model is considered capable of providing more accurate performance prediction of an LHP.

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Giraudon, R., S. Lips, D. Fabrègue, L. Gremillard, E. Maire, and V. Sartre. "Effect of the wick characteristics on the thermal behaviour of a LHP capillary evaporator." International Journal of Thermal Sciences 133 (November 2018): 22–31. http://dx.doi.org/10.1016/j.ijthermalsci.2018.07.003.

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Santos, Paulo H. D., Edson Bazzo, and Amir A. M. Oliveira. "Thermal performance and capillary limit of a ceramic wick applied to LHP and CPL." Applied Thermal Engineering 41 (August 2012): 92–103. http://dx.doi.org/10.1016/j.applthermaleng.2012.02.042.

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Wu, S. C., B. H. Hsieh, D. Wang, and Y. M. Chen. "Manufacture of a biporous nickel wick and its effect on LHP heat transfer performance enhancement." Heat and Mass Transfer 51, no. 11 (February 20, 2015): 1549–58. http://dx.doi.org/10.1007/s00231-015-1503-9.

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27

Zhu, Kai, Xiaoqing Chen, Baomin Dai, Mingzhu Zheng, Yabo Wang, and Hailong Li. "Operation characteristics of a new-type loop heat pipe (LHP) with wick separated from heating surface in the evaporator." Applied Thermal Engineering 123 (August 2017): 1034–41. http://dx.doi.org/10.1016/j.applthermaleng.2017.05.140.

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Carone, Christopher D., Raymundo Ramos, and Marc Sher. "LHC constraints on the Lee–Wick Higgs sector." Physics Letters B 732 (May 2014): 122–26. http://dx.doi.org/10.1016/j.physletb.2014.03.025.

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Xin, Gongming, Kehang Cui, Yong Zou, and Lin Cheng. "Reduction of effective thermal conductivity for sintered LHP wicks." International Journal of Heat and Mass Transfer 53, no. 13-14 (June 2010): 2932–34. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.02.056.

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Rizzo, Thomas G. "Searching for Lee-Wick gauge bosons at the LHC*." Journal of High Energy Physics 2007, no. 06 (June 20, 2007): 070. http://dx.doi.org/10.1088/1126-6708/2007/06/070.

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Xu, Jiyuan, Yong Zou, Mingxiu Fan, and Lin Cheng. "Effect of pore parameters on thermal conductivity of sintered LHP wicks." International Journal of Heat and Mass Transfer 55, no. 9-10 (April 2012): 2702–6. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.01.028.

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Álvarez, Ezequiel, Leandro Da Rold, Carlos Schat, and Alejandro Szynkman. "Vertex displacements for acausal particles: testing the Lee-Wick standard model at the LHC." Journal of High Energy Physics 2009, no. 10 (October 8, 2009): 023. http://dx.doi.org/10.1088/1126-6708/2009/10/023.

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Kalinowska-Witek, Barbara. "Troska o wychowanie – w poglądach i działalności pedagogów II Rzeczypospolitej (1918–1939)." Lubelski Rocznik Pedagogiczny 35, no. 1 (February 21, 2017): 259. http://dx.doi.org/10.17951/lrp.2016.35.1.259.

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Ellen Key w 1905 roku nazwała wiek XX „stuleciem dziecka”. Przedstawiciele nurtu nowego wychowania z Europy Zachodniej i ze Stanów Zjednoczonych już w pierwszych latach rozpoczynającego się stulecia zwrócili uwagę na konieczność zmiany podejścia do dziecka, przyznania praw najmłodszym oraz przeprowadzenia w szkołach reform dydaktyczno-wychowawczych. Polscy pedagodzy okresu dwudziestolecia międzywojennego, którzy utrzymywali częste kontakty z zagranicznymi ośrodkami naukowymi, również podkreślali znaczenie poznania dziecka i jego potrzeb oraz dostosowania do nich oddziaływań opiekuńczo-wychowawczych. Szczególną uwagę zwrócili na konieczność zapewnienia opieki i wychowania dzieciom osieroconym, opuszczonym, upośledzonym i chorym, jako jednostkom najbardziej poszkodowanym przez los. Apelowali też o właściwe zorganizowanie środowiska wychowawczego oraz o odpowiedni dobór osób, które podejmowały się pracy z dziećmi i młodzieżą.

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Włoch, Stanisława. "Pedagogika transgresyjna w wychowaniu przedszkolnym." Lubelski Rocznik Pedagogiczny 37, no. 1 (November 6, 2018): 11. http://dx.doi.org/10.17951/lrp.2018.37.1.11-21.

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Wiek XXI cechuje się przyśpieszonym tempem życia, zachodzącymi zmianami cywilizacyjnymi, kulturalnymi i technologicznymi, dlatego wymaga innego spojrzenia na człowieka przyszłości. Decydującą rolę w tym zakresie odgrywa edukacja od przedszkola do dorosłości. Współczesna pedagogika przedszkolna poszukuje innowacyjnych rozwiązań w zakresie wyzwalania potencjału genetycznego i rozwoju wielowymiarowej osobowości. Jedną z koncepcji stanowi pedagogika transgresyjna, która polega na przekraczaniu własnych możliwości przez działanie, doświadczanie, samodzielność i odpowiedzialność. W artykule ukazano podstawy teoretyczne transgresji, czynniki wyzwalające możliwości dziecka, organizację pola edukacyjnego oraz procesu rozwoju wynikającego z transgresji.

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Wardoyo, Suwaji Handaru, and Sholichan Badri. "Kajian Terapi Akupunktur [Kombinasi Titik Lokal dan YNSA] terhadap Low Back Pain : Biokimiawi Kolesterol Darah." Care : Jurnal Ilmiah Ilmu Kesehatan 10, no. 3 (November 21, 2022): 469–77. http://dx.doi.org/10.33366/jc.v10i3.2325.

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Low back pain (LBP) commonly happens and affects people in various types of work. High cholesterol level is not only a risk for plaque in the blood vessels but also a risk for LBP pain. The aim was to analyze the biochemistry of cholesterol in LBP patients receiving acupuncture therapy. The quasi-experimental design with a pretest-posttest control group design was used at Griya Sehat Dewandaru and Prima Diagnostik Main Clinical Laboratory from March to November 2020. The total sample used was 30 patients, aged 40-60 years old, and reported Visual Analog Scale (VAS) pain scale 5-7. Acupuncture therapy was performed 10 times. Data were taken directly before therapy [T0], after five times [T5], and after ten times of therapy [T10]. The blood lipid profile assessment was carried out at T0, T5, and T10 and analyzed using SPSS version 23. The normality test using the Shapiro-Wilk test showed cholesterol, HDL, LDL, and VAS were normally distributed, while triglycerides were normally distributed by the Chi-Square test. Paired T-test results on cholesterol, LDL, and VAS showed a significant difference for all groups (p=0.000). Acupuncture therapy with a combination of local points and Yamamoto New Scalp Acupuncture [YNSA] points as much as 10 times was proven to reduce cholesterol by 12.6%, LDL by 20%, and VAS by 67.67%.

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Kirenko, Janusz. "Asertywność a radzenie sobie w sytuacjach trudnych studentów kierunków nauczycielskich z różnym poziomem samooceny." Lubelski Rocznik Pedagogiczny 37, no. 4 (April 29, 2019): 9. http://dx.doi.org/10.17951/lrp.2018.37.4.9-23.

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Za pomocą Kwestionariusza Asertywności Nauczyciela/Wychowawczego (KAN/W Teresy Zubrzyckiej-Maciąg i Janusza Kirenki), Kwestionariusza COPE (Charlesa S. Carvera, Michaela S. Scheier, Jagdisha K. Weintrauba) i Skali Samooceny (SES Marshalla Rosenberga) przebadano 244 studentów kierunków nauczycielskich, w tym 222 kobiety (90,98%) i 22 mężczyzn (9,02%). Wiek badanych mieścił się w przedziale od 21 do 46 lat, ze średnią na poziomie 25,29 lat. Byli to studenci pedagogiki, filologii angielskiej oraz pedagogiki przedszkolnej i wczesnoszkolnej z trzech uczelni: Wyższej Szkoły Ekonomii i Innowacji w Lublinie, Uniwersytetu Marii Curie-Skłodowskiej w Lublinie i Państwowej Wyższej Szkoły Zawodowej w Chełmie. Uzyskano specyficzną strukturę związków wybranych zmiennych: zależnej (gotowości do asertywności), niezależnej (radzenia sobie w sytuacjach trudnych) i moderującej (samooceny). Uwypuklano te, które mają znaczne oparcie w empirii. Zastosowana regresja wieloraka umożliwiła przyjęcie w miarę precyzyjnych charakterystyk otrzymanych związków. Pretendują one do miana autonomicznych wniosków.

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Auger, Kyle, Gregory Shedlock, Kasey Coutinho, Nicole E. Myers, and Santiago Lorenzo. "Effects of osteopathic manipulative treatment and bio-electromagnetic energy regulation therapy on lower back pain." Journal of Osteopathic Medicine 121, no. 6 (March 2, 2021): 561–69. http://dx.doi.org/10.1515/jom-2020-0132.

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Abstract Context Lower back pain (LBP) is prevalent and is a leading contributor to disease burden worldwide. Osteopathic manipulative treatment (OMT) can alleviate alterations in the body that leads to musculoskeletal disorders such as LBP. Bio-electromagnetic Energy Regulation (BEMER; BEMER International AG), which has also been shown to relieve musculoskeletal pain, is a therapeutic modality that deploys a biorhythmically defined stimulus through a pulsed electromagnetic field (PEMF). Therefore, it is possible that combined OMT and BEMER therapy could reduce low back pain in adults more than the effect of either treatment modality alone. Objectives To investigate the individual and combined effects of OMT and BEMER therapy on LBP in adults. Methods Employees and students at a medical college were recruited to this study by email. Participants were included if they self-reported chronic LBP of 3 months’ duration or longer; participants were excluded if they were experiencing acute LBP of 2 weeks’ duration or less, were currently being treated for LBP, were pregnant, or had a known medical history of several conditions. Ultimately, 40 participants were randomly assigned to four treatment groups: an OMT only, BEMER only, OMT+BEMER, or control (light touch and sham). Treatments were given regularly over a 3 week period. Data on LBP and quality of life were gathered through the Visual Analog Scale (VAS), Short Form 12 item (SF-12) health survey, and Oswestry Low Back Pain Questionnaire/Oswestry Disability Index prior to treatment and immediately after the 3 week intervention protocol. One-way analysis of variance (ANOVA) was performed retrospectively and absolute changes for each participant were calculated. Normal distribution and equal variances were confirmed by Shapiro–Wilk test (p>0.05) and Brown-Forsythe, respectively. Significance was set at p<0.05. Results Despite a lack of statistical significance between groups, subjective reports of pain reported on the VAS showed a substantial mean percentage decrease (50.8%) from baseline in the OMT+BEMER group, compared with a 10.2% decrease in the OMT-only and 9.8% in BEMER-only groups when comparing the difference in VAS ratings from preintervention to postintervention. Participants also reported in quality of life assessed on the Oswestry Low Back Pain Questionnaire/Oswestry Disability Index, with the OMT+BEMER group showing a decrease of 30.3% in score, the most among all groups. The OMT+BEMER group also reported the greatest improvement in score in the physical component of the SF-12, with an increase of 21.8%. Conclusions The initial data from this study shows a potential additive effect of combination therapy (OMT and BEMER) for management of LBP, though the results did not achieve statistical significance.

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Kirenko, Janusz. "Podmiotowe korelaty umiejętności prospołecznych studentów kierunków nauczycielskich." Lubelski Rocznik Pedagogiczny 38, no. 3 (December 28, 2019): 221. http://dx.doi.org/10.17951/lrp.2019.38.3.221-235.

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Rozwiązując główny problem badawczy, zawarty w pytaniu o związki między zmiennymi, zależnej – umiejętności prospołecznych, i niezależnymi, zwanymi podmiotowymi, w wymiarach: asertywności, radzenia sobie w sytuacjach trudnych i samooceny, przebadano za pomocą: Kwestionariusza umiejętności społecznych (KUS – A.P. Goldstein), Kwestionariusza asertywności nauczyciela-wychowawcy (KAN/W – T. Zubrzycka Maciąg, J. Kirenko), Kwestionariusza COPE (COPE – C.S. Carver, M.S. Scheier, J.K. Weintraub) i Skali samooceny (SES – M. Rosenberg) 244 studentów kierunków nauczycielskich, w tym 222 kobiety (90,98%) i 22 mężczyzn (9,02%). Wiek badanych mieścił się w przedziale od 21 do 46 lat, ze średnią na poziomie 25,29 lat. Byli to studenci pedagogiki, filologii angielskiej oraz pedagogiki przedszkolnej i wczesnoszkolnej z trzech uczelni regionu lubelskiego. Uzyskano specyficzną strukturę związków wybranych zmiennych, uwypuklano te, które mają znaczne oparcie w empirii. Zastosowana regresja wieloraka umożliwiła przyjęcie w miarę precyzyjnych charakterystyk otrzymanych związków, pretendujących do miana autonomicznych wniosków.

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Nasseh, O. M., and I. A. Moharam. "Forecasting of outbreaks ofSpodoptera exempta Wik. (Lep., Noctuidae) based on sex-pheromone trapping in the republic of Yemen." Anzeiger für Schädlingskunde Pflanzenschutz Umweltschutz 64, no. 5 (June 1991): 93–96. http://dx.doi.org/10.1007/bf02021215.

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Valdivia P., Eduardo, and Magda Lingán. "Carcinoma de vulva. Estudio de 14 casos con especial énfasis en el tratamiento quirúrgico radical." Revista Peruana de Ginecología y Obstetricia 2, no. 2 (June 28, 2015): 177–94. http://dx.doi.org/10.31403/rpgo.v2i1116.

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Del 1 de junio de 1952 hasta 31 de mayo de 1956. hemos visto 14 casos de cáncer de la vulva en el Instituto Nacional de Enfermedades Neoplásicas. Esto representa un 0,82% de los todos los tumores malignos del tracto genital lhe (1.691 casos). Este porcentaje es inferior a la reportada por otros autores, Esto, sin embargo, es Relativo, porque tenemos una alta frecuencia de carcinoma de cuello uterino. AII estos pacientes eran de la edad de la menopausia pasado. El más joven tenía 58 una de las más antiguas de 85 años. El mayor número de casos fueron entre las edades de 60 y 70 años, tal como se encuentra Taussig. En el 71% de estos pacientes encontramos lesiones precancerosas como la leucoplasia y prurito. El intervalo de tiempo entre esta lesión y la aparición de malignidad variada de meses a años. El diagnóstico clínico fue corroborada por la biopsia, con la excepción de un caso, en wich el diagnóstico clínico era Hidradenoma y el informe patológico era carcinoma. Histológicamente, todos los casos fueron carcinoma epidermoide. La frecuencia de metástasis ganglionar no pudimos detectar clínicamente pero la malignidad demostrado por los estudios patológicos, muestra que el tratamiento quirúrgico radical es el mejor. Los últimos 4 casos que vimos nos tratan con cirugía radical, siguiendo la técnica Stanley Way, con resultados satisfactorios. No ha transcurrido suficiente tiempo para nosotros hablar de curación, pero hasta ahora no ha habido recurrencia de malignidad.

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González Palacio, Enoc Valentín, Andrés Felipe Ramírez González, and Alexander Mauricio Hernández Villa. "Diseño y validación de tres pruebas de potencia aeróbica y velocidad en niños nadadores (Design and validation of three tests of aerobic power and speed in swimming children)." Retos 44 (February 20, 2022): 1001–8. http://dx.doi.org/10.47197/retos.v44i0.87910.

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El presente artículo tuvo como finalidad el diseño y validación de tres test de campo que permiten valorar la potencia aeróbica y la velocidad en niños nadadores de 9 y 10 años, se realizó un muestreo probabilístico, aleatorio estratificado, con una muestra final de 77 deportistas. Para el proceso validación se tomaron como Gold Standar los test de: potencia aeróbica de 1000 metros y Test de velocidad de 50 y 20 metros (Jauregui y Ordoñez, 1993), frente a los test propuestos: 300 metros en estilo libre con vuelta abierta, salida desde clavado piso, y Velocidad 25 metros libre con salida clavado y 10 metros lanzados; para establecer la Confiabilidad intra, se realizó el procedimiento test re test (TRT). Resultados: Se aplicó la prueba de Shapiro – Wilk para la determinación de normalidad, en las correlaciones (ICC) inter instrumentos en las pruebas de velocidad los valores fueron aceptables (0,569) y muy buenos (0,904), en la prueba de potencia aeróbica fueron buenos (0,725 – 0,818); en las comparaciones intra instrumentos (ICC) en la velocidad los valores fluctuaron entre aceptables (0,618) y muy buenos (0,982), en la potencia aeróbica fue en general bueno (0,725 – 0,818). Finalmente se propone una escala percentilar que permite valoras las capacidades abordadas. Abstract: The purpose of this article was to design and validate three field tests, of aerobic power and speed in 9 and 10-year-old swimmers, a probabilistic, stratified random sampling was performed with a final sample of 77 athletes. For the validation process, the tests of: aerobic power of 1000 meters and speed test of 50 and 20 meters (Jauregui and Ordoñez, 1993) were taken as Gold Standard, compared to the proposed tests: 300 meters in freestyle with open lap, exit from nailed floor, and Speed 25 meters free with nailed exit and 10 meters thrown; To establish intra-reliability, the test re test (TRT) procedure was performed. Results: The Shapiro - Wilk test was applied for the determination of normality, in the inter-instrument correlations (ICC) in the speed tests the values were acceptable (0.569) and very good (0.904), in the aerobic power test they were good (0.725 - 0.818); in intra-instrument comparisons (ICC) in speed the values fluctuated between acceptable (0.618) and very good (0.982), in aerobic power it was generally good (0.725 - 0.818). Finally, a percentile scale is proposed that allows you to assess the capabilities addressed.

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Gerganov, G., T. Georgiev, T. Shivacheva, S. Bogdanova-Petrova, S. Dimitrov, R. Moraliyska, D. Simeonova, and S. Hristova. "POS0653 DIAGNOSTIC VALUE OF COMPUTER TOMOGRAPHY FEATURES OF SACROILIITIS FOR ANKYLOSING SPONDYLITIS." Annals of the Rheumatic Diseases 82, Suppl 1 (May 30, 2023): 605.2–605. http://dx.doi.org/10.1136/annrheumdis-2023-eular.5879.

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BackgroundRadiologic evidence of sacroiliitis is important for the diagnosis, classification, and management of patients with ankylosing spondylitis (AS)[1]. Conventional radiography (CR) has been the most widely utilized imaging modality for the assessment of sacroiliac involvement in axial spondyloarthritis (AxSpA) because of the low radiation dose, ease of operation, and low expenses. CR is used in both the 1984 modified New York criteria and ASAS criteria for classifying AS and AxSpA but lacks sensitivity for early changes. Though MRI detects early changes of the sacroiliac joints, as well as chronic structural changes, its use is limited by the associated cost, procedural time and certain contraindications. Computed tomography (CT) is a modality that enables visualization of erosions, sclerosis, and new bone formation, with the added benefit of multiplanar cross-sectional imaging.ObjectivesWe aimed to analyze the diagnostic value of computer tomography (CT) features of sacroiliitis for ankylosing spondylitis in patients with inconclusive CR evidence for sacroiliitis.MethodsIn this retrospective monocentric observational study, 50 patients with chronic low back pain (LPB) with a duration longer than three months in the lumbosacral region were included. Using the patient record data were extracted on age, pain duration, and plain radiography. Eligible patients should have had plain radiography without evident radiographic sacroiliitis. All the patients had undergone a CT scan of the sacroiliac joint that a radiologist and rheumatologist evaluated for subchondral osteosclerosis, erosions, joint space narrowing (JSN), subchondral cysts, and ankylosis. Based on the clinical and instrumental findings, including structural changes characteristic of radiographic sacroiliitis, a final decision by a certified rheumatologist was made and a diagnosis of ankylosing spondylitis was set or ruled out.ResultsThe mean age and duration of LBP of the patients were 44.7 (14.7) years and 63.9 months, respectively. Of the 50 included patients, 28 (56%) were females. The mean values of c-reactive protein and erythrocyte sedimentation rate were 13.9 mg/l and 39.4 mm/h. Subchondral osteosclerosis was found in 44 patients (88%), JSN – in 21 patients (42%), erosions – in 17 patients (34%), subchondral cysts – in 10 patients (20%), ankylosis – in 18 patients (36%). Definite CT data for sacroiliitis was seen in 24 patients (48%) and the diagnosis of ankylosing spondylitis was set in 23 patients (46%) of the study group. The likelihood ratios (LR+) for diagnosis of AS were high for erosions (18.4), subchondral cysts (11), ankylosis (6.9) and low for JSN (LR+ 1.9) and ankylosis (LR+ 1.1).ConclusionNearly half of the patients with inconclusive CR evidence for sacroiliitis were diagnosed with AS after CT imaging. Erosions seen on CT increase the likelihood of assuming AS diagnosis. Computed tomography is a useful tool in diagnosing AS, but it is associated with higher ionizing radiation doses.Reference[1]Mandl P, Navarro-Compán V, Terslev L, Aegerter P, van der Heijde D, D’Agostino MA, Baraliakos X, Pedersen SJ, Jurik AG, Naredo E, Schueller-Weidekamm C, Weber U, Wick MC, Bakker PA, Filippucci E, Conaghan PG, Rudwaleit M, Schett G, Sieper J, Tarp S, Marzo-Ortega H, Østergaard M; European League Against Rheumatism (EULAR). EULAR recommendations for the use of imaging in the diagnosis and management of spondyloarthritis in clinical practice. Ann Rheum Dis. 2015 Jul;74(7):1327-39. doi: 10.1136/annrheumdis-2014-206971. Epub 2015 Apr 2. PMID: 25837448.Acknowledgements:NIL.Disclosure of InterestsNone Declared.

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Ning, Wenjing, Jun Ma, Cheng Jiang, Yingwen Cao, Chunsheng Guo, and Yong Zou. "Experimental Study on Preparation and Heat Transfer of Nickel-Based Ammonia Loop Heat Pipe." Journal of Heat Transfer 143, no. 11 (September 8, 2021). http://dx.doi.org/10.1115/1.4051784.

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Abstract The loop heat pipe (LHP) is a passive heat sink used in aerospace and electronic devices. As the core component of the LHP, the physical property parameters of porous wick directly affect the overall performance of the LHP. In this paper, the performance of the porous wick is improved by adjusting the pore size, thereby improving the performance of the LHP. The nickel-based double-pore porous wicks are prepared by T225 nickel powder and NaCl particles, and the pore size of the porous wicks can be changed by different cold pressing force (30 kN, 40 kN, 50 kN, and 60 kN). The effects of different cold pressing force on the porosity, permeability, and other physical property parameters are studied when the ratio of pore former is 20 wt.%. In the end, we select the cold pressing force of 30 kN to prepare the porous wick of the LHP. Then the effects of constant load and variable load of the heat transfer performance under different placement elevations are studied. The results show that the heat load range is 10 W–100 W, the minimum evaporator thermal resistance is 0.424 K/W, and the minimum LHP thermal resistance is 0.598 K/W. When β = 0 deg, there is a “backflow” phenomenon at the initial stage of low thermal load. With the increase of thermal load, the “backflow” duration decreases until it disappears, and the startup time becomes shorter. The thermal resistances of the evaporator and LHP decrease rapidly and then slowly increase. When β = –90 deg, the LHP appears to demonstrate “reverse startup” phenomenon.

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Singh, Randeep, Aliakbar Akbarzadeh, and Masataka Mochizuki. "Effect of Wick Characteristics on the Thermal Performance of the Miniature Loop Heat Pipe." Journal of Heat Transfer 131, no. 8 (June 4, 2009). http://dx.doi.org/10.1115/1.3109994.

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Two phase heat transfer devices based on the miniature version of loop heat pipe (LHP) can provide very promising cooling solutions for the compact electronic devices due to their high heat flux management capability and long distance heat transfer with minimal temperature losses. This paper discusses the effect of the wick properties on the heat transfer characteristics of the miniature LHP. The miniature model of the LHP with disk-shaped evaporator, 10 mm thick and 30 mm disk diameter, was designed using copper containment vessel and water as the working fluid, which is the most acceptable combination in electronic cooling applications. In the investigation, wick structures with different physical properties including thermal conductivity, pore radius, porosity, and permeability and with different structural topology including monoporous or biporous evaporating face were used. It was experimentally observed that copper wicks are able to provide superior thermal performance than nickel wicks, particularly for low to moderate heat loads due to their low heat conducting resistance. With monoporous copper wick, maximum evaporator heat transfer coefficient (hev) of 26,270 W/m2 K and evaporator thermal resistance (Rev) of 0.06–0.10°C/W were achieved. For monoporous nickel wick, the corresponding values were 20,700 W/m2 K for hev and 0.08–0.21°C/W for Rev. Capillary structure with smaller pore size, high porosity, and high permeability showed better heat transfer characteristics due to sufficient capillary pumping capability, low heat leaks from evaporator to compensation chamber and larger surface area to volume ratio for heat exchange. In addition to this, biporous copper wick structure showed much higher heat transfer coefficient of 83,787 W/m2 K than monoporous copper wick due to improved evaporative heat transfer at wick wall interface and separated liquid and vapor flow pores. The present work was able to classify the importance of the wick properties in the improvement of the thermal characteristics for miniature loop heat pipes.

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Yakomaskin, Alexander A., Valery N. Afanasiev, Nikolay N. Zubkov, and Dmitry N. Morskoy. "Investigation of Heat Transfer in Evaporator of Microchannel Loop Heat Pipe." Journal of Heat Transfer 135, no. 10 (September 11, 2013). http://dx.doi.org/10.1115/1.4024502.

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Loop heat pipes (LHP) are heat transfer devices which use evaporation and condensation of working fluid to transfer heat and use capillary forces to provide fluid circulation in a closed loop. One of the main applications of LHP is cooling of electronic components. Further development of this field is associated with miniaturization. Thus, there are strict limits imposed upon size of elements of heat transfer devices in electronics cooling. One of such elements is an evaporator of the LHP, its main element. This paper deals with the LHP evaporator and is aimed at showing dependence of wick conductivity, thickness, and vapor flow geometry on overall heat transfer performance. An open loop experimental setup was created. Experiments were carried out with various configurations. The evaporator consisted of a microchannel (MC) plate, with groove widths of 100 and 300 μm, wick (metal and nonmetal porous materials were used) and a compensation chamber (CC). Heat load varied from 20 to 140 W in steps of 20 W. The area of the heater was equal to 19 × 19 mm2. The working fluid is de-ionized water. Experimental results include data on temperature distribution across the wick's height, temperature of microchannel's surface, and temperature of water in the compensation chamber. The results reveal a potential for performing optimization of the zone of evaporation in order to produce thinner LHP evaporators.

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Kariya, H. Arthur, Teresa B. Peters, Martin Cleary, Daniel F. Hanks, Wayne L. Staats, John G. Brisson, and Evelyn N. Wang. "Development and Characterization of an Air-Cooled Loop Heat Pipe With a Wick in the Condenser." Journal of Thermal Science and Engineering Applications 6, no. 1 (October 25, 2013). http://dx.doi.org/10.1115/1.4025049.

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Thermal management of modern electronics is rapidly becoming a critical bottleneck of their computational performance. Air-cooled heat sinks offer ease and flexibility in installation and are currently the most widely used solution for cooling electronics. We report the characterization of a novel loop heat pipe (LHP) with a wick in the condenser, developed for the integration into an air-cooled heat sink. The evaporator and condenser are planar (102 mm × 102 mm footprint) and allow for potential integration of multiple, stacked condensers. The condenser wick is used to separate the liquid and vapor phases during condensation by capillary menisci and enables the use of multiple condensers with equal condensation behavior and performance. In this paper, the thermal–fluidic cycle is outlined, and the requirements to generate capillary pressure in the condenser are discussed. The LHP design to fulfill the requirements is then described, and the experimental characterization of a single-condenser version of the LHP is reported. The thermal performance was dependent on the fan speed and the volume of the working fluid; a thermal resistance of 0.177 °C/W was demonstrated at a heat load of 200 W, fan speed of 5000 rpm and fluid volume of 67 mL. When the LHP was filled with the working fluid to the proper volume, capillary pressure in the condenser was confirmed for all heat loads tested, with a maximum of 3.5 kPa at 200 W. When overfilled with the working fluid, the condenser was flooded with liquid, preventing the formation of capillary pressure and significantly increasing the LHP thermal resistance. This study provides the detailed thermal–fluidic considerations needed to generate capillary pressure in the condenser for controlling the condensation behavior and serves as the basis of developing multiple-condenser LHPs with low thermal resistance.

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Samanta, Sudip K., Bharat B. Sharma, Prosenjit Das, and A. K. Lohar. "DEVELOPMENT OF TUBULAR Ni WICK USED IN LHP FOR SPACE APPLICATIONS." Frontiers in Heat Pipes 2, no. 4 (February 10, 2012). http://dx.doi.org/10.5098/fhp.v2.4.3004.

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Guo, Chunsheng, Cheng Jiang, Jun Ma, Yingwen Cao, Yong Zou, and Yong Liu. "Experimental Study on Comprehensive Performance of Sintering Biporous Wicks Prepared by Salt Dissolution and Cold Pressing Process." Journal of Heat Transfer 142, no. 1 (November 8, 2019). http://dx.doi.org/10.1115/1.4045140.

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Abstract Porous wicks are a key component of loop heat pipes (LHPs). In order to enhance the antigravity and long-distance operation ability of the LHP, a porous wick is required to have the characteristics of high permeability and high capillary suction capability. In this paper, biporous wicks were prepared by salt dissolution pore-forming technology, and a gas resistance testing platform and a capillary suction testing platform were setup to test the samples. The current research studies the effects of different pore-forming agent mass ratios (10%, 30%, and 40%) and different cold pressing pressures (30 kN, 40 kN, 50 kN, and 60 kN) on the porosity, permeability, and the suction speed. The study finds that the porosity, permeability, and the total suction mass of the porous wicks all increase when the NaCl mass increases; the increase of the suction speed is proportional to the increase of the porosity and the permeability, and hence, proportional to the increase of NaCl mass. The total suction mass and suction speed is inversely proportional to cold pressing pressure.

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Lin, Bingyao, Nanxi Li, Shiyue Wang, Leren Tao, Guangming Xu, and Yinong Wu. "Theoretical Analysis of Thin Film Evaporation in the Wicks of Loop Heat Pipes." Journal of Thermal Science and Engineering Applications 14, no. 5 (August 17, 2021). http://dx.doi.org/10.1115/1.4051840.

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Abstract In this paper, a thin film evaporation model that includes expressions for energy, mass, and momentum conservation was established through the augmented Young–Laplace model. Based on this model, the effects of pore size and superheating on heat transfer during thin film evaporation were analyzed. The influence of the wick diameter of the loop heat pipe (LHP) on the critical heat flux of the evaporator is analyzed theoretically. The results show that pore size and superheating mainly influence evaporation through changes in the length of the transition film and intrinsic meniscus. The contribution of the transition film area is mainly reflected in the heat transfer coefficient, and the contribution of the intrinsic meniscus area is mainly apparent in the quantity of heat that is transferred. When an LHP evaporator is operating in a state of surface evaporation, a higher heat transfer coefficient can be achieved using a smaller pore size.

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Hu, Zhuohuan, Sixian Sun, Chengwei Yuan, Yan Cao, and Jiayin Xu. "Effect of the Wick Deflection Angles on Heat Transfer Characteristics for the Flat LHP." Frontiers in Heat and Mass Transfer, 2023, 1–17. http://dx.doi.org/10.32604/fhmt.2023.041837.

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Journal articles on the topic 'LHP Wick'

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