Academic literature on the topic 'LHP Wick'
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Journal articles on the topic "LHP Wick"
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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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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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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%.
Dissertations / Theses on the topic "LHP Wick"
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Suh, Junwoo. "Proof of Operation in a Planar Loop Heat Pipe (LHP) Based on CPS Wick." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131033062.
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SURYAMOORTHY, SOWMYA. "ETCHING TECHNOLOGIES IN SUPPORT OF THE DEVELOPMENT OF A COHERENT POROUS SILICON WICK FOR A MEMS LHP." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078211112.
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ARRAGATTU, PRAVEEN KUMAR. "OPTIMAL SOLUTIONS FOR PRESSURE LOSS AND TEMPERATURE DROP THROUGH THE TOP CAP OF THE EVAPORATOR OF THE MICRO LOOP HEAT PIPE." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1152120112.
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HAMDAN, MOHAMMAD OMAR. "LOOP HEAT PIPE (LHP) MODELING AND DEVELOPMENT BY UTILIZING COHERENT POROUS SILICION (CPS) WICKS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1049987207.
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Hamdan, Mohammad Omar Mohammad. "Loop heat pipe (LHP) modeling and development by utilizing coherent porous silicon (CPS) wicks." Cincinnati, Ohio : University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1049987207.
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Anand, A. R. "Investigations on Miniature Loop Heat Pipe with Flat Evaporator." Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4308.
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The present investigation on a miniature loop heat pipe (LHP) with flat evaporator is motivated by two factors. Firstly, miniature loop heat pipes are required for thermal management of small electronics in spacecraft with heat dissipation ranging from 50 W to 100 W (heat flux up to ~ 10 W/cm2). An LHP with flat evaporator is easier to mount on an electronic package (heat source) without a saddle. Though axially grooved aluminium – ammonia heat pipes are being used for thermal management in spacecraft, when the electronic package is located far away from the radiator, conventional heat pipes are no longer useful as the number of bends in axially grooved heat pipes is restricted. LHPs can overcome this issue since they have smooth walled tubes for vapour and liquid transport lines that can easily be bent and routed inside the spacecraft. Furthermore, high pressure fluids such as ammonia require thick-walled container to withstand the high operating pressure and are more hazardous to humans in human space programs. For thermal management of small electronics with heat dissipation in the above range, there is scope for alternate working fluids that are less hazardous. Thus, issues related to design, miniaturization of the heat transport devices and use of working fluids that are less hazardous are still open for research. Secondly, the operating characteristics of an LHP are strongly influenced by the flow and heat transfer characteristics in the wick which need to be explored in detail. Thus, the present research focuses on the investigation of an LHP with a flat evaporator with various working fluids – acetone, methanol, n-pentane and ethanol.
An LHP with a flat evaporator has been built and tested with acetone, methanol, n-pentane and ethanol for heat inputs starting from 25 W till deprime for two coolant set points (-20 °C and 0 C). The LHP is also provided with a visualization arrangement to observe the phenomena occurring inside the compensation chamber (CC). Experimental results reveal that methanol has the highest deprime limit, followed by acetone, ethanol and n-pentane in decreasing order. It was also found that n-pentane has the lowest operating temperature followed by acetone, methanol and ethanol in increasing order. It was observed that increase in the sink temperature causes an increase in the operating temperature, a decrease in the deprime limit and a decrease in the total thermal resistance offered by the LHP to the heat transport from the evaporator to the sink. Visualization studies reveal that the LHP operates without any nucleation in the CC for all the heat inputs till deprime. However, the deprime of the LHP is characterised by intense nucleation inside the CC, an increase in the operating temperature and a decrease in the condenser exit temperature indicating ceasing of the fluid flow inside the LHP. Since the LHP evaporator will be directly in contact with the electronic package for its temperature control, the evaporator wall temperature will influence the electronic package temperature and its life. Hence, a model for prediction of the evaporator wall temperature under the assumption that the wick is always saturated with liquid is developed which can serve as a design platform for miniature LHPs for thermal management of electronic packages. The maximum underprediction of the evaporator wall temperature with respect to the measured evaporator wall temperature in the model is found to be 16.4 °C. Based on the results of this model, it is inferred that there exists a vapour blanket in the wick causing an additional resistance for the heat flow from the evaporator to the working fluid for its vapourization and another model is developed to estimate the vapour blanket thickness.
By balancing the loop pressure drop with the capillary pressure, an equivalent apparent contact angle which is a measure of wettability of a working fluid is estimated on a relative scale for each working fluid. It was found that ethanol has the highest wetting, followed by methanol, acetone, and n-pentane in decreasing order, or the lowest contact angle, followed by methanol, acetone, and n-pentane in increasing order. It was also found that fluid with less wetting recedes faster into the wick.
The impact of the location of liquid-vapour interface on the evaporative heat transfer coefficient is studied for all the fluids. It was found that decrease in the evaporative heat transfer coefficient is mainly due to increase in the vapour blanket thickness in the wick.
In order to compare different working fluids with respect to their operating characteristics, an improved LHP figure of merit with a correction factor is presented. This figure of merit clearly distinguishes the operating temperatures of a given LHP with different working fluids and is superior to other figures of merit available in literature. The proposed figure of merit can serve as a predictive tool for making qualitative assessment of the operating characteristics of an LHP.
Book chapters on the topic "LHP Wick"
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Pantic, Maja. "Face for Interface." In Encyclopedia of Multimedia Technology and Networking, Second Edition, 560–67. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-014-1.ch075.
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The human face is involved in an impressive variety of different activities. It houses the majority of our sensory apparatus: eyes, ears, mouth, and nose, allowing the bearer to see, hear, taste, and smell. Apart from these biological functions, the human face provides a number of signals essential for interpersonal communication in our social life. The face houses the speech production apparatus and is used to identify other members of the species, to regulate the conversation by gazing or nodding, and to interpret what has been said by lip reading. It is our direct and naturally preeminent means of communicating and understanding somebody’s affective state and intentions on the basis of the shown facial expression (Lewis & Haviland-Jones, 2000). Personality, attractiveness, age, and gender can also be seen from someone’s face. Thus the face is a multisignal sender/receiver capable of tremendous flexibility and specificity. In general, the face conveys information via four kinds of signals listed in Table 1. Automating the analysis of facial signals, especially rapid facial signals, would be highly beneficial for fields as diverse as security, behavioral science, medicine, communication, and education. In security contexts, facial expressions play a crucial role in establishing or detracting from credibility. In medicine, facial expressions are the direct means to identify when specific mental processes are occurring. In education, pupils’ facial expressions inform the teacher of the need to adjust the instructional message. As far as natural user interfaces between humans and computers (PCs/robots/machines) are concerned, facial expressions provide a way to communicate basic information about needs and demands to the machine. In fact, automatic analysis of rapid facial signals seem to have a natural place in various vision subsystems and vision-based interfaces (face-for-interface tools), including automated tools for gaze and focus of attention tracking, lip reading, bimodal speech processing, face/visual speech synthesis, face-based command issuing, and facial affect processing. Where the user is looking (i.e., gaze tracking) can be effectively used to free computer users from the classic keyboard and mouse. Also, certain facial signals (e.g., a wink) can be associated with certain commands (e.g., a mouse click) offering an alternative to traditional keyboard and mouse commands. The human capability to “hear” in noisy environments by means of lip reading is the basis for bimodal (audiovisual) speech processing that can lead to the realization of robust speech-driven interfaces. To make a believable “talking head” (avatar) representing a real person, tracking the person’s facial signals and making the avatar mimic those using synthesized speech and facial expressions is compulsory. The human ability to read emotions from someone’s facial expressions is the basis of facial affect processing that can lead to expanding user interfaces with emotional communication and, in turn, to obtaining a more flexible, adaptable, and natural affective interfaces between humans and machines. More specifically, the information about when the existing interaction/processing should be adapted, the importance of such an adaptation, and how the interaction/ reasoning should be adapted, involves information about how the user feels (e.g., confused, irritated, tired, interested). Examples of affect-sensitive user interfaces are still rare, unfortunately, and include the systems of Lisetti and Nasoz (2002), Maat and Pantic (2006), and Kapoor, Burleson, and Picard (2007). It is this wide range of principle driving applications that has lent a special impetus to the research problem of automatic facial expression analysis and produced a surge of interest in this research topic.
Conference papers on the topic "LHP Wick"
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Xin, Gongming, Kehang Cui, Yan Chen, Wenjing Du, Yong Zou, and Lin Cheng. "Experimental Investigation of Effective Thermal Conductivity for LHP Wicks." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22272.
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In this study, the effective thermal conductivity (ETC) of sintered loop heat pipe wicks, with pure nickel powders, pure copper powders, Ni-10wt%Cu powders and Ni-20wt%Cu powders were experimentally investigated. The ETC of sintered Ni-Cu wicks is found less than those of sintered pure nickel wick and sintered pure copper wicks. In the same porosity level, addition of copper into nickel will reduce ETC of the sintered Ni-Cu wicks. The sintered Ni-20wt%Cu wick presents the lowest ETC among the tested wick samples. Compared to experimental results, Alexander model can provide a reasonable prediction in some wick samples.
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Anderson, W. G., P. M. Dussinger, S. D. Garner, J. R. Hartenstine, and D. B. Saraff. "Loop Heat Pipe Design, Manufacturing, and Testing: An Industrial Perspective." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88525.
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Loop Heat Pipes (LHPs) are two-phase devices that can passively transport heat over long distances relative to other passive two phase systems such as heat pipes. Most of the art of LHP fabrication is in the primary and secondary wick. The manufacturing steps for an LHP are described, including the tests to validate the LHP during manufacture. The tests include wick property testing (pore size, permeability, and thermal conductivity), secondary wick testing, and parallel flow balance design and testing. The required tests after the LHP is fabricated include low power starts, shutdown through compensation chamber heating, unbalanced condenser temperature tests, transient testing — both power cycling and condenser temperature changes, and maximum power tests.
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Cai, Qingjun, Chung-Lung Chen, and Julie F. Asfia. "Multilayer Wick Structure of Loop Heat Pipe." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41162.
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Loop heat pipe (LHP) is known as a two-phase heat transfer device that utilizes the evaporation and condensation of an operating fluid to transfer heat. At the LHP low operating temperatures, heat leakage induced by saturated temperature differences between the evaporator and compensation chamber is more serious than at high operating temperatures, due to inherent thermophysical properties of the operating liquid. The serious heat leakage at the low operating temperature not only causes high liquid subcooling requirement but also leads to high total temperature difference and degraded heat transfer performance. In this paper, research efforts are placed on reducing the heat leakage by introducing a multilayer wick structure into the LHP. Based on the previous research results of LHP non-metallic wick structures, the multilayer wick LHP combines advantages of both metallic and non-metallic wick structures, retains good heat conduction from the evaporator case to the liquid/vapor interface and inhibits the reverse heat transfer from the interface to compensation chamber. By demonstrating the concept on a methanol LHP, experimental results exhibit a significant enhancement in reducing heat leakage and the total heat transfer resistance.
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Remella, Karthik S., Frank M. Gerner, Ahmed Shuja, and Praveen Medis. "Steady State Numerical Modeling of Non-Conventional Loop Heat Pipes (LHPs)." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88217.
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Loop heat pipes (LHPs) transport energy from an evaporator to a condenser in the form of latent heat. In conventional LHPs, the vapor pressure is significantly higher than the liquid pressure across the liquid-vapor interface due to the small pores and the corresponding capillary forces in the wick. This large pressure difference transports the single phase vapor after evaporation from the evaporator to the condenser and once the vapor is condensed, a single phase liquid from the condenser back to the evaporator. This current work involves the development of a steady state design model of the LHP system consisting of a planar evaporator package and a finned copper tube loop, which serves as an air-cooled condenser. Although evaporation due to the heat transfer creates the pressure in the vapor which drives the flow, contrasting to the conventional loop heat pipes, the pressure drop across the liquid-vapor interface is much smaller. A positive hydrostatic head is applied to the liquid above the wick and there is entrainment of liquid from the wick in the evaporator. Therefore, the fluid flow leaving the evaporator package is a two-phase flow, assumed to be saturated liquid and saturated vapor in equilibrium. The primary objective of this non-conventional LHP device is to remove the thermal energy dissipated from a Light Emitting Diode (LED) array. A major portion of this energy causes evaporation of the working fluid within the wick. The remaining energy reheats the liquid in both the liquid return line and within the evaporator package. The evaporator package is modeled as a one-dimensional thermal resistance network and these resistances are empirically determined from experiments. It is found that the convective heat transfer co-efficient of air plays a pivotal role in the heat dissipation and hence, is empirically determined in this work. This value is fairly agreeable with the Nusselt number correlation on the air side developed by Hahne et al. [1]. A mass balance relates the fill volume with the length of the condenser. The temperatures within the LHP are predicted by applying the principle of conservation of energy over the evaporator, the condenser and the sub-cooler sections of the heat exchanger loop. Finally, this LHP model predicts an approximate fill volume necessary for the LHP to operate properly.
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Atabaki, Nima, and B. Rabi Baliga. "Steady-State Operation of a Loop Heat Pipe: Network Thermofluid Model and Results." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-43968.
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A network thermofluid model of a loop heat pipe (LHP) operating under steady-state conditions is presented. Attention is focused on a simple LHP, with one evaporator, a vapor transport line, a single condenser, a liquid transport line, and a compensation chamber. The evaporator is an internally grooved circular pipe, with a cylindrical wick installed on its inner surface. The wick is made of a sintered metal. The condenser is a horizontal tube covered with a high-thermal-conductivity sleeve, and the outer temperature of the sleeve is maintained at a constant sink temperature. Quasi one-dimensional mathematical models of the fluid flow and heat transfer in each of the elements of the LHP, and collectively of the entire LHP, are proposed and discussed. The working fluid considered in this work is ammonia, but the proposed model can work with any suitable fluid. Results pertaining to the LHP performance for a range of operating conditions are presented, compared (qualitatively) to corresponding results of an earlier experimental investigation in the literature, and discussed.
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Tanaka, K. "Development of the Loop Heat Pipe (LHP)." In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56047.
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First, I describe the basic equations that resolve the physical development of the LHP and how to estimate the maximum heat transfer capability of the LHP. Second, I describe the outline of experimental manufacture of the LHP. This LHP is made from copper. The evaporator is φ19×95mm, the vapor tube is φ5×300mm, the condenser is φ3.5×600mm and the liquid tube is φ3.5×300mm. The wick is made from the sintering cupper. The working fluid is methanol. Finally, I briefly describe the test result of heat transfer capability of this LHP.
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Tanaka, K., M. Katsuta, Y. Ohuchi, and K. Saitho. "Thermal Performance of the Mini-Loop Heat Pipe (LHP)." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88403.
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In this paper, we describe the outline of experimental manufacture of the LHP. This LHP is made of a copper. The evaporator is φ19×95mm, the vapor tube is φ5×300mm, the condenser is φ3.5×600mm and the liquid tube is φ 3.5×300mm. The wick is made of the sintering copper. The working fluid is methanol. Second, we describe the test result of heat transfer capability of this LHP. Finally, I describe the basic equations that resolve the physical development of the LHP and how to estimate the each temperatures of the LHP.
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Watson, Heather, Charlotte Gerhart, George Mulholland, and Donald Gluck. "Steady-State Operation of a Loop Heat Pipe With Analytical Prediction." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1551.
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Abstract The steady-state performance of an 800W, sintered nickel powder wick, loop heat pipe (LHP) has been analyzed using a modified Dynatherm LHP Thermal Model. Results from characterization tests of this LHP performed at the Air Force Research Laboratory in Albuquerque, NM are used as the basis for comparison and discussion of results for the analytical model. The analytical predictions gave excellent correlation to the measured data for power levels ranging from 50 to 1500W at condenser chiller settings between −40°C and 20°C, with the LHP in a horizontal orientation.
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Chuang, Po-Ya Abel, John M. Cimbala, Jack S. Brenizer, C. Thomas Conroy, A. A. El-Ganayni, and David R. Riley. "Comparison of Experiments and 1-D Steady-State Model of a Loop Heat Pipe." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33542.
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A modern, effective, two-phase heat transfer device, a loop heat pipe (LHP), was studied analytically and experimentally. A 1-D steady-state model was developed based on energy balance equations. The mathematical modeling procedures of each component are explained in detail, including a model of the secondary wick in the evaporator. Other models neglect the existence of the secondary wick because the detailed designs of the secondary wick are often proprietary. Three sets of experiments were performed at different elevations. Results of experimental data are compared with 1-D steady-state model predictions. The comparisons show that the model predictions of steady state operating temperatures for both zero elevation and adverse elevation are within 2 percent. It has been clearly demonstrated that the 1-D steady-state model is a useful tool for future LHP study.
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Sung, Byung-ho, Jeehoon Choi, Jaehyung Ki, Junghyun Yoo, Minwhan Seo, and Chul-ju Kim. "The Sintered Porous Metal Media Development and Measurement of LHP Systems for Electronic Cooling Device." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67300.
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Due to the continuous increase of power applied in electric device, the growing demand on cooling systems have led with using various cooling device to conduct the thermal management. As a new cooling device, a Loop Heat Pipe (LHP) system has been taken notice recently. The performance of the LHP systems depends mainly upon the operating performance of the wick structure should possess flow properties such as permeability, maximum capillary pressure and so on. However, expressions on packed metal spherical particles are not related with various particle shapes. In this work, therefore, an experimental apparatus was set up to measure the flow properties of sintered porous metal wicks manufactured with spherical, needled, and corn shape particles. The results of the such experiments gave very accurate and consistent.