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Статті в журналах з теми "Flat Evaporator"
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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.
Повний текст джерелаАнотація:
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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Chien, L. H., and Y. C. Shih. "An Experimental Study of Mesh Type Flat Heat Pipes." Journal of Mechanics 27, no. 2 (June 2011): 167–76. http://dx.doi.org/10.1017/jmech.2011.18.
Повний текст джерелаАнотація:
ABSTRACTFlat heat pipes having mesh capillaries were investigated experimentally in this study. An apparatus was designed to test thermal performance of plate type copper water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5 to 50 W heat input. The working fluid, water, is charged in volumes equivalent to 25%, 33%, or 50% of the internal space. In addition to horizontal orientation, heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances were calculated separately. The effects of mesh size, charge volume fraction, and inclination angle on thermal resistance were discussed. In general, the #80 mesh yielded lower thermal resistance than the #50 mesh. Inclination angle has a more significant effect on condenser than evaporator. Analysis of evaporation and condensation in flat heat pipes was conducted and semi-empirical correlations were derived. The present evaporation correlation predicts evaporation resistance between −20% and +30%, and the condensation correlation predicts most condensation resistance data within ±30% for 25% and 33% charge volume fraction.
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Hu, Wenju, and Xin Zhang. "Study on the Coupling Effect of Heat Transfer and Refrigerant Distribution in the Flat Tube of a Microchannel Evaporator." Energies 15, no. 14 (July 20, 2022): 5252. http://dx.doi.org/10.3390/en15145252.
Повний текст джерелаАнотація:
Refrigerant maldistribution severely deteriorates the heat transfer performance of a microchannel evaporator. Compared with the refrigerant distribution among flat tubes along the header, refrigerant distribution among microchannels in the flat tube in the airflow direction has barely been paid attention. In this paper, a heat transfer mathematical model of a microchannel evaporator’s flat tube composed of vertically placed parallel microchannels in the airflow direction was developed. The Refrigerant distribution among the microchannels was evaluated and its influence on heat transfer between air and refrigerant was analyzed. The results showed that the refrigerant distribution and heat transfer performance between air and refrigerant were interrelated and interacted with each other. The temperature of the air leaving the microchannel evaporator changed along the microchannel because of uneven refrigerant distribution among the microchannels, and the air temperature difference between air leaving out of the bottom and the top of the evaporator was approximately 2.13 °C. Ignoring the heat transfer from adjacent microchannels will lead to a small heat transfer deviation for the flat tube; thus, heat transfer among microchannels can be neglected.
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Santos, Paulo, Thiago Alves, Amir Oliveira, and Edson Bazzo. "Analysis of a flat capillary evaporator with a bi-layered porous wick." Thermal Science 24, no. 3 Part B (2020): 1951–62. http://dx.doi.org/10.2298/tsci180419240s.
Повний текст джерелаАнотація:
A numerical evaluation of the heat and mass transfer concerning a flat capillary evaporator provided by a bi-layered porous wick is presented. The wick has a shape of a flat disc and is assembled between the liquid feeding channel and the vapor chamber. An external heat input is applied into the upper surface of the bi-layered wick, where the working fluid evaporates. The mass and heat transfer are modeled using the mass and energy conservation equations. The model allows to verify the effect of design variables, such as working fluids, dimensions, permeability, average pore radius and thermal conductivity of the wick, in the performance of the capillary evaporator. It can be used as a predictive tool to design similar capillary pumping systems for thermal control of satellite or electronics systems in general.
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Gai, Dongxing, Wei Liu, ZhiChun Liu, and JinGuo Yang. "Temperature Oscillation of mLHP with Flat Evaporator." Heat Transfer Research 40, no. 4 (2009): 321–32. http://dx.doi.org/10.1615/heattransres.v40.i4.40.
Повний текст джерела
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Ninolin, Emerald, Godson Asirvatham Lazarus, and K. Ramachandran. "Thermal Performance of a Compact Loop Heat Pipe with Silver-Water Nanofluid." Applied Mechanics and Materials 852 (September 2016): 666–74. http://dx.doi.org/10.4028/www.scientific.net/amm.852.666.
Повний текст джерелаАнотація:
The thermal performance of a compact loop heat pipe is fabricated and tested for different heat inputs ranging from 30 W to 500 W using water and silver-water nanofluid with low volume concentrations of silver nanoparticles (0.03% and 0.09%) in vertical orientation. A flat square evaporator having a bottom area of 30 mm × 30 mm and a height of 15 mm is used in the present study. The effect of heat input on the thermal resistance, evaporation and condensation heat transfer coefficient is experimentally investigated. The results showed that a reduction in the evaporator thermal resistance of 26.45% is achieved with 0.09 volume percentage of silver nanoparticles when compared with that of water. Further an enhancement in the convective heat transfer coefficient of 25.23% has been observed with the same volume concentration of silver nanoparticles. Addition of small amount of nanoparticles enhanced the operating range of heat pipe beyond 500 W and without the occurrence of any dry out conditions. From the outcome of this study, it is concluded that the compact loop heat pipe with flat square evaporator can be used for thermal control of electronic equipments with limited space.
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Gabsi, Inès, Samah Maalej, and Mohamed Chaker Zaghdoudi. "Modeling of Loop Heat Pipe Thermal Performance." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 81, no. 1 (March 5, 2021): 41–72. http://dx.doi.org/10.37934/arfmts.81.1.4172.
Повний текст джерелаАнотація:
The present work deals with the heat transfer performance of a copper-water loop heat pipe (LHP) with a flat oval evaporator in steady-state operation. Modeling the heat transfer in the evaporator was particularly studied, and the evaporation heat transfer coefficient was determined from a dimensionless correlation developed based on experimental data from the literature. The model was based on steady-state energy balance equations for each LHP component. The model results were compared to the experimental ones for various heat loads, cooling temperatures, and elevations, and a good agreement was obtained. Finally, a parametric study was conducted to show the effects of different key parameters, such as the axial conductive heat leaks between the evaporator and the compensation chamber cases, the capillary structure porosity and material, and the groove dimensions.
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Merzah, Basil Noori, Majid H. Majeed, and Fouad A. Saleh. "Numerical study of flat plate solar collector performance with square shape wicked evaporator." Al-Qadisiyah Journal for Engineering Sciences 12, no. 2 (June 30, 2019): 90–97. http://dx.doi.org/10.30772/qjes.v12i2.592.
Повний текст джерелаАнотація:
In this work, a system of a heat pipe is implemented to improve the performance of flat plate solar collector. The model is represented by square shape portion of the evaporator section of wicked heat pipe with a constant total length of 510 mm, and the evaporator section inclined by an angle of 30o. In this models the evaporator, adiabatic and condenser lengths are 140mm, 140mm, and 230mm respectively. The omitted energies from sunlight simulator are 200, 400, 600, 800 and 1000 W/m2 which is close to the normal solar energy in Iraq. The working fluid for all models is water with fill charge ratio of 240%. The efficiency of the solar collector is investigated with three values of condenser inlet water temperatures, namely (12, 16 and 20o C). The numerical result showed an optimum volume flow rate of cooling water in condenser at which the efficiency of collector is a maximum. This optimum agree well with the ASHRAE standard volume of flow rate for conventional tasting for flat plate solar collector. When the radiation incident increases the thermal resistance of wicked heat pipe is decreases, where the heat transfer from the evaporator to condenser increases. The numerical results showed the performance of solar collector with square shape evaporator greater than other types of evaporator as a ratio 15 %.
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Dongxing, Gai, Sun Jingyu, Chen Chen, and Chen Ting. "Hysteresis phenomena in flat-type loop heat pipe." Thermal Science, no. 00 (2020): 166. http://dx.doi.org/10.2298/tsci191010166d.
Повний текст джерелаАнотація:
Testing of loop heat pipes (LHPs) showed that the heat-load dependence of the operating temperature was not always unambiguous. It may have hysteresis phenomena. The temperature hysteresis had a certain relationship with previous history of the power variation, and also related to the initial parameters of the LHP. It has been found that the temperature hysteresis of the LHP was related to the gas-liquid distribution in the compensation chamber (CC) which depended on the interaction between heat leak of evaporator and the reflux liquid from condenser. The temperature of the LHP evaporator rose with the gas phase in the compensation chamber increased.
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Khrustalev, D., and A. Faghri. "Thermal Characteristics of Conventional and Flat Miniature Axially Grooved Heat Pipes." Journal of Heat Transfer 117, no. 4 (November 1, 1995): 1048–54. http://dx.doi.org/10.1115/1.2836280.
Повний текст джерелаАнотація:
A detailed mathematical model of low-temperature axially grooved heat pipes (AGHP) is developed in which the fluid circulation is considered along with the heat and mass transfer processes during evaporation and condensation. The results obtained are compared to existing experimental data. Both capillary and boiling limitations are found to be important for the flat miniature copper-water heat pipe, which is capable of withstanding heat fluxes on the order of 40 W/cm2 applied to the evaporator wall in the vertical position. The influence of the geometry of the grooved surface on the maximum heat transfer capacity of the miniature AGHP is demonstrated.
Дисертації з теми "Flat Evaporator"
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Tanguy-Sai, Gaëlle. "Concentration de produits laitiers dans les évaporateurs à flot tombant : facteurs limitants et alternatives technologiques." Thesis, Rennes, Agrocampus Ouest, 2018. http://www.theses.fr/2018NSARB318/document.
Повний текст джерелаАнотація:
Les poudres laitières sont obtenues par concentration du produit liquide (membranes, évaporation sous vide) puis séchage du concentré. Contrairement au séchage par atomisation, peu de travaux ont été menés sur la concentration par évaporation sous vide. Pourtant, la maîtrise du schéma global de production des poudres gagnerait en une meilleure compréhension de cette opération réalisée dans des évaporateurs à flot tombant. Le présent travail vise à étudier comment améliorer les performances des évaporateurs ; il s’appuie sur deux facteurs limitants de l’opération : l’encrassement des surfaces d’échange et la viscosité maximale en sortie des évaporateurs. La contribution des différents constituants des produits à l’encrassement a été étudiée grâce à une méthodologie développée sur un évaporateur pilote.Les résultats obtenus ont permis d’identifier les éléments minéraux qui contribuent à l’encrassement lors de la concentration de microfiltrat et d’ultrafiltrat de lait, de lactosérums acides chlorhydrique et lactique. Afin de dépasser l’extrait sec maximal en sortie des évaporateurs à flot tombant, deux évaporateurs rotatifs à couche mince, de conceptions différentes, ont été testés à l’échelle pilote. Les études de faisabilité ont été menées jusqu’à la poudre. Le potentiel des équipements a été évalué suivant les propriétés fonctionnelles des poudres et le coût énergétique d’élimination de l’eau. Dans l’un des cas, le remplacement de la tour de séchage par deux évaporateurs rotatifs en série constitue une rupture technologique pour la production de poudres de perméat et dimiDairy powders are produced using a two-step process: concentration of the liquid product (membrane, concentration by vacuum evaporation) and drying of the concentrate. Contrary to spray-drying, vacuum concentration has been poorly investigated. However, a better understanding of this unit operation carried out in falling-film evaporators would lead to an improved control of the global process scheme for the production of powders. This PhD project aims to highlight how to enhance the performances of falling-film evaporators; it focuses on two limiting factors of the vacuum concentration: the fouling of the heating surfaces and the maximal viscosity at the outlet of the falling-film evaporators. The contribution of the different product components to the fouling was investigated using a methodology developed at pilot-scale.Our results showed which mineral elements favored the fouling of falling-film evaporators during the concentration of milk microlfiltrate and ultrafiltrate as well as hydrochloric and lactic acid wheys. Besides, two thin-film rotative evaporators of different designs were tested at pilot-scale in order to exceed the maximum dry matter achieved in falling-film evaporators. The feasibility studies were conducted up to the production of powders. The capabilities of the equipment were evaluated according to the functional properties of powders and the specific energy costs relative to the removal of water. In one case, the combination of two rotative evaporators replacing the spray drier constitutes a technological breakthrough in the production of permeate p
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Caldas, Pereira Silveira Arlan. "Caractérisation expérimentale et comportement de constituants protéiques et minéraux laitiers en concentration sous vide." Thesis, Rennes, Agrocampus Ouest, 2015. http://www.theses.fr/2015NSARB269/document.
Повний текст джерелаАнотація:
Les évaporateurs à flot tombant (EFT) sont largement utilisés dans les industries chimiques, de la réfrigération, du raffinage du pétrole, et alimentaires. Dans l'industrie laitière, les EFT sont appliqués pour la concentration de solutions avant l'étape de séchage. Malgré l'importance économique du procédé d'évaporation sous vide dans la fabrication de produits laitiers déshydratés, la connaissance du procédé est essentiellement empirique. Des recherches visant à améliorer l'efficacité du procédé sont donc nécessaires. L'objectif de ce projet de doctorat est de caractériser expérimentalement un EFT lors de la concentration de produits laitiers, par des approches thermo et hydro-dynamiques, afin d'étudier les interactions entre les propriétés des produits et les paramètres opérationnels. Un évaporateur à flot tombant, simple effet, à l’échelle pilote, qui décrit le même processus que celui à l'échelle industrielle, d'un point de vue hydrodynamique, a été instrumenté et utilisé pour établir les bilans massiques et énergétiques. La capacité évaporatoire et le coefficient global de transfert de chaleur ont été calculés à partir des données expérimentales. Une méthodologie pour la détermination expérimentale des fonctions distribution des temps de séjour (DTS) a été développée. En effet, les fonctions de DTS fournissent des informations essentielles sur l'écoulement des produits lors de la concentration dans un EFT. L'augmentation de la concentration, du débit massique et de la distance parcourue par le produit entraîne une augmentation de la dispersion des particules dans le flux. Ces fonctions ont été modélisées par une combinaison de réacteurs en cascade, parfaitement agités. D’après l'interprétation de ce modèle, deux flux, un principal et un secondaire, correspondant à deux couches superposées de produit circulant à travers des tubes d'évaporateur, a été proposé. La méthodologie développée pour le calcul des fonctions de DTS a été appliqué pour la concentration de produits laitiers (lait écrémé, lactosérum doux et acide). Par la suite, l'étude a été étendue à la formation de l'encrassement pendant la concentration par évaporation sous vide. Il a été montré que le temps de séjour moyen était plus sensible pour identifier l'encrassement que le coefficient global de transfert de chaleur et la capacité évaporatoire. Ainsi, cette étude a souligné le rôle crucial de l’importance de la caractérisation des EFT sous vide afin d’en améliorer leurs performances et la qualité des produits qui en sont issuFalling film evaporators (FFE) are widely used in the chemical, refrigeration, petroleum refining, desalination and food industries. In the dairy industry FFE is applied for the concentration of solutions prior to the drying step. Despite the economic importance of the vacuum evaporation process in the manufacture of dairy dried products, the knowledge about the process is mostly empirical. Research aiming to improve the efficiency of the process is therefore necessary. The objective of this PhD project was to characterize experimentally a FFE during the concentration of dairy products by means of thermodynamic and hydrodynamic approaches, in order to study the interactions between the products properties and the operating parameters. A pilot-scale, single-stage falling film evaporator that describes the same process as that of an industrial scale from a hydrodynamic point of view was instrumented and used to establish the mass and energy balances. The evaporation rate and the overall heat transfer coefficient were calculated from the experimental data to follow up the process. A methodology for the determination of the experimental residence time distribution (RTD) functions was developed. RTD functions provide global information about the flow of the products during concentration in a FFE. Increasing of the concentration of skim milk, mass flow rate and the distance covered by the product resulted in an increase in the dispersion of the products particles. The experimental RTD functions were modelled by a combination of two perfectly mixed reactor tanks in series. From the interpretation of this model, two different flows, a main and a minor flow, were identified. The RTD methodology developed on skim milk was applied to sweet whey and lactic acid whey and the study was extended to the formation of fouling during a 5-hour concentration. The mean residence time was more sensitive to identify fouling than the overall heat transfer coefficient and the evaporation rate. This study emphasized the crucial role of process characterization to improve the performance of FFE and product quality
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Aza-Gnandji, Cocou Davis Ruben. "Salinity of irrigation water in the Philippi farming area of the cape flats, Cape Town, South Africa." University of the Western Cape, 2011. http://hdl.handle.net/11394/2921.
Повний текст джерелаАнотація:
Magister Scientiae - MScThis research investigated the nature, source and the spatial variation of the salinity of the water used for irrigation in the urban farming area of Philippi, which lies in the Cape Flats region of the Cape Town Metropolitan Area, South Africa. The irrigation water is mainly drawn from the Cape Flats aquifer, and pumped into ponds for eventual crop irrigation. Water samples were collected in summer and in winter from fifteen selected sites using standard water sampling procedures. Each site consisted of one borehole and one pond. The samples were routinely analyzed for salinity levels, and concentrations of major and minor ions. From the same boreholes and ponds, water was sampled in summer for isotope analysis to assess effects of evaporation on the water quality and salinity. Descriptive statistics were used to display the variation in range of specific ions in order to compare them with the recommended ranges. Geographical Information Systems analysis described the spatial distribution of the salinity across the study area, and hydrogeochemical analysis characterized the various waters and detected similarities between the water samples in the study area and other waters found in the Cape Flats region. In addition, the US salinity diagram classification of irrigation water developed by Richards (1954) was used to assess the current suitability of groundwater and pond water samples collected during the entire sampling period for irrigation activities. The research indicated that the concentrations of some ions such as chloride, nitrate, potassium and sodium exceeded in places in the study area, the target range values set by the Department of Water Affairs and Forestry (DWAF, 1996) and the Food and Agriculture Organization (Ayers and Westcot, 1985). It revealed that borehole and pond water were mostly brackish across the area regarding their total dissolved salts content, and fresh water was only found in the middle part of the study area. The research found that sea water does not intrude into the aquifer of the study area, and the accumulation of salts in groundwater and soil in the study area is mainly due to the agricultural activities and partially due to the natural movement of water through the geological formation of the Cape Flats region. The conceptual model of the occurrence of the salinization process supported these findings. From this investigation it is understood that the groundwater and pond water in the study area were generally suitable for irrigation purposes but they have to be used with caution as the vegetables are classified as sensitive and moderately sensitive to salt according to DWAF Irrigation water guidelines (1996). The quality of these waters was mainly affected by the land use activities.
South Africa
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Ali-Adib, Tarif. "Estimation et lois de variation du coefficient de transfert de chaleur surface/ liquide en ébullition pour un liquide alimentaire dans un évaporateur à flot tombant." Phd thesis, AgroParisTech, 2008. http://pastel.archives-ouvertes.fr/pastel-00004544.
Повний текст джерелаАнотація:
Le coefficient de transfert de chaleur est nécessaire pour concevoir et dimensionner un évaporateur utilisé pour concentrer un liquide, tel que rencontré couramment dans les industries alimentaires. Le coefficient de transfert de chaleur le plus variable et le plus incertain est du coté produit, entre paroi et liquide, noté « h ». Il varie à la fois avec les propriétés thermo-physiques du liquide traité (ηL, σL, λL, ρL , CpL, ω, ...) et avec les paramètres du procédé (type d'évaporateur, φ ou Δθ, Γ (δ), P, rugosité de la surface, encrassement, etc), ces grandeurs étant définies dans le texte. Mais h est aussi lié au régime d'ébullition (nucléée ou non nucléée), et pour les évaporateurs de type « flot tombant », au régime d'écoulement laminaire ou turbulent, selon le nombre de Reynolds en film Ref. Nous avons étudié le cas des évaporateurs « à flot tombant », très utilisés dans les industries alimentaires pour concentrer le lait et les produits laitiers, les jus sucrés, les jus de fruits et légumes. L'objectif de notre travail était de définir une méthode fiable et économique pour évaluer a priori le coefficient de transfert de chaleur h coté liquide en ébullition, dans un évaporateur flot tombant. La première partie de la thèse a été consacrée à l'analyse bibliographique, qui a révélé une grande incertitude actuelle dans la prévision de h, sur la base des formules de la littérature, et des paramètres descripteurs proposés. La deuxième partie de la thèse a été de concevoir et construire un pilote utilisable pour estimer h, dans des conditions stationnaires connues et reproductibles. Dans la troisième partie, on présente les résultats et commente les lois de variations de h en fonction de la concentration de matière sèche du liquide XMS, de la température d'ébullition de liquide θL (ou P), du flux de chaleur φ ou (Δθ), et du débit massique de liquide par unité de périmètre de tube Γ, pour des propriétés de surface de chauffe fixées (ici, paroi en acier inoxydable poli Rs ≈ 0,8 μm). On commente l'effet sur h de chaque variable isolément, les autres étant maintenues constantes, ce qui confirme l'importance de la transition du régime non-nucléé au régime nucléé, cette transition variant avec la nature du liquide, sa concentration, et le flux de chaleur. On a montré la possibilité de modéliser un produit donné dans l'ensemble du domaine expérimental, où tous les paramètres peuvent varier simultanément, avec peu de coefficients, selon deux types d'équations (polynomiale et puissance). On a comparé le cas d'un liquide Newtonien (jus sucré) et non-Newtonien (solution de CMC dans l'eau). On a aussi observé le débit de mouillage critique Γcri et ses lois de variation. On a aussi démontré la possibilité de simplifier le plan d'expérience, aussi bien pour les liquides Newtoniens que non-Newtoniens, tout en gardant un coefficient de corrélation satisfaisant dans le domaine Γ > Γcri, cette modélisation pouvant servir de base de données produit pour l'ingénierie.
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Wang, Yu-Hsuan, and 王御軒. "Preliminary Study of Dual Loops LHP with Flat Evaporator." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/87967754299842194091.
Повний текст джерелаАнотація:
碩士淡江大學
機械與機電工程學系碩士班
97
This paper presented an preliminary study on a copper- methanol based Loop Heat Pipes(LHP) with a 82 mm long, 42mm wide and 10 mm thick flat rectangular evaporator. A novel concept to have dual vapor lines and liquid lines loops design from evaporator to condenser was devised to achieve higher vapor flow rate and reduce the heat leakage to compensation chamber. Thermal performance of loop heat pipe was evaluated experimentally in a fan-heat sink CPU test apparatus with heating area of 31mm x 31mm. After the evaluation, the LHP with 40% filling rate showed the lowest evaporator-to-ambient resistance of 0.83 K/W , corresponding to a heater temperature of 80 ℃ at an input power of 60 watts.
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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.
Повний текст джерелаАнотація:
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.
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Chen, Chung-Wei, and 陳仲威. "Visualization and Evaporation Resistance Measurement for Groove-Wick Evaporator of Operating Flat-Plate Heat Pipes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56864342489570572865.
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Wu, Cheng-Yu, and 吳昌瑀. "Effect of wick evaporation area on thermal performance for loop heat pipe with flat evaporator." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/09314070664185237929.
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碩士中華科技大學
飛機系統工程研究所在職專班
102
This study investigates the effects of increasing the evaporating area of wick in a Flat Loop Heat Pipe(FLHP). This work attempts to improve the performance of the FLHP by increasing the number of grooves and thereby the surface area of the wick. The number of grooves is increased from 0%(grooves 8) to 90%(grooves 16). Production results are limited that we cannot be successfully produced the wick structure of 16 grooves, so the thermal permormance of the test and wick parameters of testing only for grooves 8~14. Experimental results show that increasing the number of grooves not only increases the surface area of the wick but also enhances FLHP performance. When the evaporating surface area increases by 45%(grooves 12),which corresponds to increasing the number of grooves 8 to 14, We can get most of the heat transfer performance, also the heat transfer capacity increases to 260W and enhance the heat transfer performance about 30%. Wick permeability:13-20×〖10〗^(-13)(m^2)、pore size:3.1~3.7(μm)、porosity:60~66%. The rate of change of the wick is tiny,also good production within the range suggested in the literature. Produced by the simplicity and success rate, we recommend that the evaporation area is increased by 45%(grooves 12),thermal resistance is reduced to 0.2℃/W, The heat transfer raised to 260W, enhancethe heat transfer performance about 30%.
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YU, YEN-YI, and 游晏宜. "Design and discuss of the flat tubes and parallel flow evaporator." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/t8c67v.
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碩士國立中央大學
機械工程研究所
94
This project will discuss the flat tubes and parallel flow heat exchangers air-conditioner. The traditional round tube evaporator and condenser in an air-conditioner will be replaced by flat tube parallel flow evaporator. In this project not only design the flat tube parallel flow evaporator but also test the flat tube evaporator. The compressor, expansion valve and other components in the air-conditioner will also be modified according to the changes of heat transfer and pressure loss of the heat exchangers. This project will be performed by the cooperation with the TECO Electric and Machinery Co., Ltd. The ME department will design and test the flat tube evaporator and condenser and the TECO will take charge of other components. A compact, low noise and high performance air-conditioner will be developed in this project.
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GUN-NING, KUO, and 郭君寧. "Thermal Performance of a Loop Heat Pipe with a Flat Evaporator." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/38977099709502269606.
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碩士國立臺灣科技大學
機械工程系
92
The heat transfer characteristics of a loop heat pipe with flat-shaped evaporator was studied experimentally . Thermocouples were used to measure temperatures along the loop. Trends of steady-state operating temperature are presented and explained for two different tilt angles of the loop. Temperature hysteresis and low-power start-up problems were observed and discussed. The maximum heat transport capacity was up to 100W with a thermal resistance of 0.212℃/W and an operating temperature around 60℃.
Книги з теми "Flat Evaporator"
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Spahr, Norman E. Estimation of evaporation from Ned Wilson Lake, Flat Tops Wilderness Area, Colorado. Lakewood, Colo: U.S. Dept. of the Interior, Geological Survey, 1985.
Знайти повний текст джерелаЧастини книг з теми "Flat Evaporator"
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Terekhov, Viktor I., and Maksim A. Pakhomov. "Laminar Mist Flows Over a Flat Plate with Evaporation." In Flow and Heat and Mass Transfer in Laminar and Turbulent Mist Gas-Droplets Stream over a Flat Plate, 9–11. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04453-8_2.
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Adelung, Rainer, Rainer Kunz, Frank Ernst, Lutz Kipp, and Michael Skibowski. "Self-Organized Structures on Flat Crystals: Nanowire Networks Formed by Metal Evaporation." In Advances in Solid State Physics, 463–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-44838-9_33.
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Ong, Yen Chin. "Hiscock and Weems: Modeling the Hawking Evaporation of Asymptotically Flat Charged Black Holes." In Evolution of Black Holes in Anti-de Sitter Spacetime and the Firewall Controversy, 101–19. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-48270-4_4.
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Ionascu, Georgeta, Lucian Bogatu, Tudor Catalin Apostolescu, Elena Manea, and Edgar Moraru. "Research on Distribution of the Condensed Substance on a Flat Support and Obtaining Vacuum Evaporation Thin Films with Uniform Thickness by Correction Masks." In Lecture Notes in Networks and Systems, 328–44. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-40628-7_28.
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"Experimental Investigation of Miniature Loop Heat Pipe with Flat Evaporator." In Inaugural US-EU-China Thermophysics Conference-Renewable Energy 2009 (UECTC 2009 Proceedings), 1–5. ASME Press, 2009. http://dx.doi.org/10.1115/1.802908.paper126.
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McElroy, Michael B. "Hydro: Power From Running Water." In Energy and Climate. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190490331.003.0016.
Повний текст джерелаАнотація:
As discussed in Chapter 4 and illustrated in Figure 4.1, close to 50% of the solar energy intercepted by the Earth is absorbed at the surface. Approximately half of this energy, 78 W m– 2, is used to evaporate water, mainly from the ocean. What this means is that evaporation of water accounts for as much as a third of the total solar energy absorbed by the Earth (atmosphere plus surface). The atmosphere has a limited ability to retain this water. Evaporation is balanced in close to real time by precipitation. A portion of this precipitation reaches the surface in regions elevated with respect to sea level— in mountainous locations, for example. It is endowed in this case with what we refer to as potential energy (Chapter 4). This potential energy can be stored (in lakes or dams, for instance), or it can be released, converted to kinetic energy (directed motion) as the water flows downhill on its return to the ocean. And along the way, energy can be captured and channeled to perform useful work. An early application involved exploiting the power of running water to turn a flat stone, one of two that constituted the apparatus used to grind grain, the other remaining stationary during the grinding process. The Domesday Book records that by AD 1086 as many as 5,624 water mills were operational in England south of the River Trent, deployed not just to grind grain but for a multitude of other tasks, including, but not confined to, sawing wood, crushing ore, and pumping the bellows of industrial furnaces (Derry and Williams 1960). Later, running water would provide the motive force for the textile industry that marked the beginning of the industrial age in North America, specifically in New England (Steinberg 1991; McElroy 2010). The most important contemporary application of water power involves the generation of electricity, the bulk of which is obtained by tapping the potential energy stored in high- altitude dams, a lesser fraction from the kinetic energy supplied by free- flowing streams (what is referred to as run- of- the- river sources).
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Hasan Hamood Al-Masoodi, Abtisam, Boon Tong Goh, Ahmed H.H. Al-Masoodi, and Wan Haliza Binti Abd Majid. "Deposition of Silver Nanoparticles on Indium Tin Oxide Substrates by Plasma-Assisted Hot-Filament Evaporation." In Thin Films [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94456.
Повний текст джерелаАнотація:
Nanoparticles of noble metals have unique properties including large surface energies, surface plasmon excitation, quantum confinement effect, and high electron accumulation. Among these nanoparticles, silver (Ag) nanoparticles have strong responses in visible light region due to its high plasmon excitation. These unique properties depend on the size, shape, interparticle separation and surrounded medium of Ag nanoparticles. Indium tin oxide (ITO) is widely used as an electrode for flat panel devices in such as electronic, optoelectronic and sensing applications. Nowadays, Ag nanoparticles were deposited on ITO to improve their optical and electrical properties. Plasma-assisted hot-filament evaporation (PAHFE) technique produced high-density of crystalline Ag nanoparticles with controlling in the size and distribution on ITO surface. In this chapter, we will discuss about the PAHFE technique for the deposition of Ag nanoparticles on ITO and influences of the experimental parameters on the physical and optical properties, and electronic structure of the deposited Ag nanoparticles on ITO.
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Ramos, Jorge, and Rubén Rodriguez Puertas. "Deactivated Saltpans." In Cases on Traveler Preferences, Attitudes, and Behaviors, 54–72. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-6919-4.ch003.
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In coastal areas, there are economic activities that have been established for some time now – decades or even centuries – which help to maintain not only the local economy, but also to achieve a balanced relationships with nature. Tourism and leisure activities benefit from this balance. Sometimes, due to disturbing causes, these balances are destabilized, which generates setbacks. For example, in Salinas de Cabo de Gata (Almeria, Spain), heavy rains in the spring of 2022 caused an obstruction in the channel that carries seawater to the wetland located there. This occurrence caused a desiccation of the area that is dramatically affecting the waterfowl that depended on the evaporators of the salt flats. The involvement of different interested parties put pressure on to resolve the problem, which however was technically resolved, but whose results in a broad sense are gradual. In this chapter, this case study is explored in more detail.
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Dunne, Thomas, and Leal Anne Kerry Mertes. "Rivers." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0012.
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River basins and river characteristics are controlled in part by their tectonic setting, in part by climate, and increasingly by human activity. River basins are defined by the tectonic and topographic features of a continent, which determine the general pattern of water drainage. If a major river drains to the ocean, its mouth is usually fixed by some enduring geologic structure, such as a graben, a downwarp, or a suture between two crustal blocks. The largest river basins constitute drainage areas of extensive low-lying portions of Earth’s crust, often involving tectonic downwarps. The magnitude of river flow is determined by the balance between precipitation and evaporation, summed over the drainage area. Seasonality of flow and water storage within any basin are determined by the seasonality of precipitation in excess of evaporation, modified in some regions by water stored in snow packs and released by melting, and by water stored in wetlands, lakes, and reservoirs. Increasingly the flows of rivers are influenced by human land use and engineering works, including dams, but in South America these anthropogenic influences are generally less intense and widespread than in North America, Europe, and much of Asia. Thus the major rivers of South America can be viewed in the context of global and regional tectonics and climatology. For reference, figure 5.1 outlines South America’s three largest river basins—the Orinoco, Amazon, and Paraguay-Paraná systems—while figure 5.2 shows the locations of rivers referred to in the text against a background of the continent’s density of population per square kilometer. The geologic history of South America has bequeathed to the continent a number of structural elements that are relevant to the form and behavior of its three major river systems. These structural elements are (1) the Andes; (2) a series of foreland basins, approximately 500 km wide immediately east of the Andes and extending southward from the mouth of the Orinoco to the Chaco-Paraná basin, where the crust is depressed by the weight of the Andes and the sediment derived from the mountains; (3) the Guiana and Brazilian shields reflecting Precambrian cratons and orogenic belts of mostly crystalline metamorphic rocks, partly covered with flat-lying sedimentary rocks and deeply weathered regolith; and (4) the Central Amazon Basin, a large cratonic downwarp with some graben structures dating back to early Paleozoic time, which runs generally east-west between the two shields, connecting the foreland basins to the west with a graben that localizes the Amazon estuary at the Atlantic coast.
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Roiaz, Matteo, Paolo Scialla, Fabrizio Cadenaro, Marco Nardo, and Gabriele Sancin. "Classifying the Innovation: The Certification of New Designs for Power Generation, Conversion and Energy Storage Focusing on the Reduction of Ships Emissions." In Progress in Marine Science and Technology. IOS Press, 2022. http://dx.doi.org/10.3233/pmst220033.
Повний текст джерелаАнотація:
In recent times the ship building and yacht industries have seen a surge in the requests for the application to the power generation, conversion and energy storage of technologies which were previously reserved to land-based uses or to niche sectors such as space, military, and scientific research. Such requests are often driven by seeking cleaner exhaust emissions, more efficient fuel consumption and higher passenger and crew comfort. Among these novel technologies we can mention fuel cells and (large) batteries based on Li-ion chemistries. These solutions are not only unconventional per se, they also carry along the necessity for advanced electrical system integration (even more so if combined in a hybrid architecture) or, for fuel cells, the need for the storage of dedicated fuels, e.g., liquid, or compressed hydrogen or methanol, and fuel treatment, e.g., evaporators and chemical reformers. The lack of prescriptive regulations covering such innovative solutions, both in terms of equipment and fuel, adds in challenge to their acceptance and certification from Regulatory Bodies and Flag Administrations. Furthermore, although high-level guidelines are provided, they often need to be tailored on a case-by-case basis and integrated with risk assessment exercises. The aim of this work is to give a comprehensive overview of the Classification tools available to date – be it prescriptive or risk-based – for the approval of novel designs and how do they relate to the existing statutory guidelines and to the established risk analysis instruments. The discussion will be corroborated by insights into some hands-on case studies in the yacht and cruise ship industry segments.
Тези доповідей конференцій з теми "Flat Evaporator"
1
Yun, James, Ed Kroliczek, John Cennamo, Sukhvinder Kang, and Walter Zimbeck. "Flat Plate Evaporator for Electronic Cooling." In 6th International Energy Conversion Engineering Conference (IECEC). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-5670.
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Singh, Randeep, Aliakbar Akbarzadeh, Masataka Mochizuki, Thang Nguyen, and Vijit Wuttijumnong. "Experimental Investigation of the Miniature Loop Heat Pipe With Flat Evaporator." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73498.
Повний текст джерелаАнотація:
Loop heat pipe (LHP) is a very versatile heat transfer device that uses capillary forces developed in the wick structure and latent heat of evaporation of the working fluid to carry high heat loads over considerable distances. Robust behaviour and temperature control capabilities of this device has enable it to score an edge over the traditional heat pipes. In the past, LHPs has been invariably assessed for electronic cooling at large scale. As the size of the thermal footprint and available space is going down drastically, miniature size of the LHP has to be developed. In this paper, results of the investigation on the miniature LHP (mLHP) for thermal control of electronic devices with heat dissipation capacity of up to 70 W have been discussed. Copper mLHP with disk-shaped flat evaporator 30 mm in diameter and 10 mm thickness was developed. Flat evaporators are easy to attach to the heat source without any need of cylinder-plane-reducer saddle that creates additional thermal resistance in the case of cylindrical evaporators. Wick structure made from sintered nickel powder with pore size of 3–5 μm was able to provide adequate capillary forces for the continuos circulation of the working fluid, and successfully transport heat load at the required distance of 60 mm. Heat was transferred using 3 mm ID copper tube with vapour and liquid lines of 60 mm and 200 mm length respectively. mLHP showed very reliable start up at different heat loads and was able to achieve steady state without any symptoms of wick dry-out. Tests were conducted on the mLHP with evaporator and condenser at the same level. Total thermal resistance, R total of the mLHP came out to be in the range of 1–4°C/W. It is concluded from the outcomes of the investigation that mLHP with flat evaporator can be effectively used for the thermal control of the electronic equipments with restricted space and high heat flux chipsets.
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Chien, Liang-Han, and Y. C. Shih. "Thermal Characters of Mesh Structure in a Flat Heat Pipe." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35095.
Повний текст джерелаАнотація:
In this study plate type heat pipes having mesh capillaries were investigated experimentally and theoretically. A test apparatus was designed to test thermal performance of plate type copper-water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5-to-50 W heat input. The working fluid, water is charged with 25% or 33% volume of the heat pipe internal space. In addition to horizontal orientation, the heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances of the heat pipe were calculated separated. The effects of mesh size, charge volume, and inclination angle on each thermal resistance were discussed. In general, the #80 mesh yields lower thermal resistances than the #50 mesh; inclination angle has more significant effect on condenser than evaporator. Theoretical models of evaporation and condensation in flat heat pipes were proposed to interpolate the experimental results. The present evaporation model predicts the experimental data of evaporation resistance between −20% and +30%, and the condensation model predicts most condensation resistance data within ±30%.
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Conroy, C., Robert Mahorter, John Savchik, Triem Hoang, Tamara O'Connell, and John Rosenfeld. "Multiple Flat Plate Evaporator Loop Heat Pipe Demonstration." In 1st International Energy Conversion Engineering Conference (IECEC). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-6047.
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Zimbeck, Walter, Jared Chaney, Patricio Espinoza, Edward Kroliczek, David C. Bugby, and James Yun. "Ceramic Flat Plate Evaporator for Loop Heat Pipe Cooling of Electronics." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73124.
Повний текст джерелаАнотація:
Two-phase loops are extremely efficient devices for passively transporting heat over long distances with low temperature drop. The heat acquisition component of a two-phase loop, the evaporator, is commonly made from conventional metal materials (aluminum, copper, etc.) and has cylindrical geometry. Neither characteristic is optimally suited for close integration to common electronic or photonic heat sources, which generally have flat interfaces and are constructed from low thermal expansion coefficient (CTE) semiconductor materials. This paper describes the development of a ceramic flat plate evaporator for cooling processor chips in network computers used onboard Navy submarines. The unique requirements of submarines give added motivation for the advantages offered by two-phase loops. The ceramic flat plate evaporator is constructed of low CTE, high thermal conductivity material and thus enables a low thermal resistance interface between the heat source and the working fluid of the loop heat pipe. Alumina and aluminum nitride flat plate evaporators were integrated into a water-based two-phase loop and thermally tested to a heat flux of 30 W/cm2.
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Shikazono, Naoki, Yasushi Suehisa, Nobuhide Kasagi, and Hiroshi Iwata. "Modeling and Design of Micro-Grooved Flat Plate Evaporator." In ASME 3rd International Conference on Microchannels and Minichannels. ASMEDC, 2005. http://dx.doi.org/10.1115/icmm2005-75141.
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A micro-grooved flat plate evaporator is modeled and its heat transfer characteristics are investigated numerically and experimentally. A test model is developed for the vapor compression cycle evaporator, where pressure gradient drives the vapor and the liquid flow. In this study, the effect of pressure gradient is implicitly introduced through the Smith’s equation for predicting void fraction from given quality. The film thickness profile in the micro region near the contact line is obtained by solving the 4th order differential equation. Then the local heat flux is obtained by assuming that the heat conduction through the liquid is one dimensional in the wall normal direction. The shape of liquid-vapor interface is assumed to be a circular arc in the macro region, whose radius is directly linked to the void fraction. This curvature radius is used as the boundary condition for the micro region model at the micro-macro interface. Finally, the heat transfer coefficient on a micro-grooved flat plate evaporator is measured in a HFC134a experimental loop and compared with the numerical prediction. The present model assumptions are validated and assessed.
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Yarmak, Jr., Edward. "Analyzing the Performance of a Flat-Loop Evaporator Thermosyphon." In 10th International Symposium on Cold Regions Development. Reston, VA: American Society of Civil Engineers, 2013. http://dx.doi.org/10.1061/9780784412978.062.
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Riehl, Roger R., and Nadjara dos Santos. "Thermal Characteristics of a Flat Evaporator Miniature Loop Heat Pipe." In International Conference On Environmental Systems. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2007. http://dx.doi.org/10.4271/2007-01-3195.
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Gurudatt, H. M., G. S. V. L. Narasimham, and B. Sadashive Gowda. "Performance of Flat-Tube Louvered-Fin Automotive Evaporator With R1234yf." In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-94116.
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Abstract Following the Kyoto Protocol and the more recent Kigali agreement, Hydrofluoroolefins (HFOs) are considered as the low global warming drop-in or substitute refrigerants for hydrofluorocarbons (HFCs) which have high global warming potential. The HFO R1234yf gained significant importance as a replacement for R134a in automobile air conditioning. In this context, the performance of a two-slab automotive evaporator with R1234yf numerical simulation is reported in this paper. The simulation is conducted by considering the heat transfer from air to the outside wetted surface consisting of louvered fins and tube wall, from there to the inside tube wall, and from there to the bulk of the boiling refrigerant inside the tube. The combined effect of heat and mass transfer from air to the wetted surface is described by the enthalpy potential method. For the two-phase and superheating regions suitable heat transfer correlations are employed. The results show that the refrigerant side heat transfer coefficient increases with increase in vapour quality up to around 80% and then decreases with further increase in the vapour quality. The major contribution to the cooling capacity is the latent heat abstraction during the flow boiling process occurring inside the tube. The temperatures of the condensate water film surface and the inner and outer tube wall surfaces are nearer to the bulk temperature of the refrigerant because of the high heat transfer coefficient on the refrigerant side. Results are also presented for the refrigerant side pressure drop and the evaporator exit air temperature and humidity ratio.
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Khan, Tariq Amin, Wei Li, Yan Xiaolong, and Zhuo Yang. "Experimental Study on the Thermal-Hydraulic Performance of Louvered Fin and Flat Tube Heat Exchangers." In ASME 2020 Heat Transfer Summer Conference collocated with the ASME 2020 Fluids Engineering Division Summer Meeting and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ht2020-8990.
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Abstract In this study, the air side heat transfer and pressure drop characteristics of flat tube with louvered fins compact heat exchangers have been experimentally investigated. Three samples of heat exchangers, i.e., one without fins, one with flat louver fins and one with corrugated louver fins are studied. The louvers in the present samples have small louver pitch (Lp = 0.8mm) and high louver angle (θl = 37°) due to the space constraints in automotive applications. The performance tests were conducted in a high standard test facility which are composed of an evaporator chamber, condenser chamber and auxiliary units. In our study, only evaporators are tested and hence the condenser section is the same during the tests. Experimental results under the wet surface conditions show that the cooling capacity and pressure drop performances of evaporator with flat louver fins (HX2) is higher than the one with corrugated louver fins (HX3) while the evaporator without fins has the minimum heat transfer due to no interruptions. This can be due to higher number of tubes in the case of HX2 having small tube pitch. However, the overall performance (ratio of heat transfer per unit volume to pressure drop per unit volume) of HX2 is better than HX3 which signifies the importance of corrugated louver fins.
Звіти організацій з теми "Flat Evaporator"
1
M. Cerza, R.C. Herron, and J.J. Harper. The Effect of Sink Temperature on a Capillary Pumped Loop Employing a Flat Evaporator and Shell and Tube Condenser. Office of Scientific and Technical Information (OSTI), June 2002. http://dx.doi.org/10.2172/821698.
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2
Estimation of evaporation from Ned Wilson Lake, Flat Tops Wilderness Area, Colorado. US Geological Survey, 1985. http://dx.doi.org/10.3133/wri854244.
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