Experimental research of capillary structure technologies for heat pipes

Krambeck, Larissa; Bartmeyer, Guilherme Antonio; Fusão, Davi; Santos, Paulo Henrique Dias Dos; Alves, Thiago Antonini

doi:10.4025/actascitechnol.v42i1.48189

Cited by 7 publications

(7 citation statements)

References 28 publications

(29 reference statements)

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“…Thermosyphons, in general, have three distinct regions: evaporator, adiabatic section, and condenser [10]. In the evaporator, the heat is transferred from an external source to working fluid, which boils, and the steam rises afterward [11]. The adiabatic section is the section in which twophase flow is observed.…”

Section: Methodsmentioning

confidence: 99%

Experimental study of hydrodynamic parameters regarding on geyser boiling phenomenon in glass thermosyphon using wire-mesh sensor

et al. 2022

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The thermosyphon is a type of heat exchanger that has been widely used in many applications. The use of thermosyphons has been intensified in recent years, mainly in the manufacture of solar collectors and various industrial activities. A thermosyphon is a vertical sealed tube filled with a working fluid, consisting of, from bottom to top, by an evaporator, an adiabatic section, and a condenser. The study of geyser-boiling phenomena, which occurs inside the thermosyphon is of extreme importance, therefore the experimental analysis of the parameters related to the two-phase flow (liquid-steam), such as void fraction, bubble frequency, bubble velocity, and bubble length are necessary, since these parameters have a significant influence on heat transfer. In this work, a pair of wire mesh sensors was used, a relative innovative technology to obtain experimental values of the reported quantities for measuring these parameters of slug flow in thermosyphons. An experimental setup is assembled and the sensors are coupled to the thermosyphon enabling the development of the experimental procedure. Here is presented an experimental study of a glass thermosyphon instrumented with two Wire-Mesh Sensors, in which the aforementioned slug flow hydrodynamic parameters inherent to the geyser type boiling process are measured. It was measured successfully, as a function of the heat load (110, 120, 130, 140, and 150W), the void fraction (instantly and average), liquid film thickness, translation velocity of the elongated bubbles, lengths of the bubbles, and the liquid slug (displaced by the bubble rise up). It was observed that the higher the heat load, the lower is the bubble translation velocity. For all heat loads, based on the measured length of liquid slug (consequent displacement of liquid volume), caused by bubbles rise from evaporator to condenser, it could be affirmed to some extent that both boiling regime (pool and film) exist in the evaporator. The measured average void fraction (80%) and liquid film thickness (around 2.5mm) during the elongated bubble passages were approximately constant and independent of the heat load.

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Section: Methodsmentioning

confidence: 99%

Experimental study of hydrodynamic parameters regarding on geyser boiling phenomenon in glass thermosyphon using wire-mesh sensor

et al. 2022

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“…Os termossifões também são utilizados em coletores solares a vácuo, altamente eficazes e aplicáveis no aquecimento de água para uso diário, ambientes e também piscinas. Outra área de aplicação é a secagem e desidratação de produtos alimentícios e tecidos, além do resfriamento eletroeletrônico (KRAMBECK et al, 2020(KRAMBECK et al, , 2021NISHIDA et al, 2020).…”

Section: Termossifõesunclassified

Seleção de termossifões para aplicação em um sistema híbrido fotovoltaico/térmico

Machado

Dimbarre

et al. 2021

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Neste trabalho foi realizada uma análise térmica experimental de termossifões distintos para aplicação em um sistema híbrido fotovoltaico/térmico. Os termossifões foram fabricados a partir de tubos de cobre possuindo comprimento total de 840mm. O fluido de trabalho utilizado foi água destilada com razão de preenchimento de 50% do volume do evaporador. O evaporador tem comprimento de 650mm, enquanto a seção adiabática e o condensador têm comprimentos de 80mm e 110mm, respectivamente. O condensador foi resfriado por convecção forçada de água, a seção adiabática foi isolada e o evaporador foi aquecido por um resistor elétrico. Testes experimentais foram realizados para uma carga térmica de 80W a 140W em uma posição a 25° da horizontal (evaporador acima do condensador). A análise térmica foi baseada na distribuição de temperaturas ao longo dos dispositivos passivos de transferência de calor, sua resistência térmica e eficiência térmica. O Termossifão B, que possui maior diâmetro, apresentou melhores resultados nas condições testadas, se mostrando assim a melhor escolha entre os dois termossifões para compor um sistema híbrido fotovoltaico/térmico.

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“…In the condenser, the heat absorbed in the evaporator and transported by the steam is dissipated to the external environment, causing the condensation of this steam. When condensing, due to the action of gravity, the working fluid in liquid form flows through the walls of the tube, returning to the evaporator region, completing the thermodynamic cycle [8].…”

Section: Figure 1 Etsc Tubementioning

confidence: 99%

Thermal Performance of Thermosyphons Intended for Evacuated Tube Solar Collector Using Graphene Oxide Nanofluids

Alves¹

2021

JANSET

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Vacuum tube solar collectors are composed by two concentric glass tubes with the annular space evacuated. At the inner tube a thermosyphon is placed inside a metallic fin in order to absorb sun’s irradiation and heat running water placed at a manifold. Thermosyphons are passive heat transfer devices that absorb heat at the evaporator region, evaporating the working fluid that reaches the condenser in the form of steam. At the condenser, heat is dissipated to the environment, condensing the working fluid that returns to the evaporator, closing the thermodynamic cycle. In this study, thermosyphons with three different working fluids (5 and 10% graphene oxide nanofluids and distilled water) were built and experimentally tested. The evaporator and the adiabatic section have an outer diameter of 8.33mm and lengths of 1,600mm and 40mm, respectively. The condenser has an outer diameter of 13.40mm and a length of 35mm. The filling ratio used was 50% of the evaporator’s volume. A resistive tape wrapped at the evaporator and connected to a power supply was responsible for heating the working fluid by Joule effect, and water flow rates of 0.50, 0.75, and 1.00L/min were responsible for condensing the working fluid at the condenser. Heat loads of 35, 55, and 75W were applied to the devices and K-type thermocouples were responsible for acquiring temperature data from the thermosyphons, allowing the thermal analysis based in the temperature distribution and thermal resistance for each working fluid. The best working fluid for the conditions proposed, out of the three investigated, was 5% graphene oxide.

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Experimental research of capillary structure technologies for heat pipes

Cited by 7 publications

References 28 publications

Experimental study of hydrodynamic parameters regarding on geyser boiling phenomenon in glass thermosyphon using wire-mesh sensor

Experimental study of hydrodynamic parameters regarding on geyser boiling phenomenon in glass thermosyphon using wire-mesh sensor

Seleção de termossifões para aplicação em um sistema híbrido fotovoltaico/térmico

Thermal Performance of Thermosyphons Intended for Evacuated Tube Solar Collector Using Graphene Oxide Nanofluids

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