Sintered Nickel Powder Wicks for Flat Vertical Heat Pipes

Hansen, Geir Karsten; Næss, Erling; Kristjansson, Kolbeinn Jakob

doi:10.3390/en8042337

Cited by 15 publications

(9 citation statements)

References 18 publications

(44 reference statements)

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“…The decrease in the graphite content for the specimen treated at 700 °C for 60 min as compared with reference and the sample treated at 600 °C can be observed. This can be explained by the graphite oxidation with CO 2 /CO generation, a process that occurs between 600–800 °C for graphite powder with particle sizes smaller than 20 microns [ 24 ].…”

Section: Resultsmentioning

confidence: 99%

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials

2022

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Fireproof inorganic coatings based on sodium silicate solution with intumescent additions were prepared and tested to assess their ability to limit the negative effect of a fire. The intumescent materials were obtained by the alkali activation of waste glass powder (obtained by the grinding of recycled soda-lime culet) and slag (waste resulting from the metallurgical industry). The replacement of talc (used as filler in paint formulation) with the intumescent materials obtained by the alkaline activation of waste glass powder (WGP), determined an increase in the intumescence coefficient (up to 65%) and decreased the activation temperature of this process. To evaluate these coatings’ abilities to prevent or delay the temperature increase in metal structures, the paints were applied on steel plates and tested in direct contact with the flame of a butane burner for 60 min. The coatings prevented the increase in the steel substrate temperature over one considered critical (500°C) for steel mechanical properties; the combination of two coatings, with different intumescence activation temperatures, correlated with the increase in the coating’s thickness, sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate.

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Section: Resultsmentioning

confidence: 99%

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials

2022

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“…Besides developing new capillary structures with new techniques and new materials, a strong challenge is to determine the properties of existing capillary structures and to develop predictive tools that can be used in heat pipe models. The measurement of the permeability of a porous medium can be performed easily (Ameli et al, 2013;Hansen et al, 2015). However, the effective permeability of the capillary structure inside a heat pipe may be different from the bulk permeability of the medium because of the influence of the liquid-vapour interface.…”

Section: Capillary Structure Characterisationmentioning

confidence: 99%

Overview of Heat Pipe Studies During the Period 2010-2015

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et al. 2016

Interfac Phenom Heat Transfer

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Despite the numerous studies on heat pipes over the last fifty years, the development of predictive tools for the design of heat pipes remains challenging, even for conventional technologies. As a result, heat pipes are still the object of more than 250 scientific articles a year. The present review aims to identify and understand the current scientific approaches followed by scientists in heat pipe science. The different types of heat pipe are reviewed in order to identify the main phenomena involved in these systems. A brief overview of the heat pipe history is given and the different applications are presented. A global review of the recent studies on heat pipes is then presented. Advances are identified in terms of heat pipe characterisation, scientific issues linked to the working fluid, understanding of phase-change heat transfer in thin liquid films and system modelling. Examples of recent works are detailed to highlight the strategies that can be followed to answer the current issues. This global review enables to highlight the main advances on heat pipe science of the last five years and to draw perspectives on the forthcoming scientific results.

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“…In the vapor static pressure-limited range the capillary pressure term (2σ/r e f f ) in Equation (5) is replaced by the vapor pressure of the working fluid [21].…”

Section: Wick Performancementioning

confidence: 99%

“…Metals are the dominating envelope and wick materials, but high temperature wickless heat pipes (thermosyphons) of ceramic material are also being developed; results from promising experiments with sodium and zinc as working fluids were reported recently [20]. Nickel is compatible with potassium [4], but starts oxidizing rapidly at about 350˝C [21] and a protective/reducing gas atmosphere of 5 %(v) H 2 , 95 %(v) Ar is therefore often used during the heat treatments and preparations of the nickel wicks and heat pipe envelopes. Stainless steel 304 is also reported to be compatible with potassium [4], and may be a more economical choice than nickel for heat pipes for industrial applications.…”

Section: Introductionmentioning

confidence: 99%

Analysis of a Vertical Flat Heat Pipe Using Potassium Working Fluid and a Wick of Compressed Nickel Foam

2016

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Heat at high temperatures, in this work 400-650˝C, can be recovered by use of cooling panels/heat pipes in the walls of aluminum electrolysis cells. For this application a flat vertical heat pipe for heat transfer from a unilateral heat source was analyzed theoretically and in the laboratory, with special emphasis on the performance of the wick. In this heat pipe a wick of compressed nickel foam covered only the evaporator surface, and potassium was used as the working fluid. The magnitudes of key thermal resistances were estimated analytically and compared. Operating temperatures and wick performance limits obtained experimentally were compared to predictions. Thermal deformation due to unilateral heat flux was analyzed by the use of COMSOL Multiphysics ® . The consequences of hot spots at different locations on the wick were analyzed by use of a numerical 2D model. A vertical rectangular wick was shown to be most vulnerable to hot spots at the upper corners.

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Sintered Nickel Powder Wicks for Flat Vertical Heat Pipes

Cited by 15 publications

References 18 publications

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials

Overview of Heat Pipe Studies During the Period 2010-2015

Analysis of a Vertical Flat Heat Pipe Using Potassium Working Fluid and a Wick of Compressed Nickel Foam

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