Experimental evidence of a new regime for boiling of water at subatmospheric pressure

Giraud, Florine; Rullière, Romuald; Toublanc, Cyril; Clausse, Marc; Bonjour, Jocelyn

doi:10.1016/j.expthermflusci.2014.07.011

Cited by 64 publications

(31 citation statements)

References 14 publications

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“…Vapour bubbles start to nucleate at the solid-liquid interface according to the surface tension. Formation of gas bubbles is favoured when the surface tension increases as the atmospheric pressure and temperature of the liquid-gas interface decrease (Cengel & Ghajar 2014;Giraud et al 2015). Surface roughness also favours bubble formation, because it creates nucleation sites required for bubble initiation.…”

Section: Stability Of Liquid Water At the Surface Of Marsmentioning

confidence: 99%

“…At 278 K we observe limited production of small-sized pellets while at T s = 297 K we observe greater numbers of large-sized pellets with the lifting of the pellets and sliding over the surface with reduced surface friction. The capacity for pellets to slide may be giving us insight into the different boiling regimes being experienced with changes in excess temperature (Cengel & Ghajar 2014;Giraud et al 2015;Liang & Mudawar 2017). We think that experiments at sand temperatures of 278 K (ΔT excess ≈ 3 K) are experiencing a different boiling regime, probably a nucleate boiling regime, compared with those at temperature of 297 K (ΔT excess ≈ 22 K) for which the behaviour appears to be closer to a film boiling regime with the related Leidenfrost effect (Cengel & Ghajar 2014;Liang & Mudawar 2017).…”

Section: Sediment Transport Mechanisms By Boiling Watermentioning

confidence: 99%

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Downslope sediment transport by boiling liquid water under Mars-like conditions: experiments and potential implications for Martian gullies

Herny

Conway

Raack

et al. 2018

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Gullies are widespread morphological features on Mars for which current changes have been observed. Liquid water has been one of the potential mechanisms to explain their formation and activity. However, under present-day Martian conditions, liquid water is unstable and should only be transiently present in small amounts at the surface. Yet little attention has been paid to the mechanisms by which unstable water transports sediment under low atmospheric pressure. Here we present the results of laboratory experiments studying the interaction between liquid water flowing over a sand bed under Mars-like atmospheric pressure (c. 9 mbar). The experiments were performed in a Mars Simulation Chamber (at the Open University, UK), in which we placed a test bed of fine sand at a 25°slope. We chose to investigate the influence of two parameters: the temperature of the water and the temperature of the sand. We performed 27 experiments with nine different combinations of water and sand temperatures ranging from 278 to 297 K. Under all experimental conditions, the water was boiling. We investigated and compared the types and timing of sediment transport events, and the shapes, characteristics and volumes of the resulting morphologies. In agreement with previous laboratory studies we found that more intense boiling increased the volume of sediment transported for a given volume of water. We found four main types of sediment transport: entrainment by overland flow; grain ejection; grain avalanches; and levitation of saturated sand pellets. Our results showed that increasing sand temperature was the main driving parameter in increasing the sand transport and in modifying the dominant sediment transport mechanism. The temperature of the water played a negligible or minor role, apart from the duration of sand ejection and avalanches, which lasted longer at low water temperature. At low sand temperature the majority of the sand was transported by overland flow of the liquid water. At higher sand temperatures the transport was dominated by processes triggered by the boiling behaviour of the water. At the highest temperatures, sediment transport was dominated by the formation of levitating pellets, dry avalanches and ejection of the sand grains. This resulted in a transport volume about nine times greater at a sand temperature of 297 K compared with 278 K. Our heat transfer scaling shows that the boiling behaviour will be enhanced under Martian low gravity, resulting in more efficient transport of sediment by levitating sand pellets even at temperatures close to the triple point. Our results showed that the boiling intensity played an important role in the physics of sediment transport by liquid water. This implied that the amount of water required to produce morphological changes at the surface of Mars could be lower than previously estimated by assuming stable liquid water. Boiling is a critical process to be considered when assessing gully formation and modification mechanisms mobilized by liquid water. Our work could ha...

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Section: Stability Of Liquid Water At the Surface Of Marsmentioning

confidence: 99%

Section: Sediment Transport Mechanisms By Boiling Watermentioning

confidence: 99%

Downslope sediment transport by boiling liquid water under Mars-like conditions: experiments and potential implications for Martian gullies

Herny

Conway

Raack

et al. 2018

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“…It is widely acknowledged in the literature that boiling heat transfer strongly depends on the nucleation site density, and bubble departure size and frequency. Large bubbles generated from a given area reduce the heat transfer efficiency due to the reduction of growth rate and emission frequency (Giraud et al, 2014).…”

Section: 1 Heat Transfer Ratesmentioning

confidence: 99%

Heat transfer enhancement of a loop thermosyphon with a hydrophobic spot-coated surface

Shen

Chen

et al. 2018

JTST

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Heat transfer characteristic of a closed two-phase thermosyphon with enhanced boiling surface is studied and compared with that of a copper mirror surface. Two-phase cooling is widely used in application of thermal engineering and considerably more efficient than single-phase liquid cooling. The evaporator surfaces, coated with a pattern of hydrophobic circular spots (0.5 -2 mm in diameter and 1.5 -3 mm in pitch) on Cu substrates, achieve very high heat transfer coefficient and low incipience temperature overshoot with water as working fluid. Sub-atmospheric boiling on the hydrophobic spot-coated surface shows a much better heat transfer performance. Tests under heat loads 30 W to 260 W reveal the coated surfaces enhance nucleate boiling performance by increasing the bubbles nucleation-site density. The surface with hydrophobic spots with diameter 1 mm and pitch 1.5 mm achieves the maximal heat transfer enhancement with the minimum boiling thermal resistance as low as 0.03 K/W. A comparison of three evaporator surfaces with identical wettability patterns but with different surface topographies and coating thicknesses is carried out experimentally. The results show superior heat transfer rates and wear resistance on the surface coated with HNTs spots thanks to the large contact angle, great thickness, and durability of the coating layer. He, Shen, Chen, Hidaka, Takahashi, Kohno and Takata, Journal of Thermal Science and Technology, Vol.13, No.1 (2018) wettability with the contact angle close to 0 o after being exposed to UV light for several hours. Sarwar et al. (2007) performed a sub-cooled flow boiling experiment with microporous TiO2 and Al2O3 surfaces to enhance CHF by 20% to 25% compared to a smooth one. They found that microporous Al2O3 surface had high wettability, which led to water moving in pores easily. Chang et al. (1997) also demonstrated CHF enhancement on DOA (Diamond particles, Omegabomd 101 epoxy, and alcohol)-coated surfaces with different particle sizes. Significant CHF increase was achieved, which delayed the onset of film boiling effectively. Furthermore, nanoparticle deposition was found to be an advanced method to modify the surface wettability significantly and in turn to improve CHF. Forrest et al. (2010) developed a PAH/SiO2 (poly, allylamine, and hydrochloride) nanoparticle coating, whose application on a nickel wire in a boiling experiment brought about surface wettability change that led to 100% enhancement of CHF. Nanoparticle coatings of Al2O3-water/ethanol was studied in pool boiling experiments by Kwark et al. (2010). They found a strong relationship between quasi-static contact angle and CHF. That is, with increasing wettability, CHF increased gradually.Prior studies have demonstrated how to enhance the performance of HTC. The influence of surface wettability on HTC was made clear by . From a comparison between weakly wetted surface and strongly wetted surface, they found that excellent HTC can be achieved both at very low contact angle close to 0 o and at a contact an...

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“…So it plays a significant role for the optimization of the whole system that the evaporator heat transfer enhancement in refrigeration and heat pump systems working at sub-atmospheric pressure. Even though the literature on evaporation of water is extensive, data on the characteristics of water evaporation under vacuum conditions are still scarce [6,7]; the heat flux is much higher than that of an evaporator. Moreover, the design of these evaporators still remains mainly empirical [6].…”

Section: Introductionmentioning

confidence: 99%

“…Even though the literature on evaporation of water is extensive, data on the characteristics of water evaporation under vacuum conditions are still scarce [6,7]; the heat flux is much higher than that of an evaporator. Moreover, the design of these evaporators still remains mainly empirical [6]. So research on water boiling heat transfer at sub-atmospheric pressure has become an important issue.…”

Section: Introductionmentioning

confidence: 99%

Experimental Research on Water Boiling Heat Transfer on Horizontal Copper Rod Surface at Sub-Atmospheric Pressure

et al. 2015

Energies

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Abstract:In recent years, water (R718) as a kind of natural refrigerant-which is environmentally-friendly, safe and cheap-has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important issue. There are many research papers on the evaporation of water, but there is a lack of data on the characteristics at sub-atmospheric pressures, especially lower than 3 kPa (the saturation temperature is 24 °C). In this paper, the experimental research on water boiling heat transfer on a horizontal copper rod surface at 1.8-3.3 kPa is presented. Regression equations of the boiling heat transfer coefficient are obtained based on the experimental data, which are convenient for practical application.

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Experimental evidence of a new regime for boiling of water at subatmospheric pressure

Cited by 64 publications

References 14 publications

Downslope sediment transport by boiling liquid water under Mars-like conditions: experiments and potential implications for Martian gullies

Downslope sediment transport by boiling liquid water under Mars-like conditions: experiments and potential implications for Martian gullies

Heat transfer enhancement of a loop thermosyphon with a hydrophobic spot-coated surface

Experimental Research on Water Boiling Heat Transfer on Horizontal Copper Rod Surface at Sub-Atmospheric Pressure

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