Boiling regimes in a closed two-phase thermosyphon

Niro, Alfonso; Beretta, Gian Paolo

doi:10.1016/0017-9310(90)90112-8

Cited by 46 publications

(17 citation statements)

References 15 publications

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“…Explosive eruption can be recognized clearly by the sharp falls in the heated section temperature and the sudden rises in riser channel temperature. The temperatures in the heated section experience continuous fluctuations, but these are limited to 0.3 K. These fluctuations, which present higher frequencies compared with that of riser channel, are due to the intrinsically stochastic nature of boiling which was reported by Niro et al [31] that nucleation frequencies (<0.1 Hz) which were related to high liquid superheats brought about the intermittent boiling regime. It should be noted that the maximum and the lowest temperature during each cycle in the riser channel are lower when compared with those of the heated section, and there is relatively a larger temperature drop than that in the heated section.…”

Section: Typical Flow Phenomenonmentioning

confidence: 91%

Experimental investigation of effective parameters on geyser periodicity in a vertical heated system

Chen

Yang

Liao

et al. 2015

Experimental Thermal and Fluid Science

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Section: Typical Flow Phenomenonmentioning

confidence: 91%

Experimental investigation of effective parameters on geyser periodicity in a vertical heated system

Chen

Yang

Liao

et al. 2015

Experimental Thermal and Fluid Science

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“…The circulating flow resulting from ebullition may be unable to effectively replenish all the fluid between the tightly-grouped fins. As a result, heated fluid does not get carried away quickly and the waiting time required to heat the small volume of liquid between the fins to temperatures suitable for bubble formation is reduced [9]. This may increase the frequency of bubble departure.…”

Section: Effect Of Fin Gapmentioning

confidence: 99%

“…Recently, the boiling regimes of water and acetone at low pressure in a closed two-phase thermosiphon were examined [9]. Experimental and analytical results of the boiling mechanisms were used to examine the regime between intermittent and fully-developed boiling.…”

Section: Introductionmentioning

confidence: 99%

Pool boiling enhancement techniques for water at low pressure

McGillis

Carey

Fitch³

et al.

1991 Proceedings, Seventh IEEE Semiconductor Thermal Measurement and Management Symposium

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The Western Research Laboratory (WRL) is a computer systems research group that was founded by Digital Equipment Corporation in 1982. Our focus is computer science research relevant to the design and application of high performance scientific computers. We test our ideas by designing, building, and using real systems. The systems we build are research prototypes; they are not intended to become products.There is a second research laboratory located in Palo Alto, the Systems Research Center (SRC). Other Digital research groups are located in Paris (PRL) and in Cambridge, Massachusetts (CRL).Our research is directed towards mainstream high-performance computer systems. Our prototypes are intended to foreshadow the future computing environments used by many Digital customers. The long-term goal of WRL is to aid and accelerate the development of high-performance uni-and multi-processors. The research projects within WRL will address various aspects of high-performance computing.We believe that significant advances in computer systems do not come from any single technological advance. Technologies, both hardware and software, do not all advance at the same pace. System design is the art of composing systems which use each level of technology in an appropriate balance. A major advance in overall system performance will require reexamination of all aspects of the system.We do work in the design, fabrication and packaging of hardware; language processing and scaling issues in system software design; and the exploration of new applications areas that are opening up with the advent of higher performance systems. Researchers at WRL cooperate closely and move freely among the various levels of system design. This allows us to explore a wide range of tradeoffs to meet system goals.We publish the results of our work in a variety of journals, conferences, research reports, and technical notes. This document is a research report. Research reports are normally accounts of completed research and may include material from earlier technical notes. We use technical notes for rapid distribution of technical material; usually this represents research in progress. UUCP: decwrl!wrl-techreportsTo obtain more details on ordering by electronic mail, send a message to one of these addresses with the word ''help'' in the Subject line; you will receive detailed instructions. Pool Boiling Enhancement Techniques for AbstractSaturated pool boiling of water at low, sub-atmospheric pressures from a heated, 12.7 x 12.7 mm horizontal surface was examined. Rectangular fins, fluidized particulate beds, and surface finishes were used to enhance heat transfer. Water at low pressure significantly decreases the boiling performance below that of water at atmospheric pressure. However, surface temperatures are reduced to values acceptable for cooling electronic components. All rectangular fin geometries were found to enhance heat transfer, although certain geometries were more effective. The finned surfaces extended the base area critical heat flux (CHF) ...

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“…Hydrophobic spots with a rough texture may contribute significantly to bubble nucleation because of the accumulation of entrapped vapour. In other words, the larger roughness and thickness of the coated-spot on the evaporator surface can lead to facilitated initial nucleation and lowered wall superheat at the onset of nucleate boiling (Forrest et al, 2010;Niro and Beretta, 1990;Parker and Genk, 2005). The comparison of bubble behaviours on surfaces Type X, Type Y, and Type D at heat fluxes of 130 kW/m 2 and 200 kW/m 2 are presented in Fig. 14.…”

Section: Effect Of Hydrophobic Coating Materialsmentioning

confidence: 99%

“…It was considered that the bubble departure time and departure radius increased substantially with decreasing operating pressure (1975). Niro et al (1990) showed, by combining the ClausiusClapeyron equation with the Laplace equation, the superheat necessary for bubble nucleation at low pressures was much higher than that at high pressures. The average departure diameter increases with decreasing pressure.…”

mentioning

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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Boiling regimes in a closed two-phase thermosyphon

Cited by 46 publications

References 15 publications

Experimental investigation of effective parameters on geyser periodicity in a vertical heated system

Experimental investigation of effective parameters on geyser periodicity in a vertical heated system

Pool boiling enhancement techniques for water at low pressure

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

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