STUDY ON SUPERHEATED LIQUID LAYER IN POOL BOILING

2018 ◽  
Author(s):  
Mao Takeyama ◽  
Tomoaki Kunugi ◽  
Takehiko Yokomine ◽  
Zensaku Kawara
Keyword(s):  
Liquid Layer ◽  
Pool Boiling ◽  
Superheated Liquid

Study on Subcooled-Forced Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture

1999 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Manabu Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Liquid Layer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Superheated Liquid ◽  
Flow Boiling Heat Transfer

Abstract The effect of solid particle introduction on subcooled-forced flow boiling heat transfer and a critical heat flux was examined experimentally. In the experiment, glass beads of 0.6 mm diameter were mixed in subcooled water. Experiments were conducted in a range of the subcooling of 40 K, a velocity of 0.17–6.7 m/s, a volumetric particle ratio of 0–17%. When particles were introduced, the growth of a superheated liquid layer near a heat trasnsfer surface seemed to be suppressed and the onset of nucleate boiling was delayed. The particles promoted the condensation of bubbles on the heat transfer surface, which shifted the initiation of a net vapor generation to a high heat flux region. Boiling heat trasnfer was augmented by the particle introduction. The suppression of the growth of the superheated liquid layer and the promotion of bubble condensation and dissipation by the particles seemed to contribute that heat transfer augmentation. The wall superheat at the critical heat flux was elevated by the particle introduction and the critical heat flux itself was also enhanced. However, the degree of the critical heat flux improvement was not drastic.

The rate of bubble growth in a superheated liquid in pool boiling

2017 ◽  
Vol 53 (12) ◽  
pp. 3433-3442
Author(s):  
Mohammad Reza Abdollahi ◽  
Mehdi Jafarian ◽  
Mohammad Jamialahmadi
Keyword(s):  
Bubble Growth ◽  
Pool Boiling ◽  
Superheated Liquid

A New Perspective on Heat Transfer Mechanisms and Sonic Limit in Pool Boiling

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Superheated Liquid ◽  
Heater Surface ◽  
Liquid Stream ◽  
Maximum Heat ◽  
Pool Boiling Heat Transfer ◽  
Maximum Heat Transfer ◽  
Secondary Evaporation

Pool boiling is postulated as a single-phase heat transfer process with nucleating bubbles providing a liquid pumping mechanism over the heater surface. This results in three fluid streams at the heater surface—outgoing vapor and liquid streams, and an incoming liquid stream. Heat transfer during periodic replacement of the liquid in the influence region around a nucleating bubble is well described by transient conduction (TC) and microconvection (MiC) mechanisms. Beyond this region, free convection (FC) or macroconvection (MaC) contributes to heating of the liquid. A bubble growing on the heater surface derives its latent heat from the surrounding superheated liquid and from the microlayer providing a direct heat conduction path. Secondary evaporation occurs in the bubbles rising in the bulk after departure, and at the free surface. This secondary evaporation does not directly contribute to the heat transfer at the heater surface but provides a means of dissipating liquid superheat. A sonic limit-based model is then presented for estimating the theoretical upper limit for pool boiling heat transfer by considering the three fluid streams to approach their respective sonic velocities. Maximum heat transfer rates are also estimated using this model with two realistic velocities of 1 and 5 m/s for the individual streams and are found to be in general agreement with available experimental results. It is postulated that small bubbles departing at high velocity along with high liquid stream velocities are beneficial for heat transfer. Based on these concepts, future research directions for enhancing pool boiling heat transfer are presented.

Boiling Heat Transfer Surface Capable of Transient Heating and Nucleation Control

2010 ◽  
Author(s):  
Manabu Tange ◽  
Shu Takagi ◽  
Fumio Takemura ◽  
Masahiro Shoji
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Layer ◽  
Boiling Heat Transfer ◽  
High Heat ◽  
Heat Transfer Surface ◽  
Superheated Liquid ◽  
High Heat Flux ◽  
Subcooled Boiling ◽  
Transient Heating

Using MEMS technique, we develop a novel boiling heat transfer surface with three types of circuits: a heater, a bubbling trigger, and thermocouples. This paper presents the design of the heat transfer surface and experimental results of bubbling behavior on this surface during highly subcooled boiling at high heat flux. The heater makes superheated liquid layer transiently. Then the bubbling trigger make a tiny hydrogen bubble playing a role of a nuclei of a boiling bubble. The thermocouple signal reveals a growth of superheated liquid layer, vaporization of the liquid layer beneath the bubble, and rewetting. It has been known that highly subcooled boiling at high heat flux results in atomization of vapor bubbles on heat transfer surfaces due to the violent condensation. Parametric experiments were conducted to clarify the occurrence condition of the atomization by changing heat flux and heating time before nucleation. Bubbling behavior was categorized into four patterns: Oscillating, Not-Oscillating, Single-bubble emission, and Multi-bubbles emission.

A Digital Photographic Study on Nucleate Boiling in Subcooled Flow for Water and Refrigerant 134a Fluids

2002 ◽  
Author(s):  
In Cheol Bang ◽  
Won-Pil Baek ◽  
Soon Heung Chang
Keyword(s):  
Heat Flux ◽  
Liquid Layer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Heated Wall ◽  
Superheated Liquid ◽  
Mass Fluxes ◽  
Subcooled Flow ◽  
Bubble Layer ◽  
Near Wall

The behavior of near-wall bubbles in subcooled flow boiling has been investigated photographically for water flow in vertical, one-side heated and rectangular channels at mass fluxes of 500, 1500, 2000 kg/m2s under atmospheric pressure and for R134a in channels of the same kind at mass fluxes of 1000, 2000 kg/m2s under 7 bar. Digital photographic techniques are used for the visualization, which are rapidly advanced in recent. Primary attention is given to the bubble coalescence phenomenon and the structure of the near-wall bubble layer. At subcooled and low-quality conditions of both fluids, discrete attached bubbles, sliding bubbles, small coalesced bubbles and large coalesced bubbles or vapor clots are observed on the heated surface as the heat flux is increased from a low value. Particularly for R134a, vapor remnants below discrete bubble on the heating surface are observed. Nucleation site density increases with the increases in heat flux and channel-averaged enthalpy, while discrete bubbles coalesce and form large bubbles, resulting in large vapor clots. Waves formed on the surface of the vapor clots are closely related to Helmholtz instability. At sufficiently high heat fluxes, three characteristic layers were observed in the heated channel: (a) a superheated liquid layer with small bubbles attached on the heated wall, (b) a flowing bubble layer consisting of large coalesced bubbles over the superheated liquid layer, and (c) the liquid core over the flowing bubble layer.

Pool Boiling Mechanism of HFE-7100

Volume 4 ◽  
2004 ◽  
Author(s):  
Saeed Moghaddam ◽  
Kenneth T. Kiger
Keyword(s):  
Experimental Data ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Transient Heat Conduction ◽  
Constant Heat Flux ◽  
Current Data ◽  
Heated Wall ◽  
Superheated Liquid ◽  
Fundamental Parameters ◽  
Boiling Mechanism

To study the pool boiling mechanism of HFE-7100, a micro array of forty-four Resistance Temperature Detectors (RTD’s) covering a 1mm in diameter circular area was microfabricated around a single cylindrical cavity on a thin silicon membrane. Constant heat flux was applied to the surface using a thin film heater microfabricated on the backside of the membrane. Images of the bubbles and the temperature of the heated wall underneath and around the bubble were recorded during the pool boiling process. Using the images of the bubbles, their volume, velocity, and frequency of departure was calculated. The acquired experimental data provided the fundamental parameters required for evaluating several boiling models whose development was based on the bubble diameter, frequency of departure, and velocity. For the conditions of this experiment, it seems that the current data can be best explained by transient heat conduction to the liquid adjacent to the heated wall and subsequent pumping of the superheated liquid by the bubbles. However, more experimental data in different conditions are required before solid conclusions can be reached. Details of the experimental results, models, and comparison between the two are presented in this paper.

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