Sub-Atmospheric Pressure Pool Boiling of Water on a Screen Laminate-Enhanced, Wavy-Fin Array

2010 ◽  
Author(s):  
P. J. Laca ◽  
R. A. Wirtz
Keyword(s):  
Atmospheric Pressure ◽  
Pool Boiling ◽  
Bubble Nucleation ◽  
High Density ◽  
Wire Mesh ◽  
Effective Surface ◽  
Nucleation Sites ◽  
Semi Empirical ◽  
Very High ◽  
Reduced Pressures

Saturated pool boiling on vertically oriented, copper, wavy-fin surfaces in water at reduced pressures is investigated. A lamination of fine-filament, wire mesh is an effective surface enhancement for boiling since the surface can be configured to provide a very high density of potential bubble nucleation sites. Two surfaces are considered: a 0.75mm thick 4-layer laminate with approximately 4000 pores per cm2 and a 0.42mm thick 8-layer laminate with approximately 26,000 pores per cm2. The results show that the 8-layer laminate outperforms the 4-layer laminate. At reduced pressures a reduction in performance is seen for both surfaces. A semi-empirical boiling model is developed. The model predicts the boiling performance of our data within an error of 30%. The model shows that shorter fins improve boiling performance.

Boiling and Evaporation From Heat Pipe Wicks With Water and Acetone

1974 ◽  
Vol 96 (3) ◽  
pp. 331-337 ◽  
Author(s):  
A. Abhat ◽  
R. A. Seban
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Atmospheric Pressure ◽  
Saturated Vapor ◽  
Pool Boiling ◽  
Tube Surface ◽  
Evaporation Surface ◽  
Nucleation Sites ◽  
Boiling And Evaporation ◽  
Vertical Tubes

Heat transfer for pool boiling with flaxes in the range of 5 × 102 5 × 104 Btu/(ft2 hr) and the associated excess of wall over saturation temperatures are presented, primarily for atmospheric pressure, for vertical tubes in water, ethanol, and acetone, bare or wrapped with screen or felt metal. For the wrapped tubes, this performance is given also for evaporation into surrounding saturated vapor with the liquid being supplied by the wick: this is the significant mode in respect to heat pipe applications. For this mode maximum evaporation rates are also indicated and it is shown that this maximum can be rationalized either in terms of a partially full wick with conduction transfer to the evaporation surface or in terms of a full wick with vapor holes originating at nucleation sites on the tube surface.

Pool Boiling Critical Heat Flux in Reduced Gravity

1999 ◽  
Vol 121 (4) ◽  
pp. 865-873 ◽  
Author(s):  
D. P. Shatto ◽  
G. P. Peterson
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Qualitative Data ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Reduced Gravity ◽  
Empirical Correlations ◽  
Using Data ◽  
Semi Empirical ◽  
Reduced Pressures

An experimental investigation has been conducted to measure pool boiling critical heat fluxes in reduced gravity. A horizontal cylindrical cartridge heater immersed in water at reduced pressures during parabolic flights on NASA’s KC-135 resulted in boiling on the heater surface. Visual observations and qualitative data trends indicate that the conventional Taylor-Helmholtz. instability model still governs the critical heat flux mechanism over the range of gravitational accelerations of the current study, which range from 0.0005 < g/go < 0.044. Using data from more than 40 individual tests, two semi-empirical correlations have been developed to account for the effect of thermocapillary flow, which tends to decrease the critical heat flux below the predictions of previous correlations.

scholarly journals Numerical investigation of nucleate pool boiling heat transfer

2016 ◽  
Vol 20 (suppl. 5) ◽  
pp. 1301-1312
Author(s):  
Andrijana Stojanovic ◽  
Vladimir Stevanovic ◽  
Milan Petrovic ◽  
Dragoljub Zivkovic
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Heated Wall ◽  
Wall Surface ◽  
Two Phase ◽  
Site Density ◽  
Nucleation Sites ◽  
Nucleation Site Density

Multidimensional numerical simulation of the atmospheric saturated pool boiling is performed. The applied modelling and numerical methods enable a full representation of the liquid and vapour two-phase mixture behaviour on the heated surface, with included prediction of the swell level and heated wall temperature field. In this way the integral behaviour of nucleate pool boiling is simulated. The micro conditions of bubble generation at the heated wall surface are modelled by the bubble nucleation site density, the liquid wetting contact angle and the bubble grow time. The bubble nucleation sites are randomly located within zones of equal size, where the number of zones equals the nucleation site density. The conjugate heat transfer from the heated wall to the liquid is taken into account in wetted heated wall areas around bubble nucleation sites. The boiling curve relation between the heat flux and the heated wall surface temperature in excess of the saturation temperature is predicted for the pool boiling conditions reported in the literature and a good agreement is achieved with experimentally measured data. The influence of the nucleation site density on the boiling curve characteristic is confirmed. In addition, the influence of the heat flux intensity on the spatial effects of vapour generation and two-phase flow are shown, such as the increase of the swell level position and the reduced wetting of the heated wall surface by the heat flux increase.

scholarly journals Pool boiling of ethanol and FC-72 on open microchannel surfaces

2018 ◽  
Vol 180 ◽  
pp. 02042 ◽  
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Pool Boiling ◽  
Experimental Investigations ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nucleation Sites ◽  
Open Microchannel ◽  
Acquisition Speed ◽  
Parallel Microchannels

The paper presents experimental investigations into pool boiling heat transfer for open microchannel surfaces. Parallel microchannels fabricated by machining were about 0.3 mm wide, and 0.2 to 0.5 mm deep and spaced every 0.1 mm. The experiments were carried out for ethanol, and FC-72 at atmospheric pressure. The image acquisition speed was 493 fps (at resolution 400 × 300 pixels with Photonfocus PHOT MV-D1024-160-CL camera). Visualization investigations aimed to identify nucleation sites and flow patterns and to determine the bubble departure diameter and frequency at various superheats. The primary factor in the increase of heat transfer coefficient at increasing heat flux was a growing number of active pores and increased departure frequency. Heat transfer coefficients obtained in this study were noticeably higher than those from a smooth surface.

Correlation of Subatmospheric Pressure, Saturated, Pool Boiling of Water on a Structured-Porous Surface

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Sean J. Penley ◽  
R. A. Wirtz
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Bubble Nucleation ◽  
Distilled Water ◽  
Heat Transfer Correlation ◽  
Subatmospheric Pressure ◽  
Strong Function ◽  
Nucleation Sites ◽  
Boiling Heat Transfer Coefficient

Saturated pool-boiling experiments at 1 atm and subatmospheric pressure assess the utility of fine-filament screen-laminate enhanced surfaces as effective bubble nucleation sites. Experiments were conducted on vertically oriented, multilayer laminates in saturated distilled water at pressures of 0.2–1.0 atm. The performance of 12 different copper-filament surfaces, having pore hydraulic diameters ranging from 14 μm to 172 μm, is documented. Experimental results show that boiling performance is a strong function of screen-laminate geometry. In the present work, enhancement of up to 27 times that of an unenhanced surface was obtained at a superheat of 8 K and a pressure of 0.2 atm. Dimensional analysis and multiparameter regression are used to develop a heat transfer correlation that relates the boiling heat transfer coefficient to the lamination geometry.

scholarly journals Pool boiling visualization of Novec-649 and FC-72 on copper microchannels

2019 ◽  
Vol 213 ◽  
pp. 02037
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Atmospheric Pressure ◽  
Pool Boiling ◽  
Entire Surface ◽  
Working Fluids ◽  
Nucleation Sites ◽  
Parallel Microchannels

Saturated pool boiling from copper microchannel surfaces was examined using Novec-649 and FC-72 as working fluids. Parallel microchannels fabricated by machining were about 0.2 mm wide, and 0.2 to 0.4 mm deep and spaced every 0.4 mm. The experiments were carried out at atmospheric pressure. The images of the growing and departing bubbles for the entire surface of the specimen were taken with a Photonfocus PHOT MV-D1024-160-CL camera and an EX-FH20 (Casio) camera. At low superheats, the bubbles departing from enhanced surfaces were spherical in shape and did not coalesce. At higher superheats, the bubbles interacted with each other intensively, forming flattened spherical, funnel-shaped bubbles at the bottom. The visualization study aimed at identifying nucleation sites of the departing bubbles and determining their diameters and frequency at various superheats.

scholarly journals Zur Theorie der Neutronensterne

1966 ◽  
Vol 21 (12) ◽  
pp. 2009-2012
Author(s):  
P. Gombás ◽  
D. Kisdi
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Critical Mass ◽  
Average Energy ◽  
High Density ◽  
Empirical Theory ◽  
Atomic Nuclei ◽  
A Value ◽  
Semi Empirical ◽  
Very High

Using a semi-empirical theory of interaction between neutrons in atomic nuclei, the average energy of a neutron, the equation of state, and the pressure-compressibility relation is computed for a neutron gas of very high density (n ≈ 1015 gcm-3). The results are applied to the computation of the mass and the radius of a neutron star as a function of the central density. For the critical mass, above which a neutron star cannot exist, a value of 0.96 solar masses is found.

Pool Boiling on Polished and Chemically Etched Stainless-Steel Surfaces

1968 ◽  
Vol 90 (2) ◽  
pp. 231-238 ◽  
Author(s):  
R. I. Vachon ◽  
G. E. Tanger ◽  
D. L. Davis ◽  
G. H. Nix
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Stainless Steel ◽  
Atmospheric Pressure ◽  
Pool Boiling ◽  
304 Stainless Steel ◽  
Distilled Water ◽  
Preparation Technique ◽  
Nucleation Sites ◽  
Steel Surfaces

This paper presents pool boiling data at atmospheric pressure for mechanically polished and chemically etched 304 stainless-steel surfaces in contact with distilled water. The surfaces were prepared by these techniques to produce variation in nucleation sites. Surface roughness was varied from 2–61 rms. The results show the changes in heat transfer with varying rms surface roughness and preparation technique. The Rohsenow pool boiling correlation was used to discuss the data.

Bubble Dynamics Around a Vertical Heating Element During Nucleate Pool Boiling

2003 ◽  
Author(s):  
Ahmed Z. ElGafy ◽  
Khalid Lafdi
Keyword(s):  
Growth Rate ◽  
Atmospheric Pressure ◽  
Analytical Study ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nucleate Pool Boiling ◽  
Nucleation Sites ◽  
Surface Length ◽  
Core Volume

The present work is a description analytical study to express the bubbles dynamic during nucleate pool boiling arises from boiling of water by a vertical cylindrical heating surface under atmospheric pressure conditions. The study includes the description of bubbles formation, detachment, rise and growth around the vertical heating surface. Different formulas are considered to evaluate each of, the number of active nucleation sites on the heating surface, bubbles departure diameter along the heating surface length, bubbles frequency, bubbles rising velocity and growth rate of the diameter of the bubble through its uprising motion around the vertical heating surface. An equation for evaluating the vapor bubble core volume and its thickness around a vertical heating surface is introduced.

Sign in / Sign up

Export Citation Format

Share Document