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 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.

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.

scholarly journals Bubble departure diameter determination for pool boiling on surface with microchannels

2018 ◽  
Vol 70 ◽  
pp. 02008
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko ◽  
Joanna Kowalczyk ◽  
Łukasz Nowakowski
Keyword(s):  
Atmospheric Pressure ◽  
Buoyancy Force ◽  
Pool Boiling ◽  
Surface Tension Force ◽  
Copper Sample ◽  
Heat Fluxes ◽  
Force Balance ◽  
Saturated Water ◽  
Open Microchannel ◽  
Parallel Microchannels

The paper presents visualization investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated water, ethanol, FC-72 and Novec-649 at atmospheric pressure. Parallel microchannels fabricated by machining copper sample were about 0.2 to 0.5 mm wide and 0.2 to 0.5 mm deep. The diameter of departing bubble was calculated for the microchannel surface on the basis of buoyancy force and surface tension force balance. The visualization carried out was aimed at determining the diameters of the departing bubbles at various heat fluxes for four working fluids.

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.

scholarly journals Study of pool boiling heat transfer with FC-72 on open microchannel surfaces

2019 ◽  
Vol 213 ◽  
pp. 02038
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko ◽  
Milena Bedla-Pawlusek ◽  
Łukasz Nowakowski
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Fold Increase ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Nucleation Sites ◽  
Open Microchannel ◽  
Parallel Microchannels

The paper presents investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated FC-72 at atmospheric pressure. Parallel microchannels fabricated by machining were about 0.2 to 0.4 mm wide and 0.2 to 0.5 mm deep. Analyzed surfaces with microchannels allowed to obtain heat transfer coefficients within the range of 6.1 – 9.8 kW/m2K, which in relation to the flat surface gives a 3 – 5 - fold increase in HTC. One of the reasons for the increase in the heat transfer coefficient when increasing the heat flux was the growing number of active nucleation sites at the bottom of microchannels and its side surfaces.

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.

scholarly journals Effect of Uniformly and Nonuniformly Coated Al2O3 Nanoparticles over Glass Tube Heater on Pool Boiling

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Nitin Doifode ◽  
Sameer Gajghate ◽  
Abdul Najim ◽  
Anil Acharya ◽  
Ashok Pise
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Pool Boiling ◽  
Glass Tube ◽  
Al2o3 Nanoparticles ◽  
High Speed Camera ◽  
Coated Nanoparticles ◽  
Nucleation Sites ◽  
Coated Surface

Effect of uniformly and nonuniformly coated Al2O3 nanoparticles over plain glass tube heater on pool boiling heat transfer was studied experimentally. A borosilicate glass tube coated with Al2O3 nanoparticle was used as test heater. The boiling behaviour was studied by using high speed camera. Result obtained for pool boiling shows enhancement in heat transfer for nanoparticle coated surface heater and compared with plain glass tube heater. Also heat transfer coefficient for nonuniformly coated nanoparticles was studied and compared with uniformly coated and plain glass tube. Coating effect of nanoparticles over glass tube increases its surface roughness and thereby creates more nucleation sites.

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