scholarly journals Enhancement of the pool boiling heat transfer coefficient using the gas injection into the water

2012 ◽  
Vol 14 (4) ◽  
pp. 100-109 ◽  
Author(s):  
M.M. Sarafraz ◽  
S.M. Peyghambarzadeh ◽  
S.A. Alavi Fazel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Pool Boiling Heat Transfer ◽  
Site Density ◽  
Boiling Heat Transfer Coefficient ◽  
Nucleation Site Density

Abstract In this paper, a new method for enhancing the pool boiling heat transfer coefficient of pure liquid, based on the gas injection through the liquids has been introduced. Hence, the effect of gas dissolved in a stagnant liquid on pool boiling heat transfer coefficient, nucleation site density, and bubble departure diameter has experimentally been investigated for different mole fractions of SO2 and various heat fluxes up to 114 kW/ m2. The presence of SO2 in captured vapor inside the bubbles, particularly around the heat transfer surface increases the pool boiling heat transfer coefficient. The available predicted correlations are unable to obtain the reasonable values for pool boiling heat transfer coefficient in this particular case. Therefore, to predict the pool boiling heat transfer coefficient accurately, a new modified correlation based on Stephan-Körner relation has been proposed. Also, during the experiments, it is found that nucleation site density is a strictly exponential function of heat flux. Accordingly, a new correlation has been obtained to predict the nucleation site density. The major application of the nucleation site density is in the estimating of mean bubble diameters as well as local agitation due to the rate of bubble frequency.

scholarly journals Experimental investigation on partial pool boiling heat transfer in pure liquids

2016 ◽  
Vol 22 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Seyed Fazel ◽  
Goharshad Hosseyni
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Pool Boiling Heat Transfer ◽  
Heating Section ◽  
Boiling Heat Transfer Coefficient ◽  
Improved Performance

Saturated partial pool boiling heat transfer has been experimentally investigated on a horizontal rod heater. The boiling liquids are including water and ethanol. The heating section is made by various materials including SS316, copper, aluminum and brass. Experiments have been performed at several degrees of surface roughness ranging between 30 and 360 micrometer average vertical deviation. The measurements are including boiling heat transfer coefficient, bubble departing diameter and frequency and also nucleation site density. The data have been compared to major existing correlations. It is shown that experimental data do not match with major correlations at the entire range of experiments with acceptable accuracy. In this article, the boiling heat transfer area has been divided in two complementary areas, the induced forced convection area and the boiling affected area. Based on two dimensionless groups, including E?tv?s and Roshko numbers, a semi-empirical model have been proposed to predict the boiling heat transfer coefficient. It is shown that the proposed model provides improved performance in prediction of the boiling heat transfer coefficient in comparison with to existing correlations.

Saturated Nucleate Pool Boiling of Ethanol-Water Binary Mixtures on Smooth and Enhanced Laser Processed Metal Surfaces

2018 ◽  
Author(s):  
Matevž Zupančič ◽  
Jure Voglar ◽  
Peter Gregorčič ◽  
Iztok Golobič ◽  
Peter Zakšek
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Binary Mixtures ◽  
Pure Water ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Site Density ◽  
Nucleation Frequency ◽  
Nucleation Site Density

Pool boiling experiments of water and ethanol-water binary mixtures were conducted on smooth and laser textured stainless steel foils. High-speed IR thermography was used to measure transient temperature field during boiling in order to determine nucleation frequencies, nucleation site densities, bubble activation temperatures, wall-temperature distributions and average superheats as well as heat transfer coefficients. Saturated pool boiling experiments were conducted at atmospheric pressure over a heat flux range of 5–250 kW m−2 for pure water and ethanol-water mixtures (1% and 10% m/m). For both mixtures and both types of surfaces we measured significant decrease in average heat transfer coefficient and increase in bubble activation temperatures in comparison to pure water. However, laser textured surface in average provided around 60% higher nucleation frequency and more than 100% higher nucleation site density compared to smooth surface for both of the tested binary mixtures. Consequentially, heat transfer coefficient was enhanced for more than 30%. Our results show that laser textured surfaces can improve boiling performance for water and ethanol-water mixtures, but at the same time the addition of ethanol reduces heat transfer coefficient despite the enhancement of nucleation site density and nucleation frequency. This is also in agreement with available experimental data and existing theoretical models.

scholarly journals Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Suchismita Sarangi ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Transfer Enhancement ◽  
Pool Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient ◽  
Coating Characteristics

Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux (CHF). However, there is no unified understanding of the role of coating characteristics on pool boiling heat transfer enhancement. The morphology and size of the particles affect the pore geometry, permeability, thermal conductivity, and other characteristics of the sintered coating. In turn, these characteristics impact the heat transfer coefficient and CHF during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular and spherical morphologies for a range of porosities (∼40–80%). Particles of the same effective diameter (90–106 μm) are sintered to yield identical coating thicknesses (∼4 particle diameters). The porous structure formed by sintering is characterized using microcomputed tomography (μ-CT) scanning to study the geometric and effective thermophysical properties of the coatings. The boiling performance of the porous coatings is analyzed. Coating characteristics that influence the boiling heat transfer coefficient and CHF are identified and their relative strength of dependence analyzed using regression analysis. Irregular particles yield higher heat transfer coefficients compared to spherical particles at similar porosity. The coating porosity, pore diameter, unit necking area, unit interfacial area, effective thermal conductivity, and effective permeability are observed to be the most critical coating properties affecting the boiling heat transfer coefficient and CHF.

Experimental and Numerical Study of Nucleate Pool Boiling Heat Transfer and Bubble Dynamics in Saline Solution

2020 ◽  
Author(s):  
Qi Liu ◽  
Yuxin Wu ◽  
Yang Zhang ◽  
Junfu Lyu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Saline Solution ◽  
Numerical Study ◽  
Pool Boiling ◽  
Pool Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

Abstract A visual pool boiling experimental device based on ITO coating layer heater and high-speed shooting technology was established for studying the bubble behavior and heat transfer characteristics of saline solution, which is of great significance for ensuring heat transfer safety in nuclear power plants, steam injection boilers and seawater desalination. Volume of fluid method was applied to simulate numerically the liquid–vapor phase change by adding source terms in the continuity equation and energy equation. The predictions of the model are quantitatively verified against the experimental data. It can be found based on the experimental data that the pool boiling heat transfer coefficient is enhanced as the salt concentration increases. Visualization studies and numerical data have shown that the presence and precipitation of salt leads to a decrease in the detachment diameter and growth time of the bubble and an increase in the frequency of detachment, thereby increasing the pool boiling heat transfer coefficient.

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