Theoretical and Experimental Analysis of Increasing Pressure During Pool-Boiling

2018 ◽  
Author(s):  
Smreeti Dahariya ◽  
Amy Rachel Betz
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Copper Surface ◽  
System Pressure ◽  
Nucleation Sites ◽  
Wide Range ◽  
Fluid Properties

The thermo-fluid properties of water change at high pressure. The performance of high pressure pool boiling greater than 50 Psi has not been studied widely. The aim of this paper is to analyze the experimental data to describe the effect of increasing pressure during pool boiling. Hsu’s correlation was used to predict the active nucleation sites. The maximum and minimum radii of the active nucleation sites were determined as a function of heat flux or degree of wall superheats over a wide range of pressures. The bubble dynamics are discussed using the predicted values of fundamental boiling quantities such as bubble departure diameter, active nucleation site density and bubble release frequency. The thickness of the boundary layer was assumed to be 30 microns. Rohsenow’s and Forster’s correlations were used to predict the pool boiling curve for different pressures. The comparison was made with the experimental data for water of a plain copper surface of increasing pressure. The parametric trend provides fundamental insight and explains how the system pressure can maximize the boiling efficiency of new generation boilers.

Bubble Dynamics for Nucleate Pool Boiling of Electrolyte Solutions

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Seyed Ali Alavi Fazel ◽  
Seyed Baher Shafaee
Keyword(s):  
Experimental Data ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Close Relation ◽  
Electrolyte Solutions ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Experimental Results ◽  
Nucleate Pool Boiling ◽  
Wide Range

Bubble dynamics is the most important subphenomenon, which basically affects the nucleate pool boiling heat transfer coefficient. Previous investigations state that the effect of physical properties of liquid and vapor phases on bubble departure diameter are often conflicting. In this article, extensive new experimental data are presented for the bubble departure diameter for various electrolyte aqueous solutions over a wide range of heat fluxes and concentrations. Experimental results show that the bubble detachment diameter increase with increasing either boiling heat flux or electrolyte concentration. Experimental results also present a close relation between the dimensionless capillary and bond numbers. A new model for the prediction of vapor bubble departure diameter in nucleate boiling for the electrolyte solutions is proposed, which predicts the experimental data with a satisfactory accuracy.

Design and Fabrication of an Experimental Facility for High-Pressure Pool Boiling

2014 ◽  
Author(s):  
Nanxi Li ◽  
Amy Rachel Betz
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Pool Boiling ◽  
Future Research ◽  
Experimental Setup ◽  
Transfer Coefficients ◽  
Structured Surfaces ◽  
Advantages And Disadvantages ◽  
System Pressure ◽  
Coated Surfaces

In this work, we present the design and fabrication a high-pressure pool boiling facility to conduct pool boiling experiments on horizontal heated surfaces under elevated pressures, up to 20 bar. Previous research has shown that micro- and/or nano-structured surfaces and coated surfaces will increase heat transfer coefficients up to one order of magnitude at atmospheric pressure. However, most boiling applications are subjected to high pressure, especially in the power industry. Pressure inside a boiling water reactor in a nuclear power plant will reach as high as 75 atm (75.99 bar). In order to determine how heat transfer is enhanced at increased pressures, with deionized water and refrigerants, on modified surfaces, a special experimental setup needs to be designed and fabricated. Difficulties in making such an experimental setup come from stabilizing the system pressure, sealing the test setup and visualizing the boiling conditions in the vessel. Both advantages and disadvantages of this design will be discussed and possible methods for improvements will be proposed. Preliminary test results on a plane copper surface are also included. Future research will be focusing on boiling of water and refrigerants on micro-structured copper surfaces, graphene coated, and Teflon© coated surfaces under high pressure.

scholarly journals Bubble dynamics and mechanistic boiling heat transfer prediction on a scored copper surface

2021 ◽  
Vol 2116 (1) ◽  
pp. 012009
Author(s):  
Zhen Cao ◽  
Zan Wu ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Mechanistic Model ◽  
Transient Heat Conduction ◽  
Nucleation Site ◽  
Copper Surface ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Microlayer Evaporation

Abstract In this study, pool boiling heat transfer of de-ionized water was experimentally studied on a scored copper surface at a heat-flux range of 0 - 60 W/cm2. Bubble dynamics in an isolated bubble region were carefully investigated, including bubble departure diameters, bubble departure frequencies, and active nucleation site densities. The bubble dynamics were compared with available models, indicating the suitable models regarding the present experimental results. Then, based on the bubble dynamics, a mechanistic heat transfer model, developed in our previous studies, was employed to predict the present boiling curve. In the mechanistic model, heat fluxes from natural convection, transient heat conduction, and microlayer evaporation were incorporated.

Experimental Study of Effect of Nucleation Site Size on Bubble Dynamics during Nucleate Pool Boiling Heat Transfer

2014 ◽  
Vol 592-594 ◽  
pp. 1596-1600 ◽  
Author(s):  
Abdul Najim ◽  
Anil R. Aacharya
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Growth Period ◽  
Nucleation Site ◽  
Hypodermic Needle ◽  
Nucleate Pool Boiling ◽  
Pool Boiling Heat Transfer

In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

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.

Prediction of the Critical Gas Velocity of Liquid Unloading in a Horizontal Gas Well

SPE Journal ◽  
2017 ◽  
Vol 23 (02) ◽  
pp. 328-345 ◽  
Author(s):  
Zhibin Wang ◽  
Liejin Guo ◽  
Suyang Zhu ◽  
Ole Jørgen Nydal
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
Empirical Model ◽  
Force Balance ◽  
Real Field ◽  
Entrainment Rate ◽  
Gas Velocity ◽  
Liquid Loading ◽  
Wide Range ◽  
Fluid Properties

Summary Analysis of the experimental data for liquid-entrainment rate, forces exerted on liquid droplet, and secondary flow occurring in the gas core show that the liquid is mainly carried in the form of film in the inclined annular flow. Therefore, it is more reasonable to establish a mathematical model from the bottom-film reversal than from the droplet reversal. In this study, a new analytical model is developed from force balance of the bottom film of the inclined tubing after studying the bottom-film thickness and gas/liquid interfacial friction factor to reveal the liquid-loading mechanism. Furthermore, a new Belfroid-like empirical model is proposed that is based on the calculation results of a wide range of flowing parameters from the new analytical model to predict the liquid-loading status of gas wells. The new empirical model introduces a coefficient Cd,p,uSL,T to consider how the fluid properties under downhole flow condition affect the critical gas velocity. Cd,p,uSL,T in the new empirical model increases with the pipe diameter, liquid velocity, and flowing pressure, and decreases with the flowing temperature. The new analytical model, having an average error of 8.45%, agrees well with the published experimental data, and it also performs well in predicting the pressure gradient at liquid unloading condition. The new empirical model could be applied for the prediction of real field operations and has been validated with an accuracy rate of 95% against data newly collected from 60 horizontal wells. The new work can accurately and easily judge the liquid-loading status, and it also reveals how the fluid properties under downhole flowing condition affect the liquid loading.

Effect of Surface Wettability on Active Nucleation Site Density During Pool Boiling of Water on a Vertical Surface

1993 ◽  
Vol 115 (3) ◽  
pp. 659-669 ◽  
Author(s):  
C. H. Wang ◽  
V. K. Dhir
Keyword(s):  
Nearest Neighbor ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Optical Microscope ◽  
Nucleation Site ◽  
Vertical Surface ◽  
Cumulative Number ◽  
Copper Surfaces ◽  
Average Value ◽  
Nucleation Sites

Pool boiling of saturated water at 1 atm pressure has been investigated. In the experiments, copper surfaces prepared by following a well-defined procedure were used. The cumulative number density of the cavities and their shapes were determined with an optical microscope. The surface had a mirror finish and had a surface Ra (centerline average) value of less than 0.02 μm. The wettability of the surface was changed by controlling the degree of oxidation of the surface. In the experiments with the primary surface, the wall heat flux and superheat were determined with the help of thermocouples embedded in the test block. The density, spatial distribution, local distribution, and nearest-neighbor distance distribution of active nucleation sites in partial and fully developed nucleate boiling were determined from still pictures.

Critical Heat Flux of Graphene Coated Copper Surface at High Pressures

2015 ◽  
Author(s):  
Nanxi Li ◽  
Amy Rachel Betz
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Pressures ◽  
Pool Boiling ◽  
Copper Surface ◽  
Test Fluid ◽  
System Pressure ◽  
Wall Superheat ◽  
Copper Cylinder

Boiling is an efficient way to transfer heat due to the latent heat of vaporization. Many variables, such as surface properties, fluid properties, and system pressure, will affect the performance of pool boiling. Enhanced pool boiling has extensive applications in chemical, microelectronics, and power industries. Previous research has shown that micro- or nanostructured surfaces and coated surfaces will increase heat transfer coefficients up to one order of magnitude at atmospheric pressure. Graphene as a very good material with superb mechanical and electrical properties also has potential to enhance pool boiling performance. The purpose of this research is to investigate heat transfer enhancement on a graphene coated surface compared to a plane copper surface at atmospheric pressure and increased pressures with deionized water. The effect of the graphene coating on the critical heat flux is also investigated. To carry out the experiments, we designed and fabricated a special experimental facility that will withstand the high pressures (up to 20 bar) and high temperatures. Graphene is coated on a 1 cm2 copper surface using spray coating. The boiling vessel is pressurized with nitrogen and the system pressure is controlled by a back pressure regulator. The test fluid is preheated to saturation temperature by two 500 W cartridge heaters. Multiple 150 W cartridge heaters are inserted in a copper cylinder to provide wall superheat for bubbles to nucleate on the studied surface. When the system reaches steady state, a process controller controls these cartridge heaters to increase the heat flux gradually from 0 kW/m2 to the critical heat flux. The copper cylinder is insulated with PTFE to minimize heat loss from the side. The gap between the copper cylinder and the insulation surface is carefully sealed with high temperature epoxy to reduce undesired nucleation sites. The wall superheat corresponding to each heat flux is extrapolated using Fourier’s law from three thermocouple readings. The heat transfer coefficient can thus be calculated at each heat flux for the every test fluid at its corresponding pressure. A camera with 3.2 cm field of view at a working distance of 12 cm to 15 cm is used to visualize the bubble formation on the heated surface.

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.

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