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Dissertations / Theses on the topic 'Nucleate boiling'

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Published: 4 June 2021
Last updated: 29 July 2024

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1

Pascual, Christopher C. "EHD enhancement of nucleate pool boiling." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19027.

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2

Michta, Edouard. "Modeling of Subcooled Nucleate Boiling with OpenFOAM." Thesis, KTH, Reaktorteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32042.

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Within the course of this master thesis project, subcooled nucleate boiling in a vertical pipe has been modeled using CFD. The modeling has been carried out within the OpenFOAM framework and a two-phase Eulerian approach has been chosen. The code can be used to predict the distribution of the local ow parameters, i.e.the void fraction, the bubble diameter, the velocity of both liquid and gas, the turbulent intensity as well as the liquid temperature. Special attention has been devoted to the phenomena which govern the void fraction distribution in the radial direction. Two di erent solvers have been implemented and the simulations have been performed in two dimensions. Firstly, isothermal turbulent bubbly ow is mechanistically modeled in a solver named myTwoPhaseEulerFoa-mAdiabatic. The conservation equations of mass and momentum are solved for the two phases, taking special care in the modeling of the interfacial forces. The turbulence phenomena are described by a classical k- model in combination with standard wall functions for the near-wall treatment. Furthermore, an interfacial area concentration equation is solved and two di erent models for its sink- and source terms (corresponding to bubble coalesence and bubble breakup) have been investigated. Secondly, a solver named myTwoPhaseEulerFoamBoiling has been developed based on the rst solver in order to model a heated wall leading to subcooled nucleate boiling and subsequent condensation in the subcooled liquid. Additional terms accounting for the phase change have been included in the mass and momentum conservation equations as well as in the interfacial area equation. Assuming the gas phase being at saturation conditions, only one energy equation for the liquid phase needs to be solved. The adiabatic solver has been validated against the DEDALE experiment and the simulation results showed satisfactory agreement with the measured data. The predictions obtained from myTwoPhaseEulerFoam-Boiling have been compared to the DEBORA experimental data base. They are qualitatively similar but rather high quantitative discrepancies exist. Grid dependence tests revealed that the latter solver depends on the near-wall grid resolution, a yet unresolved issue related to the application of the wall heat ux as the boundary condition. However, the results were shown to be insensitive to small variations in the applied inlet conditions.
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3

Breen, R. J. "PWR safety studies : nucleate boiling heat transfer." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236258.

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4

Bertsch, George M., Stephen B. Memory, and P. J. Marto. "Nucleate pool boiling characteristics of R-124." Thesis, Monterey, California: Naval Postgraduate School, 1993. http://hdl.handle.net/10945/24202.

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5

Athavale, Advait D. "EXPERIMENTAL STUDY OF SATURATED NUCLEATE POOL BOILING IN AQUEOUS POLYMERIC SOLUTIONS." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1314758640.

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6

Henry, Christopher Douglas. "Nucleate pool boiling characteristics from a horizontal microheater array." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3185.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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7

Ellepola, Jerome. "Nucleate boiling : nonlinear spatio-temporal variations in wall temperature." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389327.

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8

Holland, Adrian Mark. "Control of nucleate boiling with micro-machined surface features." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/11343.

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This thesis discusses the production and use of laser-machined boiling grids that provide controlled nucleate boiling and enhanced heat transfer characteristics for application primarily to IC engine cooling systems. The surface features of heated plates are known to have a significant effect on nucleate boiling heat transfer and bubble growth dynamics. Nucleate boiling starts from discrete bubbles that form on surface imperfections, such as cavities or scratches. The gas or vapours trapped in these imperfections serve as nuclei for the bubbles. After inception, the bubbles grow to a certain size and depart from the surface. The bubble departure process significantly increases heat transfer rates compared to pure convection. In this work, special heated surfaces were manufactured by laser machining cavities into polished aluminium plates. This was accomplished with an Nd:YAG laser system, which allowed drilling of cavities of a known diameter. The size range of cavities was 25 to 300 micrometers. The resulting nucleate pool boiling was analysed using a high-speed imaging system comprising an infrared laser and high resolution CCD camera. This system was operated up to a 2 kHz frame rate and digital image processing allowed bubbles to be analysed statistically in terms of departure diameter, departure frequency, growth rate, shape and velocity. Data were obtained for heat fluxes up to 150 kW.m'2. Bubble measurements were obtained working with water at atmospheric pressure. The surface cavity diameters were selected to control the temperature at which vapour bubbles started to grow on the surface. The selected size and spacing of the cavities was also explored to provide optimal heat transfer. Insights into the interaction and interseeding mechanism were obtained. The research has demonstrated that nucleate boiling can be controlled by optimally sized and spaced laser-machined cavities in heated metal surfaces.
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9

Neu, Samuel Charles. "Experimental and Computational Investigation of Electrohydrodynamically –Enhanced Nucleate Boiling." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/405.

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"The importance of two-phase heat transfer for thermal management of aerospace avionic systems has become increasingly important as these systems have become miniaturized. Embedded active cooling systems are used to remove heat from processors and other electronic components and transferring this heat to radiators or other heat exchangers. As the characteristic dimension of flow channels for two-phase flow becomes comparable to bubble size, the mini-channels (< 3 mm) used to direct the cooling fluid can complicate nucleate boiling heat transfer. Bubbles can encounter other heated walls, rapidly expanding and greatly reducing heat transfer as well as causing pressure oscillations and flow instabilities. The use of eletrohydrodynamic (EHD) effects, through the introduction of non-uniform electric fields, can help mitigate this problem by altering the behavior of nucleating bubbles. A combined experimental and computational study was undertaken using HFE-7100, an engineered fluid used in heat transfer applications, to investigate the potential for enhancement of nucleate boiling using EHD effects induced by applying a non-uniform electric field. In the experimental study, a minichannel was constructed consisting of an upper and lower copper electrode and glass side walls to allow visualization. The channel height and width were 3mm and 4.76 mm respectively, representative of the minichannel regime. The upper electrode was grounded while the lower electrode was heated and biased to high voltage. Optical imaging combined with post-processing and statistical analysis was used to quantify the effect of EHD on the bubble behavior. Bubbles were found to form preferentially on nucleation sites resulting from imperfections in the heated copper surface over artificially created nucleation sites. When a high voltage is applied across the electrodes, the electric field enhancement along the rim of the nucleation site is believed to influence the force balance on the forming bubble and thereby influence the bubble departure size and frequency. EHD forces also act on the bubble surface as a result of the variation in permittivity between the liquid and vapor phases, altering its shape as has been previously reported in the literature. Test results are presented that demonstrate that the application of EHD increases the nucleation site density on the heated surface and increase the bubble departure frequency from individual sites. In addition, test results are presented to show that EHD forces alter the shape of bubbles during growth and the vertical position of the detached bubbles as they are carried along in the cross flow. To better understand the underlying phenomena affecting the bubble shape and departure frequency, a numerical simulation of the bubble growth and departure was performed using COMSOL multiphysics software customized to incorporate a user-defined body force based on the Maxwell Stress Tensor. Tracking of the bubble surface, including coalescence and breakup was incorporated using the phase field variable method in which the Navier-Stokes and heat transfer equations are solved for each phase of the fluid. Results from the simulations confirmed the sensitivity of the bubble elongation and neck formation to the nucleation site geometry, specifically the angle along the rim where field enhancement occurs. The enhanced constriction of the bubble neck resulted in early detachment of bubbles when compared to simulations in which EHD was not applied. This finding provides some insight into the higher bubble departure frequency and nucleation site density observed in the experiment. The results from the combined experimental and numerical study suggest that EHD enhancement may provide a mechanism for extending the use of nucleate heat transfer to minichannels, thereby enabling additional options for cooling in compact, embedded systems. "
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10

Wasekar, Vivek Mahadeorao. "Nucleate Pool Boiling Heat Transfer in Aqueous Surfactant Solutions." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin994964318.

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11

Arata, Frank A. "Nucleate boiling heat transfer study of direct immersion cooling of a 3x3 array of vertically orientated electronic components in a dielectric fluid." Thesis, Monterey, California : Naval Postgraduate School, 1992. http://handle.dtic.mil/100.2/ADA257558.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 1992.
Thesis Advisor: Kelleher, M. D. "September 1992." Description based on title screen as viewed on April 16, 2009. Includes bibliographical references (p. 92). Also available in print.
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12

Robinson, Anthony James Judd R. L. "Bubble growth dynamics in boiling /." *McMaster only, 2003.

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13

Cryer, Matthew A. "An experimental study of high heat flux removal using micro-droplet spray cooling." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FCryer.pdf.

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14

Kelley, Mitchell Joseph. "Experimental design for study of nucleate boiling in porous structures." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68530.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 48).
The superheat required to initiate nucleate boiling inside porous wicks is not well understood in practice. This thesis reports the design of an experimental setup for investigating the onset of vapor nucleation in sintered porous structures. Pressure sensing was evaluated as an effective means of detecting the onset of nucleation. Thermal studies were conducted with a custom finite difference script in conjunction with finite element analysis. Heat conduction through a three dimensional wick was reduced to one dimensional conduction via symmetry and design constraints. The wick was optimized to achieve a temperature drop of 30 *C at a common heat pipe operating temperature of 70 °C.
by Mitchell Joseph Kelley.
S.B.
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15

Campbell, Niall A. F. "The influence of nucleate boiling in engine cooling and temperature control." Thesis, University of Bath, 2001. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581995.

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16

Lenci, Giancarlo. "Prediction of departure from nucleate boiling in PWR fast power transients." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80659.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 89-91).
An assessment is conducted of the differences in predicted results between use of steady state versus transient Departure from Nucleate Boiling (DNB) models, for fast power transients under forced convective heat exchange conditions. Theoretical DNB models based on liquid film thickness variation are adapted and modified from existing studies into a generalized formulation to allow implementation into a reactor simulation code. The formulation is validated using experimental data available at low pressure. An application is performed at Pressurized Water Reactor (PWR) operating conditions, simulating rod ejection accidents. The transient DNB model is applied to PWR rod ejection accident cases computed by the reactor dynamics code SIMULATE-3K. Rod power profiles deriving from pin power reconstruction are used in a subchannel simulation done with VIPRE to obtain local pin parameters. Results show that a significant delay exists for the occurrence of transient DNB compared to quasi steady-state DNB and in some cases DNB does not occur, even if predicted by quasi steady-state methods. Most modem codes for PWR thermal hydraulic simulation use quasi steady-state approaches to predict DNB, thus applying a steady-state correlation to time-dependent cases. However, according to the transient DNB model used in this work, a time lag exists between DNB as predicted by steady-state correlations, and effective transient DNB. During that time lag, the liquid film between the wall and the bubbly layer thins until the heated surface is eventually dried out. Such DNB prediction by steady state models is a conservative estimate. This work assesses the consequences of the use of more accurate models for predicting transient DNB, which are desirable to get better knowledge of design margins, to allow optimization of plant safety and efficiency.
by Giancarlo Lenci.
S.M.
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17

Osborne, William F. "Influence of Heater Orientation on Fluctuations in Steady-state Nucleate Boiling." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/4958.

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In observations of steady-state nucleate boiling, fluctuations in the temperature and heat flux might initially appear to be completely random. However, it was shown that, for a vertically mounted platinum wire in liquid nitrogen, the fluctuations about the steady-state exhibit an average counterclockwise circulation when the heat flux is plotted versus the superheat temperature. An area associated with the average circulation was proposed as a numerical measure of stability for steady-state nucleate boiling. The mechanisms for the generation of these fluctuations are thought to be the feedback of the bubbles rising past the wire and the differential heating and cooling that this engenders. Data similar to the data on the vertical wire have been obtained using the same wire mounted horizontally. Although the counterclockwise circulation mentioned above is still seen, the measure of stability as proposed earlier, is less useful for prediction of the transition to film boiling. This reduced sensitivity can be attributed to the fact that the possibility of feedback through the rising bubbles has been eliminated.
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18

Sanna, Antonio. "Numerical investigation of saturated flow boiling on thin walls." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4615.

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Boiling heat transfer provides a means of removing high heat fluxes at low temperature differences in many applications in the power and process industries. A strong interest has been also developed for the cooling of silicon-based devices, such as electronic chips. However, a complete model to describe the processes involved has not been developed as yet. This PhD project focused on the study of nucleate pool boiling via numerical simulations for a solid plate horizontally immersed in a saturated liquid with a large number of potential nucleation sites. The simulations were developed by a FORTRAN code based on a hybrid approach, combining the 3-dimensional time-dependent solution for the temperature field on the substrate with semi-empirical models for phenomena occurring on the liquid side. The starting point of the project was the modification of a previous version of the code in order to reduce the computational time (in collaboration with Dr. Nelson at Los Alamos National Laboratory) and improve the modelling of the physics of the processes. One of the key features of the code is the flexibility in adapting to different conditions. In fact the code was used to study bubble growth, site activation frequency and superheat variations, as well as the interactions between nucleation sites. The differences in behaviour between very thin metal foils immersed in water and thicker silicon substrates in FC-72 were studied. The results were compared with experimental results produced at the University of Edinburgh and the University of Ljubljana, both partners of this project. Both the numerical and physical modifications introduced made it possible to have simulations for a large number of sites, of the order of 100, in reasonable times, of the order of days, so that the code can be now used as a tool for the design of new test sections.
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19

Alfama, Marco. "Theoretical and experimental investigation of the heat transfer and pressure drop optimisation on textured heat transfer surfaces." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/62792.

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Modern nuclear reactors still use Zirconium-4 Alloy (Zircaloy®) as the cladding material for fuel elements. A substantial amount of research has been done to investigate the boiling heat transfer behind the cooling mechanism of the reactor. Boiling heat transfer is notoriously difficult to quantify in an acceptable manner and many empirical correlations have been derived in order to achieve some semblance of a mathematical model. It is well known that the surface conditions on the heat transfer surface plays a role in the formulation of the heat transfer coefficient but on the other hand it also has an effect on the pressure drop alongside the surface. It is therefore necessary to see whether there might be an optimum surface roughness that maximises heat transfer and still provides acceptably low pressure drop. The purpose of this study was to experimentally measure pressure drop and heat transfer associated with vertical heated tubes surrounded by flowing water in order to produce flow boiling heat transfer. The boiling heat transfer data was used to ascertain what surface roughness range would be best for everyday functioning of nuclear reactors. An experimental set-up was designed and built, which included a removable panel that could be used to secure a variety of rods with different surface roughnesses. The pressure drop, surface temperature, flow rate and heat input measurements were taken and captured in order to analyse the heat transfer and friction factors. Four rods were manufactured with different roughnesses along with a fifth rod, which remained standard. These rods were tested in the flow loop with water in the upward flow direction. Three different system mass flow rates were used: 0kg/s, 3.2kg/s and 6.4kg/s. Six repetitions were done on each rod for the tests; the first repetition was not used in the results since it served the purpose to deaerate the water in the flow loop. The full range of the power input was used for each repetition in the tests. For the heat transfer coefficient at a system mass flow rate of 3.2kg/s, satisfactory comparisons were made between the test results and those found in literature with an average deviation of 14.53%. At 6.4kg/s system mass flow rate the comparisons deviated on average 55.45%. The velocity of the fluid in the test section was calculated from the pressure drop and was validated using separate tests. The plain rod, with no added roughness, was found to be the optimal surface roughness which is what is used in industry today. The flow loop was in need of a couple of redesigns in order to produce more accurate results. Future work suggestions include adding more rods in the test section in order to investigate the nature of heat transfer in a rod bundle array as well as implementing all the suggested changes listed in the conclusion.
Dissertation (MEng)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
MEng
Unrestricted
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20

Al-Maeeni, Lway. "Sub-cooled nucleate boiling flow cooling experiment in a small rectangular channel." Thesis, KTH, Fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-170396.

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21

Chilman, Scott V. "Nucleate boiling characteristics of R-113 in a small enhanced tube bundle." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28404.

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22

Rabhi, Achref. "Numerical Modelling of Subcooled Nucleate Boiling for Thermal Management Solutions Using OpenFOAM." Licentiate thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-53307.

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Two-phase cooling solutions employing subcooled nucleate boiling flows e.g. thermosyphons, have gained a special interest during the last few decades. This interest stems from their enhanced ability to remove extremely high heat fluxes, while keeping a uniform surface temperature. Consequently, modelling and predicting boiling flows is very important, in order to optimise the two-phase cooling operation and to increase the involved heat transfer coefficients.  In this work, a subcooled boiling model is implemented in the open-source code OpenFOAM to improve and extend its existing solver reactingTwoPhaseEulerFoam dedicated to model boiling flows. These flows are modelled using Computational Fluid Dynamics (CFD) following the Eulerian two-fluid approach. The simulations are used to evaluate and analyse the existing Active Nucleation Site Density (ANSD) models in the literature. Based on this evaluation, the accuracy of the CFD simulations using existing boiling sub-models is determined, and features leading to improve this accuracy are highlighted. In addition, the CFD simulations are used to perform a sensitivity analysis of the interfacial forces acting on bubbles during boiling flows. Finally, CFD simulation data is employed to study the Onset of Nucleate Boiling (ONB) and to propose a new model for this boiling sub-model, with an improved prediction accuracy and extended validity range. It is shown in this work that predictions associated with existing boiling sub-models are not accurate, and such sub-models need to take into account several convective boiling quantities to improve their accuracy. These quantities are the thermophysical properties of the involved materials, liquid and vapour thermodynamic properties and the heated surface micro-structure properties. Regarding the interfacial momentum transfer, it is shown that all the interfacial forces have considerable effects on boiling, except the lift force, which can be neglected without influencing the simulations' output. The new proposed ONB model takes into account convective boiling features, and it able to predict the ONB with a very good accuracy with a standard deviation of 2.7% or 0.1 K. This new ONB model is valid for a wide range of inlet Reynolds numbers, covering both regimes, laminar and turbulent, and a wide range of inlet subcoolings and applied heat fluxes.
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23

Stumm, Brian J. "An investigation on bubble departure in subcooled flow boiling /." Online version of thesis, 1993. http://hdl.handle.net/1850/11186.

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24

Sloan, Alison D. "Pool boiling at reduced pressure with screen-laminate surface enhancements." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460779.

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25

Talari, Kiran. "LIQUID CRYSTAL THERMOGRAPHY STUDIES IN WATER POOL BOILING AT SUBATMOSPHERIC PRESSURES." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3388.

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A pool boiling experimental facility has been designed and built to investigate nucleate pool boiling in water under sub atmospheric pressure. Liquid crystal thermography, a non intrusive technique, is used for the determination of surface temperature distributions. This technique uses encapsulated liquid crystals that reflect definite colors at specific temperatures and viewing angle. Design of the test section is important in this experimental study. Since a new TLC is required for every new set of test conditions, a permanently sealed test section is not an option. The real challenge is to design a leak proof test section which is flexible so that it can be taken apart easily. A plexiglass test section, including a top chamber with an internal volume of 60.9 x 60.9 x 66.4 mm and a bottom plate of 5.5mm thickness is designed and assembled together using quick grips. In the test section, water is boiled using 85.0mm x 16.0mm and 0.050mm thick Fecralloy® as the heating element. The TLC sheet is attached to the bottom plate and the heating element is placed on top of TLC so that the temperature distribution of the heating element during boiling can be interpreted from TLC. A camera system fast enough to capture the thermal response of the TLC and an arrangement to capture both hue of the TLC and growth of the bubble on the same frame has been designed and successfully used. This system allowed recording of position, size and shape of the bubble with synchronized surface temperature. In order to get hue vs. temperature relation, in-situ calibration of the TLC is performed for each test condition with the present experimental setup and lighting conditions. It is found that the calibration curve of the TLC at atmospheric pressure is different from the calibration curve of the same TLC at subatmospheric pressures. The maximum temperature difference between the two curves for the same hue is found to be only 0.6°C. The experiment is run at four different test conditions of subatmospheric pressure and low heat flux. It is run at system pressures of 6.2kPa (0.89Psi) and 8.0kPa (1.16Psi) with a constant heat flux of 1.88kW/m2 and 2.70kW/m2, and a constant heat flux of 2.70kW/m2, 3.662kW/m2 and 4.50 kW/m2 respectively. Analysis of nucleating surface temperatures using thermochromic liquid crystal technique is performed for these test conditions and the bubble dynamics is studied. The temperature distribution is quite varied in each case and the temperature is at its maximum value at the center of the bubble and it decreases radially from the center. The dry spot observed during the experiments indicates that the process of evaporation of the microlayer is dominant at subatmospheric pressures. It is observed that at very low pressure and heat flux the bubble growth is accompanied by the neck formation. Boiling parameters such as bubble frequency, bubble size and contact are also analyzed and a summary of these results for four different test conditions is presented and the relevant differences between the cases are discussed and the effect of increase in pressure and heat flux is noted.
M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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26

Jackson, Jelliffe Kevin. "Cryogenic two-phase flow during chilldown flow transition and nucleate boiling heat transfer /." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014782.

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27

Zimmermann, Anton. "A modelling and experimental study of nucleate boiling for application to IC engines." Thesis, Loughborough University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398042.

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28

Thiagarajan, Naveenan Bhavnani S. H. "Experimental investigation of thermo-hydraulic characteristics of two-phase flow of FC72 in microchannel heat sinks." Auburn, Ala., 2009. http://hdl.handle.net/10415/1954.

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29

Rudemiller, Gary R. "A fundamental study of boiling heat transfer mechanisms related to impulse drying." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/5757.

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30

Shim, Sang Yong. "Turbulent fluid flow, heat transfer and onset of nucleate boiling in annular finned passages." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23663.pdf.

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31

Haas, Russell E. "Nucleate pool boiling of R-114/oil mixtures in a small enhanced tube bundle." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23733.

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32

Takeyama, Mao. "Convective heat transfer of saturation nucleate boiling induced by single and multi-bubble dynamics." Kyoto University, 2021. http://hdl.handle.net/2433/261621.

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33

Mizo, Viktor R. "Investigation of inertia controlled bubble departure mechanism in subcooled flow boiling using high speed photography /." Online version of thesis, 1995. http://hdl.handle.net/1850/12084.

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34

Cartwright, Michael D. "Experimental and analytical investigation of the bubble nucleation characteristics in subcooled flow /." Online version ot thesis, 1995. http://hdl.handle.net/1850/12048.

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35

Sugiyama, Dean C. "Nucleate pool boiling of R-114 and R-114/oil mixtures from single enhanced tubes." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/27170.

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Approved for public release; distribution is unlimited
Nucleate pool boiling heat transfer is an integral part of any vapor-compression refrigeration cycle. With a view to improving overall cycle efficiency, the heat transfer performance in the evaporator can be improved by using enhanced boiling surfaces. This thesis looks at the pool boiling characteristics of R-114 (presently used in large shipboard AC systems) from 10 enhanced single copper tubes and compares performance with a smooth copper tube. Since small amounts of oil escape into the refrigerant as it passes through the compressor of a refrigeration system, tests have also been conducted with up to 10% (by weight) of a miscible oil to see what effect this may have on overall evaporator performance..
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36

Lake, Lannie R. "The influence of a lower heated tube on nucleate pool boiling from a horizontal tube." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23702.

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37

Stehle, Gregory Raymond. "Confinement of Nucleation Sites in Nucleate Pool Boiling Using Atomic Layer Deposition and Constrictive Heaters." Thesis, University of Pittsburgh, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10645783.

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Boiling heat transfer is a powerful cooling mechanism used in a variety of industries to efficiently dissipate heat by taking advantage of latent heat. Nucleation site interactions have been demonstrated to affect behaviors in the bulk fluid, in the solid substrate and coalescence. Despite extensive studies of multi-site interactions, the conclusions of these studies are not in agreement. Namely, hydrodynamic effects are explained by some studies to promote nucleation while other studies find that, even with thermally isolated heat supplies, the presence of nearby sites diminishes nucleation. The present study identifies superheated fluid as a possible explanation for this variability. Hydrodynamic factors are determined to only promote single site nucleation if there is an appreciable thermal boundary layer present. Even with a thermal boundary layer, the presence of other sites causes competition over the superheated fluid; thus, diminishing the promotive effects of hydrodynamic factors. There have also been studies that have characterized the changing dimensions of the microlayer and the heat transfer that occurs beneath it. However, there is not a complete study of bubble behavior resulting from varying heater areas; specifically heater areas smaller than the microlayer. The present study quantifies the effect of heater diameter on vapor effectiveness and determines the optimal heater diameter. A metric for the coincidence of vapor production and microlayer coverage is proposed. Vapor effectiveness and the coincidence metric are shown to have similar relationships with heater diameter.

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38

Munro, Troy. "Heater Geometry and Heat Flux Effects On Subcooled, Thin Wire, Nucleate Pool Boiling In Microgravity." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1235.

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Nucleate boiling is widely used as a means of heat transfer in thermal management systems because of its high heat transfer rates. This study explored the effects of heat flux and surface geometry on heat transfer behavior and bubble dynamics of nucleate pool boiling in microgravity. A single platinum wire, a twist of three platinum wires, and a twist of four platinum wires were used as boiling surfaces for two separate experiments performed in microgravity on board NASA’s parabolic flight aircraft. Wire temperature, thermocouple, and video measurements were taken during a total of 44 microgravity parabolas. Results show that the crevices formed by wire twisting provide regions of localized superheating and are able to reduce the heat flux necessary for boiling onset to occur. This localized heating results in a lower average heater temperature and shortened superheating periods, but this effect decreases when more wires are present in the twist. This behavior was investigated and confirmed with a finite volume, transient conduction model. This model also showed that the water temperature profile at the bubble onset indicates that water at a certain distance from the wire surface, in this experiment 50 μm, needs to be heated to above saturation temperature in order to initiate and generate a burst of bubbles. A relative bubble area analysis method was able to quantify vapor production and bubble behavior across multiple frames of video. Application of this method revealed a transition of bubble behavior from large isolated bubbles to jet flows of small bubbles, and this method allowed the heat flux contribution of jet flows to be approximated. Additionally, a new mode of jet flows was observed. Particle image velocimetry was used to provide approximate velocities of small bubble jet flows and their influence on heat transfer to the bulk fluid.
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Diana, Antoine. "Liquid-vapour phase change : nucleate boiling of pure fluid and nanofluid under different gravity levels." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/65842/1/Antoine_Diana_Thesis.pdf.

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This research was a step towards the comprehension of the nano-particles interaction with bubbles created during boiling. It was aimed at solving the controversies of whether the heat transfer is enhanced or deteriorated during the boiling of the nanofluid. Experiments were conducted in normal gravity and reduced gravity environments on-board the European Space Agency Parabolic Flight Program. The local modification of the thermo-physical properties of the fluid and moreover the modification experienced in the liquid microlayer under the growing vapour bubble were the dominant factors in explaining the mechanisms of the boiling behaviour of the nanofluid.
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40

Subedi, Jeewan. "Experimental Explorations in Pool Boiling of Aqueous Surfactant Solutions." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543994284010763.

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41

Joo, Daniel. "EXPERIMENTS IN POOL BOILING HEAT TRANSFER AND NUCLEATIONDYNAMICS OF HIGH PRESSURE REFRIGERANTS." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3057.

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A high pressure pool boiling experiment of pressurized R134a is designed and built, utilizing thermochromatic liquid crystal techniques. Liquid crystals thermo-chromatography uses encapsulated liquid crystals that are sensitive to temperature. When exposed to hot temperatures the crystal reflect a blue/violet color, and when exposed to cooler temperatures it reflects a red/orange color. The color value or hue is proportional to its temperature. Using this technique this experiment is capable of studying the physics and thermodynamics of refrigerants under nucleate pool boiling. The main objective of this experiment was the design of the experimental setup. Various designs were tested and validated, of which all incorporated a pressure resistant chamber constructed out of aluminum and glass viewing ports. Design parameters such as the heating element thickness were verified using a transient FEA thermal model. This model, which was developed in ANSYS, verified that this design would be able to capture the thermal response of the thermochromatic liquid crystals. This analysis concluded that a negligible error of 0.02°C is expected due to transient effects. Difficulties were encountered during early stages of development; most notable were imaging limitations such as low camera frame-rates and poor resolution. Since a TLC technique was used to measure the temperature of the boiling surface, a camera system fast enough to capture the thermal response was needed. At bubble frequencies of 30 nucleations per second, it was necessary for the camera to have much higher frame rates. Through the use of two synchronized cameras, the surface temperature, position, size and shape of the bubbles were recorded simultaneously. Two camera systems were designed and tested. The first system consisted of a high speed CMOS camera capable of capturing 1,000 frames per second, and an RBG CCD color camera capable of 30 Frames per second. However, this system was limited the slow frame rate and low resolution of the RBG camera. The second system used two high resolution and fast shutter speed cameras, which were able to capture fast bubble nucleations. This method required the assumption that under constant operating conditions, the path of one bubble was identical to the next. This method was tested utilizing the high speed camera, and was shown that there was less than a .04% deviation from the path any bubble to that of the next. Detailed analysis of nucleating surface temperatures using thermochromatic liquid crystal technique and temporal-temperature response under various heat flux and at 813.6kPa (118Psia) and 882.5kPa (128Psia) was performed. It is seen that temperature distribution is quite varied in each case. At high pressures the size of nucleation site decreases, giving rise to an increase in the surface temperature. Bubble growth is also analyzed through the use of high speed cameras and compared to temperature distributions. Simultaneous temperature and bubble size measurements provided a correlation between bubble growth and heat transfer. Boiling parameters such as bubble frequency, bubble size, and contact area are also analyzed. From the surface temperature plots, the local and average heat transfer coefficients were calculated as a function of time and bubble dynamics.
M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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42

Akcasayar, Nezih. "Nucleate pool boiling performance of finned and high flux tube bundles in R-114/oil mixtures." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27168.

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Approved for public release; distribLUion is unlimited
The heat transfer characteristics of pure R-114 and R-114/oil mixtures during nucleate pool boiling from a small bundle of finned and High Flux tubes were measured. The bundles had 5 instrumented and 10 additional heated tubes of 15.8 mm outside diameter which were arranged in an equilateral triangular pitch of 19.1 mm giving a pitch-to-diameter ratio of 1.2. Pure refrigerant with York-C lubrication oil mass con-centrations of 1, 2, 3, 6 and 10% was used. All experiments were performed at 2.2C corresponding to a pressure slightly below atmospheric. Data sets were taken using decreasing heat flux only in order to avoid the boiling hysterisis phenomenon. An enhancement in heat-transfer performance of the finned tube bundle due to oil applications was observed. The enhancement increased with up to 3% oil concentration over all heat flux ranges. Further oil additions showed better performances than pure R-114 at high heat flux levels but poorer performance was obtained at lower heat fluxes. High flux tube experiments indicated that the heat transfer performance of the bundle was approximately 2.5 times better than the finned tube bundle performance for pure R-114. No positive performance enhancement was observed from the High Flux tube bundle due to oil addition. The performance immediately degraded with 1% oil and stayed almost constant with 2% and 3% oil additions. A decrease of performance became significant at high heat flux levels with oil concentrations of 6% and 10%. The performance of these two tube bundles was compared to smooth tube operation.
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43

Guion, Alexandre Nicolas. "Modeling and simulation of liquid microlayer formation and evaporation in nucleate boiling using computational fluid dynamics." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112380.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 243-252).
The transport of latent heat makes boiling one of the most efficient modes of heat transfer, allowing a wide range of systems to improve their thermal performance, from microelectronic devices to nuclear power plants. In particular, Boiling Water Reactors (BWR) use boiling as the primary mode of heat transfer in the reactor core to accommodate very high heat fluxes. In Pressurized Water Reactors (PWR) subcooled flow boiling can occur in hot sub-channels. As a bubble grows outside of a surface imperfection during nucleate boiling, viscous stresses at the wall can be strong enough to impede liquid motion and trap a thin liquid layer - referred to as microlayer, underneath the growing bubble. The contribution of microlayer evaporation to overall heat transfer and bubble growth can be large, in particular in the case of water1. In practice, numerical simulations of nucleate boiling resolve the macroscopic interface of the bubble and resort to subgrid models to account for the evaporation of the microlayer at the microscopic scale. The applicability of this subgrid modeling approach relies on the capacity to initialize the microlayer shape and extension, prior to its evaporation. However, existing models of microlayer formation are either physically incomplete2 or purely empirical3. In this work, we first confirm through a sensitivity study the need for accurate modeling of microlayer formation to initialize boiling simulations and to reproduce physical boiling dynamics (a). Then, we build the first generally applicable model for microlayer formation through direct computations of the hydrodynamics of bubble growth at the wall for a wide range of conditions and fluids, including water at 0.101MPa (lab experiments) and 15.5MPa (PWR), capillary numbers Ca [is element of] [0.001; 0.1], and contact angles [theta] [is element of] [10°; 90°] (b). In addition, we modify an existing experimental pool boiling setup to measure with unprecedented accuracy initial bubble growth rates needed to predict microlayer formation (c). Lastly, we develop a numerical procedure based on hydrodynamics theories to obtain mesh-independent results in moving contact line simulations for a wide range of contact angles and viscosity ratios (d). In particular, we use direct computations of the transition to a Landau-Levich-Derjaguin film in forced dewetting to inform the onset of microlayer formation in nucleate boiling. These contributions(a) (b) (c) (d) bridge a significant gap in our understanding of how boiling works and can be modeled at the microscopic scale, which represents a first step in designing surfaces with higher heat transfer performance and in building safer and more efficient energy systems.
by Alexandre Nicolas Guion.
Ph. D.
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44

Joshua, Nihal E. "Direct Immersion Cooling Via Nucleate Boiling of HFE-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699916/.

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This study experimentally investigated the effect of hydrophobic and hydrophilic surfaces characteristics on nucleate boiling heat transfer performance for the application of direct immersion cooling of electronics. A dielectric liquid, HFE – 7100 was used as the working fluid in the saturated boiling tests. Twelve types of 1-cm2 copper heater samples, simulating high heat flux components, featured reference smooth copper surface, fully and patterned hydrophobic surface and fully and patterned hydrophilic surfaces. Hydrophobic samples were prepared by applying a thin Teflon coating following photolithography techniques, while the hydrophilic TiO2 thin films were made through a two step approach involving layer by layer self assembly and liquid phase deposition processes. Patterned surfaces had circular dots with sizes between 40 – 250 μm. Based on additional data, both hydrophobic and hydrophilic surfaces improved nucleate boiling performance that is evaluated in terms of boiling incipience, heat transfer coefficient and critical heat flux (CHF) level. The best results, considering the smooth copper surface as the reference, were achieved by the surfaces that have a mixture of hydrophobic/hydrophilic coatings, providing: (a) early transition to boiling regime and with eliminated temperature overshoot phenomena at boiling incipience, (b) up to 58.5% higher heat transfer coefficients, and (c) up to 47.4% higher CHF levels. The studied enhanced surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.
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45

ZHANG, JUNTAO. "EXPERIMENTAL AND COMPUTATIONAL STUDY OF NUCLEATE POOL BOILING HEAT TRANSFER IN AQUEOUS SURFACTANT AND POLYMER SOLUTIONS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1077304904.

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46

Katta, Kiran Kumar. "Phase change cooling applications engine cooling /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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47

Nunes, Jéssica Martha. "Análise experimental da ebulição nucleada em superfícies nanoestruturadas sob condições de confinamento." Ilha Solteira, 2018. http://hdl.handle.net/11449/157255.

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Orientador: Elaine Maria Cardoso
Resumo: A intensificação da transferência de calor por meio de alterações na morfologia da superfície aquecida vem sendo estudada no meio científico, a fim de suprir a crescente demanda de resfriamento de dispositivos com alta capacidade de processamento e dimensões cada vez menores. O presente trabalho apresenta o estudo experimental do efeito de superfícies nanoestruturadas e do espaçamento do canal de confinamento durante a ebulição em piscina da água deionizada, à temperatura de saturação na pressão atmosférica, sobre o coeficiente de transferência de calor, HTC, e fluxo crítico de calor, CHF. As superfícies nanoestruturadas foram obtidas pelo processo de ebulição do nanofluido de Al2O3-água deionizada em duas diferentes concentrações más-sicas: 0,03 g/l (“baixa” concentração, LC) e 0,3 g/l (“alta” concentração, HC). Foram realizados testes livres, com espaçamento, entre a superfície aquecida e a superfície adiabática, de 30 mm (correspondendo a Bo = 12), e testes sob condições de confinamento, com espaçamento de 1,0 mm (Bo = 0,4). As superfícies de teste foram caracterizadas por meio de medição da rugosidade média (Ra), do ângulo de contato estático (molhabilidade), e imagens MEV. Foi observado um aumento médio de 45% no HTC do teste com superfície lisa nanoestruturada em baixa concentração de nanofluido, em relação à superfície lisa sem deposição. Esse ganho está relacionado com o aumento do número de sítios ativos de nucleação causado pela deposição das nanopartículas sobre a ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The intensification of heat transfer through changes in the heated surface morphology has been studied in the scientific community to meet the increase demand for cooling of devices with high processing power and smaller dimensions. This work presents the experimental study of the effect of nanocoated surfaces and gap size during nucleated boiling of deionized water, in saturation temperature at atmospheric pressure, about heat transfer coefficient, HTC, and critical heat flux, CHF. The pool boiling process of Al2O3-water based nanofluid at two different mass concentrations: 0.03 g/l (“low” concentration, LC) and 0.3 g/l (“high” concentration, HC), produced nanostructured surfaces. Unconfined tests were analyzed, with gap size between the heated surface and the adiabatic surface of 30 mm (corresponding to Bo = 12), and tests under confinement conditions, with gap size of 1.0 mm (Bo = 0.4). The tested surfaces were characterized by means of surface roughness (Ra) measurement, static contact angle (wettability), and SEM images. An average increase of 45% in HTC of the test with nanocoated smooth surface in low nanofluid concentration was observed in relation to smooth surface without deposition. This enhancement is related to the increase in the number of active nucleation sites caused by the nanoparticle’s deposition on the smooth surface. For all tests with rough nanocoated surfaces and nanocoated smooth one with high nanofluid concentration, there was degradation of the HTC ... (Complete abstract click electronic access below)
Mestre
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48

Romanchuk, Bradley J. "Computational Modeling of Bubble Growth Dynamics in Nucleate Pool Boiling for Pure Water and Aqueous Surfactant Solutions." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406809980.

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49

Schweizer, Nils [Verfasser], Peter [Akademischer Betreuer] Stephan, and Marco Paolo [Akademischer Betreuer] Di. "Multi-Scale Investigation of Nucleate Boiling Phenomena in Microgravity / Nils Schweizer. Betreuer: Peter Stephan ; Paolo Di Marco." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2010. http://d-nb.info/1106453506/34.

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Sielaff, Axel [Verfasser], Peter [Akademischer Betreuer] Stephan, and Andrea [Akademischer Betreuer] Luke. "Experimental Investigation of Single Bubbles and Bubble Interactions in Nucleate Boiling / Axel Sielaff. Betreuer: Peter Stephan ; Andrea Luke." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110791690/34.

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