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Sriraman, Sharan Ram. "Pool boiling on nano-finned surfaces." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2091.
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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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Ghiu, Camil-Daniel. "Pool Boiling from Enhanced Structures under Confinement." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16229.
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A study of pool boiling of a dielectric liquid (PF 5060) from single-layered enhanced structures was conducted. The parameters investigated were the heat flux, the width of the microchannels and the microchannel pitch. The boiling performance of the enhanced structures increases with increase in channel width and decrease in channel pitch. Simple single line curve fits are provided as a practical way of predicting the data over the entire nucleate boiling regime.
The influence of confinement on the thermal performance of the enhanced structures was also assessed. The main parameter investigated was the top space (0 mm { 13 mm). High-speed visualization was used as a tool . For the total confinement ( = 0 mm), the heat transfer performance of the enhanced structures was found to depend weakly on the channel width. For >0 mm, the enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. The maximum heat flux for a prescribed 85 oC surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime.
A semi-analytical predictive model applicable to pool boiling under confinement is developed. The model requires a limited number of empirical constants and is capable of predicting the experimental heat flux within 30%.
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Rice, Elliott Charles. "Sub-Cooled Pool Boiling Enhancement with Nanofluids." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3310.
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Phase-change heat transfer is an important process used in many engineering thermal designs. Boiling is an important phase change phenomena as it is a common heat transfer process in many thermal systems. Phase change processes are critical to thermodynamic cycles as most closed loop systems have an evaporator, in which the phase change process occurs. There are many applications/processes in which engineers employ the advantages of boiling heat transfer, as they seek to improve heat transfer performance. Recent research efforts have experimentally shown that nanofluids can have significantly better heat transfer properties than those of the pure base fluids, such as water.
The objective of this study is to improve the boiling curve of de-ionized water by adding aluminum oxide nanopthesiss in 0.1%, 0.2%, 0.3% and 0.4% wt concentrations in a sub-cooled pool boiling apparatus. Enhancement to the boiling curve can be quantified in two ways: (i) the similar heat fluxes of de-ionized water at smaller excess temperature, indicating similar quantity of heat removal at lower temperatures and (ii) greater heat fluxes than de-ionized water at similar excess temperatures indicating better heat transfer at similar excess temperatures. In the same fashion, the secondary objective is to increase the convective heat transfer coefficient due to boiling by adding different concentrations of aluminum oxide nanopthesiss.
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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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Kim, Sung Joong Ph D. Massachusetts Institute of Technology. "Pool boiling heat transfer characteristics of nanofluids." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41306.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.<br>Includes bibliographical references (leaves 79-83).<br>Nanofluids are engineered colloidal suspensions of nanoparticles in water, and exhibit a very significant enhancement (up to 200%) of the boiling Critical Heat Flux (CHF) at modest nanoparticle concentrations (50.1% by volume). Since CHF is the upper limit of nucleate boiling, such enhancement offers the potential for major performance improvement in many practical applications that use nucleate boiling as their prevalent heat transfer mode. The nuclear applications considered are main reactor coolant for PWR, coolant for the Emergency Core Cooling System (ECCS) of both PWR and BWR, and coolant for in-vessel retention of the molten core during severe accidents in high-power-density LWR. To implement such applications it is necessary to understand the fundamental boiling heat transfer characteristics of nanofluids. The nanofluids considered in this study are dilute dispersions of alumina, zirconia, and silica nanoparticles in water. Several key parameters affecting heat transfer (i.e., boiling point, viscosity, thermal conductivity, and surface tension) were measured and, consistently with other nanofluid studies, were found to be similar to those of pure water. However, pool boiling experiments showed significant enhancements of CHF in the nanofluids. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometry (EDS) analyses revealed that buildup of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly improves the surface wettability, as shown by measured changes in the static contact angle on the nanofluid-boiled surfaces compared with the pure-water-boiled surfaces. It is hypothesized that surface wettability improvement may be responsible for the CHF enhancement.<br>by Sung Joong Kim.<br>S.M.
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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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Zeng, Yi. "Effect of peripheral wall conduction in pool boiling." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/22397.
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Lüttich, Torsten. "Modeling and identification of pool boiling heat transfer /." Düsseldorf : VDI-Verl, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014597255&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Glavin, Nicholas R. "Photonically Enhanced and Controlled Pool Boiling Heat Transfer." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343401685.
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Gopalakrishnan, Vishnu. "Characterization Of Pool Boiling Heat transfer of Nanofluids." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309231.
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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.<br>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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Jackson, Jenny E. "Investigation into the pool-boiling characteristics of gold nanofluids." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4914.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 4, 2008) Includes bibliographical references.
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Xu, Yonghui. "Effects of electric fields on pool boiling heat transfer." Thesis, London South Bank University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336423.
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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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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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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.<br>M.S.<br>Department of Mechanical, Materials and Aerospace Engineering;<br>Engineering and Computer Science<br>Mechanical Engineering
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Zhang, Ke. "Enhanced boiling heat transfer on micro/nano structured surfaces." Thesis, Boston University, 2013. https://hdl.handle.net/2144/21284.
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Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.<br>Boiling heat transfer is a critical process in large-scale industrial applications such as steam engines and heat exchangers in power plants, and in microscopic heat transfer devices such as heat pipes and microchannels for cooling electronic chips. Enhancing boiling heat transfer thus has great significance on lots of energy transportation and utilization systems. Recent studies has suggested that micro/nano structured surfaces can produce considerably different boiling heat transfer curves than normal plain surfaces, resulting in different values of the critical heat flux (CHF) and heat transfer coefficient (HTC). In this thesis, pool boiling on several new micro/nano structured surfaces was experimentally investigated to further understand the mechanism of boiling heat transfer and increase boiling performance.
We first evaluated enhanced boiling heat transfer on three kinds of micro/nano structured super-hydrophilic surfaces: 1) nanowire coated super-hydrophilic surfaces, 2) hybrid microscale cavity and nanowire structured surfaces and 3) hybrid microscale pillar and nanowire structured surfaces. All three surfaces showed significant enhancement of CHF and HTC compared to plain silicon surfaces. Combined micro/nano structured surfaces presented better performance than nanowire coated surfaces suggesting that both active nucleation density and surface roughness significantly affect boiling heating transfer. Experimental investigations indicate an optimum design both in size (~ 20μ𝑚) and density (between 0 and 10000=cm^2) of cavities for microscale cavity/nanowire structured surfaces. The highest CHF and peak HTC values were obtained on microscale pillar/nanowire structured surfaces. Among the test surfaces, the largest enhancements of CHF and peak HTC were 228% and 298%, respectively, compared to plain silicon surfaces.
For a better understanding of the boiling phenomena, pool boiling on super-hydrophobic surfaces was also studied. We found that, for super-hydrophobic surfaces, the major heat transfer mechanism at the initial boiling regime is natural convection of liquid water.
In conclusion, micro/nano structured surfaces can greatly influence nucleate boiling heat transfer. The various physical attributes employed with the structured surfaces further revealed the profound influence of surface topography on enhancing boiling heat transfer.<br>2031-01-01
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Sathyamurthi, Vijaykumar. "Pool boiling studies on nanotextured surfaces under highly subcooled conditions." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1155.
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Pasek, Ari Darmawan. "Pool boiling on porous surfaces in cryogenic and refrigerant liquids." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315511.
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Truong, Bao H. (Bao Hoai). "Determination of pool boiling Critical Heat Flux enhancement in nanofluids." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41689.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, June 2007.<br>"May 2007."<br>Includes bibliographical references (leaves 51-53).<br>Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed CHF enhancement up to 68% and there seems to be a monotonic relationship between nanoparticle concentration and magnitude of enhancement. Alumina nanofluids had CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. SEM images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater's surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica. Inductively Coupled Plasma Spectroscopy (ICP-OES) analyses were also attempted to quantify the mass of the particle deposition but the results were inconsistent with the estimates from the SEM measurement.<br>by Bao H. Truong.<br>S.B.
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Li, Nanxi. "High-pressure pool boiling and physical insight of engineered surfaces." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35561.
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Doctor of Philosophy<br>Department of Mechanical and Nuclear Engineering<br>Amy R. Betz<br>Boiling is a very effective way of heat transfer due to the latent heat of vaporization. Large amount of heat can be removed as bubbles form and leave the heated surface. Boiling heat transfer has lots of applications both in our daily lives and in the industry. The performance of boiling can be described with two important parameters, i.e. the heat transfer coefficient (HTC) and the critical heat flux (CHF). Enhancing the performance of boiling will greatly increase the efficiency of thermal systems, decrease the size of heat exchangers, and improve the safety of thermal facilities. Boiling heat transfer is an extremely complex process. After over a century of research, the mechanism for the HTC and CHF enhancement is still elusive. Previous research has demonstrated that fluid properties, system pressures, surface properties, and heater properties etc. have huge impact on the performance of boiling. Numerous methods, both active and passive, have been developed to enhance boiling heat transfer. In this work, the effect of pressure was investigated on a plain copper substrate from atmospheric pressure to 45 psig. Boiling heat transfer performance enhancement was then investigated on Teflon© coated copper surfaces, and graphene oxide coated copper surfaces under various system pressures. It was found that both HTC and CHF increases with the system pressure on all three types of surfaces. Enhancement of HTC on the Teflon© coated copper surface is contributed by the decrease in wettability. It is also hypothesized that the enhancement in both HTC and CHF on the graphene oxide coated surface is due to pinning from micro and nanostructures in the graphene oxide coating or non-homogeneous wettability. Condensation and freezing experiments were conducted on engineered surfaces in order to further characterize the pinning effect of non-homogeneous wettability and micro/nano structure of the surface.
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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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Douglas, Zachary W. "Acoustically Enhanced Boiling Heat Transfer." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16325.
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An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.
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Mlakar, Genesis. "Effects of Surface Engineering on HFE-7100 Pool Boiling Heat Transfer." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1619036502968687.
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Verma, Utkarsh. "Experimental study of saturated pool boiling in water with a fluorinated reagent." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1343085793.
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Sathyanarayana, Aravind. "Pool and flow boiling of novel heat transfer fluids from nanostructured surfaces." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50299.
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Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints have led to the use of Novec fluids and fluroinerts as coolants. Although these fluids are chemically stable and have low dielectric constants, they are plagued by poor thermal properties. These factors necessitate the development of new heat transfer fluids with improved heat transfer properties and applicability. Computer Aided Molecular Design (CAMD) approach was used in this work to systematically design novel heat transfer fluids that exhibit significantly better properties than those of current high performance electronic coolants. The candidate fluids generated by CAMD were constrained by limiting their boiling points, latent heat of vaporization and thermal conductivity. The selected candidates were further screened using a figure of merit (FOM) analysis. Some of the fluids/additives that have been identified after the FOM analysis include C₄H₅F₃O, C₄H₄F₆O, C₆H₁₁F₃, C₄ H₁₂O₂Si, methanol, and ethoxybutane. The heat transfer performance of these new fluids/fluid mixtures was analyzed through pool boiling and flow boiling experiments. All the fluid mixtures tested showed an improvement in the critical heat flux (CHF) when compared to the base fluid (HFE 7200). A pool boiling model was developed using the phase field method available in COMSOL. Although these simulations are computationally expensive, they provide an alternate solution to evaluate several candidate fluids generated using the CAMD approach.
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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.<br>M.S.<br>Department of Mechanical, Materials and Aerospace Engineering;<br>Engineering and Computer Science<br>Mechanical Engineering
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Bailey, Wendell O. S. "Applications of pool boiling heat transfer on modulated surfaces in organic liquids." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437112.
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Coyle, Carolyn Patricia. "Synthesis of CRUD and its effects on pool and subcooled flow boiling." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103652.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 127-132).<br>This work is dedicated to studying the effects of synthetic CRUD (Chalk River Unidentified Deposits) on pool and subcooled flow boiling parameters. Previous pool boiling studies have demonstrated the potential of porous, hydrophilic surfaces to lead to more efficient boiling. CRUD is a naturally occurring porous, hydrophilic layer that forms on fuel rods during reactor operation. As such, CRUD deposition may have large effects on critical heat flux (CHF) and heat transfer coefficient (HTC). An investigation of such effects was conducted as part of the CASL project by creating well-defined and characterized synthetic CRUD with parameters representative of reactor CRUD on indium tin oxide-sapphire heaters. The effects of synthetic CRUD on boiling heat transfer were then experimentally studied, focusing on heat transfer coefficient (HTC), critical heat flux (CHF), nucleation site density, bubble departure frequency, and bubble departure diameter. These heaters were tested in pool and flow boiling facilities in MIT's Reactor Hydraulics Laboratory. Synthetic CRUD was created using layer-by-layer deposition of 100 nm silica nanoparticles to form porous, hydrophilic thick films. Photolithography was used to manufacture posts that were then dissolved to create characteristic boiling chimneys. Features such as thickness, wettability, pore size, and chimney diameter and pitch were verified to be representative of reactor CRUD. Silica nanoparticles were used as a surrogate for reactor CRUD nanoparticle materials (iron and nickel oxides) since they create more stable films. To ensure accurate modeling, independent of material, 10 nm silica nanoparticle and 10 nm iron oxide nanoparticle boiling tests were conducted and found to be similiar. During testing, IR thermography and high-speed video (HSV) are used to obtain two dimensional temperature profiles of the active heater area to quantify properties such as HTC, nucleation site density, bubble departure frequency, and bubble departure diameter. The bubble parameters follow expected trends with mass flux and heat flux. IR/HSV flow data (Chapter 6) has shown that HTC increases with the presence of chimneys, increasing thickness and increasing chimney diameter. However the HTC is relatively unaffected by the chimney pitch and is decreased by the presence of an LbL layer. The boiling curves and CHF data obtained from pool boiling experiments with iron oxide and silica oxide nanoparticles with and without chimneys also confirm these trends. The largest HTC is observed in the case of uncoated heaters, followed by heaters with chimneys, with heaters with an LbL layer without chimneys having the lowest HTC. From pool boiling data, the benefit of a CRUD layer is observed in the enhancement of CHF. The flow boiling trends are further supported by the combination of measured basic bubble parameters according to the heat flux partitioning model. The statistical significance of these trends varies with mass flux. The data generated here may inform advanced models of boiling heat transfer and/or validate existing models.<br>by Carolyn Patricia Coyle.<br>S.M.
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Tarrad, Ali Hussain. "Pool boiling of pure fluids and mixtures on plain and enhanced surfaces." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/865.
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The thesis contains a comprehensive literature survey of the important aspects of the boiling heat transfer process. The effect of different parameters on the performance of the heating element is reviewed in detail which includes the heating surface condition and pressure. The fundamentals of bubble growth rate and departure parameters, diameter and time, are reviewed and discussed. An experimental investigation of pool boiling on an electrically heated horizontal 90% copper:10% nickel 19 mm o.d and 56 mm long tube is described. Boiling heat transfer coefficients were obtained for four enhanced surfaces and compared to those of a plain tube in the heat flux range 5-60 kW /m2 at atmospheric pressure. Three integrally formed tube surfaces, Turbo-B, 19 FPI Gewa-TX and 19 FPI Low Finned and one sintered porous surface, High Flux, were used in the tests. The boiling pure liquids were water, ethanol, n-pentane and R113. The plain tube was tested with p-xylene in addition to these liquids in the heat flux range 5-50 kW /m2. The te~ts were carried out on two types of mixtures, the wide boiling range n-pentane/tetradecene mixture and the narrow boiling range ethanol/water mixture. Qualitative and quantitative information gained from the mass of data obtained in this investigation together with some unreported phenomenon accompanying the boiling process are reported. Longitudinal temperature variation in the tube section was measured in the tests. This was achieved by locating four thermocouples in three different longitudinal positions in the tube section. A numerical finite difference analysis was employed to predict the temperature distribution in the tube section using apxxxvi propriate boundary conditions. The model failed to predict the exact measured temperature variation in the tube section. However, the temperature profile was predicted well. A new approach to prediction of bubble growth rate in pure liquids and binary mixt,ures is developed. This technique is considered a new application for the numerical moving boundary problems in the polar coordinates and including the convection effect produced from the density difference between the vapour and liquid phases. The analysis employs the boundary conditions at the vapour /liquid interface to trace the motion of the bubble wall together with any associated variables. The mass and/or energy equations were solved for the liquid domain in the vicinity of the bubble wall. Good agreement between the calculated bubble growth rate in pure liquids and that of other investigators was obtained . The prediction of mixture growth rate is lower than that of existing correlations.
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Gorgy, Evraam I. "Pool boiling of R-134a and R-123 on smooth and enhanced tubes." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/804.
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Griffin, Alison. "FUNDAMENTAL STUDY OF FC-72 POOL BOILING SURFACE TEMPERATURE FLUCTUATIONS AND BUBBLE BEHAVIOR." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3153.
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A heater designed to monitor surface temperature fluctuations during pool boiling experiments while the bubbles were simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 microns wide and overlapped to form a 25 micron by 25 micron junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. A trigger sent to the camera by the DAQ synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were demonstrated. On the heaters with fused silica insulation layers, 1-2 C temperature drops on the order of 1 ms occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure. These temperature drops during bubble growth and departure were due to microlayer evaporation and liquid rewetting the heated surface, respectively. Microlayer evaporation was not distinguished as the primary method of heat removal from the surface. Heaters with sapphire insulation layers did not display the measurable temperature drops observed with the fused silica heaters. The large thermal diffusivity of the sapphire compared to the fused silica was determined as the reason for the absence of these temperature drops. These findings were confirmed by a comparison of temperature drops in a 2-D simulation of a bubble growing over the TFTC junction on both the sapphire and fused silica heater surfaces. When the fused silica heater produced a temperature drop of 1.4 C, the sapphire heater produced a drop of only 0.04 C under the same conditions. These results verified that the lack of temperature drops present in the sapphire data was due to the thermal properties of the sapphire layer. By observing the bubble departure frequency and site density on the heater, as well as the bubble departure diameter, the contribution of nucleate boiling to the overall heat removal from the surface could be calculated. These results showed that bubble vapor generation contributed to approximately 10% at 1 W/cm^2, 23% at 1.75 W/cm^2, and 35% at 2.9 W/cm^2 of the heat removed from a fused silica heater. Bubble growth and contact ring growth were observed and measured from images obtained with the high-speed camera. Bubble data recorded on a fused silica heater at 3 W/cm^2, 4 W/cm^2, and 5 W/cm^2 showed that bubble departure diameter and lifetime were negligibly affected by the increase in heat flux. Bubble and contact ring growth rates demonstrated significant differences when compared on the fused silica and sapphire heaters at 3 W/cm^2. The bubble departure diameters were smaller, the bubble lifetimes were longer, and the bubble departure frequency was larger on the sapphire heater, while microlayer evaporation was faster on the fused silica heater. Additional considerations revealed that these differences may be due to surface conditions as well as differing thermal properties. Nucleate boiling curves were recorded on the fused silica and sapphire heaters by adjusting the heat flux input and monitoring the local surface temperature with the TFTCs. The resulting curves showed a temperature drop at the onset of nucleate boiling due to the increase in heat transfer coefficient associated with bubble nucleation. One of the TFTC locations on the sapphire heater frequently experienced a second temperature drop at a higher heat flux. When the heat flux was started from 1 W/cm^2 instead of zero or returned to zero only momentarily, the temperature overshoot did not occur. In these cases sufficient vapor remained in the cavities to initiate boiling at a lower superheat.<br>Ph.D.<br>Department of Mechanical, Materials and Aerospace Engineering<br>Engineering and Computer Science<br>Mechanical Engineering PhD
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Michaïe, Sandra. "Experimental study of the fundamental phenomena involved in pool boiling at low pressure." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI040/document.
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L’ébullition est un mode de transfert de chaleur intervenant dans de nombreux systèmes thermiques ou énergétiques de par son efficacité. Dans certains, elle se produit à basse pression. La pression statique induite par la colonne de liquide au-dessus de la surface de formation des bulles n’est alors pas négligeable devant la pression de saturation à la surface libre. Dès lors, la pression et le sous-refroidissement induit ne peuvent plus être considérés homogènes autour des bulles, d’où des inhomogénéités des propriétés thermophysiques dans le fluide. Les influences relatives des forces s’exerçant sur une bulle pendant sa croissance sont modifiées par rapport aux pressions plus élevées : une dynamique de bulles différente apparaît. Ces conditions particulières affectent également les transferts thermiques. L’influence de la pression sur l’ébullition en vase a été étudiée expérimentalement dans le régime de bulles isolées en site unique. L’eau a d’abord été testée sur une large gamme de pressions subatmosphériques. Quatre comportements de dynamique de bulles ont été identifiés d’après la visualisation par caméra rapide. Plusieurs paramètres de la dynamique ont été quantifiés grâce à un traitement d’images adapté appliqué aux vidéos. Pour généraliser le concept d’ébullition à « basse pression » et mieux en appréhender les phénomènes fondamentaux, de nouveaux essais ont été réalisés avec un second fluide, le cyclohexane, choisi pour sa similitude thermodynamique avec l’eau bouillant en deçà de la pression atmosphérique. La comparaison des comportements des deux fluides a permis d’identifier certains paramètres responsables des spécificités du phénomène. En outre, de nouvelles fonctionnalités sont apportées au dispositif expérimental pour – notamment – effectuer la mesure rapide du flux transféré sous la bulle pendant sa croissance, synchroniser ces mesures thermiques avec l’acquisition d’images et étudier des surfaces d’ébullition structurées. Les résultats obtenus sont encourageants pour l’analyse des comportements spécifiques de l’ébullition à basse pression et ses applications<br>Boiling is an efficient heat transfer mode used in numerous thermal or energy systems. In some systems boiling takes place at low pressure. The static head of the liquid column over the wall where bubbles nucleate is then not negligible against the saturation pressure at the free surface level. The pressure and the induced subcooling degree therefore cannot be considered as homogeneous around growing bubbles, resulting in non-homogeneous thermophysical properties in the fluid. The relative influence of the forces acting on a growing bubble differs from higher pressure conditions, yielding specific bubble dynamics features. Heat transfer is consequently also affected. The effect of the pressure on pool boiling was experimentally investigated during the isolated bubbles regime taking place from a single activated nucleation site. Experiments were first conducted with water for a wide range of subatmospheric pressures. Four distinct bubble dynamics behaviors were identified through high-speed camera visualizations. An adapted image processing of the recordings enabled the measurement of several bubble dynamics characteristics. In order to generalize the concept of pool boiling at "low pressure" and to get a better understanding of the related fundamental phenomena, new experiments were performed with a second fluid, cyclohexane, chosen from original thermodynamic similarity with water boiling at pressures lower than atmospheric. The comparison of fluids’ behaviors made possible the identification of parameters governing the specific phenomena occurring during boiling at low pressure. Besides, the experimental facility was improved to provide new functionalities. The high-speed measurement of the heat flux transferred under the growing bubble, its synchronization with the high-speed videos images and the study of boiling on enhanced surfaces are in particular made possible. Results are encouraging for a better understanding of the specific behaviors of low pressure boiling and for its future implementation in practical applications
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Sayee, Mohan Kaushik. "Pool Boiling of FC 770 on Graphene Oxide Coatings: A Study of Critical Heat Flux and Boiling Heat Transfer Enhancement Mechanisms." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71873.
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This thesis investigates pool boiling heat transfer from bare and graphene-coated NiCr wires in a saturated liquid of FC 770, a fluorocarbon fluid. Of particular interest was the effect of graphene-oxide platelets, dip-coated onto the heater surface, in enhancing the nucleate boiling heat transfer (BHT) rates and the critical heat flux (CHF) value. In the course of the pool boiling experiment, the primary focus was on the reduction mechanism of graphene oxide. The transition from hydrophilic to hydrophobic behavior of the graphene oxide-coated surface was captured, and the attendant effects on surface wettability, porosity and thermal activity were observed. A parametric sensitivity analysis of these surface factors was performed to understand the CHF and BHT enhancement mechanisms.
In the presence of graphene-oxide coating, the data indicated an increase of 50% in CHF. As the experiment continued, a partial reduction of graphene oxide occurred, accompanied by (a) further enhancement in the CHF to 77% larger compared to the bare wire. It was shown that the reduction of graphene oxide progressively altered the porosity and thermal conductivity of the coating layer without changing the wettability of FC 770. Further enhancement in CHF was explained in terms of improved porosity and thermal activity that resulted from the partial reduction of graphene-oxide. An implication of these results is that a graphene-oxide coating is potentially a viable option for thermal management of high-power electronics by immersion cooling technology.<br>Master of Science
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Searle, Matthew Clark. "Thermal Transport at Superhydrophobic Surfaces in Impinging Liquid Jets, Natural Convection, and Pool Boiling." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7065.
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This dissertation focuses on the effects of superhydrophobic (SHPo) surfaces on thermal transport. The work is divided into two main categories: thermal transport without phase change and thermal transport with phase change. Thermal transport without phase change is the topic of four stand-alone chapters. Three address jet impingement at SHPo surfaces and the fourth considers natural convection at a vertical, SHPo wall. Thermal transport with phase change is the topic of a single stand-alone chapter exploring pool boiling at SHPo surfaces. Two chapters examining jet impingement present analytical models for thermal transport; one considered an isothermal wall and the other considered an isoflux wall. The chapter considering the isothermal scenario has been archivally published. Conclusions are presented for both models. The models indicated that the Nusselt number decreased dramatically as the temperature jump length increased. Further, the influence of radial position, jet Reynolds number, Prandtl number and isoflux versus isothermal heating become negligible as temperature jump length increased. The final chapter concerning jet impingement reports an experimental exploration of jet impingement at post patterned SHPo surfaces with varying microfeature pitch and cavity fraction. The empirical results show a decrease in Nusselt number relative to smooth hydrophobic surfaces for small pitch and cavity fraction and the isoflux model agrees well with this data when the ratio of temperature jump length to slip length is 3.1. At larger pitch and cavity fractions, the empirical results have higher Nusselt numbers than the SHPo surfaces with small pitch and cavity fraction but remain smaller than the smooth hydrophobic surface. We attribute this to the influence of small wetting regions. The chapter addressing natural convection presents an analytical model for buoyant flow at a vertical SHPo surface. The Nusselt number decreased dramatically as temperature jump length increased, with greater decrease occurring near the lower edge and at higher Rayleigh number. Thermal transport with phase change is the topic of the final stand-alone chapter concerning pool boiling, which has been archivally published. Surface heat flux as a function of surface superheat was reported for SHPo surfaces with rib and post patterning at varying microfeature pitch, cavity fraction, and microfeature height. Nucleate boiling is more suppressed on post patterned surfaces than rib patterned surfaces. At rib patterned surfaces, transition superheat decreases as cavity fraction increases. Increasing microfeature height modestly increases the transition superheat. Once stable film boiling is achieved, changes in surface microstructure negligibly influence thermal transport.
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Ahmad, Syed Waqas. "Combined effect of electric field and surface modification on pool boiling of R-123." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6600.
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The effect of surface modification and high intensity electric field (uniform and non – uniform) acting separately or in combination on pool boiling of R-123 is presented in this thesis. The effect of surface modification was investigated on saturated pool boiling of R-123 for five horizontal copper surfaces modified by different treatments, namely: an emery polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam (EB) enhanced surface and a sintered surface. Each 40 mm diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the convective heat transfer regime to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the EB enhanced and sintered surfaces. The emery polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. The effect of uniform and non-uniform electric fields on saturated pool boiling of R-123 at 1.01 bar pressure was also examined. This method of heat transfer enhancement is known as electrohydrodynamic abbreviated as EHD-enhancement. A high voltage potential was applied at the electrode located above the heating surface, which was earthed. The voltage was varied from 0 to 30 kV. The uniform electric field was provided through a 40 mm diameter circular electrode of stainless steel 304 wire mesh having an aperture of 5.1 mm, while the non-uniform electric field was obtained by using a 40 mm diameter circular rod electrode with rods 5 and 8 mm apart. The effect of uniform electric field was investigated using all five modified surfaces, i.e. emery polished, fine sandblasted, rough sandblasted, EB enhanced and sintered surfaces, while non – uniform electric field was tested using the emery polished, fine sandblasted, EB enhanced and sintered surfaces. The effect of pressure on EHD enhancement was also examined using emery polished surface at saturation pressure of 2 and 4 bars while the electric field was fix at 20 kV corresponding to 2 MV/m. Further, the bubble dynamics is presented for the emery polished surface obtained using a high-speed high – resolution camera.
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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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Bockwoldt, Todd S. "Induced convective enhancement of the critical heat flux for partially heated surfaces in pool boiling." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/13094.
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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<br>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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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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Chen, Ci Yuan, and 陳慈源. "Pool boiling at subatmospheric pressure." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/49101752623347940441.
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劉明輝. "Pool film boiling of binary mixtures." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/76670966028912269742.
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Tsai, Yun-Tzu, and 蔡昀孜. "Subcooled Pool Boiling of Electrolyte Solutions." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/b5zmx2.
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碩士<br>國立清華大學<br>核子工程與科學研究所<br>106<br>In this experiment, a platinum wire with a diameter of 0.3 mm and a purity of 99.95% is used as the test section, and the electric power supplied by the DC power supply is converted into heat flux. Through the oil bath test beforehand, the highly correlation between the platinum temperature and the resistance is used to predict the wall temperature of the platinum wire, which is limited by the narrow wire diameter. In order to avoid the surface changes of the experimental electrodes and the wire in electrolyte solutions, the electrodes are covered with the heat-shrink tubes and two electronic insulating glues are also used to separate the test section from electrolyte solutions preventing electrochemical reaction. The stainless steel tanks with ceramic coating are filled with six liters of solution and the required subcooling are adjusted by PID hot plate. Four T-type thermocouples in the tank are used to measure and MX-100 data acquisition system records the pool temperature and voltage.
Through image comparison, we can find that the bubbles in sodium chloride solution are smaller than in deionized water. With surrounding ion hydration force and Coulomb electrical force, the bubbles in the sodium chloride solution do not combine, even they are touched with each other will get repelled. In terms of bubble generation rate, the sodium chloride solution is similar to deionized water, and vapor generation is enhanced when the heat flux increases. Because there is no ion effect in deionized water, at high heat flux, the bubble generation rate is faster than the bubble detachment rate, which will cause adjacent bubbles to merge, forming a vapor film cover the heating wire, and finally the platinum wire will burn. On the contrary, the bubbles in the sodium chloride solution are not easy to combine, so that the hot surface can contact with the colder working fluid and the continuously generated and rushed away bubbles can also take heat away.
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Lai, Jun Liang, and 賴俊良. "Pool boiling of methanol at subatmospheric pressure." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/03300655765663196682.
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Subrahmanya, Praveena Alangar, and 蘇邁亞. "Pool boiling on open trapezoidal channel surface." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82191724169102979509.
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碩士<br>國立中央大學<br>能源工程研究所<br>103<br>In this thesis pool boiling experiment is carried out on open trapezoidal channel surface to study the effect of channel top width (0.4mm, 0.8mm, 1.4mm and 2.0mm) and fin pitch using saturated methanol as working fluid at one atmospheric pressure along with bubble dynamic visualisation. The channel were cut using wire electro-discharge machining technique and results are compared with corresponding plane surfaces.
Plain boiling surface with comparatively high roughness value (manufactured by wire electro-discharge machining) consistently showed higher heat transfer performance than emery surface with lower roughness value. All channel surfaces performed better than plain surface prepared by emery paper. For all the tested trapezoidal channel surfaces, bubbles only generated from the channel surface because of high roughness on channel surface. There was no bubble generation from fin top surface. Therefore overall channel surface area played major role along with the effect of channel geometry on HTC & CHF and the results are meant to compare with plain surface made by EDM process.
Two distinctive bubble dynamics are observed as the channel top width increased. For channel having top width 0.4mm, single bubble generated across the channel and it attached to channel side surface and grew on top of channel till the departure. Therefore the heat transfer performance increased as the fin pitch reduced. But in comparison with Plain EDM surface, its nucleate boiling HTC found to be lower because overall available boiling surface area (ie channel surface area) is lower.
From channel having top width 0.8mm to 2.0mm, number of nucleation sites across channel surface increased accordingly with the channel cross section area. Therefore multiple bubble nucleation sites were observed. On these channel top width surfaces, a heat transfer enhancement mechanism observed. Therefore even though the channel surface area was lower than that of plain EDM surface, nucleate boiling HTC were either equal or more than plain EDM surface observed. Reduction in fin pitch had no major effect on HTC.
For channel made by EDM process having different roughness value in comparison with fin top surface has different liquid and vapor flow path ways. Majority of the liquid supply to rewet the boiling surface (i.e channel surface) were from fin top surface. As the fin pitch decreases, CHF found to increase for all tested channel top widths because of increases in channel surface area as well as enhancement in heat transfer mechanism over channel surface.
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Wang, Chung-Kai, and 王仲愷. "Enhanced Pool Boiling Heat Transfer by Nanofluids." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/35128125311405067657.
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碩士<br>臺灣大學<br>機械工程學研究所<br>96<br>Nanofluid is expected to be one of the most potential techniques for heat transfer enhancement. Hence, recently studies have been carried out on the heat transfer behavior of nanofluids in two-phase heat transfer regimes such as pool boiling. However, the amount and performance of proposed works are scant and insignificant. Therefore, the aim of this article attempts to explore whether a further enhancement could be achieved by altering the nanoparticle/base-fluid combination used in previous studies. This research, a two-step procedure was used to disperse titania (TiO2) nanoparticles into 1,1,1,2-tetrafluoroethane (R-134a) to prepare nanofluid. The preliminary qualitative analysis of the pool boiling heat transfer enhancement of nanofluid was conducted through nanofluid and pool boiling correlations in order to indicate the relationship between thermal conductivity and boiling heat transfer coefficient.
Results of this study showed the boiling heat transfer coefficient of R-134a was shown to be increased by up to 150 % for nanofluid consisting of R-134a containing approximately 0.005 %vol. TiO2 nanoparticles of mean diameter 20 ~ 25 nm. On the other hand, the critical heat flux maintained the same by little deposition of nanoparticles. The short-range re-dispersibility and repeatability of data were found to be acceptable.
To conclude, the R134a-based nanofluids may be better than water-based in pool boiling heat transfer enhancement application. Further, our modified empirical correlations need to be proved by detail experiments and theories precisely.
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Wenzel, Ulrich. "Saturated pool boiling and subcooled flow boiling of mixtures at atmospheric pressure." 1992. http://hdl.handle.net/2292/2190.
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An experimental and theoretical investigation of heat transfer to liquid mixtures has been performed using binary and ternary mixtures of acetone, isopropanol and water. Two data-bases were established which contain measurements of the heat transfer coefficient under saturated pool boiling and subcooled flow boiling conditions. A third database comprises measurements of heat transfer and pressure drop in a plate heat exchanger. The performance of two heat transfer enhancement techniques, namely the coating of the heat transfer surface with teflon and a perforated brass foil, was studied under saturated pool boiling conditions. A model was developed, which can be used to predict the heat transfer coefficient. The model is based on the additive superposition of convective and boiling heat transfer coefficients. It is applicable for heat transfer to mixtures and single component fluids under saturated and subcooled boiling conditions. The empirical parameters in the correlations used in the model were not altered to fit the measurements of this study. The predictions of the model were compared to the experimental data, which covers the convective heat transfer regime, the transition region and the fully developed nucleate boiling regime. It was found that the best agreement between predicted an measured values was achieved, if the linear mixing law was used to calculate the ideal heat transfer coefficient rather than the correlations by Stephan-Preußer or Stephan-Abdelsalam. The heat transfer coefficient under saturated pool boiling conditions could be predicted with an accuracy of 12.6 %. A comparison between over 2000 measured heat transfer coefficients under subcooled flow boiling conditions in an annulus and the predictions of the model showed good agreement with a mean error of 10.3 %. The accuracy of the model was found to be independent of the fluid velocity and composition, as well as of the magnitude and mechanism of heat transfer. The heat flux in a plate heat exchanger could be predicted with a mean error of 6.9 % for a wide range of fluid velocities, subcoolings and compositions. The heat transfer coefficient on the test liquid side of the exchanger could be predicted with a mean error of 10 %. The heat transfer model was used for a theoretical study of the heat transfer to mixtures boiling on a finned surface. It was found that the fin geometry and thermal conductivity have a distinct influence on the local and mean heat transfer coefficients. The results indicate that the application of fins is more effective for boiling of mixtures than for boiling of single component liquids.
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TANG, HUI-JUN, and 唐回俊. "Pool boiling at reduced pressures-loci of steady state two mode boiling." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/61414177067061306826.
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Schmidt, Don. "Initiation of subcooled pool boiling during pressure transients." 1985. http://hdl.handle.net/2097/27533.
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