Enhancement of boiling in highly wetting fluids
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Naval Postgraduate School, Available from National Technical Information Service , Monterey, Calif, Springfield, Va
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The boiling of a highly wetting dielectric fluid, in an oscillating environment, has been investigated. Because of low surface tension, these liquids require very high superheat to initiate nucleate boiling. This high degree of superheat required can be reduced by oscillation of the fluid. This oscillation removes the bubbles, which are forming in the nucleation sites on the wire, which allows new bubbles to form. The amplitude and frequency of the oscillation has been varied in an attempt to find optimum values. All attempted oscillation amplitudes and frequencies reduced the required superheat necessary to initiate nucleate boiling. Some oscillation amplitudes and frequencies were more effective than others. No global optimum amplitude or frequency was specifically located. Several local optimum values were found. Once oscillation amplitude was found to produce equal required superheat values at various frequencies, thus appearing to be independent of frequency.
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Enhancement of boiling heat transfer using highly wetting liquids with pressed-on fins at low contact forces STANLEY J. REED and ISSAM MUDAWARt Boiling and Two-phase Flow Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, INby: The goal, then, of schemes to enhance boiling heat transfer in highly wetting fluids, is to maximize the size and number of the trapped embryos to promote early boiling incipience and the gradual spread of boiling with increasing heat flux while increasing the area available for Cited by: This study concerns boiling incipience of highly wetting liquids (n-pentane), in transient conditions, in horizontal confined space between a vertical heating cylinder and a two controlled parameters were the heat flux, ranging from 50 to kW m −2 and the thickness of the liquid in the confined space, ranging from 0 to μm.
Experiments were conducted with both smooth and porCited by: 6. Recently, Hu et al. [13, 14] improved the heat transfer during pool boiling of heptanol-water mixture and attributed the enhancement to: (i) the accelerated wetting of the dried spots, due to the.
Transient nucleate boiling under stepwise heat generation for highly wetting fluids Article in International Journal of Heat and Mass Transfer 47(25) December with 21 Reads. In pool boiling tests, a boiling system using horizontal heated wires was employed. Furthermore, in order to clarify the heat transfer enhancement mechanism of pool boiling with self-rewetting fluid, the nucleate boiling processes have been recorded using a high speed CCD.
The experimental results are shown as follows. Experimental detailsCited by: To clarify the fundamental heat transfer characteristic and heat transfer enhancement of subcooled pool boiling with self-rewetting fluid (SRWF), using dilute heptanol aqueous solution as SRWF, a serial boiling experiments have been carried out.
During the experiments, a boiling system using a horizontal heated wire was by: Experiments of transient nucleate boiling are carried out on highly wetting fluids from two metallic specimen, a thick flat sample and a wire.
Details Enhancement of boiling in highly wetting fluids FB2
The initial condition is controlled in terms of the system temperature as well as by a primary activation of the nucleation by: Experimental results on pool boiling heat transfer from a horizontal cylinder in an electronic cooling fluid (FC) are presented.
The effects on the boiling curve of having air dissolved in the fluid are documented, showing that fluid in the vicinity of the heating element is apparently liberated of dissolved gas during by: An experimental pool boiling study was conducted using plain and nanocoated heater surfaces immersed in various working fluids.
Working fluids include water, ethanol and HFE and pool boiling tests were performed on a flat 1 cm × 1 cm heaters. Unlike in water, CHF enhancement of the nanocoating seems to be less or marginal in ethanol and HFE at 1 atm. The boiling inception of highly wetting liquids is delayed to a higher wall superheat, which is far above the saturation temperature of the working fluid.
As shown in Fig. 10, boiling with superheat excursion of and 23 K occurred at (Δ T sat) ONB = and K for Δ T sub = and K, by: You, S.M., Simon,T.W., Bar-Cohen, A., c, “Experiments on Boiling Incipiencewith a Highly-Wetting Dielectric Fluid; Effects of Pressure, Subcooling and Dissolved Gas Content,” Heat Transfer - Vol 2, Proceedings of 9th International Heat Transfer Conference, Hemisphere Publishing Company, New York, pp – Google ScholarCited by: 5.
Experiments are performed to understand the effects of surface orientation on the pool boiling characteristics of a highly wetting fluid from a flush-mounted, micro-porous-enhanced square heater.
Micro-porous enhancement was achieved by applying copper and Cited by: Abstract. Pool boiling enhancement techniques with all their aspects have been presented in this chapter. Many different types of textured surfaces like abrasives, open groves, three-dimensional cavities, electroplating, attached wire and screen promoters, pierced three-dimensional cover sheets, etched surfaces, coatings, porous surfaces, structured surfaces, combined structured and porous Author: Sujoy Kumar Saha, Hrishiraj Ranjan, Madhu Sruthi Emani, Anand Kumar Bharti.
sites for bubble nucleation. However, in the case of highly wetting dielectric fluids like HFE, the effect of wetting enhancement due to the nanowires may be small, and the presence of the voids of the optimum shape and size may be the more important factor in the boiling enhancement.
The use of enhanced surfaces on spray cooling has. Droplet Wetting and Evaporation provides engineers, students, and researchers with the first comprehensive guide to the theory and applications of droplet wetting and evaporation. Beginning with a relevant theoretical background, the book moves on to consider specific aspects, including heat transfer, flow instabilities, and the drying of complex fluid droplets.
Spray Freezing onto Cryogenic Fluids. Briggs and Maxvell invented the process of spray freezing onto cryogenic fluids. In this technique, the drug and the carrier (mannitol, maltose, lactose, inositol, or dextran) were dissolved in water and atomized above the surface of a boiling agitated fluorocarbon by: A brief introduction to the current theory on boiling heat transfer of highly wetting fluids on smooth surfaces is presented in addition to a detailed explanation of the experimental design from the perspective o f fluid and surface selection.
A discussion of the plausible mechanisms that bring about the observed trends is provided. Rahman, and M. McCarthy, "Boiling Enhancement on Nanostructured Surfaces with Engineered Variations in Wettability and Thermal Conductivity", Heat Transfer Engineering (in press).
Shabgard, H. Hu, P.A. Boettcher, M. McCarthy, and Y. Sun, "Heat Transfer Analysis of PCM Slurry Flow between Parallel Plates", International Journal of Heat and Mass Trans pp. A Novel Concept for Boiling Heat Transfer Enhancement temperature for increasing heat flux and that for decreasing heat flux.
At given fluid subcooling of 14 K, boiling hysteresis with a maximum superheat excursion of K occurred, irrespectively of the location of the thermocouple. However, as the sound source intensity is. Cambridge Core - Thermal-Fluids Engineering - Two-Phase Flow, Boiling, and Condensation - by S.
Mostafa GhiaasiaanAuthor: S. Mostafa Ghiaasiaan. 3M™ Microporous Metallic Boiling Enhancement Coating (BEC) L Applications 3M™ BEC L can be applied to make boilers in a variety of 2-phase heat transfer systems: • Indirect thermosyphons can be used to cool microprocessors, LEDs.
Thermal management has become a critical issue for high heat flux electronics and energy systems. Integrated two-phase microchannel liquid-cooling technology has been envisioned as a promising solution, but with great challenges in flow instability.
Description Enhancement of boiling in highly wetting fluids PDF
In this work, silicon nanowires were synthesized in situ in parallel silicon microchannel arrays for the first time to suppress the flow.
A free-particles-based technique for boiling heat transfer enhancement in a wetting liquid Tae Young Kim*, Justin A. Weibel, and Suresh V. Garimella† Cooling Technologies Research Center, an NSF IUCRC School of Mechanical Engineering, Purdue University Purdue Mall, West Lafayette, IN USA Abstract.
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Having just received the good news that Ive passed the PE exam, its only fair for me to pass along the knowledge, tips, advice that Ive used that ultimately proved successful.
Ive been a lurker on the board for a few years now and gathered a lot of information before I decided to take the Electrohydrodynamic augmentation was applied to a finned tube bundle, resulting in nearly a percent increase in the average boiling heat transfer coefficient of the bundle [Cheung et al.
()]. The working fluid was an alternate refrigerant Ra, and the maximum EHD power consumption was percent of the bundle heat transfer rate. "Pool boiling experiments have been conducted with self-rewetting fluids consisting of aqueous butanol and pentanol solution to study the boiling heat transfer enhancement at pressures of 1 ~ 4 bars.
Although self-rewetting fluids have been used to enhance the performance of heat pipes, boiling heat transfer characteristics are yet to be fully understood especially at pressures above : Mostafa Morovati. This is common for enhanced boiling surfaces as exemplified by the conclusion to Anderson and Mudwar's investigation of surfaces covered in square pins (approximately m tall and m across) [ 54 ] They concluded, Common incipience theories based on cavity radius do not apply to highly wetting fluids such as FC 72 and Incipience is.
In this study, two kinds of copper micro-patterned surfaces with different heights were fabricated by using a powder injection molding (PIM) process.
The micro-pattern’s size was μm, and the gap size was 50 μm. The short micro-pattern’s height was μm, and the height of the tall one was μm. A copper powder and wax-polymer-based binder system was used to fabricate the micro Cited by: 1.
wetting and topography on ice nucleation, to the wetting behavior of superhydrophobic surfaces in icing conditions, and to ice adhesion, highlighting the role of environmental conditions where relevant.
A brief discussion of practical issues, challenges, and innovations in using non-wetting coatings will also presented. Short Bio. surface are capable of providing a threefold to fivefold improvement in boiling heat transfer7.
However, despite initial claims to the contrary, the use of these commercial surfaces does not appear to eliminate the superheat excursion encountered in the boiling of highly-wetting liquids.Lin et Flu () The equation introduced by Pukhnachov4 and later studied, e.g., in Hinch and Kelmanson7 and Karabut,8 was amended by Thiele9 who introduced a Derjaguin (or disjoining) pressure term.3,10 This allows for a study of the influence of wettability on the drop and film behavior on a rotating.additive-enhanced phase change", ASTFE First Thermal and Fluids Engineering Summer Conference (TFESC ), New York City, NY, AugustM.
M. Rahman, E. Ölçeroğlu, and M. McCarthy, "Boiling heat transfer enhancement on structured surfaces.
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