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Relevant bibliographies by topics / Critical Heat Flux (CHF)

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Academic literature on the topic 'Critical Heat Flux (CHF)'

Author: Grafiati

Published: 4 June 2021

Last updated: 3 February 2022

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Journal articles on the topic "Critical Heat Flux (CHF)"

1

Sulaksono, Santiko Tri, Sudjatmi Kustituantini Alfa, and Dani Gustaman Syarif. "CRITICAL HEAT FLUX NANOFLUIDS MEASUREMENTS SYSTEM USING ARDUINO." JURNAL TEKNOLOGI REAKTOR NUKLIR TRI DASA MEGA 23, no. 1 (February 17, 2021): 9. http://dx.doi.org/10.17146/tdm.2021.23.1.6005.

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Crtical heat flux (CHF) is an important characteristic of nanofluids. The CHF measurements were carried out in nanofluid research at the Center for Applied Nuclear Science and Technology. These measurements are done manually using a variable power supply and a multimeter. However, it was difficult to record the voltage and current due to the sudden break of the wire. In this study, Arduino was used to measure CHF automatically. The voltage is applied to the wire and increases automatically along with the measurement of the voltage and current in the wire. The results of the voltage and current measurements were compared with a multimeter and were not significantly different. It can be concluded that the CHF measurement system using arduino can be used to measure nanofluid CHF.

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Bergles, A. E., and S. G. Kandlikar. "On the Nature of Critical Heat Flux in Microchannels." Journal of Heat Transfer 127, no. 1 (January 1, 2005): 101–7. http://dx.doi.org/10.1115/1.1839587.

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The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

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Monde, M. "Analytical Study of Critical Heat Flux in Two-Phase Thermosyphon: Relationship Between Maximum Falling Liquid Rate and Critical Heat Flux." Journal of Heat Transfer 118, no. 2 (May 1, 1996): 422–28. http://dx.doi.org/10.1115/1.2825861.

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An analytical study has been done on the critical heat flux of a two-phase thermosyphon, in which a liquid film and a vapor flow exist in a countercurrent annular flow. The CHF point on the thermosyphon is proved to correspond to a maximum falling liquid rate fed to the thermosyphon, which can be determined from three equations of momentum, its partial derivative with void fraction, and mass balance in the thermosyphon. This maximum point, furthermore, becomes identical to the point at which an envelope line generated from the momentum equation and its partial derivative intersects the mass balance line. The CHF calculated from the maximum liquid rate is found to be in fairly good agreement with the existing CHF data.

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Leroux, K. M., and M. K. Jensen. "Critical Heat Flux in Horizontal Tube Bundles in Vertical Crossflow of R113." Journal of Heat Transfer 114, no. 1 (February 1, 1992): 179–84. http://dx.doi.org/10.1115/1.2911244.

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The critical heat flux (CHF) on a single tube in a horizontal bundle subject to an upward crossflow of R113 has been studied in three bundle geometries. Effects of local quality, mass flux, pressure, and bundle geometry on the CHF were investigated. The shapes of the CHF-quality curves display three distinct patterns, which progress from one to another as mass flux increases. At low mass fluxes, the CHF data monotonically decreased with increasing quality. At intermediate mass fluxes with increasing quality, the CHF data initially decreased to a relative minimum, then increased to a relative maximum, and finally began to decrease again as the higher qualities were reached. At high mass fluxes, as quality increased, the CHF rose gradually from the zero quality value to a maximum and then began to decrease. For all mass fluxes, the zero-quality CHF points clustered around an average value, which varied slightly with test section geometry. Mechanisms for the CHF condition are suggested.

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Hu, Zhi Hong, and Ting Kuan Chen. "Effects of Non-Uniform Circumferential Heating and Inclination on Critical Heat Flux in Smooth Round Tubes." Applied Mechanics and Materials 291-294 (February 2013): 1657–60. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.1657.

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Experimental investigation of the critical heat flux (CHF) in smooth round tubes with circumferentially variable heating was carried out. The riser tubes with 0, 20, 90-degree inclinations from the horizontal were electrically heated. The measurements were carried out for pressure between 13 and 21MPa, mass flux between 600 and 900kg/m2s. The peak-to average heat flux ratio was amounted to 1.6. CHF data of uniform heating were also tested. The test results show that the initial CHF is always observed at location of peak heat flux in vertical tubes with non-uniform heating. In horizontal and inclined tubes with side-heating the transit from a top to side initial indication of CHF occurs by increasing the mass flux and the pressure to certain values. The Initial CHF of non-uniformly heated tubes is fairly agreement with the values of uniformly heated tubes.

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Lin, Lanchao, and Rengasamy Ponnappan. "Critical Heat Flux of Multi-Nozzle Spray Cooling." Journal of Heat Transfer 126, no. 3 (June 1, 2004): 482–85. http://dx.doi.org/10.1115/1.1738418.

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Tiny nozzles are developed that are capable of creating the swirling flow necessary to generate a full cone spray. Eight miniature nozzles are embedded in a multi-nozzle plate used to generate a spray array for the cooling of high heat flux laser diodes. The target spray cooling area is a 1×2 cm2 flat surface of a copper heater plate. A closed loop spray cooling test setup is established. FC-87, FC-72 and methanol are used as the working fluids. Critical heat flux (CHF) is experimentally investigated at various spray saturation temperatures and nozzle pressure drops (from 0.690 bar to 3.10 bar). It is demonstrated that the spray cooler can reach the CHF levels up to 91.5 W/cm2 with FC-87 and 490 W/cm2 with methanol.

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Visaria, Milan, and Issam Mudawar. "A Systematic Approach to Predicting Critical Heat Flux for Inclined Sprays." Journal of Electronic Packaging 129, no. 4 (March 26, 2007): 452–59. http://dx.doi.org/10.1115/1.2804095.

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This study provides a new systematic approach to predicting the effects of spray inclination on critical heat flux (CHF). Experiments were performed with three pressure spray nozzles over a broad range of inclination angles at five flow rates and subcoolings of 15°C and 25°C. These experiments also included high-speed video analysis of spray formation, impact, and recoil for a 1.0×1.0cm2 test surface. Inclined sprays produced elliptical impact areas, distorted by lateral liquid flow that provided partial resistance to dryout along the downstream edge of the impact ellipse. These observations are used to determine the locations of CHF commencement along the test surface. A new theoretical model shows that increasing inclination angle away from normal decreases both the spray impact area and the volumetric flux. These trends explain the observed trend of decreasing CHF with increasing inclination angle. Combining the new model with a previous point-based CHF correlation shows great success in predicting the effects of spray inclination on CHF.

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Pasamehmetoglu, K. O., R. A. Nelson, and F. S. Gunnerson. "Critical Heat Flux Modeling in Forced Convection Boiling During Power Transients." Journal of Heat Transfer 112, no. 4 (November 1, 1990): 1058–62. http://dx.doi.org/10.1115/1.2910478.

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In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is exceptionally good. The new model also is compared with the semi-empirical transient CHF model in the literature.

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Koşar, Ali, and Yoav Peles. "Critical Heat Flux of R-123 in Silicon-Based Microchannels." Journal of Heat Transfer 129, no. 7 (July 10, 2006): 844–51. http://dx.doi.org/10.1115/1.2712852.

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Critical heat flux (CHF) of R-123 in a silicon-based microchannel heat sink was investigated at exit pressures ranging from 227kPato520kPa. Critical heat flux data were obtained over effective heat fluxes ranging from 53W∕cm2to196W∕cm2 and mass fluxes from 291kg∕m2sto1118kg∕m2s. Flow images and high exit qualities suggest that dryout is the leading CHF mechanism. The effect of mass velocity, exit quality, and system pressure were also examined, and a new correlation is presented to represent the effect of these parameters.

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Lee, T. Y. Tom, Mali Mahalingam, and Peter J. C. Normington. "Subcooled Pool Boiling Critical Heat Flux in Dielectric Liquid Mixtures." Journal of Electronic Packaging 115, no. 1 (March 1, 1993): 134–37. http://dx.doi.org/10.1115/1.2909294.

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The beneficial effect of using dielectric liquid mixture in reducing temperature overshoot in pool boiling has been studied by the authors (Normington et al., 1992). The current experimental work addresses the influence of mixtures of dielectric liquids on the critical heat flux (CHF) in pool boiling. Two families of dielectric liquids were evaluated: perfluorocarbon liquids and perfluoropolyether liquids. Each set of the family consisted of two liquids with boiling points ranging from 80°C−110°C. Both 100 percent of each liquid and mixtures of two liquids were tested. Video filming was used along with electronic data collection. The perfluoropolyether liquids showed an increase in CHF as more high boiling liquid was added to the mixture, while the perfluorocarbon liquids had a constant CHF for all mixtures.

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Dissertations / Theses on the topic "Critical Heat Flux (CHF)"

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Kiameh, Bassam Philip. "Prediction of critical heat flux (CHF) for non-aqueous fluids in forced convective boiling." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/21731.

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Altalidi, Sulaiman Saleh. "Two-Phase Spray Cooling with HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics using Practical Enhanced Surfaces." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011876/.

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The objective of this research was to investigate the performance of two-phase spray cooling with HFC-134a and HFO-1234yf refrigerants using practical enhanced heat transfer surfaces. Results of the study were expected to provide a quantitative spray cooling performance comparison with working fluids representing the current and next-generation mobile air conditioning refrigerants, and demonstrate the feasibility of this approach as an alternative active cooling technology for the thermal management of high heat flux power electronics (i.e., IGBTs) in electric-drive vehicles. Potential benefits of two-phase spray cooling include achieving more efficient and reliable operation, as well as compact and lightweight system design that would lead to cost reduction. The experimental work involved testing of four different enhanced boiling surfaces in comparison to a plain reference surface, using a commercial pressure-atomizing spray nozzle at a range of liquid flow rates for each refrigerant to determine the spray cooling performance with respect to heat transfer coefficient (HTC) and critical heat flux (CHF). The heater surfaces were prepared using dual-stage electroplating, brush coating, sanding, and particle blasting, all featuring "practical" room temperature processes that do not require specialized equipment. Based on the obtained results, HFC-134a provided a better heat transfer performance through higher HTC and CHF values compared to HFO-1234yf at all tested surfaces and flow rates. While majority of the tested surfaces provided comparable HTC and modestly higher CHF values compared to the reference surface, one of the enhanced surfaces offered significant heat transfer enhancement.

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Gourbil, Ange. "Etude expérimentale de l'ébullition convective en milieu poreux : assèchement et flux critique." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/18597/1/GOURBIL_Ange.pdf.

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Cette thèse est motivée par le besoin de compléter les connaissances actuelles des phénomènes ayant lieu lors d’un renvoi d’eau dans un lit de débris radioactifs, opération appelée « renoyage » et qui intervient dans une séquence d’accident grave où un cœur de réacteur nucléaire est dégradé suite à une perte prolongée de refroidissement primaire. Notre étude, de nature expérimentale, vise à mieux caractériser la crise d’ébullition en convection forcée, dans un milieu poreux chauffant. Le cœur du dispositif expérimental est un milieu poreux modèle quasibidimensionnel, composé de 276 cylindres disposés entre deux plaques de céramique distantes de 3 mm, dont l’une, transparente, permet de visualiser les écoulements. Les cylindres, de 2 mm de diamètre, sont des sondes thermo-résistives qui ont une double fonction : elles sont utilisées comme éléments chauffants et comme capteurs de température. Une boucle fluide permet de contrôler le débit d’injection de liquide dans la section test, la température d’injection ainsi que la pression. La section test est placée verticalement, le liquide est injecté par le bas à une température proche de la saturation. Dans une première série d’expériences, la puissance thermique dissipée globalement par un ensemble de cylindres chauffants est augmentée de façon progressive jusqu’à atteindre l’assèchement d’une zone du milieu poreux. Les résultats montrent deux types de phénoménologies dans le déclenchement de la crise d’ébullition. Pour des débits d’injection faibles (densités de flux massique de l’ordre de 4 kg.m^-2.s^-1 maximum), l’atteinte de la puissance d’assèchement se traduit par un lent recul du front diphasique jusqu’à sa stabilisation en haut de la zone chauffée ; en aval de la zone chauffée, l’écoulement est monophasique vapeur. Pour des débits d’injection plus élevés, la crise d’ébullition apparaît autour d’un des éléments chauffants, conduisant à une ébullition en film localisée, tandis qu’un écoulement diphasique liquide-vapeur continue de parcourir l’aval de la section test. Les visualisations de ces expériences permettent d’identifier qualitativement la structure des écoulements. D’autres expériences consistent à mesurer le flux critique local autour d’un cylindre choisi, pour différentes configurations d’écoulements. Le débit d’injection est fixé. Une puissance de chauffe est imposée à une ligne horizontale de cylindres en amont du cylindre choisi. Les résultats montrent que le flux critique sur ce cylindre diminue en fonction de la puissance délivrée à la ligne chauffée. La distance du cylindre étudié à la ligne chauffée semble avoir peu d’influence sur le flux critique. Des visualisations expérimentales sont utilisées pour caractériser l’écoulement diphasique en aval de la ligne chauffée, dans le but de mettre en relation le flux critique local avec des paramètres hydrodynamiques (saturations, vitesses des phases). Les images obtenues sont difficiles à exploiter. Afin de calibrer les paramètres des algorithmes de traitement d’images, nous avons reproduit une cellule d’essai de géométrie identique à l’originale, mais où l’on injecte du gaz par une ligne de cylindres en amont de la section test dans une configuration d’écoulement diphasique isotherme. Dans ce dispositif, le débit d’injection de gaz est contrôlé et mesuré. Les visualisations obtenues servent alors de références auxquelles sont comparées les visualisations d’ébullition convective.

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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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5

Wong, Y. L. "Generalized CHF prediction for horizontal tubes with uniform heat flux." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5471.

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Yang, Jun. "Effect of non-uniform axial heat-flux distribution on critical heat flux." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26816.

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An experimental study of the effect of axial flux distribution (AFD) on critical heat flux (CHF) was conducted in directly heated tubes at the Freon-equivalent CANDU reactor conditions of interest. CHF measurements were obtained on test sections with four nonuniform AFD profiles as well as a uniform AFD profile using HFC-134a as a test fluid. Each of the non-uniform AFD test sections had a stepped cosine heat flux profile with approximately 16 heat flux steps. The test conditions covered a pressure range of 1662 to 2389 kPa, a mass flux range of 2827 to 4648 kg m-2 s -1 and an inlet quality range of -0.909 to -0.002. The results showed that the AFD has a strong effect on CHF at high dryout qualities. (Abstract shortened by UMI.)

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Manning, Jonathan Paul. "Critical heat flux in non-circular channels." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/61534.

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In the design of nuclear reactors adequate cooling must be demonstrated for all operational states as well as during and after design basis accidents. A key aspect of this design activity is the prediction of the Critical Heat Flux (CHF). The focus of the work in this thesis was the prediction of CHF in non-circular channels. The Look Up Table was used to analyse several burnout studies for non-circular channels in the literature and was found to be a poor predictive tool for these geometries. A conventional phenomenological model developed for round tubes was also shown to give poor predictions, with a mean error of 25% and root mean square error of 31%. Phenomenological modelling requires correlations for the mass transfer processes in annular flow. Deposition rates for annular flow in rectangular channels have been determined by an analysis of upstream burnout data. This showed good agreement with the rates in round tubes and validated this aspect of the phenomenological approach. The conventional one-dimensional phenomenological model was extended to include a variation in film thickness around the periphery. This model was fitted to experimental data from the literature for burnout in asymmetrically heated tubes. The low mean and root mean square errors, 0.8% and 3.0% respectively, confirmed the principle of the model. A flow visualisation rig has been designed and successfully operated to produce a flow-regime map for a rectangular channel of 25 mm by 2.5 mm. This map showed that the gas momentum flux required to cause annular flow was higher than that in round tubes. A wide range of annular flow conditions were observed and shown to be generally consistent with the phenomenological modelling approach. However it was seen that there were novel flow features that will need to be accounted for when predicting CHF in these geometries.

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Thompson, Jordan Lee. "Direct Measurement of Boiling Water Heat Flux for Predicting and Controlling Near Critical Heat Flux." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23091.

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A novel method for measuring heat flux of boiling water is designed and built to study critical heat flux (CHF) and observe the response of a heat flux sensor when CHF occurs. A high temperature heat flux sensor is embedded in the wall of a pipe to get a direct measurement of the surface heat flux and sensor temperature. By submerging the pipe in water and applying a controlled heat flux to the inside diameter over the area where the sensor is located, boiling is created on the outer surface while measuring the heat flux. The heat flux is gradually increased up to CHF and the heat flux response is observed to determine if the heat flux sensor could sense CHF when it occurred. The heat flux sensor is able to consistently measure the value for CHF, which is approximately 510 kW/m" for this system. It is also observed during the experiments that the heat flux response undergoes an inflection of the heat transfer coefficient at a consistent temperature just before reaching CHF. This observed inflection caused the heat flux response to deviate from its cubic relationship with the temperature and drastically increase for a very small change in temperature. This inflection response can be used as an indication for approaching CHF and can also be used to approximate its value without prior knowledge of when it occurs.
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9

Joober, Khaled. "The effect of flow geometry on critical heat flux." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6544.

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An extensive and systematic literature review on the effect of flow geometry on the Critical Heat Flux (CHF) has been performed. This review covers most of the flow geometries such as tubes, concentric and eccentric annuli, rectangular channels, irregular-shaped channels and bundles. The following geometric parameters have been found to strongly influence the CHF: (i) hydraulic-equivalent diameter, (ii) heated-equivalent diameter, (iii) gap size, (iv) unheated adjacent surface, (v) heated adjacent surface, (vi) curvature, (vii) eccentricity (including bowing), and (viii) channel shape. It is found that some of the geometric effects on CHF depend on the flow conditions and the CHF type. For each geometry the parametric trends have been described, whenever sufficient experimental results are available. A review and assessment of the available prediction methods is conducted. The following trends have been identified in this study: (i) in general the CHF in annuli (concentric and eccentric) is lower than that in tubes, especially for high quality and narrow gaps; (ii) for rectangular channels and irregular-shaped channels, corners can cause a large CHF reduction; (iii) the CHF for concave surface is significantly higher than the CHF for a convex surface; (iv) the effect of gap size in concentric annuli is different for a departure from nucleate boiling (DNB) type CHF and CHF type for the annular flow regime. For the first CHF type reduction in gap size results in a CHF decrease, while for the second CHF type it results in CHF enhancement; and (v) heating the adjacent surface results in a CHF increase. Based on the observed trends, CHF correction factors have been derived for each geometry. Finally, an interim CHF prediction method for subchannels and flow conditions of interest to CANDU$\sp*$ reactors has been proposed. ftn$\sp*$CANDU--CANada Deuterium Uranium, a registered trademark.

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Kuan, Wai Keat. "Experimental study of flow boiling heat transfer and critical heat flux in microchannels /." Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/1887.

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Books on the topic "Critical Heat Flux (CHF)"

1

Cheung, F. B. Critical heat flux (CHF) phenomenon on a downward facing curved surface: Effects of thermal insulation. Washington, DC: Division of Systems Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1998.

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Saha, Sujoy Kumar, and Gian Piero Celata. Critical Heat Flux in Flow Boiling in Microchannels. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17735-9.

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Centre, Bhabha Atomic Research. Flux mapping system for AHWR critical facility. Mumbai: Bhabha Atomic Research Centre, 2007.

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Tain, Ra-Min. Assessment of critical heat flux correlations for high steam quality condition. Lung-Tan, Republic of China: Institute of Nuclear Energy Research, 1987.

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Sjöberg, Anders. Assessment of RELAP5/MOD 2 against 25 dryout experiments conducted at the Royal Institute of Technology. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1986.

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Sjöberg, Anders. Assessment of RELAP5/MOD 2 against 25 dryout experiments conducted at the Royal Institute of Technology. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1986.

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Sjöberg, Anders. Assessment of RELAP5/MOD 2 against 25 dryout experiments conducted at the Royal Institute of Technology. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1986.

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Cramond, Wallis R. Shutdown decay heat removal analysis of a combustion engineering 2-loop pressurized water reactor: Case study. Washington, DC: Division of Reactor and Plant Systems, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1987.

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U.S. Nuclear Regulatory Commission., ed. Critical Heat Flux (CHF) Phenomenon On A Downward Facing Curved Surface... NUREG/CR-6507... U.S. Nuclear Regulatory Commission... 1997. [S.l: s.n., 1997.

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K, Tuzla, U.S. Nuclear Regulatory Commission. Office of Nuclear Regulatory Research. Division of Reactor and Plant Systems., and Lehigh University. Institute of Thermo-Fluid Engineering and Science., eds. Thermodynamic nonequilibrium in post-critical-heat-flux boiling in a rod bundle. Washington, DC: Division of Reactor and Plant Systems, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1988.

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Book chapters on the topic "Critical Heat Flux (CHF)"

1

Celata, Gian Piero, and Andrea Mariani. "Critical Heat Flux, Post-CHF Heat Transfer and Their Augmentation." In Modelling and Experimentation in Two-Phase Flow, 325–82. Vienna: Springer Vienna, 2003. http://dx.doi.org/10.1007/978-3-7091-2538-0_7.

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Saha, Sujoy Kumar, and Gian Piero Celata. "Critical Heat Flux." In Critical Heat Flux in Flow Boiling in Microchannels, 13–51. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17735-9_2.

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Kanizawa, Fabio Toshio, and Gherhardt Ribatski. "Critical Heat Flux and Dryout." In Mechanical Engineering Series, 217–40. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68704-5_6.

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Akimoto, Hajime, Yoshinari Anoda, Kazuyuki Takase, Hiroyuki Yoshida, and Hidesada Tamai. "Boiling Heat Transfer and Critical Heat Flux." In An Advanced Course in Nuclear Engineering, 315–46. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-55603-9_16.

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Thome, J. R., and L. Consolini. "Prediction of Critical Heat Flux in Microchannels." In Microfluidics Based Microsystems, 107–20. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-9029-4_6.

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Celata, Gian Piero. "Critical Heat Flux in Subcooled Flow Boiling." In Energy and Environment, 126–61. Tokyo: Springer Japan, 2001. http://dx.doi.org/10.1007/978-4-431-68325-4_6.

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Vishnoi, A. K., A. Dasgupta, D. K. Chandraker, A. K. Nayak, Nandan D. Hegde, and A. Rama Rao. "A Study on Premature Occurrence of Critical Heat Flux." In Thorium—Energy for the Future, 517–27. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-2658-5_43.

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Nishiguchi, S., and M. Shoji. "Boiling Heat Transfer of Butanol Aqueous Solution-Augmentation of Critical Heat Flux." In Film and Nucleate Boiling Processes, 198–208. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2011. http://dx.doi.org/10.1520/stp49340t.

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Nishiguchi, S., and M. Shoji. "Boiling Heat Transfer of Butanol Aqueous Solution-Augmentation of Critical Heat Flux." In Film and Nucleate Boiling Processes, 198–208. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2011. http://dx.doi.org/10.1520/stp153420120011.

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Saha, Sujoy Kumar, and Gian Piero Celata. "Introduction." In Critical Heat Flux in Flow Boiling in Microchannels, 1–11. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17735-9_1.

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Conference papers on the topic "Critical Heat Flux (CHF)"

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Shim, W. Jaewoo, Joo-Yong Park, Ji-Su Lee, and Dong Kook Kim. "Critical Heat Flux in Tubes With Cosine Axial Heat Flux." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72504.

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In this study a method to predict CHF (Critical Heat Flux) in vertical round tubes with cosine heat flux distribution was examined. For this purpose a uniform correlation, based on local condition hypothesis, was developed from 9,366 CHF data points of uniform heat flux heaters. The CHF data points used were collected from 13 different sources had the following parameter ranges: 1.01 ≤ P (pressure) ≤ 206.79 bar, 9.92 ≤ G (mass flux) ≤ 18,619.39 kg/m2s, 0.00102 ≤ D (diameter) ≤ 0.04468 m, 0.0254 ≤ L (length) ≤ 4.966 m, 0.11 ≤ qc (CHF) ≤ 21.42 MW/m2, and −0.87 ≤ X (exit qualities) ≤ 1.58. The result of this work showed that the uniform CHF correlation could be used to predict CHF accurately in a non-uniform heat flux heater for wide flow conditions. Furthermore, the location, where CHF occurs in non-uniform heat flux distribution, can also be determined accurately with the local variables: the system pressure (P), tube diameter (D), mass flux of water (G), and true mass flux of vapor (GXt). The new correlation predicted CHF with cosine heat flux, 297 data points from 5 different published sources, within the root mean square error of 12.42% and average error of 1.06% using the heat balance method.

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Zhao, Dawei, Wanyu Xiong, Wenxing Liu, and Jianjun Xu. "Study on DNB-Type Critical Heat Flux With Chopper-Cosine Axial Heat Flux Distributions." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30945.

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Departure from nucleate boiling (DNB) type critical heat flux (CHF) is one of most important thermal criteria for nuclear reactor design. Concerning on the typical chopper-cosine heat flux profile at reactor core, it is of great significance to predict the CHF under non-uniform heating conditions for reactor design and the performance promotion of reactor system. Some correction factors are proposed for the prediction of CHF with non-uniform axial power shapes. In this study, a mechanistic DNB-type CHF model has been developed on the basis of liquid sublayer dryout mechanism. The non-uniform axial heat flux is taken into account of upstream memory effect on boiling crisis in this model. The predictions of present model and Tong’s non-uniform heat flux shape factor method are compared with the experimental results in the vertical tube with chopper-cosine axial heat flux distributions. The comparison results show the present model has fairly good prediction capability for DNB-type CHF under non-uniform heating condition.

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Umekawa, Hisashi, Mamoru Ozawa, and Takeshi Sanami. "Restriction of Critical Heat Flux by Critical Flow Condition in Capillary Tube." In ASME 2003 1st International Conference on Microchannels and Minichannels. ASMEDC, 2003. http://dx.doi.org/10.1115/icmm2003-1073.

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Critical heat flux (CHF) is a very important design factor of boiling channel, then, so many investigations have been conducted so far. In the case of small diameter channel, the main interest is related with the heat removal of high heat flux component. Therefore, CHF of that system should be predicted by DNB condition. On the other hand, CHF under low heat flux condition in small channel can be considered as the relation with two kinds of restrictions. In this investigation, the confirmation of the relationship of two restrictions in CHF was principal purpose. The CHF of this system was basically decided by the dryout condition, but it deviated from the dryout under certain conditions. In those conditions, the critical flow condition achieved in lower heat flux compared with that of the dryout. Owing to this restriction of the flow rate by critical flow condition, pseudo CHF condition occurs. Experimental results have expressed these relationships between CHF and critical flow condition well.

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Sykes, David M., Gregory S. Cole, Daniel A. Staples, Ali Kosar, and Arthur E. Bergles. "Critical Heat Flux in Cooling Channels for Flow-Field Probes." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23276.

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Probes (sampling, temperature, pressure) for high-temperature environments, such as gas turbine combustors, can survive only if they are cooled. To keep probe size small, the cooling passages must be microchannels, [O] 100 micrometer internal diameter. For logistical reasons, the length-to-diameter ratio is considerable. Heat fluxes are high, so that boiling occurs even with high velocities. The limiting factor for probe survivability, then, is the critical heat flux (CHF). This paper summarizes an experimental study of CHF in cooling channels that might be used for probes. A CHF correlation for water coolant is developed for design. An orifice at the channel inlet, originally conceived for enhancement, was found to dramatically improve the flow stability and increase the CHF. Pumping power requirements for plain tubes and orificed tubes are also documented.

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Nishiguchi, Shotaro, Naoki Ono, and Masahiro Shoji. "Critical Heat Flux of Butanol Aqueous Solution." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62378.

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Aqueous solutions of some alcohols such as butanol show peculiar temperature dependence of surface tension. Contrary to ordinary liquids or solutions, the surface tension increases with temperature at the range of high liquid temperature. So at the triple-phase point on a heated surface, the thermo-capillary force acts for the liquid to wet the heated surface, so the solutions are sometimes called as “self-wetting liquids”. Self-wetting liquids may prohibit the dry-out of a heated surface so that the heat transfer performance would be enhanced. For this reason, applications of self-wetting liquids to heat transfer devices such as heat pipes are actively studied in recent years. However, the heat transfer characteristics of boiling of self-wetting liquids are not fully understood. In the present research, a boiling experiment of butanol aqueous solution was performed on a heated fine wire in order to make clear the fundamental heat transfer characteristics. A heated wire configuration is easy to observe the phenomena and easy to address the fundamental issues of boiling. In the present experiment, nucleate boiling heat transfer were investigated with special attention to critical heat flux (CHF), by changing solution concentration and temperature. Bubbling aspects were observed by high-speed video camera. It is found from the experiment that CHF is generally enhanced 20 to 50% when compared to the case of pure water. It is also found that at a certain concentration and at a certain liquid temperature, peculiar boiling takes place where very small bubbles are emitted from the heated wire and CHF enhancement becomes very large from 2 to 3 times higher than CHF of pure water. The temperature when the peculiar boiling takes place is close to boiling temperature of the solution. These results suggest the possibility of application of aqueous solution to high-performance cooling devices utilizing micro-scaled channels because generating bubbles are small enough so that the pressure loss of the flow passage is small and heat transfer rate is very large.

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de Oliveira @sJr., Fernando, Fernando Lepsch, and Tulio Coletto. "Ethanol Sensor using the Critical Heat Flux (CHF) principle." In SAE Brasil 2011 Congress and Exhibit. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2011. http://dx.doi.org/10.4271/2011-36-0115.

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Bergles, A. E., and S. G. Kandlikar. "On the Nature of Critical Heat Flux in Microchannels." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42383.

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The critical heat flux (CHF) limit is an important consideration in the design of any flow boiling unit. Before the use of microchannels under flow boiling conditions becomes widely accepted in critical applications, such as electronics cooling and laser lenses, it is essential to develop CHF data for microchannels. The experiments required to obtain this information pose unique challenges as the channel dimensions become smaller. The issues of parallel channel instability, experimental control, experimental uncertainty, and conjugate effects need to be carefully addressed. These issues are addressed in the present paper, and guidelines helpful in the design of CHF experiments are outlined.

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Chuanxin, Peng, and Zan Yuanfeng. "Experimental Investigation on Critical Heat Flux in Horizontal Tube." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81107.

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The critical heat flux (CHF) in horizontal tube under low flow condition is investigated in this paper. It is found that the boiling crisis occurs at the upper surface of the horizontal tube. According to the exit quality and flow pattern, the category of boiling crisis in the horizontal tube under low flow is considered to be Dryout. The prediction results of Bowring correlation and Lookup table are much larger than the experimental data. Because the Bowring correlation and Lookup table are proposed for the CHF prediction of vertical round tube. The distribution of liquid film in horizontal annular flow is asymmetrical due to gravity. The non-uniform distribution of the liquid film reduces the CHF.

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Chen, Tailian, and Suresh V. Garimella. "A Study of Critical Heat Flux During Flow Boiling in Microchannel Heat Sinks." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44083.

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The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels.

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Wu, Zan, and Wei Li. "Correlations for Saturated Critical Heat Flux in Microchannels." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22533.

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Experimental results of the saturated-flow boiling critical heat flux (CHF) in microchannels for both multi- and single-channel configurations were obtained from the literature. The collected database contains 629 data points, covering 5 refrigerants, nitrogen, and water, for a wide range of operational conditions, and different micro-channel dimensions. The whole database was analyzed by using four empirical correlations to verify their respective accuracies. However, none of the existing correlations could predict the entire database precisely. A saturated CHF correlation was proposed by using boiling number, length-to-diameter ratio, and exit quality. The new correlation can predict the overall micro-channel database accurately on the whole. It predicts almost 97.0% of the non-aqueous data (except R12 data points located in the macro-scale region) and 94.0% of the water data within the ± 30% error band.

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Reports on the topic "Critical Heat Flux (CHF)"

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Cheung, F. B., K. H. Haddad, and Y. C. Liu. Critical heat flux (CHF) phenomenon on a downward facing curved surface. Office of Scientific and Technical Information (OSTI), June 1997. http://dx.doi.org/10.2172/491560.

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Jafri, T., T. J. Dougherty, and B. W. Yang. Correlation of critical heat flux data for uniform tubes. Office of Scientific and Technical Information (OSTI), September 1995. http://dx.doi.org/10.2172/111456.

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Shumway, R. New critical heat flux method for RELAP5/MOD3: Completion report. Office of Scientific and Technical Information (OSTI), January 1989. http://dx.doi.org/10.2172/6044085.

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Rao, D. V., and M. S. El-Genk. Critical heat flux predictions for the Sandia Annular Core Research Reactor. Office of Scientific and Technical Information (OSTI), August 1994. http://dx.doi.org/10.2172/10196536.

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Kim, Sung J., and Jungho Kim. Surface De-Wetting Based Critical Heat Flux Model Development and Validation. Fort Belvoir, VA: Defense Technical Information Center, February 2013. http://dx.doi.org/10.21236/ada578387.

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Shadday, M. A. Jr. Critical heat flux concerns during the flow instability phase of a DEGB LOCA. Office of Scientific and Technical Information (OSTI), August 1990. http://dx.doi.org/10.2172/5037231.

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Shadday, M. A. Jr. Critical heat flux concerns during the flow instability phase of a DEGB LOCA. Office of Scientific and Technical Information (OSTI), August 1990. http://dx.doi.org/10.2172/10155739.

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Kirillov, P. L., and I. P. Smogalev. On the look-up tables for the critical heat flux in tubes (history and problems). Office of Scientific and Technical Information (OSTI), September 1995. http://dx.doi.org/10.2172/111418.

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Symolon, P. D., W. E. Moore, and D. F. Wolf. Critical heat flux experiments in a heated rod bundle with upward crossflow of Freon 114. Office of Scientific and Technical Information (OSTI), February 1997. http://dx.doi.org/10.2172/319773.

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Feldman, E. Computer Spreadsheet Representation of the Groeneveld et al. 2006 Critical Heat Flux Look-Up Table. Office of Scientific and Technical Information (OSTI), October 2014. http://dx.doi.org/10.2172/1159036.

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