Journal articles: '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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8

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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10

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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11

Gersey, C. O., and I. Mudawar. "Orientation Effects on Critical Heat Flux From Discrete, In-Line Heat Sources in a Flow Channel." Journal of Heat Transfer 115, no. 4 (November 1, 1993): 973–85. http://dx.doi.org/10.1115/1.2911394.

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The effects of flow orientation on critical heat flux (CHF) were investigated on a series of nine in-line simulated microelectronic chips in Fluorinert FC-72. The chips were subjected to coolant in upflow, downflow, or horizontal flow with the chips on the top or bottom walls of the channel with respect to gravity. Changes in angle of orientation affected CHF for velocities below 200 cm/s, with some chips reaching CHF at heat fluxes below the pool boiling and flooding-induced CHF values. Increased subcooling was found to dampen this adverse effect of orientation slightly. Critical heat flux was overwhelmingly caused by localized dryout of the chip surface. However, during the low velocity downflow tests, low CHF values were measured because of liquid blockage by vapor counterflow and vapor stagnation in the channel. At the horizontal orientation with downward-facing chips, vapor/liquid stratification also yielded low CHF values. Previously derived correlations for water and long, continuous heaters had limited success in predicting CHF for the present discontinuous heater configuration. Because orientation has a profound effect on the hydrodynamics of two-phase flow and, consequently, on CHF for small inlet velocities, downflow angles should be avoided, or when other constraints force the usage of downflow angles, the inlet liquid velocity should be sufficiently large.

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12

Raza, Md Qaisar, Nirbhay Kumar, and Rishi Raj. "Effect of foamability on pool boiling critical heat flux with nanofluids." Soft Matter 15, no. 26 (2019): 5308–18. http://dx.doi.org/10.1039/c8sm02565g.

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Foaming due to the presence of stabilizing agents such as surfactants deteriorates the critical heat flux (CHF) during boiling of nanofluids. A master curve is developed to demonstrate an inverse relation between CHF and the foamability.

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13

Kefer, V., W. Kḧler, and W. Kastner. "Critical heat flux (CHF) and post-CHF heat transfer in horizontal and inclined evaoprator tubes." International Journal of Multiphase Flow 15, no. 3 (May 1989): 385–92. http://dx.doi.org/10.1016/0301-9322(89)90008-6.

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14

Park, K.-J., D. Jung, and S. E. Shim. "Nucleate boiling heat transfer coefficients of halogenated refrigerants up to critical heat fluxes." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, no. 6 (February 13, 2009): 1415–24. http://dx.doi.org/10.1243/09544062jmes1356.

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In this work, nucleate pool boiling heat transfer coefficients (HTCs) of five refrigerants of differing vapour pressures are measured on a horizontal, smooth copper surface of 9.53×9.53 mm. The tested refrigerants are R123, R152a, R134a, R22, and R32 and HTCs are taken from 10 kW/m2 to the critical heat flux (CHF) of each refrigerant. Wall and fluid temperatures are measured directly by thermocouples located underneath the test surface and in the liquid pool, respectively. Test results show that nucleate pool boiling HTCs of halogenated refrigerants increase as the heat flux and vapour pressure increase. This typical trend is maintained even at high heat fluxes above 200 kW/m2. Zuber's prediction equation for CHF is quite accurate showing a maximum deviation of 21 per cent for all refrigerants tested. For all refrigerants, Stephan and Abdelsalam's well-known correlation underpredicted nucleate boiling HTC data up to the CHF with an average deviation of 21.3 per cent, while Cooper's correlation overpredicted the data with an average deviation of 14.2 per cent. On the other hand, Gorenflo's and Jung et al.'s correlations showed 5.8 and 6.4 per cent deviations, respectively, in the entire nucleate boiling range up to the CHF.

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Mitsutake, Yuichi, and Masanori Monde. "Ultra High Critical Heat Flux During Forced Flow Boiling Heat Transfer With an Impinging Jet." Journal of Heat Transfer 125, no. 6 (November 19, 2003): 1038–45. http://dx.doi.org/10.1115/1.1621899.

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An ultra high critical heat flux (CHF) was attempted using a highly subcooled liquid jet impinging on a small rectangular heated surface of length 5∼10mm and width 4 mm. Experiments were carried out at jet velocities of 5∼60m/s, a jet temperature of 20°C and system pressures of 0.1∼1.3MPa. The degree of subcooling was varied from 80 to 170 K with increasing system pressure. The general correlation for CHF is shown to be applicable for such a small heated surface under a certain range of conditions. The maximum CHF achieved in these experiments was 211.9 MW/m2, recorded at system pressure of 0.7 MPa, jet velocity of 35 m/s and jet subcooling of 151 K, and corresponds to 48% of the theoretical maximum heat flux proposed by Gambill and Lienhard.

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16

Tan, Lu Zhi, Ji Tian Han, Chang Nian Chen, and Peng Cheng Dou. "Studies on Fluid-to-Fluid Modeling of Critical Heat Flux in a Helically-Coiled Tube." Advanced Materials Research 588-589 (November 2012): 1777–80. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1777.

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An experimental study on critical heat flux (CHF) in a helically-coiled tube cooled with R-134a has been completed in order to assess present fluid-to-fluid modeling approaches. The investigated range of flow parameters for R-134a was: pressure from 0.2 to 0.5 MPa, mass flux values from 50 to 1500 kg m-2 s-1 and inlet quality from -0.2 to 0.1. The CHF data of R-134a have been compared with that of water by applying the Ahmad and the Katto modeling. The water equivalent CHF data translated from R-134a CHF data by using the two modeling approaches have shown a good agreement with the actual water CHF data from previous studies when mass flux exceeds 600 kg m-2 s-1. The results indicate that both the Ahmad and the Katto modeling can be applied only for the high mass flux conditions in helically-coiled tubes.

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Caha, Vojtěch, and Jakub Krejčí. "POST CRITICAL HEAT TRANSFER AND FUEL CLADDING OXIDATION." Acta Polytechnica CTU Proceedings 4 (December 16, 2016): 8. http://dx.doi.org/10.14311/ap.2016.4.0008.

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The knowledge of heat transfer coefficient in the post critical heat flux region in nuclear reactor safety is very important. Although the nuclear reactors normally operate at conditions where critical heat flux (CHF) is not reached, accidents where dryout occur are possible. Most serious postulated accidents are a loss of coolant accident or reactivity initiated accident which can lead to CHF or post CHF conditions and possible disruption of core integrity. Moreover, this is also influenced by an oxide layer on the cladding surface. The paper deals with the study of mathematical models and correlations used for heat transfer calculation, especially in post dryout region, and fuel cladding oxidation kinetics of currently operated nuclear reactors. The study is focused on increasing of accuracy and reliability of safety limit calculations (e.g. DNBR or fuel cladding temperature). The paper presents coupled code which was developed for the solution of forced convection flow in heated channel and oxidation of fuel cladding. The code is capable of calculating temperature distribution in the coolant, cladding and fuel and also the thickness of an oxide layer.

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Mudawar, Issam, and Douglas E. Maddox. "Enhancement of Critical Heat Flux From High Power Microelectronic Heat Sources in a Flow Channel." Journal of Electronic Packaging 112, no. 3 (September 1, 1990): 241–48. http://dx.doi.org/10.1115/1.2904373.

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Several surface augmentation techniques were examined in an investigation of enhancement of critical heat flux (CHF) from a simulated electronic chip to a fluorocarbon (FC-72) liquid in a vertical channel. A parametric comparison of boiling performances is presented for a smooth surface and for surfaces with low-profile microgrooves, low-profile microstuds, and high-profile pin fins. Critical heat fluxes as high as 361 W/cm2 were achieved using a combination of moderate flow velocity, high subcooling and surface enhancement. A semiempirical model constructed previously for CHF from a smooth discrete heat source to saturated or subcooled liquid flow, was found successful in correlating CHF data for the three enhanced surfaces.

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Rahimian, Aref, Hosein Kazeminejad, Hosein Khalafi, Azam Akhavan, and Seyed Mohammad Mirvakili. "Boiling Heat Transfer and Critical Heat Flux Enhancement Using Electrophoretic Deposition of SiO2 Nanofluid." Science and Technology of Nuclear Installations 2019 (December 28, 2019): 1–10. http://dx.doi.org/10.1155/2019/1272156.

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The electrophoretic deposition (EPD) technique was used to create a uniform SiO2 thin film coating on boiling plates, 4 mm in width and 9 mm in length. Significant enhancement in critical heat flux (CHF), for the hydrophilic surfaces generated by this anodic EPD method, has been observed. In order to increase the coating strength, the plates were sintered at various temperatures. To find the thickness and uniformity of the coatings, the SEM images were captured. The captured images showed that the coating thickness uniformly increased up to 90 nm for 0.5% nanofluid percentage by the EPD method. The results show that the hydrophilic and super-hydrophilic surfaces have different boiling heat transfer (BHT) coefficients and CHF behaviors. Also, the results showed an increase of 160% in the CHF value by sintering compared to a bare surface. However, because of the setup simplicity, the shape independency, the particle-coating uniformity, and thickness controllability, the EPD technique can be an appropriate option for modification of the surface and coating on the nuclear fuel cladding.

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20

Liu, Wei, Jianqiang Shan, Shinian Peng, Guangming Jiang, and Yu Liu. "The Study of Critical Heat Flux in Upflow Boiling Vertical Round Tube under High Pressure." Science and Technology of Nuclear Installations 2019 (June 4, 2019): 1–14. http://dx.doi.org/10.1155/2019/3695685.

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The Critical Heat Flux (CHF) prediction under high pressure condition, even close to the vicinity of the critical pressure of water, is an important issue. Although there are many empirical CHF correlations, most of them have covered the pressure under 15MPa. In this study, based on the CHF experiment database of upflow boiling in vertical round tube from 15MPa to the vicinity of the critical pressure of water, the Katto, Bowring, Hall-Mudawar, Alekseev correlations, and Groeneveld LUT-2006 are comparatively studied. With an error analysis of the predicted CHF to the experiment database, the prediction capability and the applicability of these correlations are evaluated and the parametric trends of CHF varying with pressure from 15MPa to critical pressure are proposed. Simultaneously, according to the characteristics of Departure from Nucleate Boiling (DNB) type CHF under high pressure condition, the constitutive correlations of Weisman & Pei model are proposed. The prediction results of three entrainment and deposition correlations of Kataoka, Celata, and Hewitt corresponding to the Dry-Out (DO) type CHF are analyzed. Based on the two improved models above, a comprehensive CHF mechanistic model under high pressure condition combining the DNB and DO type CHF is established. The verification based on the experiment database of upflow boiling in vertical round tube and the parametric trends analysis of CHF varying with thermal-hydraulic and geometric parameters are carried out. Findings of this study have a positive effect on further development of CHF prediction method for universal CHF mechanism, especially under high pressure region.

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Hall, David D., and Issam Mudawar. "Critical heat flux (CHF) for water flow in tubes—II." International Journal of Heat and Mass Transfer 43, no. 14 (July 2000): 2605–40. http://dx.doi.org/10.1016/s0017-9310(99)00192-1.

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Wen, Dongsheng. "Mechanisms of thermal nanofluids on enhanced critical heat flux (CHF)." International Journal of Heat and Mass Transfer 51, no. 19-20 (September 2008): 4958–65. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2008.01.034.

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Devahdhanush, V. S., and Issam Mudawar. "Review of Critical Heat Flux (CHF) in Jet Impingement Boiling." International Journal of Heat and Mass Transfer 169 (April 2021): 120893. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2020.120893.

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24

Li, Jiaqi, Daniel Kang, Kazi Fazle Rabbi, Wuchen Fu, Xiao Yan, Xiaolong Fang, Liwu Fan, and Nenad Miljkovic. "Liquid film–induced critical heat flux enhancement on structured surfaces." Science Advances 7, no. 26 (June 2021): eabg4537. http://dx.doi.org/10.1126/sciadv.abg4537.

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Enhancing critical heat flux (CHF) during boiling with structured surfaces has received much attention because of its important implications for two-phase flow. The role of surface structures on bubble evolution and CHF enhancement remains unclear because of the lack of direct visualization of the liquid- and solid-vapor interfaces. Here, we use high-magnification in-liquid endoscopy to directly probe bubble behavior during boiling. We report the previously unidentified coexistence of two distinct three-phase contact lines underneath growing bubbles on structured surfaces, resulting in retention of a thin liquid film within the structures between the two contact lines due to their disparate advancing velocities. This finding sheds light on a previously unidentified mechanism governing bubble evolution on structured surfaces, which has notable implications for a variety of real systems using bubble formation, such as thermal management, microfluidics, and electrochemical reactors.

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Li, Xiangyu, Guanghuai Wang, Yun Guo, and Songwei Li. "Critical heat flux analysis of divertor cooling flow channel in fusion reactor with CFD method." Thermal Science, no. 00 (2021): 203. http://dx.doi.org/10.2298/tsci210216203l.

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Situated at the bottom of the vacuum vessel, the divertor extracts heat and ash produced by the fusion reaction, minimizes plasma contamination, and protects the surrounding walls from thermal and neutronic loads. The vertical targets of divertor are designed to be able for up to 20 MW/m2 high heat flux. It is a great ordeal for both the material performance and the cooling ability. Critical heat flux (CHF) margin is very crucial during the design of divertor. ANSYS FLUENT is used in this paper to predict the CHF on a monoblock structure with a twisted tape inside the tube. Numerical results are validated with the corresponding sets of experimental results. In this paper, CFD method used to predict CHF of divertor cooling channel was first introduced. On the other hand, influence of inlet subcooling on CHF is studied in detail. The inlet subcooling affect the CHF much complicated for the single- side heated and swirl flow channel. Whether the influencing trend or the locations of CHF occurrence are different under different inlet subcooling. The derivations between the simulation and experimental results were no more than 32%. This study proves the CFD tools can provide efficient help on the understanding of the CHF phenomenon of complex construction.

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Hegde, Ramakrishna, Shrikantha Rao, and Ranapratap Reddy. "Flow visualization and study of CHF enhancement in pool boiling with Al2O3 - Water nano-fluids." Thermal Science 16, no. 2 (2012): 445–53. http://dx.doi.org/10.2298/tsci100511095h.

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Pool boiling heat transfer characteristics of Al2O3-Water nanofluids is studied experimentally using a NiCr test wire of 36 SWG diameter. The experimental work mainly concentrated on i) change of Critical Heat Flux(CHF) with different volume concentrations of nanofluid ii) flow visualization of pool boiling using a fixed concentration of nanofluid at different heat flux values. The experimental work revealed an increase in CHF value of around 48% and flow visualization helped in studying the pool boiling behaviour of nanofluid. Out of the various reasons which could affect the CHF enhancement, surface roughness plays a major role in pool boiling heat transfer.

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Pasamehmetoglu, K. O., R. A. Nelson, and F. S. Gunnerson. "Critical Heat Flux Modeling in Pool Boiling for Steady-State and Power Transients." Journal of Heat Transfer 112, no. 4 (November 1, 1990): 1048–57. http://dx.doi.org/10.1115/1.2910477.

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Understanding and predicting critical heat flux. (CHF) behavior during steady-state and transient conditions is of fundamental interest in the design, operation, and safety of boiling and two-phase flow devices. The results of a comprehensive study specifically conducted to model transient CHF in pool boiling are presented in this paper. The model we developed includes the analysis of thermal energy conduction within the heater coupled with a macrolayer thinning model. Statistical variations in the vapor mass behavior also are incorporated into the model. The resultant model provides new insight into the basic physics of the CHF phenomenon and indicates favorable agreement with the experimental data from cylindrical heaters with small radii.

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McGillis, W. R., V. P. Carey, and B. D. Strom. "Geometry Effects on Critical Heat Flux for Subcooled Convective Boiling From an Array of Heated Elements." Journal of Heat Transfer 113, no. 2 (May 1, 1991): 463–71. http://dx.doi.org/10.1115/1.2910584.

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The critical heat flux (CHF) condition was experimentally determined for subcooled flow boiling from an array of simulated microelectronic devices on one wall of a vertical rectangular passage. A test apparatus was used in these experiments that allowed visual observation of the boiling process while simultaneously measuring the heat flux and surface temperature for ten heat-dissipating elements. Using R-113 as the coolant, the CHF condition was determined for flush and slightly protruding heated elements. As expected, the element farthest downstream was found to reach the CHF condition first in all cases. For both the flush and slightly protruding elements, the trends in the CHF data are similar to those previously reported for subcooled flow boiling on an isolated element. At moderate flow velocities, the critical heat flux predicted by a proposed correlation for subcooled flow boiling from a single element was found to agree well with the multiple-flush-element data if the local fluid subcooling at the last element was used in the correlation. At lower velocities, however, the data deviated from the predicted values. The data for slightly protruding elements were also found to deviate from those for the flush elements at higher velocities. The apparent physical reasons for these trends are discussed in detail.

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Unal, C., K. Tuzla, O. Badr, S. Neti, and J. Chen. "Parametric Trends for Post-CHF Heat Transfer in Rod Bundles." Journal of Heat Transfer 110, no. 3 (August 1, 1988): 721–27. http://dx.doi.org/10.1115/1.3250551.

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A 3 × 3 rod bundle with a heated shroud was developed to study post-critical-heat-flux (post-CHF) dispersed-flow boiling. The hot-patch technique was applied to a rod bundle, which successfully arrested the quench front at the test section inlet. Measurements included mass flux, wall heat flux, inlet equilibrium quality, wall temperatures along the bundle axis, and actual vapor temperatures upstream and downstream of a spacer grid. The vapor superheat (up to 600°C) increased with increasing wall heat flux and decreasing mass flux and vapor quality. The heat partition ratio (fraction of total heat input that goes toward evaporation) was found to increase with increasing mass flux and decreasing inlet quality but remained essentially independent of heat flux. The results for the rod bundle were found to be in good agreement with trends previously reported for post-CHF heat transfer in single tubes.

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Gersey, C. O., and I. Mudawar. "Effects of Orientation on Critical Heat Flux From Chip Arrays During Flow Boiling." Journal of Electronic Packaging 114, no. 3 (September 1, 1992): 290–99. http://dx.doi.org/10.1115/1.2905453.

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Boiling experiments were performed with FC-72 on a series of nine in-line simulated microelectronic chips in a flow channel to ascertain the effects of channel orientation on critical heat flux (CHF). The simulated chips, measuring 10 mm × 10 mm, were flush-mounted to one wall of a 20 mm × 5 mm flow channel. The channel was rotated in increments of 45 degrees through 360 degrees such that the chips were subjected to coolant in upflow, downflow, or horizontal flow with the chips on the top or bottom walls of the channel with respect to gravity. Flow velocity was varied between 13 and 400 cm/s for subcoolings of 3, 14, 25, and 36°C and an inlet pressure of 1.36 bar. While changes in angle of orientation produced insignificant variations in the single-phase heat transfer coefficient, these changes had considerable effects on the boiling pattern in the flow channel and on CHF for velocities below 200 cm/s,’ with some chips reaching CHF at fluxes as low as 18 percent of those corresponding to vertical upflow. Increased subcooling was found to slightly dampen this adverse effect of orientation. The highest CHF values were measured with near vertical upflow and/or upward-facing chips, while the lowest values were measured with near vertical downflow and/or downward-facing chips. These variations in CHF were attributed to differences in flow boiling regime and vapor layer development on the surfaces of the chips between the different orientations. The results of the present study reveal that, while some flexibility is available in the packaging of multi-chip modules in a two-phase cooling system, some orientations should always be avoided.

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Joung, Young Soo, and Cullen R. Buie. "Hybrid Electrophoretic Deposition with Anodization Process for Superhydrophilic Surfaces to Enhance Critical Heat Flux." Key Engineering Materials 507 (March 2012): 9–13. http://dx.doi.org/10.4028/www.scientific.net/kem.507.9.

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Superhydrophilic surfaces with hydrophobic layers were successfully produced in order to enhance critical heat flux (CHF) and reduce boiling inception temperatures (BIT). The novel surfaces were fabricated by a hybrid electrophoretic deposition (EPD) method coupled with a break down anodization (BDA) process. With the BDA process, microporous superhydrophilic surfaces were created on titanium substrates. Subsequently, nanoporous hydrophobic layers were deposited with EPD on the superhydrophilic surfaces. The hydrophobic layers provide numerous nucleation sites, lowering BIT while the superhydrophilic layers prevent film boiling, resulting in increased CHF. The resulting surfaces exhibit higher CHF with lower BIT than untreated titanium surfaces .

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32

Sheng, Cheng, and Tao Zhou. "Application and Analysis of Wavelet Transform and Edge Detection in Critical Heat Flux of Natural Circulation." Advanced Materials Research 354-355 (October 2011): 333–37. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.333.

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Based on the experimental data obtained in natural circulation experiment in narrow rectangular channel, critical heat flux (CHF) was detected and analyzed through wavelet transform, and the technology of edge detection was applied in the analysis of the photos of CHF which were taken in the experiment. Results showed that the apply of wavelet transform using of db1 wavelet and edge detection using of Canny algorithm could both distinguish the singularity of CHF in one-dimensional temperature signal and regions of dry patch that represented CHF phenomena in two-dimensional photograph accurately, which can provide a new approach in the analysis of CHF experimental research of natural circulation.

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33

Liang, Gangtao, Yang Chen, Han Yang, Dashu Li, and Shengqiang Shen. "Nucleate boiling heat transfer and critical heat flux (CHF) from micro-pit surfaces." International Journal of Heat and Mass Transfer 152 (May 2020): 119510. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2020.119510.

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34

Hung, Ying-Huei, and Shi-Chune Yao. "Pool Boiling Heat Transfer in Narrow Horizontal Annular Crevices." Journal of Heat Transfer 107, no. 3 (August 1, 1985): 656–62. http://dx.doi.org/10.1115/1.3247474.

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Experimental results of the pool boiling in horizontal narrow annuli are reported. The effects of fluid properties, pool subcooling, crevice length, and gap size on the boiling behavior and the critical heat flux (CHF) are also studied. The CHF decreases with decreasing gap size or increasing length of the annuli. The lower CHF of narrow crevices may be explained by the thin film evaporation. A semi-empirical correlation is established for the CHF of pool boiling in horizontal confined spaces. This correlation is compared with the CHF data of the present experiment. Satisfactory agreement is obtained.

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35

XIAO, BOQI, SONGHUA GAO, and LINGXIA CHEN. "A FRACTAL MODEL FOR NUCLEATE POOL BOILING OF NANOFLUIDS AT HIGH HEAT FLUX INCLUDING CHF." Fractals 18, no. 04 (December 2010): 409–15. http://dx.doi.org/10.1142/s0218348x10004932.

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A fractal model for nucleate pool boiling of nanofluids at high heat flux and critical heat flux (CHF) is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces in this paper. The formula of calculating high heat flux and CHF for nanofluids in nucleate pool boiling is given by taking into account heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids. The proposed model is expressed as a function of temperature of nanofluids, the effective thermal conductivity of nanofluids, the average size of nanoparticles, the fractal dimension of nanoparticles and nucleation sites, the nanoparticles volume fraction of suspension, and physical properties of fluids. No additional/new empirical constant is introduced in this fractal model. An agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling of nanofluids at high heat flux and CHF is thus verified.

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36

Dowlati, R., M. Kawaji, I. D. Sardjono, and S. T. Revankar. "Effect of Channel Blockage on Critical Heat Flux for a Horizontal Cylinder in Crossflow." Journal of Heat Transfer 117, no. 4 (November 1, 1995): 998–1002. http://dx.doi.org/10.1115/1.2836322.

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An experimental investigation has been conducted on critical heat flux (CHF) on a horizontal tube in crossflow boiling R-113 at near atmospheric pressures. Data were obtained over a range of fluid velocities (up to 0.52 m/s), heater diameters (8 to 12.7 mm), and flow blockage factors (D/H = 0.31 to 0.5). The effect of the flow blockage on CHF was examined in detail and compared with other data and existing correlations. No significant effect of flow blockage was observed for D/H up to 0.5. An analytical modification of the Katto-Haramura CHF correlation is proposed to take into account the effect of flow blockage over a wide range of D/H.

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37

Monde, M., and T. Inoue. "Critical Heat Flux in Saturated Forced Convective Boiling on a Heated Disk With Multiple Impinging Jets." Journal of Heat Transfer 113, no. 3 (August 1, 1991): 722–27. http://dx.doi.org/10.1115/1.2910623.

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The existing data for critical heat flux (CHF) on a disk heater cooled by multiple impinging jets have been correlated successfully by deriving a generalized correlation that can predict the CHF on a disk heater cooled by a single impinging jet with high accuracy. The generalized correlation for the CHF for the single jet can be applied to predict the CHF for multiple jets with an accuracy of ±20 percent, in spite of a great difference in the flow situation on a disk between a single jet and multiple jets.

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38

DolatiAsl, K., Y. Bakhshan, E. Abedini, and S. Niazi. "Correlations for estimating critical heat flux (CHF) of nanofluid flow boiling." International Journal of Heat and Mass Transfer 139 (August 2019): 69–76. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2019.04.146.

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39

Suk, Ladislav, Taron Petrosyan, Kamil Stevanka, Daniel Vlcek, and Pavel Gejdos. "Experimental Investigation of Critical Heat Flux on Different Surfaces at Low Pressure and Low Flow." Energies 13, no. 19 (October 6, 2020): 5205. http://dx.doi.org/10.3390/en13195205.

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Steady state flow boiling experiments were carried out on several heated tubes with outer diameter 9.14 mm at outlet pressures 120, 200 and 300 kPa, inlet temperatures 64, 78 and 91 °C and approximately 400, 500, 600 and 800 kg/(m2·s) mass flux entering the vertically aligned test annulus until critical heat flux (CHF) was reached. The tubes were made of Inconel 625 with a length of 400 mm. The Inconel tubes were tested in three different modifications as smooth, abraded with 150 grit sandpaper and bead blasted. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., wettability, roughness and oxide layer morphology) on the occurrence of CHF. Despite the changes in initial wettability, the CHF dependency was not clearly observed, however, the changes in roughness led to an increase in CHF. The total number of 115 experimental runs were collected and the results were also compared with other literature experimental data.

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40

Vlček, Daniel, Ladislav Suk, Kamil Števanka, and Taron Petrosyan. "EXPERIMENTAL INVESTIGATION OF CRITICAL HEAT FLUX IN ANNULUS AT LOW PRESSURE AND LOW FLOW PARAMETERS." Acta Polytechnica CTU Proceedings 28 (December 1, 2020): 50–58. http://dx.doi.org/10.14311/app.2020.28.0050.

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Steady state flow boiling experiments were conducted on a technically smooth Inconel 625 tube with outer diameter 9.1 mm at inlet pressures 131, 220 and 323 kPa, inlet temperatures 62, 78 and 94 °C and approximately 400, 600 and 1000 kg/(m2.s) mass flow. Water of these parameters was entering into the vertically aligned annulus, where the uniformly heated tube was placed until the critical heat flux (CHF) appeared. The experimental data were compared to estimations of CHF by local PGT tube correlation and Groeneveld’s look-up tables for tubes. The results imply that in the region of low pressure and low mass flux, the differences between calculations and experiments are substantial (more than 50 % of CHF). The calculations further imply that look-up tables and tube correlations should be corrected to the annulus geometry. Here, the Doerffer’s approach was chosen and led to a substantial enhancement of CHF estimation. Yet, a new correlation for the region of low pressure and flow is needed.

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41

Yildiz, Sebiha. "Effect of length-to-diameter ratio on critical heat flux in porous-coated tubes." Thermal Science, no. 00 (2019): 462. http://dx.doi.org/10.2298/tsci190426462y.

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The critical heat flux (CHF) occurring during upflow of boiling water in vertical smooth and porous-coated tubes were investigated experimentally. The experiments were performed at low pressures from 0.11 to 0.7 MPa and at mass fluxes from 100 to 400 kg/m2s, with inlet subcoolings from 1 to 70 K. The experiments were carried out with four test sections, two of which were porous coated by sintering. The two tubes in each of the cases, porous and smooth, had the same geometries (L/D = 28.3; L/D = 38.75) to ensure a direct comparison of the measured data in the porous-coated tubes with those of the smooth tubes. In addition, the CHF data for water in uniformly heated vertical porous-coated tubes were obtained from the literature. These experiments were conducted using two smooth and four inner porous-coated tubes (L/D = 14.1, L/D = 50) in the same experimental setup used in the present study. In general, it was found that the CHF decreased with an increase in the L/D ratio for both the smooth and porous-coated tubes. The effect of porous coating on CHF can be positive, negative, or even neutral.

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42

Tan, Lu Zhi, Ji Tian Han, Chang Nian Chen, and Peng Cheng Dou. "Comparison of Critical Heat Flux for R-134a Flow Boiling in a Horizontal Straight Tube and a Helically-Coiled Tube." Advanced Materials Research 588-589 (November 2012): 1813–16. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1813.

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Experimental studies on critical heat flux (CHF) have been conducted in a uniformly heated horizontal straight tube and helically-coiled tube respectively with R-134a as the working fluid. The helically-coiled tube has the same heated length and inner diameter with the straight tube and experiments were performed under the following conditions: pressure from 0.4 to 2.5 MPa, mass flux values from 80 to 1500 kg m-2 s-1, inlet quality from -0.23 to 0.28 and critical quality from 0.65 to 0.86. The CHF data of the helically-coiled tube have been compared with that of the straight tube. The results show that the helically-coiled tube gets significant improvement in the CHF values vs. the straight tube under the same conditions and the degree of improvement depends on the mass flux, system pressure, inlet quality and critical quality.

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43

Liu, Ping, Yusheng Guo, Wenlong Ding, Mingyun Tang, Yuntao Song, Xuebing Peng, Jiadong Ji, Qinghua Chen, and Xin Mao. "Critical Heat Flux (CHF) Correlations for Subcooled Water Flow Boiling at High Pressure and High Heat Flux." Journal of Thermal Science 30, no. 1 (January 2021): 279–93. http://dx.doi.org/10.1007/s11630-021-1394-7.

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44

Monde, M. "Critical Heat Flux in Saturated Forced Convection Boiling on a Heated Disk With an Impinging Jet." Journal of Heat Transfer 109, no. 4 (November 1, 1987): 991–96. http://dx.doi.org/10.1115/1.3248215.

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Critical heat flux during forced convection boiling on an open heated disk being supplied with saturated liquids through a small round jet which impinges at the center of the disk has been studied experimentally employing refrigerant R12 at comparatively high pressures from 0.6 to 2.8 MPa. Generalized correlations, predicting the CHF within an experimental range of liquid-to-vapor density ratio 5.3–41.25 and the reciprocal of Weber number 2 × 10−3–2 × 10−7, are given for three different characteristic regimes: V-regime where the CHF increases with an increase in the jet velocity, I-regime where the CHF is nearly constant with jet velocity, and HP-regime where the CHF appears only at high pressure and again rises with an increase in the jet velocity.

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45

Jiang, Weiyu, Lili Sun, Jijin Mao, Zhang Donghui, and A. Levtsev. "Effect of Copper Particles Shape on the Heat Transfer Characteristics of Porous Microchannels During Boiling of Working Fluid." Bulletin of Science and Practice 7, no. 4 (April 15, 2021): 286–94. http://dx.doi.org/10.33619/2414-2948/65/32.

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In this paper, the heat transfer performance of porous microchannels sintered with spherical and dendritic copper particle is compared. The working fluid is deionized water. For uniform particle size sample, the dendritic-particle microchannel presents better boiling heat transfer performance than the spherical-particle one. It includes higher critical heat flux (CHF), which was related to the connected pore structure of the dendritic copper powder. For mixed particle size sample, the dendritic-particle microchannel also shows higher heat transfer coefficient and CHF. At high heat flux, the dendritic-particle microchannel can effectively suppress the pressure pulsation and maintain a relatively stable flow boiling state in the microchannel.

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46

Gersey, C. O., and I. Mudawar. "Nucleate Boiling and Critical Heat Flux From Protruded Chip Arrays During Flow Boiling." Journal of Electronic Packaging 115, no. 1 (March 1, 1993): 78–88. http://dx.doi.org/10.1115/1.2909305.

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The effects of chip protrusion on the forced-convection boiling and critical heat flux (CHF) of a dielectric coolant (FC-72) were investigated. The multi-chip module used in the present study featured a linear array of nine, 10 mm x 10 mm, simulated microelectronic chips which protruded 1 mm into a 20-mm wide side of a rectangular flow channel. Experiments were performed in vertical up flow with 5-mm and 2-mm channel gap thicknesses. For each configuration, the velocity and subcooling of the liquid were varied from 13 to 400 cm/s and 3 to 36° C, respectively. The nucleate boiling regime was not affected by changes in velocity and subcooling, and critical heat flux generally increased with increases in either velocity or subcooling. Higher single-phase heat transfer coefficients and higher CHF values were measured for the protruded chips compared to similar flush-mounted chips. However, adjusting the data for the increased surface area and the increased liquid velocity above the chip caused by the protruding chips yielded a closer agreement between the protruded and flush-mounted results. Even with the velocity and area adjustments, the most upstream protruded chip had higher single-phase heat transfer coefficients and CHF values for high velocity and/or highly-subcooled flow as compared the downstream protruded chips. The results show that, except for the most upstream chip, the performances of protruded chips are very similar to those of flush-mounted chips.

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47

Ji, Cui Lian, Ji Tian Han, Chang Nian Chen, Xia Dong, and Ling Jian Kong. "Influence of Geometry Parameters on Critical Heat Flux in Helically Coiled Tubes: Development of Correlation." Applied Mechanics and Materials 353-356 (August 2013): 3077–80. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.3077.

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Based on 2006 look-up tables to analysis the effect of pipe diameters on CHF, the correlations are established for horizontal helically coiled tube by introducing equivalent geometrical parameter. According to experimental data, it is found that the correlation is very suitable, and the regularity of horizontal helically coiled tube geometry parameters on CHF tends to be consistent with that of a vertical tube.

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48

Liu, Zhen-Hua, Tie-Feng Tong, and Yu-Hao Qiu. "Critical Heat Flux of Steady Boiling for Subcooled Water Jet Impingement on the Flat Stagnation Zone." Journal of Heat Transfer 126, no. 2 (April 1, 2004): 179–83. http://dx.doi.org/10.1115/1.1668054.

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An experimental investigation was carried out for predicting the critical heat flux (CHF) of steady boiling for a round subcooled water jet impingement on the flat stagnation zone. The experimental data were measured in a steady nucleate boiling state. Three main influencing parameters, i.e., subcooling, impact velocity and jet nozzle size were widely changed and their effects on the critical heat flux were systemically studied. An empirical correlation was obtained using the experimental data over a wide experimental range for predicting the critical heat flux of steady boiling for a round subcooled water jet impingement on the flat stagnation zone.

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49

Jensen, M. K., and M. Pourdashti. "Critical Heat Flux on a Horizontal Cylinder in an Upward Subcooled and Low-Quality Two-Phase Crossflow." Journal of Heat Transfer 108, no. 2 (May 1, 1986): 441–47. http://dx.doi.org/10.1115/1.3246943.

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An experimental investigation has been conducted to determine the low-velocity critical heat flux (CHF) behavior on a single horizontal tube in a subcooled and low-quality two-phase crossflow of R-113. Data were obtained over a range of velocities (up to 0.3 m/s), subcooling (0 to 14 K), and qualities (0 < x < +30 percent) at two pressures. There was a linear decrease in the CHF with increasing quality up to about 10 percent quality; then, due to a flow regime transition, the CHF remained relatively constant. A correlation has been developed which predicted well the subcooled and low-quality region CHF condition in the linearly decreasing portion of the curve. Data from the literature are also predicted well.

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50

Sadasivan, P., C. Unal, and R. Nelson. "Perspective: Issues in CHF Modeling—The Need for New Experiments." Journal of Heat Transfer 117, no. 3 (August 1, 1995): 558–67. http://dx.doi.org/10.1115/1.2822614.

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Nucleate boiling and critical-heat-flux (CHF) phenomena have been studied extensively for several decades. However, a satisfactory mechanistic description remains elusive. Although the influences of some system parameters such as heater geometry, body forces, etc., have been elucidated, the influences of several others remain in dispute. In this paper, we present our perspective on the current state of CHF modeling. We list possible parameters that are relevant in the process and discuss the interactions among these parameters. The consequences of such interactions are also discussed. We focus on the simplest configuration—saturated pool boiling on flat heaters. Additional complexities such as orientation effects, flow effects, enhanced surfaces, etc., are not addressed. We highlight specific areas on which we believe experimental efforts should focus to obtain improved mechanistic models of CHF. Experimental techniques used in previous studies are evaluated, and recommendations for new or modified techniques are discussed. We believe CHF must be looked at in the boiling plane (q and ΔT) rather than merely as a single heat-flux point. Mechanistically, this leads us to view CHF as the limiting point of the nucleate boiling region rather than as an independent entity. Experimentally, this means that issues related to the high-heat-flux region must be studied and their effects on CHF investigated.

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

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