Journal articles: 'Superheat'

1

SIMÕES-MOREIRA, J. R., and J. E. SHEPHERD. "Evaporation waves in superheated dodecane." Journal of Fluid Mechanics 382 (March 10, 1999): 63–86. http://dx.doi.org/10.1017/s0022112098003796.

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We have observed propagating adiabatic evaporation waves in superheated liquid dodecane, C12H26. Experiments were performed with a rapid decompression apparatus at initial temperatures of 180–300°C. Saturated dodecane in a tube was suddenly depressurized by rupturing a diaphragm. Motion pictures and still photographic images, and pressure and temperature data were obtained during the evaporation event that followed depressurization. Usually, a front or wave of evaporation started at the liquid free surface and propagated into the undisturbed regions of the metastable liquid. The evaporation wave front moved with a steady mean velocity but the front itself was unstable and fluctuating in character. At low superheats, no waves were observed until a threshold superheat was exceeded. At moderate superheats, subsonic downstream states were observed. At higher superheats, the downstream flow was choked, corresponding to a Chapman–Jouguet condition. At the most extreme superheat tested, a vapour content of over 90% was estimated from the measured data, indicating a nearly complete evaporation wave. Our results are interpreted by modelling the evaporation wave as a discontinuity, or jump, between a superheated liquid state and a two-phase liquid–vapour downstream state. Reasonable agreement is found between the model and observations; however, there is a fundamental indeterminacy that prevents the prediction of the observed wave speeds.

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2

Chellaiah, S., and R. Viskanta. "Freezing of Water-Saturated Porous Media in the Presence of Natural Convection: Experiments and Analysis." Journal of Heat Transfer 111, no. 2 (May 1, 1989): 425–32. http://dx.doi.org/10.1115/1.3250694.

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Freezing of superheated water-porous media (glass beads) contained in a rectangular test cell has been studied both experimentally and numerically. The effects of liquid superheat and imposed temperature difference were investigated. When the superheat across the liquid region was small the flow in the porous media was weak, and the interface was almost planar. For larger superheats, natural convection flow and the solidification front shape and velocity were found to depend on the imposed temperature and the permeability of the porous medium. Due to the density inversion of water, the rate of freezing was higher, either at the top or at the bottom of the cell, depending on the amount of superheat. The measured temperature distributions were compared with predictions of numerical model that considered both conduction in the solid and natural convection in the liquid region. This model is based on volumetric averaging of the macroscopic transport equations, with phase change assumed to occur volumetrically over a small temperature range. Both Brinkman and Forchheimer extensions were added to the Darcy equations. The effect of density inversion of water on the fluid flow and heat transfer has been modeled. Good agreement has been found between the experimental data and numerical predictions.

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Zheng, Qiang, Hui Qing Liu, Zhan Xi Pang, and Fang Li. "A Study on Effect Evaluating and Parameters Sensitivity Analyzing of Superheated Steam Soak in Heavy Oil Reservoirs." Advanced Materials Research 239-242 (May 2011): 3069–73. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.3069.

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By using the technology of numerical reservoir simulation, we have compared superheated steam soak with saturated steam soak in area of heating, effect of distillation, capability of increasing oil production, volume of steam in need to evaluate the effect of superheated steam soak in heavy oil reservoirs. Analyzed the sensitivity of parameters like steam injection intensity, steam injection rate, soak time, degree of superheat to conclude the rule that they affect on recovery percentage. The research shows that, heating radius of superheated steam is greater than that of saturated steam, distillation effect of superheated steam is better than that of saturated steam, oil production of superheated steam is more than that of saturated steam, steam volume in need of superheated steam is less than that of saturated steam. Recovery percentage of superheated steam soak increases but more and more slowly with the increase in steam injection intensity, increases first and then decreases with the increase in steam injection rate, increases first and then decreases with the increase in soak time, increases but more and more slowly with the increase in degree of superheat. Influence of steam injection intensity is obvious to recovery percentage, but influence of other factors like soak time, steam injection rate, degree of superheat is insignificant.

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4

He, Congge, Anzhu Xu, Zifei Fan, Lun Zhao, and Bing Bo. "A New Mathematical Model For Heat Radius of Cyclic Superheated Steam Stimulation with Horizontal Wellbore." Mathematical Problems in Engineering 2018 (May 31, 2018): 1–11. http://dx.doi.org/10.1155/2018/7601702.

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When superheated steam flows along the horizontal wellbore, it may change to saturated steam at some point of the wellbore. In this paper, to accurately predict the heat radius of cyclic superheated steam stimulation with horizontal wellbore, the distribution of thermophysical properties of superheated steam along the horizontal wellbore is considered. The heating process is divided into 4 stages for superheated steam and 3 stages for saturated steam when the phase change undergoes in the wellbore. On this basis, the mathematical model for heat radius of cyclic superheated steam stimulation with horizontal wellbore was established according to energy conservation principle and Laplace transformation method. The calculation result of the new mathematical model is in good agreement with that of the numerical simulation (CMG STARS) for the same parameters from a specific heavy oil reservoir, which verified the correctness of the new mathematical model. The effect of degree of superheat and the cycle of stimulation are analyzed in detail after the new mathematical model is validated. The results show that the heat radius of superheated zone, steam zone, and hot fluid zone all decrease with horizontal well length and increase with the cycle of stimulation. The higher the degree of superheat is, the farther from the heel of the horizontal wellbore the phase change undergoes. Besides, the radius of superheated zone, steam zone, and hot fluid zone increases with the degree of superheat, but the value increases little at steam zone and hot fluid zone.

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5

Basu, Nilanjana, Gopinath R. Warrier, and Vijay K. Dhir. "Wall Heat Flux Partitioning During Subcooled Flow Boiling: Part 1—Model Development." Journal of Heat Transfer 127, no. 2 (February 1, 2005): 131–40. http://dx.doi.org/10.1115/1.1842784.

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In this work a mechanistic model has been developed for the wall heat flux partitioning during subcooled flow boiling. The premise of the proposed model is that the entire energy from the wall is first transferred to the superheated liquid layer adjacent to the wall. A fraction of this energy is then utilized for vapor generation, while the rest of the energy is utilized for sensible heating of the bulk liquid. The contribution of each of the mechanisms for transfer of heat to the liquid—forced convection and transient conduction, as well as the energy transport associated with vapor generation has been quantified in terms of nucleation site densities, bubble departure and lift-off diameters, bubble release frequency, flow parameters like velocity, inlet subcooling, wall superheat, and fluid and surface properties including system pressure. To support the model development, subcooled flow boiling experiments were conducted at pressures of 1.03–3.2 bar for a wide range of mass fluxes 124-926kg/m2 s, heat fluxes 2.5-90W/cm2 and for contact angles varying from 30° to 90°. The model developed shows that the transient conduction component can become the dominant mode of heat transfer at very high superheats and, hence, velocity does not have much effect at high superheats. This is particularly true when boiling approaches fully developed nucleate boiling. Also, the model developed allows prediction of the wall superheat as a function of the applied heat flux or axial distance along the flow direction.

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6

Chen, Tailian, and Jacob N. Chung. "An Experimental Study of Miniature-Scale Pool Boiling." Journal of Heat Transfer 125, no. 6 (November 19, 2003): 1074–86. http://dx.doi.org/10.1115/1.1603773.

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By generating single bubbles on a micro-heater at different wall superheats, an experimental study of miniature-scale pool boiling heat transfer has been performed to provide a fundamental understanding of the heater size effect. In this study, the constant-temperature microheater is set at different temperatures by an electronic feedback control system. The heat transfer history during the lifetime of a single bubble which includes nucleation, growth, detachment and departure has been measured. The boiling curve obtained from the microheater is composed of two regimes which are separated by a peak heat flux. It is suggested that in the lower superheat regime, the boiling is dominated by liquid rewetting and micro-layer evaporation, while in the higher superheat regime, conduction through the vapor film and micro-convection plays the key heat transfer role as the heater is covered by vapor all the time. In general, boiling on microheaters is characterized by larger bubble departure sizes, smaller bubble growth rates due to the dryout of microlayer as the bubble grows, and higher bubble incipience superheat. As the heater size decreases, the boiling curve shifts towards higher heat fluxes with corresponding higher superheats.

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7

Ramesh, Arumugam, and Ramasamy Balasubramanian. "Ability of the generalized van der Waals and Berthelot equations of state to determine the thermodynamic stability of liquid lead." Science Vision 20, no. 4 (December 31, 2020): 132–38. http://dx.doi.org/10.33493/scivis.20.04.01.

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The known van der Waals and Berthelot equations of state do-not precisely describe the thermodynamic properties of fluids. To improve its accuracy, the attractive term of the van der Waals equation of state has been modified in six different ways. These generalized equations of state have been employed to determine the spinodal (thermodynamic stability boundary) and the thermodynamic limit of superheat of liquid lead. The equations of state are rewritten in reduced form, from which follows the law of corresponding states. The appropriate modification of the attractive term of the equation of state yielding the value of thermodynamic limit of superheat agreeing with the experimental value for lead has been established. It has been established that liquid lead can be superheated, under rapid heating, up to a temperature 4565 K. That is, liquid lead can be superheated to 2544 K above the normal boiling temperature. At the thermodynamic limit of superheat, the volume of the liquid lead is 4.0095 × 10-5 m3 mol-1. This fact is to be taken into account when liquid lead is subjected to rapid heating.

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8

Ramos, R. A., and J. Castro. "A REVIEW OF THE EFFECTS OF CHANGES IN THE VOID FRACTION OF THE SUPERHEATED REGION ON THE TEV OPERATION AND EVAPORATOR STABILITY." Revista de Engenharia Térmica 15, no. 2 (December 31, 2016): 38. http://dx.doi.org/10.5380/reterm.v15i2.62175.

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A level of superheat is necessary to ensure proper operation of vapor- compression refrigeration systems. An overly superheated vapor prior to entering the compressor can render the system inefficient, while inadequate superheat can result in evaporator instability and compressor damage. The void fraction present in the suction line is directly related to evaporator stability and the hunting phenomenon in the thermostatic expansion valve (TEV). This article aims at reviewing superheated region-related researches in the field of refrigeration as they relate to the operation of the TEV and the stability of the evaporator. In a first part, literature review will explain the causes of the void fraction in the superheated region and the second part describes the effects of the lubricant oil on the void fraction. The third part of this article is a review of the effects of the superheated region on the TEV and on evaporator stability, explaining the causes of the hunting phenomena and evaporator instability.

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9

Reyes, R., and P. C. Wayner. "A Kelvin–Clapeyron Adsorption Model for Spreading on a Heated Plate." Journal of Heat Transfer 118, no. 4 (November 1, 1996): 822–30. http://dx.doi.org/10.1115/1.2822576.

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A new adsorption model for the spreading dynamics of completely wetting fluids on a heated solid substrate that emphasizes interfacial phenomena is developed and evaluated. The model is based on the premise that both interfacial intermolecular forces and temperature affect the vapor pressure in change-of-phase heat transfer and (therefore) the spreading velocity. Classical change-of-phase kinetics, and interfacial concepts like the Clapeyron, Kelvin, and the augmented Young–Laplace equations are used to evaluate the effects of stress (change in apparent dynamic contact angle), temperature, and superheat on the rewetting velocity. Explicit equations are obtained for the velocity, heat flux, and superheat in the contact line region as a function of the initial plate temperature. Comparisons with experimental data for substrate superheats below a critical value demonstrate that the resulting interfacial model of evaporation/condensation in the contact line region can describe the effect of the saturation temperature and superheat on the rewetting velocity.

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10

Ravichandar, D., Thangavel Balusamy, and K. Bommannan Nagashanmugam. "Reducing UT Rejections in Cr-Mo and High Mn Steels by Controlling Hydrogen and Optimising Superheat." Applied Mechanics and Materials 591 (July 2014): 38–42. http://dx.doi.org/10.4028/www.scientific.net/amm.591.38.

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JSW Steel Limited, Salem Works (JSWSL), is an integrated steel plant, having a production capacity of 1.0 mtpa (million tons per annum) of high-grade automotive special steels. At JSWSL, hydrogen induced cracks and center unsoundness contribute more to UT (Ultrasonic testing) rejections in chrome-molybdenum (Cr-Mo) and high manganese grade steels. Hydrogen induced cracks was controlled by increasing argon flow rate from 3-4 Nm3 to 7-9 Nm3 during vacuum degassing. Vigorous purging led to a reduction in hydrogen levels from around 2 ppm (parts per million) to less than 1.5 ppm. Center unsoundness was controlled through optimising superheats in tundish. Data of trial heats revealed that, UT rejections were more in heats cast with superheat levels more than 35°C. Based on the data obtained from trial heats superheat was optimised to 25-35°C for both Cr-Mo and high manganese steels. The present paper discusses the measures taken to reduce UT rejections in these grades.KeywordsJSWSL, Cr-Mo, High Mn steels, UT rejections, superheat, hydrogen induced cracks, center unsoundness, vacuum degassing, continuous casting.

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11

Mitrovic, J. "Effects of Vapor Superheat and Condensate Subcooling on Laminar Film Condensation." Journal of Heat Transfer 122, no. 1 (August 9, 1999): 192–96. http://dx.doi.org/10.1115/1.521450.

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Nusselt’s model is employed to illustrate the effects of vapor superheat and condensate subcooling on laminar film condensation occurring under simultaneous actions of gravity and interfacial shear. The vapor superheat affects the condensation kinetics in cooperation with heat transfer in both phases. Under comparable conditions, the condensate film is thinner and the heat transfer coefficient larger for superheated than for saturated vapor. The heat flux on the cooling surface arising from the sensible heat of condensate increases as the critical point of the condensing substance is approached and, at this point, the Nusselt condensation model gives the single-phase boundary layer solutions. [S0022-1481(00)00701-5]

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12

Parker, Jack L., and Mohamed S. El-Genk. "Effect of Surface Orientation on Nucleate Boiling of FC-72 on Porous Graphite." Journal of Heat Transfer 128, no. 11 (March 13, 2006): 1159–75. http://dx.doi.org/10.1115/1.2352783.

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Effects of orientations of porous graphite and smooth copper surfaces, measuring 10mm×10mm, on saturation nucleate boiling and critical heat flux (CHF) of FC-72 dielectric liquid and of liquid subcooling (0, 10, 20, and 30K) on nucleate boiling in the upward facing orientation are investigated. Inclination angles (θ) considered are 0deg (upward-facing), 60, 90, 120, 150, and 180deg (downward facing). The values of nucleate boiling heat flux, nucleate boiling heat transfer coefficient (NBHTC), and CHF are compared with those measured on the smooth copper surface of the same dimensions and CHF values on both copper and porous graphite are compared with those reported by other investigators on the smooth surfaces and microporous coatings. Results demonstrated higher NBHTC and CHF on porous graphite, particularly in the downward-facing orientation (θ=180deg). In the upward-facing orientation, NBHTCs on both surfaces decrease with increased subcooling, but increase with increased surface superheat reaching maxima then decrease with further increase in surface superheat. In saturation boiling on copper and both saturation and subcooled boiling on porous graphite these maxima occur at or near the end of the discrete bubble region, and near CHF in subcooled boiling on copper. Maximum saturation NBHTC on porous graphite increases with decreased surface superheat and inclination angle, while that on copper increases with increased surface superheat and decreased surface inclination. At low surface superheats, saturation nucleate boiling heat flux increases with increased inclination, but decreases with increased inclination at high surface superheats, consistent with previously reported data for dielectric and nondielectric liquids. The fractional decreases in saturation CHF with increased θ on smooth copper and microporous coatings are almost identical, but markedly larger than on porous graphite, particularly in the downward-facing orientation. In this orientation, saturation CHF on porous graphite of 16W∕cm2 is much higher than on copper (4.9W∕cm2) and as much as 53% of that in the upward-facing orientation, compared to only ∼18% on copper.

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13

Kitamura, Yoshiro, Hiroichi Morimitsu, and Teruo Takahashi. "Critical superheat for flashing of superheated liquid jets." Industrial & Engineering Chemistry Fundamentals 25, no. 2 (May 1986): 206–11. http://dx.doi.org/10.1021/i100022a005.

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14

Sivakumar, Marimuthu, and Ramasamy Balasubramanian. "Spinodal and thermodynamic limit of superheat of gold." Science Vision 21, no. 1 (March 31, 2021): 12–26. http://dx.doi.org/10.33493/scivis.21.01.03.

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A four-parameter generalized Berthelot equation of state has been employed to determine the spinodal and the thermodynamic limit of superheat of liquid gold. It is established that gold obeys the two-parameter law of corresponding states. It is also established that the new parameters introduced in the attractive term of the equation of state are thermodynamic similarity parameters. It is shown that liquid gold can be superheated to a temperature 6719K. That is, liquid gold, under rapid heating, can be superheated to temperature 3476K above the boiling temperature without undergoing liquid-vapour phase transition. Above this temperature, liquid gold will undergo explosive boiling owing to homogeneous nucleation.

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15

Yang, Fu Shuang. "Study on Interface Pattern of Zn-5wt%Al Alloy during Unidirectionally Solidification." Advanced Materials Research 482-484 (February 2012): 1271–74. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1271.

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The interface pattern of Zn-5wt%Al alloy was investigated during unidirectionally solidification with different withdrawal rate and superheat degree. It was showed that the pattern of liquid/solid interface varied with withdrawal rate and superheat degree. While the superheat degree of alloy melt was low and the withdrawal rate was increased, the change of interface pattern was the same as the normal change of interface pattern. While the superheat degree of alloy melt was high and the withdrawal rate was increased too, the change of interface pattern was different. As a result, the pattern and stability of liquid/solid interface was chosen by withdrawal rate and superheat degree mainly.

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16

Ermakov, G. V., E. V. Lipnyagov, S. A. Perminov, and A. L. Gurashkin. "Heterogeneous boiling-up of superheated liquid at achievable superheat threshold." Journal of Chemical Physics 131, no. 3 (July 21, 2009): 031102. http://dx.doi.org/10.1063/1.3179678.

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17

Stillman, Thomas B. "CONTROL OF SUPERHEAT*." Journal of the American Society for Naval Engineers 48, no. 1 (March 18, 2009): 125–43. http://dx.doi.org/10.1111/j.1559-3584.1936.tb05644.x.

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18

Zhu, Jiaming, and Jie Li. "Diagnosis Method for the Heat Balance State of an Aluminum Reduction Cell Based on Bayesian Network." Metals 10, no. 5 (May 7, 2020): 604. http://dx.doi.org/10.3390/met10050604.

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The superheat of an electrolyte is an important indicator of the heat balance state of aluminum reduction cells. In industrial practice, it costs too much to accurately measure the superheat in every cell every day. A common alternative is to calculate the superheat based on additive concentrations in the electrolyte, which has problems of high error and long delay. In this paper, a method to diagnose the heat balance state of an aluminum reduction cell based on Bayesian network is presented, a Bayesian network structure and CPT (conditional probability distribution) were built, and the continuous diagnosis process is presented. This diagnosis method takes important symptoms and factors into account, taking advantage of more useful information instead of only calculated superheat. The application examples show that this method is effective in diagnosing the heat balance state for uncertain and incomplete superheat information.

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19

Oktay, S. Tu¨rker, Chong N. Chu, Nannaji Saka, and Nam P. Suh. "Effects of Superheat and Volume Fraction in the Mixalloying Process." Journal of Engineering for Industry 111, no. 2 (May 1, 1989): 175–85. http://dx.doi.org/10.1115/1.3188747.

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Dispersed-phase microstructures of Pb-Zn, Pb-Zn-Sn, and Pb-Al immiscible alloys were produced by the Mixalloying process. The superheat and the volume fraction of the impinging metal jets were systematically varied and their effects on the resulting microstructures were examined. High superheats resulted in coarse microstructures. At lower volume fractions of the second-phase, particles of the minor phase were well dispersed. As the volume fraction approached 0.5, however, the structure became interconnected. The minor phase size, defined either as the mean particle diameter or the mean linear intercept, followed the log-normal distribution, and was the smallest in the Pb-Zn-Sn system for the entire volume fraction range.

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20

Ding, Hong Yuan, Peng Deng, Xu Yao Mao, and Chao Wu. "Flash Boiling Spray Simulation Based on Void Fraction and Superheat Controlling." Applied Mechanics and Materials 737 (March 2015): 289–95. http://dx.doi.org/10.4028/www.scientific.net/amm.737.289.

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A new flash boiling spray model whose atomization criterion based on the void fraction and superheat while evaporation model based on the dual-zone method is established to simulate the flashing sprays. The model function is implemented in KIVA program. Flash boiling spray model predicts spray penetration and spray cone angle and its development trend, in good agreement with the experimental results. The model has a good capability in simulating flash sprays at low superheat conditions, which breakup is controlled by void fraction, as well as high superheat transition process. It can also predict flare flashing sprays to some extent at higher superheat conditions.

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21

Jin, Yan Juan, Xiao Chao Cui, Zhu Zhang, Jin Bao Lin, and Jun Ting Zhang. "Numerical Simulation of Filling and Solidification Process for Low Superheat Billet Continuous Casting." Advanced Materials Research 189-193 (February 2011): 3899–903. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.3899.

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In view of the process of flowing steel before the establishment of strip casting, the low superheat forced pouring continuous casting technology, i.e. the molten steel is cooled by the rotating cooling rollers, then it is forced to flow into mold, has been put forward in order to reduce superheat of liquid steel, enhance the efficiency of heat transfer and improve inner structure of billet. The filling and solidification processes of low superheat casting and submerged entry nozzle(SEN) casting are numerical simulated using fluid dynamics software. It is gained that velocity distributing diagrams, temperature distributing diagrams and solidification distribution diagrams at different time in the filling process. Influences of twin-roller cooling pouring on velocity field, temperature field and solidification are analyzed. The results show that the superheat of liquid steel is decreased and the solidification rate of liquid steel is increased by low superheat casting of twin-roller cooling process, which is favorable to improving the quality of billet and enhancing pull speed.

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22

Hou, Zi Bing, and Guo Guang Cheng. "Model Study about the Influence of Superheat on Macrosegregation Formation in Continuously Cast Bloom of Special Steel." Advanced Materials Research 295-297 (July 2011): 1088–94. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1088.

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Aiming at the facing problems of the actual continuous caster in a certain steel mill, a solidification-process heat transfer model about continuously cast bloom of special steel was first established, then the influence of superheat on macrosegregation formation was studied. It is shown that the crater length will become longer, the shell thickness will become thinner with increasing the superheat. Meanwhile, when decreasing the superheat , the value of will decrease and the value of H will obviously increase, then the equiaxed crystal ratio will be raised greatly. However, the bloom centre solidification time will increase. Consequently, attention should be paid to this point when decreasing the superheat in order to lessen the extent of macrosegregation.

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23

Xu, An Zhu, Long Xin Mu, Xiang Hong Wu, Zi Fei Fan, and Lun Zhao. "Superiority of Superheated Steam Flooding in Development of High Water-Cut Heavy Oil Reservoir." Advanced Materials Research 616-618 (December 2012): 992–95. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.992.

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The dryness of superheated steam is 100% and it exists in the form of pure steam whose properties are like ideal gas. When the steam has a large degree of superheat, it may take a relatively long time to cool, during which time the steam is releasing very little energy and transmitted long distances. The heating radius of superheated steam in the formation is 5-10m larger than saturated steam. In the heating area of superheated steam, the comprehensive effects by superheated steam (crude oil viscosity reduction, improved flow environment, changes in rock wettability and improved oil displacement efficiency, etc.) is much higher than that of saturated steam. Superheated steam stimulation in Kenkyak high water cut heavy oil reservoir pilot test results showed that the average daily oil production of single well by superheated steam stimulation was 2-4 times than that of saturated steam stimulation. Superheated steam is more effective to heat water-invaded oil reservoir than saturated steam.

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Ramaswamy, C., Y. Joshi, W. Nakayama, and W. B. Johnson. "Effects of Varying Geometrical Parameters on Boiling From Microfabricated Enhanced Structures." Journal of Heat Transfer 125, no. 1 (January 29, 2003): 103–9. http://dx.doi.org/10.1115/1.1513575.

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The current study involves two-phase cooling from enhanced structures whose dimensions have been changed systematically using microfabrication techniques. The aim is to optimize the dimensions to maximize the heat transfer. The enhanced structure used in this study consists of a stacked network of interconnecting channels making it highly porous. The effect of varying the pore size, pitch and height on the boiling performance was studied, with fluorocarbon FC-72 as the working fluid. While most of the previous studies on the mechanism of enhanced nucleate boiling have focused on a small range of wall superheats (0–4 K), the present study covers a wider range (as high as 30 K). A larger pore and smaller pitch resulted in higher heat dissipation at all heat fluxes. The effect of stacking multiple layers showed a proportional increase in heat dissipation (with additional layers) in a certain range of wall superheat values only. In the wall superheat range 8–13 K, no appreciable difference was observed between a single layer structure and a three layer structure. A fin effect combined with change in the boiling phenomenon within the sub-surface layers is proposed to explain this effect.

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Chang, J. Y., S. M. You, and A. Haji-Sheikh. "Film Boiling Incipience at the Departure From Natural Convection on Flat, Smooth Surfaces." Journal of Heat Transfer 120, no. 2 (May 1, 1998): 402–9. http://dx.doi.org/10.1115/1.2824264.

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The present research is an experimental study of pool boiling nucleation behavior using flat, smooth surfaces immersed in saturated highly wetting liquids, FC-72 and FC-87. A flush-mounted, copper surface of 10 mm × 10 mm is used as a heat transfer surface, simulating a microelectronic chip surface. At the nucleation incipient points of higher wall superheats with steady increase of heat flux, vapor film blankets the smooth surface and remains on the surface. To predict this film boiling incipience phenomenon from the smooth surface, an incipience map is developed over the boiling curve. When the incipient heat flux is higher than the minimum heat flux (MHF) and the incipient wall superheat value is higher than the transition boiling curve value at the incipient heat flux, the transition from single-phase natural convection to film boiling is observed at the incipient point. To prevent film boiling incipience, a microporous coating is applied over the smooth surface, which decreases incipient wall superheat and increases minimum heat flux. The film boiling incipience should be avoided to take advantage of highly efficient nucleate boiling heat transfer for the cooling of high-heat-flux applications.

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26

Zhao, Su, Dong Lai Wei, Jian Hui Xu, Hui Chen, and Li Zhang. "Influence of Steel Strip-Feeding Process on Density and Segregation of Casting Ingot." Materials Science Forum 872 (September 2016): 45–49. http://dx.doi.org/10.4028/www.scientific.net/msf.872.45.

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The effect of steel strip-feeding ratio and superheat degree of molten steel on density and segregation of casting ingot is investigated by an original position analysis. It indicates that under the same degree of superheat condition, with the increase of feeding ratio, the average density of the casting ingot increases and the central segregation of the ingot decreases. Under the same feeding ratio conditions, the density and the central segregation increase with the increase of the degree of superheat.

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27

Zhu, Xiang, and Jian Zhong He. "Application of Self-Adaptive Smith Algorithm in Evaporator System." Applied Mechanics and Materials 401-403 (September 2013): 1691–94. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.1691.

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Refrigerating evaporator superheat has the characteristics of the large time delay and superheat model is uneasy to determine. But the general smith control has bad robustness and require a high model accuracy. The paper introduces a self-adaptive smith control way, this method can dynamically amend the estimated output through historical estimated Result, which can improve the predicting accuracy. Applying this control way to the evaporator superheat system, the control quality is improved, system runs stably,anti-interference performance improved and also the systems robustness.

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O’Connor, J. P., and S. M. You. "A Painting Technique to Enhance Pool Boiling Heat Transfer in Saturated FC-72." Journal of Heat Transfer 117, no. 2 (May 1, 1995): 387–93. http://dx.doi.org/10.1115/1.2822534.

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A benign method of generating a surface microstructure that provides pool boiling heat transfer enhancement is introduced. Pool boiling heat transfer results from an enhanced, horizontally oriented, rectangular surface immersed in saturated FC-72, indicate up to an 85 percent decrease in incipient superheat, a 70 to 80 percent reduction in nucleate boiling superheats, and a ∼ 109 percent increase in the critical heat flux (CHF = 30 W/cm2), beyond that of the nonpainted reference surface. For higher heat flux conditions (19 to 30 W/cm2), localized dryout results in increased wall superheats (8 to 48°C). The enhanced surface heat transfer coefficients are four times higher than those from the reference surface and similar to those from the Union Carbide High Flux surface. Photographs that identify differences in bubble size and departure characteristics between the painted and reference surfaces are presented.

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Zhao, Su, and Li Zhang. "Effect of Steel Strip-Feeding Process on Solidification Structure." Advanced Materials Research 941-944 (June 2014): 1744–47. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.1744.

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It is investigated that effect of steel strip-feeding ratio and superheat degree of molten steel on solidification structure of ingot by the steel strip-feeding experiment in the mold. The results show that: at the same superheat, with the increase of feeding ratio, the area proportion of equiaxed grain zone increases and the average size of equiaxed grain decreases, and at the same feeding ratio, the higher the superheat is, the smaller the proportion of equiaxed grain zone is, and the larger the average grain size is.

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Judd, R. L., H. Merte, and M. E. Ulucakli. "Variation of Superheat With Subcooling in Nucleate Pool Boiling." Journal of Heat Transfer 113, no. 1 (February 1, 1991): 201–8. http://dx.doi.org/10.1115/1.2910525.

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An analysis is presented that explains the variation of superheat with subcooling that has been observed by a number of researchers investigating nucleate boiling heat transfer at constant heat flux. It is shown that superheat initially increases with increasing subcooling near saturated conditions because of the way in which changes in active site density and average bubble frequency with increasing subcooling affect the rate of heat removal from the heater surface by enthalpy transport and microlayer evaporation. As subcooling increases further, natural convection begins to play an increasingly important role in the heat transfer process. Ultimately, natural convection is able to accommodate the entire imposed heat flux, after which superheat decreases as subcooling increases. The success of the analysis in explaining the variation of superheat with subcooling suggests that the rate of the heat removal from the heater surface is completely determined by the mechanisms of enthalpy transport, natural convection, and microlayer evaporation.

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Liu, Chang, Haojian Duan, and Lifeng Zhang. "Modeling of the Melting of Aluminum Particles during the RH Refining Process." Metals 9, no. 4 (April 15, 2019): 442. http://dx.doi.org/10.3390/met9040442.

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The aluminum content in oriented silicon steel obviously influences its magnetic properties. In the current work, the movement and melting process of added aluminum particles during Ruhrstahl-Heraeus (RH) treatment were simulated using a mathematical approach, considering the effect of the multiphase fluid flow on the evolution of aluminum particles and the dissolved aluminum distribution. The current model was validated by the [Al] content in the molten steel measured by an industry experiment. Most of the added aluminum particles were melted within 5 s after they connected with the molten steel under the superheat of 28 K. The statistics of the melting time and trajectory length showed a normal distribution. Furthermore, both the melting time and the trajectory length of aluminum particles decreased as the superheat increased. Since the maximum mixing time may go up when the superheat is excessive, the suggested superheat should range from 20 K to 30 K during the RH refining process. Besides, an appropriate sampling position with a short mixing time was proposed.

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32

Shen, Yi Jun, Tien Chu Lin, and Muh Ron Wang. "Production of Carbon Dioxide Snow by Flash-Atomization for Material Cleaning Process." Advanced Materials Research 569 (September 2012): 282–85. http://dx.doi.org/10.4028/www.scientific.net/amr.569.282.

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This paper investigates the production of CO2 snow by flash-atomization of liquid carbon dioxide for material cleaning process. The evolution of flash-atomization processes was recorded by means of high-speed shadowgraph. Results shows that the degree of superheat condition of liquid CO2 greatly influence the atomization modes, bobbles growth rate and concentration, and thus result in difference spray angle, spray pattern, and the structure of liquid jet which is suitable for different material cleaning applications. It is found that the spray angle first slowly increases with increase in the degree of superheat (ΔT) under external flash atomization processes. It is increased drastically as the spray transform from external-flashing to internal-flashing mode. Finally the spray angle is decreased again because of the decrease of mass flowrate due to the internal flashing processes . Moreover, the spray angle is increased as the length-to-diameter ratio (L/D) is increased. This is due to the higher bobble growth rate in terms of different pressure distribution and bobble growth time. It is also found that the external-flashing disappears at higher L/D because of the heat transfer to the liquid carbon dioxide. It is concluded that the superheated condition is useful in the control of the spray angle for material cleaning processes.

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Danish, Mohd, and Mohammed Al Mesfer. "Developing a Mathematical Model for Nucleate Boiling Regime at High Heat Flux." Processes 7, no. 10 (October 11, 2019): 726. http://dx.doi.org/10.3390/pr7100726.

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A mathematical model has been developed for heat exchange in nucleate boiling at high flux applying an energy balance on a macrolayer. The wall superheat, macrolayer thickness, and time are the parameters considered for predicting the heat flux. The influence of the wall superheat and macrolayer thickness on average heat flux has been predicted. The outcomes of the current model have been compared with Bhat’s constant macrolayer model, and it was found that these models are in close agreement corresponding to the nucleate pool boiling regime. It was concluded that the wall superheat and macrolayer thickness contributed significantly to conduction heat transfer. The average conduction heat fluxes predicted by the current model and by Bhat’s model are in close agreement for a thinner macrolayer of approximately 50 µm. For higher values of the wall superheat, which corresponds to the nucleate pool boiling condition, the predicted results strongly agree with the results of Bhat’s model. The findings also validate the claim that conduction across the macrolayer accounts for the main heat transfer mode from the heater surface to boiling liquid at high heat flux in nucleate pool boiling.

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34

Mäkinen, Mika, and Markku Uoti. "The Effect of Superheat on Micro- and Macrosegregation and Crack Formation in the Continuous Casting of Low-Alloyed Copper." Materials Science Forum 508 (March 2006): 549–54. http://dx.doi.org/10.4028/www.scientific.net/msf.508.549.

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In continuous casting, the severity of centerline macrosegregation and internal crack formation is linked to the cast structure, which can be minimized by increasing the equiaxed zone. Thus all the factors which favour an equiaxed structure are useful to quality. These are: low superheat, electro magnetic stirring (EMS) in the mould, large section size and especially in the case of internal cracks, uniform heat transfer between the strand and the mould. Microsegregation, which is the primary reason for macrosegregation, is due to the distribution coefficient and the growth rate of the solidification front. It is known that superheat has an influence on the solidification structure on both the micro- and macro- levels. Research has confirmed that superheat also affects crack formation in the solidifying front. These observations are usually reported on steels but little has been reported on low-alloyed coppers. In our experimental studies we examined the effects of superheat and uneven heat transfer on segregation behavior of phosphorus and iron in round, deoxidized, high phosphorus (DHP) copper billets. Furthermore crack formation and the solidification structure on both the micro- and macro- levels were studied. Results were verified by optical emission spectrometry (OES) and scanning electron microscopy (SEM).

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Danish, Mohd, Mohammed K. Al Mesfer, Khursheed B. Ansari, Mudassir Hasan, Abdelfattah Amari, and Babar Azeem. "Predicting Conduction Heat Flux through Macrolayer in Nucleate Pool Boiling." Energies 14, no. 13 (June 28, 2021): 3893. http://dx.doi.org/10.3390/en14133893.

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In the current work, the heat flux in nucleate pool boiling has been predicted using the macrolayer and latent heat evaporation model. The wall superheat (ΔT) and macrolayer thickness (δ) are the parameters considered for predicting the heat flux. The influence of operating parameters on instantaneous conduction heat flux and average heat flux across the macrolayer are investigated. A comparison of the findings of current model with Bhat’s decreasing macrolayer model revealed a close agreement under the nucleate pool boiling condition at high heat flux. It is suggested that conduction heat transfer strongly rely on macrolayer thickness and wall superheat. The wall superheat and macrolayer thickness is found to significantly contribute to conduction heat transfer. The predicted results closely agree with the findings of Bhat’s decreasing macrolayer model for higher values of wall superheat signifying the nucleate boiling. The predicted results of the proposed model and Bhat’s existing model are validated by the experimental data. The findings also endorse the claim that predominant mode of heat transfer from heater surface to boiling liquid is the conduction across the macrolayer at the significantly high heat flux region of nucleate boiling.

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36

Wang, Ziren, Feng Wang, Yi Peng, Zhongyu Zheng, and Yilong Han. "Imaging the Homogeneous Nucleation During the Melting of Superheated Colloidal Crystals." Science 338, no. 6103 (October 4, 2012): 87–90. http://dx.doi.org/10.1126/science.1224763.

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The nucleation process is crucial to many phase transitions, but its kinetics are difficult to predict and measure. We superheated and melted the interior of thermal-sensitive colloidal crystals and investigated by means of video microscopy the homogeneous melting at single-particle resolution. The observed nucleation precursor was local particle-exchange loops surrounded by particles with large displacement amplitudes rather than any defects. The critical size, incubation time, and shape and size evolutions of the nucleus were measured. They deviate from the classical nucleation theory under strong superheating, mainly because of the coalescence of nuclei. The superheat limit agrees with the measured Born and Lindemann instabilities.

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Chen, J. C., and K. K. Hsu. "Heat Transfer During Liquid Contact on Superheated Surfaces." Journal of Heat Transfer 117, no. 3 (August 1, 1995): 693–97. http://dx.doi.org/10.1115/1.2822632.

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Several boiling regimes are characterized by intermittent contacts of vapor and liquid at the superheated wall surface. A microthermocouple probe was developed capable of detecting transient surface temperatures with a response time better than 1 ms. The transient temperature data were utilized to determine the time-varying heat flux under liquid contacts. The instantaneous surface heat flux was found to vary by orders of magnitude during the milliseconds of liquid residence at the hot surface. The average heat flux during liquid contact was found to range from 105 to 107 W/m2 for water at atmospheric pressure, as wall superheat was varied from 50 to 450°C.

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38

Wang, Yarong, and Peirong Wang. "Analysis of thermodynamic process of water vapor in boiler." E3S Web of Conferences 252 (2021): 02043. http://dx.doi.org/10.1051/e3sconf/202125202043.

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In steam power plant, the working medium used for energy transformation is water vapor. The generation process of water vapor has experienced three stages: pre-heat, vaporization and superheat stage. There are five states in the process. They are sub-cooled liquid, saturated water, saturated liquid-vapour mixture, saturated vapor and superheated vapor. The thermodynamic properties of each state are usually obtained by using water vapor tables and charts. The constant pressure process of water vapor is very common in engineering application. In general, we first determine the state parameters by using charts and tables, and then make relevant calculations according to the first law of thermodynamics.

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39

Elliott, Matthew, Zachary Walton, Byron Bolding, and Bryan Rasmussen. "Superheat Control: A Hybrid Approach." HVAC&R Research 15, no. 6 (November 1, 2009): 1021–43. http://dx.doi.org/10.1080/10789669.2009.10390877.

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40

Corson, F. H. "STEAM CYLINDER LUBRICATION UNDER SUPERHEAT." Journal of the American Society for Naval Engineers 21, no. 4 (March 18, 2009): 1375–78. http://dx.doi.org/10.1111/j.1559-3584.1909.tb02188.x.

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41

Elias, Ezra, and P. L. Chambré. "Liquid superheat during nonequilibrium boiling." Heat and Mass Transfer 45, no. 5 (November 27, 2008): 659–62. http://dx.doi.org/10.1007/s00231-008-0467-4.

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42

Cheng, Bao Hua, Ai Guo Wu, and Yu Wen You. "Model Free Control of the Refrigeration System Based on Minimum Stable Superheat." Applied Mechanics and Materials 397-400 (September 2013): 1373–77. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.1373.

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This paper applied model free control method to the refrigeration system evaporator minimum stable superheat control. Compared with conventional PID control, model free control method has fast convergence, anti-interference ability. Meanwhile, model free control can reduce the coupling effect between evaporator superheat and evaporating temperature and be well adapted to the variable load control requirements of the refrigeration system, which has good steady state performance and dynamic performance.

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43

Ermakov, G. V., A. L. Gurashkin, E. V. Lipnyagov, and S. A. Perminov. "Video monitoring of the superheated liquid boiling up at the attainable superheat boundary." Technical Physics Letters 35, no. 12 (December 2009): 1104–7. http://dx.doi.org/10.1134/s1063785009120104.

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44

Abbasi, Tasneem, and S. A. Abbasi. "Accidental risk of superheated liquids and a framework for predicting the superheat limit." Journal of Loss Prevention in the Process Industries 20, no. 2 (March 2007): 165–81. http://dx.doi.org/10.1016/j.jlp.2005.11.002.

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45

Zhang, Rong, Chunming Zou, Zunjie Wei, and Hongwei Wang. "Effect of High Pressure and Temperature on the Evolution of Si Phase and Eutectic Spacing in Al-20Si Alloys." Crystals 11, no. 6 (June 20, 2021): 705. http://dx.doi.org/10.3390/cryst11060705.

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The microstructure of the Si phase in Al-20Si alloys solidified under high pressure was investigated. The results demonstrate that the morphology of Si phase transformed (bulk→short rod→long needle) with the increase of superheat temperature under high pressure. At a pressure of 3 GPa and a superheat temperature of 100 K, a microstructure with a uniform distribution of fine Si phases on the α-Al matrix was obtained in the Al-20Si alloy. In addition, a mathematical model was developed to analyze the spacing variation of the lamellar Al-Si eutectics under the effect of pressure. The lamellar Al-Si eutectics appeared at 2 GPa and superheat temperatures of 70–150 K, and at 3 GPa and superheat temperatures of 140–200 K. With the increase of pressure from 2 GPa to 3 GPa, the average spacing of lamellar Al-Si eutectics decreased from 1.2–1.6 μm to 0.9–1.1 μm. In binary alloys, the effect of pressure on the eutectic spacing is related to the volume change of the solute phase from liquid to solid. When the volume change of the solute phase from liquid to solid is negative, the lamellar eutectic spacing decreases with increasing pressure. When it is positive, the eutectic spacing increases with increasing pressure.

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46

Thasanaraphan, Pornsak, Pannawat Thapnuy, Duangporn Ounpanich, and Pratip Vongbandit. "Remaining Creep Life Assessment of Service Superheat Tube Boiler." Key Engineering Materials 659 (August 2015): 686–90. http://dx.doi.org/10.4028/www.scientific.net/kem.659.686.

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The demand of remaining life assessment of the boilers arises from technical, economic, and legal reasons. Creep is major damage mechanism of primary superheat tube boiler during prolong operation at high temperature and pressure in a water tube boiler. This paper presents the calculation method for the remaining life assessment due to creep damage. The service-exposed primary superheat tube made of 2.25Cr-1Mo steels. During scheduled inspection, wall thickness measurement, metallographic investigation by replica technique, design data and operating condition were used to estimate the remaining life in the form of creep damage accumulation rate calculated from life fraction using Larson-Miller Parameter. The results indicate that the primary superheat tubes satisfy in extension service life. By attaining an accurate and timely discussion of the results, the engineer can manage the maintenance and inspection schedule for the critical part in the boiler.

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47

Xu, Chang Jun, Lin Hu, Song Zhang, Ai Hua Hou, and Qi Wang. "Numerical Simulation of Flowage and Bath Surface Behavior in Continuous Casting Mold with Electromagnetic Brake." Advanced Materials Research 295-297 (July 2011): 1017–20. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1017.

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Jet shape of submerged nozzle (SEN), flowage, fluid level fluctuation and the superheat on bath surface in mold under the static electromagnetic field were 3-D simulated by using the CFX, commercial software. The results showed that electromagnetic brake (EMBR) can alter jet shape of SEN and fluid flow in the mold. And on the premise of controlling fluid level fluctuation of mold bath effectively, higher superheat of bath surface is obtained.

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48

WOODS, ANDREW W., and SHAUN D. FITZGERALD. "The vaporization of a liquid front moving through a hot porous rock. Part 2. Slow injection." Journal of Fluid Mechanics 343 (July 25, 1997): 303–16. http://dx.doi.org/10.1017/s0022112097005855.

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We present a series of similarity solutions to describe the temperature field as liquid spreads from a line source into a porous rock saturated with liquid of higher temperature. We identify slow and fast flow regimes. In the slow flow regime, the liquid is heated to the far-field temperature by conduction of heat from the far field. In the fast flow regime, there is negligible conduction of heat from the far field. Instead, the liquid is heated to the far-field temperature by cooling a region of the host rock near the source, and an internal boundary layer develops within the newly injected liquid. We successfully test our quantitative theoretical predictions with a series of laboratory experiments in which water was injected into a consolidated bed of sand filled with liquid of different temperature. We extend our model to describe the vaporization of liquid as it spreads slowly from a central source into a superheated porous rock. A further family of similarity solutions shows that the rate of vaporization depends upon the injection rate as well as upon the initial superheat of the reservoir. For high injection rates, the liquid is typically heated to the interface temperature long before reaching the interface. The rate of vaporization then becomes independent of the initial liquid temperature, and depends mainly on the reservoir superheat. For lower injection rates, heat is conducted from ahead of the boiling front into the liquid. As a result, for progressively smaller injection rates, an increasing fraction of the liquid vaporizes, until virtually all the liquid boils, and only a very small liquid zone develops in the rock. Again, we successfully test our theoretical predictions with a laboratory experiment in which liquid water was injected into a superheated layer of permeable sandstone.

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49

Indriyani, Indriyani, and Ruslan Ruslan. "ANALISIS EFISIENSI KETEL UAP PIPA AIR DENGAN KAPASITAS MAKSIMUM 10 TON PER JAM DENGAN BAHAN BAKU BATU BARA." Teknika Sains : Jurnal Ilmu Teknik 2, no. 1 (June 1, 2017): 52–60. http://dx.doi.org/10.24967/teksis.v2i1.60.

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Pengendapan minyak atau pembentukan batu ketel akan dapat menimbulkan over heating (panas berlebih yang terjadi dalam pipa yang tersumbat oleh kotoran yang membatu menyebabkan pipa ai mudah pecah), konstuksinya lebih rumit, pemeliharaannya sulit dan membutuhkan biaya yang mahal, membutuhkan pemakaian pengatur otomatis pada beberapa alat operasional ketel, perlu berhati-hati betul menjaga tenangnya air dalam ketel, karena produksi uap sangat cepat. Metodologi penelitian yang dilakukan adalah dengan menggunakan ketel uap kapasitas 10 ton/jam, dengan data-data sebagai berikut: kapasitas 10,00 ton uap/jam, tekanan 25,00 kg/cm2, temperatur uap keluar superheat 400,00 0C, bahan bakar batubara, nilai pembakaran 5.300,00 kcal/kg. Hasil penelitian sebagai berikut diantaranya: temperatur air pengisi masuk ekonomiser 80,00 0C, temperature ruang bakar 1.420,00 0C, pemakaian bahan bakar tiap jam 1.617,00 kg/jam, kalor yang diterima 6.938.300,00 kcal/k, temperature air keluar ekonomiser 170,00 0C, luas panas ekonomiser 157,90 m2, tebal pipa ekonomiser 2,41 mm, jumlah pipa ekonomiser 84,00 buah, tebal pipa-pipa air 2,75 mm, tebal pipa air pengumpul 5,88 mm, luas panas pipa air 94,60 m2, jumlah pipa air 182,00 buah, tebal plat boiler drum 22,40 mm, tebal tutup boiler drum 26,50 mm, tebal pipa superheat 2,260 mm, jumlah pipa superheat 68,00 buah, luas panas superheat 84,20 m2, total luas panas boiler 336,70 m2, kebutuhan udara pembakaran setiap jam 9,6012 kg/bahan bakar, panas yang diserap oleh boiler 8.672.875 kcal/jam.

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Tu, Yi You, and Guo Zhong Li. "Effect of Casting Overheat and Rolling Temperature on Morphology of Sulfide in 30MnVS Steel." Advanced Materials Research 457-458 (January 2012): 270–73. http://dx.doi.org/10.4028/www.scientific.net/amr.457-458.270.

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Effect of superheat and initial rolling temperature on the morphology and distribution of sulfide in non quenched and tempered free cutting steel 30MnVS has been studied by optical microscope and scanning electron microscope. Results show that proper superheat and initial rolling temperature can turn rod-shaped sulfide into massive or globular sulfide，to alleviate sulfide segregation and pro-eutectoid ferrite distribution along the boundary of pearlite clusters in 30MnVS , increase the intragranular ferrite content and optimize the structure of continuous casting slab.

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Journal articles on the topic 'Superheat'

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