scholarly journals Analysis of Transient Boiling Processes during Steel Quenching in Water PAG Solutions to Decrease Distortion

2021 ◽  
Vol 3 (6) ◽  
pp. 7-14
Author(s):  
Nikolai I. Kobasko ◽  
Anatoly A. Moskalenko
Keyword(s):  
Polymer Solutions ◽  
Industrial Condition ◽  
Nucleate Boiling ◽  
Liquid Media ◽  
Sonar System ◽  
Polyalkylene Glycol ◽  
Boiling Process ◽  
Surface Thermocouple ◽  
Transient Boiling ◽  
Physical Phenomena

The paper discusses results of testing standard cylindrical probe 12.5 mm diameter in water polymer solutions which was additionally instrumented with a surface thermocouple. It is shown that central thermocouple cannot depict many physical phenomena taking place during quenching in polymer solutions such as shoulder formation, self- regulated thermal process establishing, surface temperature transient from film boiling to nucleate boiling process. Moreover, it is shown that experimental data depicted by central thermocouple cannot be used for solving inverse problem to analyze quenching process in liquid media. Along with analyzing film and nucleate boiling processes during quenching, the paper discusses the possibility of quality quench process control via using sonar system. It is established an equation for evaluating duration of transient nucleate boiling process. As an example, the cooling characteristics of fresh and old polyalkylene glycol (PAG) polymer solutions are analyzed. It is shown that with passing time the critical heat flux density of polymer decreases and inverse solubility effect disappears. That is while the method and apparatus were developed to control in industrial condition the quality of quenched steel parts during hardening in liquid media.

scholarly journals Intense Quench Process in Slow Agitated Water Salt and Polymer Solutions

2021 ◽  
Vol 3 (3) ◽  
pp. 6-12
Author(s):  
Nikolai Mykola Kobasko
Keyword(s):  
Polymer Solutions ◽  
Water Solution ◽  
Saturation Temperature ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Liquid Media ◽  
Slow Cooling ◽  
Low Concentration ◽  
Boiling Process ◽  
Water Salt

In the paper it is shown that quenching in slow agitated water salt solution of optimal concentration and in low concentration of inverse solubility polymers is intensive quenching creating maximal temperature gradients at the beginning of cooling. The evidence to support such idea were collected by analyzing quenching process in liquid media where any film boiling process was completely absent. In this case, surface temperature at the beginning of cooling drops closely to saturations temperature of a liquid within the interval 1–2 seconds, independently on nature of water solution, and then during transient nucleate boiling process maintains at the level of boiling point of a liquid which is often called self–regulated thermal process. The computer modeling of such cooling processes provided Kondrat’ev numbered Kn which are strongly linear function of time. At the beginning of cooling Kondrat’ev number is almost equal to 1 while average Kondrat’ev number Kn≥0.8. According to US Patent, intensive quenching starts when Kn=0.8. Based on achieved results, it is possible to perform intensive quenching in slow agitated of low concentration water salt and polymer solutions, usually initiated by hydrodynamic emitters. Along with liquid agitation, emitters generate resonance wave effect which destroys film boiling processes making cooling very uniform and intensive. The proposed IQ process works perfectly when martensite starts temperature Ms>Ts. If saturation temperature Ts≥Ms, intensive austempering process via cold liquids can be successfully performed to replace slow cooling of molten salts and alkalis by intensive quenching in liquid media.

Semi-Transparent Gold Film as Simultaneous Surface Heater and Resistance Thermometer for Nucleate Boiling Studies

1981 ◽  
Vol 103 (1) ◽  
pp. 65-68 ◽  
Author(s):  
E. Oker ◽  
H. Merte
Keyword(s):  
Thin Film ◽  
Heat Source ◽  
High Speed ◽  
Gold Film ◽  
Nucleate Boiling ◽  
Resistance Thermometer ◽  
Construction Techniques ◽  
Boiling Process ◽  
Sample Application ◽  
Transient Boiling

A large (22 × 25 mm) semi-transparent thin film of gold, approximately 400 Å in thickness, is deposited on a glass substrate for simultaneous use as a heat source and resistance thermometer. Construction techniques and calibration procedures are described, and a sample application to a transient boiling process is included with simultaneous high speed photographs taken through the thin film from beneath.

scholarly journals Mechanism of Film Boiling Elimination and IQ Process Design for Hardening Steel in Low Concentration of Water Polymer Solutions

2020 ◽  
pp. 39-56
Author(s):  
Nikolai I. Kobasko
Keyword(s):  
Heat Transfer ◽  
Polymer Solutions ◽  
Heat Treating ◽  
Nucleate Boiling ◽  
Steel Part ◽  
Point Of View ◽  
Film Boiling ◽  
Slow Cooling ◽  
Low Concentration ◽  
Boiling Process

The paper considers a mechanism of the elimination of the film boiling process during intensive quenching (IQ) of steel parts in water polymer solutions of low concentration. The use of the IQ process results in improvement of material mechanical properties and steel part performance characteristics. Evaluation of ways of eliminating of the film boiling process using a modern physics point of view allows significant improvement of the IQ equipment making it less costly and more efficient. All of this cardinally simplifies the implementation of the IQ technology in heat treat practice. The paper shows how creation of a thin insulating surface layer during quenching of steel parts in low concentration of inverse solubility polymers results in eliminating of film boiling processes that makes the quench process intensive. Historically in heat treating industry, an effective heat transfer coefficient was widely used for evaluating of the nucleate boiling process. And quenching during the nucleate boiling mode of heat transfer was considered as slow cooling.

Effects of Gap Geometry and Gravity on Boiling Around a Constrained Bubble in 2-Propanol/Water Mixtures

2006 ◽  
Vol 129 (2) ◽  
pp. 114-123
Author(s):  
Chen-li Sun ◽  
Van P. Carey
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Molar Fraction ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Cold Surface ◽  
Boiling Regime ◽  
Wall Superheat ◽  
Boiling Process ◽  
Lower Heat

In this study, boiling experiments were conducted with 2-propanol/water mixtures in confined gap geometry under various levels of gravity. The temperature field created within the parallel plate gap resulted in evaporation over the portion of the vapor-liquid interface of the bubble near the heated surface, and condensation near the cold surface. Full boiling curves were obtained and two boiling regimes—nucleate boiling and pseudofilm boiling—and the transition condition, the critical heat flux (CHF), were identified. The observations indicated that the presence of the gap geometry pushed the nucleate boiling regime to a lower superheated temperature range, resulting in correspondingly lower heat flux. With further increases of wall superheat, the vapor generated by the boiling process was trapped in the gap to blanket the heated surface. This caused premature occurrence of CHF conditions and deterioration of heat transfer in the pseudo-film boiling regime. The influence of the confined space was particularly significant when greater Marangoni forces were present under reduced gravity conditions. The CHF value of x (molar fraction)=0.025, which corresponded to weaker Marangoni forces, was found to be greater than that of x=0.015 with a 6.4mm gap.

scholarly journals Lattice Boltzmann Simulation of Nucleate Pool Boiling in Saturated Liquid

2011 ◽  
Vol 9 (5) ◽  
pp. 1347-1361 ◽  
Author(s):  
Yoshito Tanaka ◽  
Masato Yoshino ◽  
Tetsuo Hirata
Keyword(s):  
Lattice Boltzmann ◽  
Solid Wall ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Immiscible Fluids ◽  
Nucleate Pool Boiling ◽  
Two Phase ◽  
Boiling Process

AbstractA thermal lattice Boltzmann method (LBM) for two-phase fluid flows in nucleate pool boiling process is proposed. In the present method, a new function for heat transfer is introduced to the isothermal LBM for two-phase immiscible fluids with large density differences. The calculated temperature is substituted into the pressure tensor, which is used for the calculation of an order parameter representing two phases so that bubbles can be formed by nucleate boiling. By using this method, two-dimensional simulations of nucleate pool boiling by a heat source on a solid wall are carried out with the boundary condition for a constant heat flux. The flow characteristics and temperature distribution in the nucleate pool boiling process are obtained. It is seen that a bubble nucleation is formed at first and then the bubble grows and leaves the wall, finally going up with deformation by the buoyant effect. In addition, the effects of the gravity and the surface wettability on the bubble diameter at departure are numerically investigated. The calculated results are in qualitative agreement with other theoretical predictions with available experimental data.

Flow Boiling on Heterogeneous Wetting Surface in a Vertical Narrow Microchannel

2020 ◽  
Author(s):  
Yuhao Lin ◽  
Junye Li ◽  
Kan Zhou ◽  
Wei Li ◽  
Kuang Sheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Instability ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Working Fluid ◽  
Hydrophilic Surface ◽  
Structured Surfaces ◽  
Boiling Process

Abstract The micro structured surfaces have significant impact on the flow patterns and heat transfer mechanisms during the flow boiling process. The hydrophobic surface promotes bubble nucleation while the hydrophilic surface supplies liquid to a heating surface, thus there is a trade-off between a hydrophobic and a hydrophilic surface. To examine the effect of heterogeneous wetting surface on flow boiling process, an experimental investigation of flow boiling in a rectangular vertical narrow microchannel with the heterogeneous wetting surface was conducted with deionized water as the working fluid. The heat transfer characteristics of flow boiling in the microchannel was studied and the flow pattern was photographed with a high-speed camera. The onset of flow boiling and heat transfer coefficient were discussed with the variation of heatfluxes and mass fluxes, the trends of which were analyzed along with the flow patterns. During the boiling process, the dominated heat transfer mechanism was nucleate boiling, with numerous nucleate sites between the hydrophilic/hydrophobic stripes and on the hydrophobic ones. In the meantime, after the merged bubbles were constrained by the channel walls, it would be difficult for them to expand towards upstream since they were restricted by the contact line between hydrophilic/hydrophobic stripes, thereby reduce the flow instability and achieve remarkable heat transfer performance.

An Investigation of the Collapse and Surface Rewet in Film Boiling in Forced Vertical Flow

1975 ◽  
Vol 97 (2) ◽  
pp. 166-172 ◽  
Author(s):  
O. C. Iloeje ◽  
D. N. Plummer ◽  
W. M. Rohsenow ◽  
P. Griffith
Keyword(s):  
Nucleate Boiling ◽  
Boiling Temperature ◽  
Film Boiling ◽  
Test Surface ◽  
Loss Of Coolant Accident ◽  
Mass Fluxes ◽  
Loss Of Coolant ◽  
Scale Deposit ◽  
Transient Boiling ◽  
Scale Deposits

A transient boiling experiment has been run in such a way that one can acquire data in forced convection film, transition, and nucleate boiling regions for a specified pressure, quality, and mass flux. Transient boiling experiments were conducted at the Nuclear Energy Division of the General Electric Company for water in a 0.492 in. ID inconel X-750 tube at mass fluxes of 50,000, 100,000, and 250,000 lbm/hr-ft2, quality range of 30–100 percent and a pressure of 1000 psia. The reduced boiling curves for these data indicated temperature differences at burnout on the order of 100–200° F and temperature differences at the minimum ranging from 700 to 1100° F. These results (higher than in other experiments) are felt to be caused by scale deposit, axial conduction, and roughnesses on the test surface. Physical evidence indicates that the test surface became coated with an appreciable scale deposit when subjected to the initial temperatures in excess of 1500 °F in a steam atmosphere. It has been found (reference [1]) that BWR fuel will normally have scale deposit on the heat transfer surface and thus the qualitative effects of scale deposits in this report are expected to apply in BWR Loss-of-Coolant accident evaluation. An empirical correlation was developed for the data for minimum film boiling temperature differences. The correlation was based on Berenson’s minimum pool film boiling temperature difference correlation in order to provide a technique for extrapolating to different pressures.

Nucleate boiling in drag‐reducing polymer solutions

1983 ◽  
Vol 27 (1) ◽  
pp. 59-76 ◽  
Author(s):  
D. D Paul ◽  
S. I. Abdel‐Khalik
Keyword(s):  
Polymer Solutions ◽  
Nucleate Boiling ◽  
Drag Reducing Polymer
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