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.

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.

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.

Modeling of Film Boiling and Film Vaporization on Engine Piston Tops

2012 ◽  
Author(s):  
Timothy H. Lee ◽  
Dimitrios C. Kyritsis ◽  
Chia-fon F. Lee
Keyword(s):  
Heat Flux ◽  
Liquid Fuel ◽  
Combustion Process ◽  
Infinite Plate ◽  
Saturation Temperature ◽  
Nucleate Boiling ◽  
Spark Ignition Engine ◽  
Film Boiling ◽  
Engine Fuel ◽  
Boiling Regime

Engine-out HC emissions resulting from liquid fuel, which escapes from the combustion process, provides the motivation to better understand the film vaporization in a combustion chamber. Previous work theorized that the removal of liquid fuel from the combustion cycle was a result of the increase in film vaporization time due to the Leidenfrost phenomenon. Currently, KIVA 3V predicts a continuous decrease in vaporization time for piston top films. The objective of this work is to improve the KIVA 3V film vaporization model through the inclusion of established boiling correlations, and thus, the Leidenfrost phenomenon. Experimental results have been reviewed from which expressions encompassing high acceleration effects for the nucleate boiling regime and the film boiling regime were investigated, implemented, and validated. Validation was conducted using published experimental data sets for boiling heat flux. As a result of the implementation, a noticeable increase in heat flux occurred due to high accelerations for films in saturated film boiling in both nucleate and film boiling. Computational simulations were conducted using a semi-infinite plate and a direct-injection spark-ignition engine. The semi-infinite plate provided a controlled environment which could separate the effects of pressure and acceleration on film boiling heat flux, film vaporization rates, and film vaporization times. The effect of decreased film vaporization rates, during the Leidenfrost phenomenon, was observed to decrease with increasing acceleration. Finally, the engine computations were used to provide the first film boiling and film vaporization rates for engine fuel films at temperatures above saturation temperature. As a result of this work, a film vaporization model capable of improved prediction of vaporization rates of piston top films in saturated boiling conditions has been created.

scholarly journals Unusual Phenomenon of Forced Heat Exchange Taking Place during Quenching Silver Probe in Cold Electrolyte

2020 ◽  
pp. 29-37
Author(s):  
Nikolai I. Kobasko
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Short Film ◽  
Contemporary Theory ◽  
Boiling Process ◽  
Unusual Phenomenon ◽  
Electrical Layer ◽  
Careful Investigation ◽  
Very High

It is shown in the paper that forced heat transfer exchange during quenching silver probes in cold electrolytes is explained by periodical replacement of short film boiling process by shock boiling. The frequency of such process is very high that increases cardinally heat transfer exchange. This phenomenon doesn’t fit contemporary theory concerning nucleate boiling processes and needs further careful investigations. The reason for existing periodical process is a double boundary electrical layer where are acting increased electrical forces during quenching in electrolytes. In contrast of quenching steel, silver generates higher heat flux density during quenching; however full film boiling cannot be developed due to presence of high electrical forces in a double electrical layer caused by increased electrical conductivity of silver. The discovered phenomenon can be used in the practice in the future after its careful investigation to force heat transfer exchange by external electrical forces to eliminate any film boiling process during batch quenching.

scholarly journals RESEARCH ON USE OF LOW CONCENTRATION INVERSE SOLUBILITY POLYMERS IN WATER FOR HARDENING MACHINE COMPONENTS AND TOOLS

2018 ◽  
Vol 2 ◽  
pp. 63-71
Author(s):  
Nikolai Kobasko ◽  
Anatolii Moskalenko ◽  
Volodymyr Dobryvechir
Keyword(s):  
Heat Flux ◽  
Cold Water ◽  
Nucleate Boiling ◽  
Optimal Concentration ◽  
Film Boiling ◽  
Accelerated Cooling ◽  
Water Solutions ◽  
Boiling Process ◽  
Improved Technology ◽  
Initial Heat

There is an optimal water concentration of inverse solubility polymers ( 1 %) where in many cases film boiling is absent. Based on accurate experimental data of French and data of authors, it was shown that during quenching from 875 oC in cold water solutions of optimal concentration film boiling is completely absent for those steel parts initial heat flux densities of which are below critical value. It is established that initial heat flux density decreases with increase sizes of tested samples. Initial process of quenching (formation of boundary boiling layer), which makes further history of cooling, is not investigated deeply and widely yet enough. When film boiling is absent, mathematical model includes only transient nucleate boiling process and convection. In this case, cooling time within the transient nucleate boiling process can be calculated using average effective Kondratjev numbers Kn. They were evaluated for inverse solubility polymers depending on their concentration and sizes of tested samples. As a result, an improved technology of hardening large gears and bearing rings is proposed by authors. Its essence consists in interruption of accelerated cooling or turning off agitation of quenchant when dissolving of surface polymeric layer starts. Examples of performing improved technology are provided by authors. Developments can be used by engineers to switch from carburized large gears quenched in oil to gears made of optimal hardenability steel and quenched in water solutions of optimal concentration.

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

2003 ◽  
Author(s):  
Chen-Li Sun ◽  
Van P. Carey
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Film 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 pseudo film boiling, the transition condition, and the critical heat flux (CHF), were identified. The observations indicate that the presence of the gap geometry pushed the nucleate boiling regime to a lower superheated temperature range and resulted in correspondingly lower heat flux. With further increases of wall superheat, the vapor generated by the boiling process was trapped in the gap and blanketed 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 at reduced gravity conditions. The value of the CHF for x = 0.025, which corresponded to weaker Marangoni forces, was found to be greater than that of x = 0.015 with a 6.35 mm gap.

scholarly journals INVESTIGATION OF BATCH INTENSIVE QUENCHING PROCESSES WHEN USING HYDRODYNAMIC EMITTERS IN QUENCH TANKS

2016 ◽  
Vol 6 ◽  
pp. 29-36 ◽  
Author(s):  
Nikolai Kobasko
Keyword(s):  
Heat Transfer ◽  
Resonance Effect ◽  
Heat Treating ◽  
Nucleate Boiling ◽  
New Method ◽  
Film Boiling ◽  
Boiling Process ◽  
Part Distortion ◽  
Water Tanks

The paper discusses patented in Ukraine a new intensive quenching IQ–2 technology based on film boiling resonance effect [1]. Namely, the paper discusses improving of the batch intensive quenching (IQ) process known as IQ-2 method by the use of hydrodynamic emitters installed in quench tanks. The hydrodynamic emitters produce oscillating waves in the quench media with the frequency of the film boiling process creating a resonance effect. Two- and three-step IQ-2 processes are considered. Specifics of the heat transfer during the IQ-2 process are presented with focusing on the first stage of quenching where film and nucleate boiling processes are taking place. Examples of production IQ-2 equipment and loads processed are also presented. Application of hydrodynamic emitters in the IQ water tanks in addition to currently used propellers is considered in details. It is shown that the proposed new method can fully eliminate the film boiling process resulting in significant reduction of part distortion during quenching. Further evaluation of the proposed method is needed for its implementation in heat treating practice.

scholarly journals The pulsating nature of bubble boiling of subcooled water flow during cooling of a metal heater

2021 ◽  
Vol 321 ◽  
pp. 01013
Author(s):  
Levin A.A
Keyword(s):  
Water Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Annular Channel ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Quantitative Prediction ◽  
Subcooled Water ◽  
Interphase Interactions ◽  
Temperature Levels

This paper presents the results of an experimental study of the subcooled water flow boiling on the surface of a metal rod 12 mm in diameter. As a result of the rapid heat release that occurs when an electric current is pulsed through a metal heater, the latter reaches certain temperature levels above the saturation temperature of water at the corresponding pressure (p = 0.17 MPa). In a system formed by a cold liquid and a heated solid body, the process of intense heat exchange begins, the cooling rate of the metal in which reaches its maximum when the nucleate boiling is realized. Interest in such scenarios is remaining high and is caused by the need for quantitative prediction of the characteristics of nucleate boiling and the existence boundaries of this boiling mode. As well-known, nucleate boiling is limited from above by the onset of film boiling and from below by the required surface temperature for which a significant number of nucleation centers are activated. The pressure waves arising during film boiling have a significant amplitude, as a result of which special conditions of interphase interactions may occur. The results of the study showed that self-oscillating pressure pulsations may occur which is associated with the nucleate boiling in an annular channel.

Development of low-cost C/C, related technology using a film-boiling process

Carbon ◽  
2021 ◽  
Vol 175 ◽  
pp. 609
Author(s):  
Hiroshi Yamauchi ◽  
Michimasa Uda ◽  
Haruhiko Soeda
Keyword(s):  
Low Cost ◽  
Film Boiling ◽  
Boiling Process

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.

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