Boiling Heat Transfer: An Overview of Longstanding and New Challenges

Shekriladze, Irakli G.

doi:10.1520/stp49342t

Cited by 3 publications

(5 citation statements)

References 83 publications

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“…Such approach cannot be used for transient nucleate boiling processes where heat transfer coefficients reach 200,000 W/m 2 K and more [11,14]. A long ago, some incorrectness has been made by metallurgical engineers in FSU who used effective HTC to calculate Bi 0.25.…”

Section: Lumped-heat-capacity Methodsmentioning

confidence: 99%

“…Calculations of HTCs were made for maximal critical heat flux density of water salt solutions which was equal to 15 MW/ m 2 [2]. Dimensionless correlations of authors [11,14] were used for this purpose. As seen from Table 2, real HTCs are very large when heat flux density approaches the critical value 15 MW/m 2 .…”

Section: The Main Differences Between Real and Effective Heat Transfementioning

confidence: 99%

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Study of Differences Between Real and Effective Heat Transfer Coefficients to Provide Correct Data on Temperature Field Calculations and Computer Simulations During Hardening of Steel

Kobasko¹

2018

EUREKA: Physics and Engineering

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The paper analyses contemporary methods and probes for testing liquid media used as a quenchant in heat treating industry. It is shown that lumped-heat-capacity method, often used for testing liquid media, produces big errors during transient nucleate boiling processes due to incorrect calculation condition Bi≤0.25 caused by use effective heat transfer coefficient (HTC). The effective heat transfer coefficients (HTCs), utilized for this purpose, are almost seven times less as compared with real HTCs that results in incorrect calculation the value of Bi. Instead of lumped-heat-capacity method, a general cooling rate equation is proposed for HTC calculation. It is underlined that effective HTCs can be used only for approximate core cooling rate and core cooling time of steel parts calculations. For investigation cooling capacity of liquid quenchants, including initial heat flux densities, HTCs and critical heat flux densities, high developed technique of solving inverse problem should be used based on accurate experimental data generated by testing liquid media with the Liscic/Petrofer probe or other similar technique.

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Section: Lumped-heat-capacity Methodsmentioning

confidence: 99%

Section: The Main Differences Between Real and Effective Heat Transfementioning

confidence: 99%

Study of Differences Between Real and Effective Heat Transfer Coefficients to Provide Correct Data on Temperature Field Calculations and Computer Simulations During Hardening of Steel

Kobasko¹

2018

EUREKA: Physics and Engineering

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“…As known, the real heat transfer coefficient during transient nucleate boiling process is evaluated as a ratio of the heat flux density produced by bubbles to the overheat of the boundary layer [4][5][6] 2It cannot be used for temperature gradients calculation. As seen from Table 1, the real HTC is almost 7 times larger as compared with the effective HTC [4,6]. According to author [4], the average heat flux density q during nucleate boiling is proportional to the cube of temperature difference…”

Section: Intense Quenching When Cooling In Low Concentration Of Watermentioning

confidence: 99%

“…Calculations of HTCs were made for maximal critical heat flux density of water salt solutions which was equal to 15 MW/m 2 [4]. Dimensionless correlations of authors [4,6] were used for this purpose. Tolubinsky Shekriladze Average 10 152248 176546 164397 20 193929 243641 218785 40 224989 241615 233302 60 271273 271323 271298 Results of calculations presented in Table 2 actually are experimental data because dimensionless equations of Tolubinsky and Kutateladze are based on thousand of accurate experiments [4,5].…”

Section: Intense Quenching When Cooling In Low Concentration Of Watermentioning

confidence: 99%

“…During transient nucleate boiling process the surface temperature of steel part maintains at the level of boiling point of a liquid insignificantly differs from it. The established new characteristics were used for developing austempering process via cold liquids [6] and also for reconstruction of surface temperature during nucleate boiling and for estimation the cooling difference between IQ-2 and IQ -3 processes (see Figure 3 a) As one can see from Figure 3, temperature difference between IQ -2 and IQ -3 processes is insignificant (see Table 9). As is well known, the transient nucleate boiling process is intensive quenching by itself [4] due to acting of thousands of vapor bubbles.…”

Section: Difference Between Iq -2 and Iq -3 Processesmentioning

confidence: 99%

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Uniform and Intense Cooling During Hardening Steel in Low Concentration of Water Polymer Solutions

Kobasko¹

2019

AJMP

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The possibility of decreasing water polymer concentration, decreasing alloy elements in steel, decreasing distortion of steel parts, and increasing service life of machine components and tools during quenching is widely discussed in this paper based on achievements of modern physics. Instead of quenching alloy steel in oils or high concentration of water polymer solutions, the accelerated quench process of optimal hardenability steel in water low concentration of inverse solubility polymers is proposed. Physics of the new approach and new technologies is explained by the author. The creation of a thin polymeric insulating layer during quenching steel in low concentration of inverse solubility polymers decreases initial heat flux density below its critical value that is reason for absence the film boiling process. Due to this fact, full film boiling during quenching is completely absent allowing use optimal hardenability steel instead of alloy steels containing costly alloy elements. Accelerated cooling provided by low concentration of water polymer solution results in creation of high surface compression residual stress, and super strengthening of material that in turn increases service life of machine components and tools. It is underlined in the paper that along with the use of a thin polymeric insulating layer, the resonance effect can be used for destroying the full film boiling process based on implementation different kinds of hydrodynamic emitters. The proposed new technology saves materials, increases service life of steel parts, and improves environment condition in heat treating industry. The patented technologies and processes can be used by engineers and scientists. and can bring great benefits if widely implemented in the practice.

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Heat Transfer Fundamentals Concerning Quenching Materials in Cold Fluids

Kobasko

2024

Heat Transfer - Advances in Fundamentals and Applications

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The current chapter discusses three principles of heat transfer related to transient nucleate boiling process when any film boiling during quenching is completely absent. They include the duration of nucleate boiling establishment, surface temperature behavior during self-regulated thermal process, and generalized fundamental equation for evaluation of transient nucleate boiling length. In fact, majority of authors in their analytical and experimental investigations always considered three classical heat transfer modes: film boiling, nucleate boiling, and convection. It is shown in the chapter that the absence of film boiling process simplifies numerical and analytical calculations. It is very important to know that mentioned principles can be used for calculation of temperature fields and stresses and development of new technologies without performing costly experiments. Such an approach can be used for measuring different forms and sizes of quenched steel parts. It is stated that universal correlation for heating and cooling time evaluation, modified by proposed principles, can be widely used for recipes development when exploring new intensive quenching technologies. Examples of calculations are provided.

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Boiling Heat Transfer: An Overview of Longstanding and New Challenges

Cited by 3 publications

References 83 publications

Study of Differences Between Real and Effective Heat Transfer Coefficients to Provide Correct Data on Temperature Field Calculations and Computer Simulations During Hardening of Steel

Study of Differences Between Real and Effective Heat Transfer Coefficients to Provide Correct Data on Temperature Field Calculations and Computer Simulations During Hardening of Steel

Uniform and Intense Cooling During Hardening Steel in Low Concentration of Water Polymer Solutions

Heat Transfer Fundamentals Concerning Quenching Materials in Cold Fluids

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