Experimental determination of the first and second critical heat flux densities and quench process characterization

Kobasko, N. I.; Moskalenko, A. A.; Totten, George E.; Webster, G. M.

doi:10.1007/s11665-997-0037-9

Cited by 48 publications

(6 citation statements)

References 3 publications

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“…Film boiling should prevail during quenching with increasing bath temperature because critical heat flux density decreases with decreasing underheat  uh (see Eq. (8)) [9], [10]. The experimental results shown in Fig.…”

Section: Analysis Of Petrash's Experimentsmentioning

confidence: 99%

New Evidences which Support Existence of the Forced Heat Exchange Phenomenon

Kobasko¹

2021

EJPHYSICS

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In the paper the forced heat exchange phenomenon is validated based on experimental data shown by different authors in different countries and published in respected scientific journals. Software IQLab and regular thermal condition theory were used for solving inverse problems. The data of silver and copper spherical probes quenching in electrolytes were used. As in previous publication, it was established in the paper that heat transfer coefficients (HTCs) increase versus time during quenching of silver and copper probes in electrolytes. As noted early, all of this contradicts the theory of transient nucleate boiling processes. The problem is solved by periodical replacement of film boiling by shock boiling with the high frequency that takes place during quenching. The new idea can be used in practice for designing new and original quenching technology to save materials, increase service life of machine components and also provide an environmentally friendly solution. The importance of new technologies is widely discussed in the paper.

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Section: Analysis Of Petrash's Experimentsmentioning

confidence: 99%

New Evidences which Support Existence of the Forced Heat Exchange Phenomenon

Kobasko¹

2021

EJPHYSICS

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“…he author of the paper was dealing a long time with testing of different kinds of water salts solutions using spherical silver probe 20 mm in diameter. The silver probe was used to evaluate critical heat flux densities of water at different temperatures [1]. However, it was impossible to evaluate critical heat flux densities of water salt solution (electrolytes) using standard silver probe 20 mm in diameter because developed film boiling during quenching was completely absent.…”

Section: Introductionmentioning

confidence: 99%

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

Kobasko¹

2020

GJSFR

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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.

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“…The vapor film acts as a resistance to heat transfer towards the bulk of the subcooled liquid and affects the cooling rate history to the point of favoring the formation of unwanted microconstituents, thus reducing the mechanical properties of the material; (b) nucleate boiling, associated with high heating rates due to the formation of bubbles that remove large amounts of heat; and (c) pure convection (either natural or forced), i.e., without boiling, during which heat extraction diminishes towards zero. Additionally, in the quenching literature the occurrence of a socalled shock-boiling regime just before a stable vapor film forms has been reported (Kobasko et al, 1997); it usually occurs during the first 0.1 s after the heated probe is submerged in the quenching medium. Through experiments involving heating of metallic parts in a subcooled liquid, a transition zone, characterized by the coexistence of film boiling and nucleate boiling, has been identified (Nukiyama and Shiro, 1966;Shiro and Nukiyama, 1984).…”

Section: Introductionmentioning

confidence: 99%

Fluid Dynamics Around Flat-End Cylindrical Quench Probes Under Isothermal and Non-Isothermal Conditions

Cervantes¹

2018

Rev. Mex. Ing. Quim.

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The most common methodology to describe the complex phenomena occurring during quenching operations is based on measuring cooling curves inside metal test probes instrumented with thermocouples. There are many variants regarding specimen shape, although the preferred shape is a flat-end cylindrical probe. However, mathematical and physical modeling studies, carried out under isothermal conditions, regarding the hydrodynamic behavior of the quenchant around flat-end cylindrical probes suggest that this type of probe should not be recommended for studies quenching. In this paper, we study fluid dynamics around an instrumented flat-end cylindrical probe, both under isothermal (un-heated probe) and non-isothermal conditions (probe heated to 900 ºC and cooled in water at 60 ºC). For this purpose, water at 60°C was used as cooling fluid; three free-stream water velocities (0.2, 0.4 and 0.6 m/s) were studied. Visualization techniques using a high-speed camera and optical filters were applied to characterize the flow around the probe and, at the same time, thermal histories were measured within the probe. The results show that fluid dynamics under non-isothermal conditions is very different from that under isothermal conditions; therefore, it is not advisable to directly correlate fluid dynamics around metal probes characterized under isothermal conditions with cooling curves or the evolution of the wetting front during an actual quench. Keywords: quenching, cooling curves, flat-end cylindrical probe, wetting front, fluid dynamics. ResumenLa metodología más común para describir los fenómenos complejos que ocurren durante las operaciones de temple se basa en la medición de curvas de enfriamiento. Existen variantes de la forma de la probeta, aunque la forma preferida es cilíndrica de base plana. Sin embargo, estudios de modelado físico y matemático realizados en condiciones isotérmicas respecto al comportamiento hidrodinámico del fluido de temple alrededor de las probetas cilíndricas de base plana, sugieren que este tipo de probetas no es recomendable para estudios de temple. En este artículo, se estudia la dinámica de fluidos alrededor de una probeta cilíndrica de base plana bajo condiciones isotérmicas (probeta sin calentar) y no-isotérmicas (probeta calentada a 900 ºC y enfriada en agua a 60 ºC). Para este propósito, se usó agua a 60°C como fluido de enfriamiento; se estudiaron tres valores de velocidad de corriente libre (0.2, 0.4 y 0.6 m/s). Se utilizó una cámara de alta velocidad y filtros ópticos para caracterizar el flujo alrededor de la probeta y, al mismo tiempo, se midieron historias térmicas al interior de la misma. Los resultados muestran que la dinámica de fluidos en condiciones no-isotérmicas es muy diferente a la que ocurre en condiciones isotérmicas; por consiguiente, no es aconsejable correlacionar la dinámica de fluidos en condiciones isotérmicas, con curvas de enfriamiento o con el frente de mojado en un temple real. Palabras

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Experimental determination of the first and second critical heat flux densities and quench process characterization

Cited by 48 publications

References 3 publications

New Evidences which Support Existence of the Forced Heat Exchange Phenomenon

New Evidences which Support Existence of the Forced Heat Exchange Phenomenon

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

Fluid Dynamics Around Flat-End Cylindrical Quench Probes Under Isothermal and Non-Isothermal Conditions

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