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This paper presents a Computational Fluid Dynamics (CFD) simulation of the quenching process based on ISO 9950, focusing on the heat flux and heat transfer coefficient integrated over a metal specimen. The numerical method, which employs the two-fluid VOF method and frozen turbulence approach (Cukrov et al., Appl. Sci. 2023, 13, 9144), is used for the transient simulation. Since quenching processes involve complex boiling phenomena shifting from film boiling to nucleate boiling, a standard method based on VOF cannot be applied. The comparison of the simulation results with the ones obtained using correlation, and the data obtained using the Inverse Heat Transfer Analysis (IHTA) method have revealed that the proposed method can accurately predict the heat flux and heat transfer coefficient in the film boiling regime of the immersion quenching process. Note that the previous paper (Cukrov et al., Energies. 2023, 16, 7926.) presented the immersion process modeling and the temperature distribution, while the current paper examines the heat transfer characteristics of the immersion quenching process.

The computational model that is able to estimate the temperature distribution inside a solid specimen during the film boiling phase of immersion quenching (water entry) process has been presented in this paper. It is based on the prescribed initial temperatures of the solid specimen and the liquid quenchant. In addition, the turbulence effects have to be considered using the assumed turbulence kinetic energy value, i.e., the "frozen turbulence" approach, that remains constant thorough the simulation. The studied material is nickel alloy, Inconel 600, for which extensive experimental data are available. The work has been carried out using ANSYS Fluent computational fluid dynamics software and the methods for solution of Stefan problem by Eulerian two fluid VOF model. A satisfactory agreement between the experimental and the calculated data has been achieved, yielding thereby the computationally obtained data that fit to a great extent the prescribed error band of ±10% during the estimated film boiling phase of the immersion quenching process itself. It was, however, found that the temperature calculated in the center of a specimen fits this error band until reaching somewhere t < 6 s due to low presumed turbulence level in the domain. In addition, the explosion of the vapor phase after the body reaches the free surface of the quenchant has also been successfully tracked using the numerical simulation model proposed herein. The major novelty of the present research lies in the fact that a moving boundary problem has been successfully resolved in conjunction with, to a great extent, basic-principle-based heat and mass transfer in a turbulent flow conjugate heat transfer (CHT) numerical simulation using moderate computational resources. [ABSTRACT FROM AUTHOR]

Boiling conjugate heat transfer is an active field of research encountered in several industries, including metallurgy, power generation and electronics. This paper presents a computational fluid dynamics approach capable of accurately modelling the heat transfer and flow phenomena during immersion quenching: a process in which a hot solid is immersed into a liquid, leading to sudden boiling at the solid–liquid interface. The adopted methodology allows us to couple solid and fluid regions with very different physics, using partitioned coupling. The energy equation describes the solid, while the Eulerian two-fluid modelling approach governs the fluid's behaviour. We focus on a film boiling heat transfer regime, yet also consider natural convection, nucleate and transition boiling. A detailed overview of the methodology is given, including an analytical description of the conjugate heat transfer between all three phases. The latter leads to the derivation of a fluid temperature and Biot number, considering both fluid phases. These are then employed to assess the solver's behaviour. In comparison with previous research, additional heat transfer regimes, extra interfacial forces and separate energy equations for each fluid phase, including phase change at their interface, are employed. Finally, the validation of the computational approach is conducted against published experimental and numerical results. [ABSTRACT FROM AUTHOR]

During the immersion quenching process, severe temperature changes and significant temperature differences between the core and superficial area can give rise to high residual stresses within the aluminum alloy thick plate to cause subsequent machining distortion of the thin-walled part. Reducing the residual stress within the thick plate can effectively minimize the distortion in part. In this research, ABAQUS software was adopted to simulate the internal temperature and stress fields of thick plates of Al7055 alloy during the quenching and pre-stretching processes, sequentially and respectively. In addition, the x-ray residual stress measurement method was used to measure and characterize the surface residual stress of the plates. The results indicate that the medium temperature affects residual stress inside the thick plate significantly during the immersion quenching process. The level of which inside the plate gradually increases as the medium temperature decreases. Further, the pre-stretching treatment can effectively reduce residual stresses within the thick plate, and the residual stress level gradually decreases with the pre-stretching ratio increasing. The experimental results verify the feasibility of numerical simulation to predict the status of quenching stress in thick plates. Subsequently, a simulation study for material removal processes was carried out based on the above studies. The results reveal that the thin-walled part’s machining distortion degree improves as the raw thick plate’s initial quench residual stress level decreases.

This paper discusses a recently improved computational fluid dynamics (CFD)methodology for virtual experimental investigation of the heat treatment for cast aluminium parts. The immersion quenching process of the heated work piece in a sub-cooled liquid pool is handled by employing the Eulerian multi-fluid modeling approach, which is implemented with in the commercial CFD code AVL FIRE®. The applied heat and mass transfer rate is modeled based on a different boiling regime, which is controlled by the Leidenfrost temperature. The objective of the presented research is to present an updated quenching model by applying variable Leidenfrost temperatures. Furthermore, simulation results are compared with a vailable measurements for a wide variety of quenching scenarios involving immersion cooling of the step plate and real cylinder head with different solid parts' orientations. The temperature histories predicted by the presented model fit very well with the available experimental data at different monitoring locations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Inconel 600 probes showed simultaneous occurrence of three stages of quenching. [•] Spatially dependent heat flux transients were estimated. [•] The axial peak heat flux was modelled as a function of probe location. [•] Variation in radial peak heat flux indicated non-uniform nature of the wetting front. [Copyright &y& Elsevier]

In the present work, wetting kinematics of water based aluminium nanofluids having nanoparticle concentrations varying from 0·001 to 0·5 vol.-% during immersion quenching of Inconel 600 probe was investigated by measuring the contact resistance. The contact resistance between the quench probe and counter electrode during quenching indicated that the duration of the film of water vapour decreased with increasing nanoparticle concentration as well as absence of stable vapour film formation with 0·05, 0·1 and 0·5 vol.-% of nanoparticles. The phenomenon of a repeated wetting process was observed during quenching in nanofluids. Further, quenching in 0·1 and 0·5 vol.-% nanofluids indicated the formation of a nanoparticle porous layer and its deposition on the quench probe. The spreading behaviour was studied by measuring the dynamic contact angle of nanofluids droplets on Inconel 600 substrate. Contact angle measurement showed that the addition of aluminium nanoparticles did not have a significant effect on the relaxation of contact angle of water droplet. However, lower static contact angles were obtained for nanofluids indicating improved wetting. [ABSTRACT FROM AUTHOR]

Aluminum alloy thin sheets are widely used to produce light-weight high-strength components and the sheets are generally quenched before forming (Q-F) to improve the final mechanical properties of components. However, the distortion in quenching will significantly affect the quality and stability of the following forming process. In this study, the distortion behavior of 2219 aluminum alloy thin sheets and its forming mechanism in quenching process were investigated through experiments and finite element analysis (FEA). The results indicate that, the quenched thin sheets basically present three distortion modes, namely saddle-shape, shovel-shape and arch-shape. The distortion modes of the quenched thin sheets are determined by the bending modes of distortion zone which is the zone of the thin sheet near the water surface. When the bending mode is one-half sine wave, the quenching thin sheets always show saddle-shape. However, for the cases where the bending mode changes to three-half sine wave and the bending of distortion zone is suppressed, the quenching thin sheets show shovel-shaped and arch-shaped distortion modes, respectively. The reasons behind the variations of the bending mode are finally analyzed based on a buckling criterion under laterally constrained conditions. These results will provide an in-depth understanding of quenching distortion behavior and lay a basic guidance for controlling the distortion of thin sheets in quenching process. [ABSTRACT FROM AUTHOR]