Transfert thermique à travers une interface de contact intermittent en régime périodique établi

Dans cet article, on présente un modèle unidirectionnel pour décrire le transfert thermique à travers une interface de contact intermittent en régime thermique périodique établi. Le champ de température et le flux transféré sont gouvernés par les paramètres d’intermittence, à savoir la fréquence d’intermittence et le coefficient de partage de la période. Ce dernier est défini comme étant le rapport de la fraction de période durant laquelle prévaut le contact sur la durée de la période. On montre que l’intermittence du contact introduit au niveau de l’interface une pseudo résistance thermique dite la résistance d’intermittence de contact dont la valeur peut être très appréciable. La résistance d’intermittence de contact varie de façon monotone décroissante suivant l’effusivité harmonique des matériaux en contact, de la fréquence d’intermittence et du coefficient de partage de la période.Mots clés: modélisation; conduction; contact intermittent; pseudo résistance de contact; résistance de contact; couplage de matériaux. In this paper, we present one-dimensional model to describe the thermal transfer through an interface of intermittent contact in the case of a thermal periodic established regime. The field of temperature and transferred flux are governed by the parameters of intermittency. The periodic established regime is characterised by two fundamental parameters: the period (τ) and the sharing coefficient period (γ), represented by the fraction of period during which the solid-solid there is contact. We showed that the intermittency of the contact introduces a pseudo thermal resistance (RIC) definite starting from the average thermal parameters at the interface. It is noted the thermal resistance of intermittent contact and present of the very appreciable values. It is monotonous decreasing according to the harmonic effusivity of materials in contact, the frequency and the sharing coefficient period.Keywords: modeling; conduction; intermittent contact; pseudo thermal resistance; resistance of contact; materials coupl

Comparison of Flow Fields in an agitated Tank for cooling of metallic piece by quenching process

During quenching process, metallurgical transformations and field of residual stresses are controlled by the cooling speed of the metallic piece. It is obvious that agitation of the bath matters thus all the industrial processes are using agitated bath in the quenching process. Actually the first role of the agitation is removing the vacuum film from the vicinity of the metallic piece. This agitation supposedly also contributes to the enhancement of convective heat coefficient, however the enhancement depends on the size and properties of the metallic piece. It is shown that the cooling process is predominated by convection in the cases of massive and/or resistive metallic pieces (Biot number higher that 10), by contrast, in the cases of thin and/or very conductive pieces, boiling is the main cooling phenomenon. This study focuses on the characterization of the fluid flow depending on the agitation system which can be a pump or a turbine. It is shown that those flows are drastically different. So the results of this study should help in better designing of the agitation systems considering the metallic piece to be treated. 

Modeling to the heating of a silicon thin film on a glass substrate during a cw argon laser crystallization process

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