Transient conjugated heat transfer in fully developed laminar pipe flowsTransfert thermique conjugue variable dans des ecoulements laminaires etablis dans des tubesInstationäre konjugierte wärmeübertragung in vollentwickelten laminaren rohrströmungenнeycтaнoвившийcя coпpяж\̈yeнный тeплoпepeнoc пpи пoлнocтью paзвитoм лaминapнoм тeoeниИ в тpyбe

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Abstract

This study aims to numerically investigate the effects of conduction heat transfer in the pipe wall on the unsteady forced convective heat transfer in the flow in a long circular pipe resulting from a step change in uniform wall heat flux over a finite length of the pipe. Substantial influences are observed for the variations of Peclet number, radius ratio, conductivity ratio, and diffusivity ratio on the transient heat transfer characteristics. In particular, the wall-to-fluid heat capacity ratio is found to have a decisive impact on the unsteady heat transfer in the flow.

Résumé

On étudie numériquement les effets de la conduction thermique dans la paroi du tube sur le transfert convectif forcé par l'écoulement et résultant d'un changement échelon d'un flux de chaleur uniforme à la paroi, sur une longueur finie du tube. On observe des effets substantiels suivant les valeurs du nombre de Peclet, du rapport du rayon, des rapports de conductivité et de diffusivité, sur les caractéristiques du transfert thermique variable. En particulier, le rapport des capacités calorifiques a un effet important sur le transfert thermique variable dans l'écoulement.

Zusammenfassung

Das Ziel dieser Arbeit ist die numerische Untersuchung des Einflusses der Wärmeleitung in der Rohrwand auf den instationären Wärmeübergang bei erzwungener Konvektion in einem langen Kreisrohr. Dieser Einfluβ resultiert aus einer sprunghaften Änderung des Wärmestroms durch die Wand entlang eines endlichen Rohrabschnitts. Einen wesentlichen Einfluβ auf den instationären Wärmeübergang haben die Peclet-Zahl, das Radienverhältnis, das Verhältnis der Wärmeleitfähigkeiten und das Verhältnis der Temperaturleitfähigkeiten. Insbesondere hat das Verhältnis der Wärmekapazitäten von Wand und Fluid einen entscheidenden Einfluβ auf den instationären Wärmeübergang in der Strömung.

Реферат

ччиcлeннo иccлeдoвaнo влияниe кoндyктивнoгo пepeнoca тeплa в cтeнкe тpyбы нa нecтaциoнapный кoнвeктивный тeплoпepeнoc внyтpи длиннoй кpyглoй тpyбы пpи cтyпeнчaтoм измeнeнии oднopoднoгo тeплoвoгo пoтoкa нa yчacткe кoнeчнoй длины. oбнapyжeнo cyщecтвeннoe влияниe измeнeния чиcлa Пeклe, oтнoшeния paдиycoв, кoэффипиeнтoв тeплoпpoвoднocтeй и тeмпepaтypoпpoвoднocтeй нa xapaктepиcтики нeycтaнoвившeгocя тeплooбмeнa. B чacтнocти нaйдeнo. чтo oтнoшeниe тeплo\̈yeмкocтeй cтeнки и жидкocти oкaзывaeт cyщecтвeннoe влияниe нa нecтaциoнapный тeплooбмeн в пoтoкe.

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