Wyniki wyszukiwania - BazTech

1

Determination of surface location between two sub-domains using the temperature distribution on the external surface

Freus K., Freus S.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2012

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Vol. 11, nr 4

35-42

EN

In the paper two sub-domains which are in thermal contact are considered. The temperature field in these domains is described by the system of two Laplace equations supplemented by the boundary conditions. The position of surface between sub-domains is unknown. Additional information necessary to solve the identification problem results from a knowledge of external surface temperature distribution. The direct problem is solved using the boundary element method. To solve the inverse problem formulated the gradient method is applied. In the final part of the paper the results of computations are shown. The algorithm proposed here can be used, among others, in the medical practice (e.g. in burns therapy).

2

A new method for determination of thermal contact resistance of a fin-to-tube attachment in plate fin-and-tube heat exchangers

Taler D., Cebula A.

Chemical and Process Engineering

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2010

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Vol. 31, z. 4

839-855

EN

Plate fin-and-tube heat exchangers are fabricated by inserting oval tubes through sheet metal strips with stamped holes and then expanding the tubes slightly to cause pressure at the tube-to-strip contacts. The gap between the fin base and the outer tube surface may be filled with air or corrosion products causing a decline in the ability of plate fins to transfer heat. The contact resistance must be accounted for in the design and performance calculations of heat exchangers. In this paper, the thermal contact resistance of the fin-to-tube attachment is estimated from the condition that the dimensionless correlations for the Colburn j factors obtained from two different methods are in good agreement. The former method is based on the experimental data, while the latter one on the CFD simulation of the flow and heat transfer in a heat exchanger.

PL

Cieplny opór kontaktowy między zewnętrzną powierzchnią rury a podstawą żebra zmniejsza strumień ciepła wymieniany między czynnikami w wymienniku ciepła. Wynika to z wpływu, jaki wywiera opór kontaktowy na temperaturę żebra. Gdy ciepło jest przekazywane od gorącego gazu przepływającego na zewnątrz do chłodnej cieczy przepływającej wewnątrz rur to w warunkach występowania oporu cieplnego między zewnętrzną powierzchnią rury a podstawą żebra średnia temperatura żebra jest znacznie wyższa w porównaniu z żebrem, które jest idealnie połączone z rurą i opór cieplny między nim a rurą nie występuje. Gdy ciepło jest przekazywane od czynnika gorącego przepływającego wewnątrz rur do chłodniejszego gazu przepływającego na zewnątrz, opór cieplny sprawia, że żebra są chłodniejsze. Zaproponowano nową metodę eksperymentalno-numeryczną wyznaczania cieplnego oporu kontaktowego występującego między zewnętrzną powierzchnią rury a podstawą żebra. Zastosowanie metody zilustrowano na przykładzie wyznaczania oporu kontaktowego w dwubiegowym wymienniku lamelowym o dwóch rzędach rur.

3

Thermal contact formulation based on the mortar method

de Sa C., Gregoire S., Moreau P., Lochegnies D.

Computer Methods in Materials Science

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2006

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Vol. 6, No. 3-4

171-177

EN

A new approach to model heat transfer between two bodies in mechanical contact is presented. The proposed method is inspired on the “mortar method”, more frequently used for mechanical contact, and its development was triggered by the necessity of correctly modelling the heat transfer between glass and moulds in glass forming processes due to the large dependence of glass viscosity on temperature. Typically, when modelling these processes with the finite element method a moving mesh, attached to the deforming glass, deals with the mechanical and thermal problems in the glass. In the moulds due to the low pressures involved only the heat transfer problem is usually addressed and consequently the same mesh is kept throughout the modelling process. In the proposed method a virtual interface, the “mortar”, is established between the two bodies to deal with the heat transfer between them. A master/slave strategy, combined with a penalty formulation, is used. Interface elements are established in the discretisation of the “mortar” surface, in which the nodes are projection of the interface nodes of the two bodies. The heat flux between the two bodies is obtained from the interpolation of the temperatures of the two bodies at the interface and the heat transfer coefficient may be evaluated from the contact pressure and viscosity on the slave body. As a result a more effective thermal contact solution is obtained and dependence on the chosen meshes and spurious oscillations, which are typical in standard penalty formulations, are avoided.