| Journal: | Journal of the Brazilian Society of Mechanical Sciences and Engineering |
| Database: | PERIÓDICA |
| System number: | 000312295 |
| ISSN: | 1678-5878 |
| Authors: | Padet, J1 |
| Institutions: | 1Universite de Reims, Faculte des Sciences, Reims, Marne. Francia |
| Year: | 2005 |
| Season: | Ene-Mar |
| Volumen: | 27 |
| Number: | 1 |
| Pages: | 74-95 |
| Country: | Brasil |
| Language: | Inglés |
| Document type: | Artículo |
| Approach: | Experimental |
| English abstract | In nature, as well as within the human-made thermal systems, the time-variable regimes are more commonly encountered, if not always, than the permanent regimes. Nevertheless, studies in convection are still more frequent in the permanent regimes, undoubtedly due to the related difficulties in calculation in terms of time and cost of computation. One may distinguish two categories of time-dependent transfers: those which are due to external causes (variable boundary conditions) and those that are due to internal causes (sources of variable power, instabilities, turbulence), and the combination of these two types may also be encountered. In this presentation, we shall analyze some situations which belong to the first category. These are concerned with: - a group of boundary layer flows in forced, natural or mixed convection, where the wall is subjected to time-variable conditions in temperature or flux. - another group of fluid flows within ducts, in laminar mixed convection regime, where the entry conditions (mass flow rate, temperature) are time-dependent. The techniques of analysis are mainly extensions to the differential method and to the integral method of Karman-Polhausen in boundary layer flows, and the finite differences solution of the vorticity and energy equations for internal flows. The results presented in the transient state are caused by steps of temperature, heat flux or velocity, and in particular show the time evolution of the dynamic and thermal boundary layers, as well of the heat transfer coefficients. Three exa |
| Disciplines: | Ingeniería |
| Keyword: | Ingeniería mecánica, Termomecánica, Transferencia de calor |
| Keyword: | Engineering, Mechanical engineering, Thermomechanics, Heat transfer |
| Full text: | Texto completo (Ver PDF) |
