Analogie entre le transfert de chaleur et le transfert de masse par sublimation d'un dépôt de naphtalène

¹ Ingénieur à la Section Thermique.
² Chef de la Section Thermique, Centre d'Etudes Nucléaires de Saclay.

Résumé

A heat and mass transfer analogy is frequently very useful for the investigation of local exchange Coefficient distributions. Forced sublimation of naphthalene in air is the technicque used here in studying convection phenomena in a bundle of rods lying parallel to the flow. Although this method undoubtedly offers material advantages over heated models it also suffers from the limitation that it cannot represent absolutely similar boundary conditions to those associated with thermal problems ; experience has shown, however, that in the simple case of a circular tube the results obtained are to within 5 per cent of the thermal data, with the mass transfer number D = (h/u) instead of the Margoulis number and the Schmidt number S = (u/rD)) instead of the Prandtl number. Experimental data on the relative variation of mass transfer, coefficients for a bundle of nineteen rods in a circular section duct are discussed and it is found that the transfer coefficients vary very much as the frictional velocities, though generally with slightly greater amplitudes. These results are then used for the boundary conditions in a heat calculation in which the fluid temperatures in each sub-channel are calculated with allowance for heat exchanges taking place throughout the cross-section. Considering the approximations involved and the amount of scatter in the measured comparative heat data this calculation method seems quite satisfactory.