Showing papers by "Ephraim M Sparrow published in 1969"
225 citations
TL;DR: In this article, a flow visualization technique is employed whereby the flow pattern is made visible by local changes of colour of the fluid itself, the colour change being brought about by a change in pH.
Abstract: Experiments are performed to demonstrate the occurrence and explore the characteristics of a secondary flow superposed upon the natural convection main flow on an inclined plate A flow visualization technique is employed whereby the flow pattern is made visible by local changes of colour of the fluid itself, the colour change being brought about by a change in pH The secondary flow consists of longitudinal vortices or rolls distributed more or less periodically across the width of the plate The number of such vortices increases with the temperature difference between the surface and the ambient fluid, but appears to be relatively insensitive to the inclination angle of the plate The secondary flow results from the destabilizing effect of the buoyancy force component, which acts normal to the plate surface The longitudinal vortices are the first stage of the laminarturbulent transition process This is in contrast to the case of natural convection on a vertical plate, where the first stage of transition is Tollmien-Schlichting waves
139 citations
TL;DR: In this article, a general method of analysis is presented for determining the developing velocity field and pressure drop for laminar flow in the entrance region of ducts having arbitrary cross sections.
Abstract: A general method of analysis is presented for determining the developing velocity field and pressure drop for laminar flow in the entrance region of ducts having arbitrary cross sections. Application of the solution method is made to rectangular ducts and to triangular ducts. Available experimental data are compared with the analytical results and good agreement is found to prevail. Development characteristics for six ducts are brought together and compared, and various trends are identified.
55 citations
TL;DR: In this article, an analysis of the strongly coupled heat and mass transfer processes which result from sublimation of mass from the walls of a duct into a flowing gas, the latent heat being provided solely by convective transfer from the gas, is performed.
Abstract: An analysis is performed of the strongly coupled heat and mass transfer processes which result from sublimation of mass from the walls of a duct into a flowing gas, the latent heat being provided solely by convective transfer from the gas. The flow is assumed to be laminar and hydrodynamically developed. Results are given for the streamward variations of the bulk and wall temperatures and mass fractions, of the heat and mass transfer rates, and of the local heat transfer coefficient. Representative temperature and mass fraction profiles are also presented. Entrance lengths characterizing the near approach to fully developed conditions are tabulated. Comparisons are made of the present results (based on a parabolic velocity profile) with those based on a slug flow velocity profile. A subsidiary analysis using the Levěque model is also performed and the results compared with those of the principal solution.
12 citations
TL;DR: In this article, mutual dependent heat and mass transfer for laminar gas flow in a parallel-plate channel is investigated analytically, and the analysis of the problem requires simultaneous treatment of the energy and mass diffusion equations, with coupling provided by the boundary conditions.
Abstract: Mutually dependent heat and mass transfer for laminar gas flow in a parallel-plate channel is investigated analytically. Sublimation occurs at one of the channel walls, while the other wall is nonsubliming. Both walls are thermally insulated from the external environment. The analysis of the problem requires simultaneous treatment of the energy and mass diffusion equations, with coupling provided by the boundary conditions. Mathematical expressions are derived and numerical results are presented for various quantities that characterize the heat and mass transfer processes. Comparisons are made with the case of symmetric transfer (i.e., both walls actively participating). In general, unsymmetric transfer is found to slow down the axial development of the temperature and mass fraction fields.
On a fait une analyse du transfert de la chaleur et de la masse (deux facteurs inter-dependants dans le cas d'un ecoulement laminaire de gaz dans un canal a plateaux paralleles. La sublimation ne s'est faite que sur une paroi du canal; les deux parois etaient isolees au point de vue thermique du milieu externe. L'analyse du probleme a exige le traitement simultane des equations de diffusion d'energie et de masse, les conditions-limites formant un raccord. On a deduit des expressions mathematiques et presente des resultats numeriques pour differentes qunntites qui caracterisent les procedes de transfert de la chaleur et de la masse. On a fait des comparaisons avec le cas du transfert symetrique (ou les deux parois out une participation active). En general, on a trouve que le transfert asymetrique ralentissait le developpement axial des champs de temperature et de friction de masse.
2 citations