Engineering topics
Publications and source records attributed to Bahrami, P. A..
An approach similar to those employed in the theories of lubrication and film condensation is applied to the problem of melting within a sphere. An approximate closed-form solution is obtained which yields relationships between the solid speed, position, and time. The results are compared with those obtained by Bareiss and Beer (1984) for the case of melting in a horizontal cylinder.
In the Stefan and Neumann problems fundamentally characterizing melting, unmolten portions of a solid undergoing phase changes within spherical containers are assumed to remain stationary. An approach to these issues that is related to the theories of lubrication and film condensation is presently employed in conjunction with an approximate, closed-form solution of melting within spheres. It is shown that a group of dimensionless parameters containing Prandtl, Archimides and Stefan numbers can describe the melting process. Also given are the results of fundamental heat transfer experiments performed on the melting of a phase-change medium in a spherical shell.
Fluid-dynamic and capillary forces can be used to form nearly perfect, very small spherical shells when a liquid that can solidify is passed through an annular die to form an annular jet. Gravity and certain properties of even the most ideal materials, however, can cause slight asymmetries. The primary objective of the present work is the control of this shell formation process in earth laboratories rather than space microgravity, through the development of facilities and methods that minimize the deleterious effects of gravity, aerodynamic drag, and uncontrolled cooling. The spherical shells thus produced can be used in insulation, recyclable filter materials, fire retardants, explosives, heat transport slurries, shock-absorbing armor, and solid rocket motors.
System for storing large amounts of heat per unit volume comprises encapsulated sealed pellets of phase-change materials dispersed and suspended in inert fluid-transport medium.
A new concept for both transport and storage of heat at high temperatures and heat fluxes is introduced and the first steps in analysis of its feasibility is taken. The concept utilizes the high energy storage capability of materials undergoing change of phase. The phase change material, for example a salt, is encapsulated in corrosion resistant sealed pellets and transported in a carrier fluid to heat source and storage. Calculations for heat transport from a typical solar collector indicate that the pellet mass flow rates are relatively small and that the required pumping power is only a small fraction of the energy transport capability of the system. Salts and eutectic salt mixtures as candidate phase change materials are examined and discussed. Finally, the time periods for melting or solidification of sodium chloride pellets is investigated and reported.