By using a non-Darcy model, they established the stability conditions for the marginal state without considering the possibility of oscillatory convection. Jou and Liaw investigated a similar problem of gravity driven thermal convection in a rotating porous layer subject to transient heating from below. They present stability curves for both monotonic and oscillatory instability. This possibility was explored by Friedrich for a non-Darcy model and by Vadasz for a Darcy model extended only to include the time derivative term. It should be pointed out that for a pure fluid (non-porous domain) convection sets in as an oscillatory instability for a certain range of Prandtl number values (Chandrasekhar ). Although the non-Darcy model considered included the time derivative in the momentum equation the possibility of convection setting-in as an oscillatory instability was not explicitly investigated by Patil and Vaidyanathan. The latter concluded that variable viscosity has a destabilising effect while rotation has a stabilising effect. Friedrich focused on the effect of Prandtl number on the convective flow resulting from a linear stability analysis as well as a non-linear numerical solution, while Patil and Vaidyanathan dealt with the influence of variable viscosity on the stability condition. The problem of a rotating porous layer subject to gravity and heated from below was originally investigated by Friedrich and by Patil and Vaidyanathan. PETER VADASZ, in Transport Phenomena in Porous Media, 1998 CORIOLIS EFFECT ON FREE CONVECTION DUE TO THERMAL BUOYANCY CAUSED BY GRAVITY FORCES These materials can be processed rapidly in standard rubber-processing equipment such as mills, internal mixers, extruders, and calenders. High-purity monomers are required since the polymerization of fluoroolefins is inhibited by a wide variety of substances. Great care must be exercised because of the potential toxicity and explosiveness of some of the monomers or monomer mixtures, particularly TFE and HFP. The product is sold in the form of pellets, chips, strips, or slabs. Centrifugation or coagulation and isolation of dry polymer by standard manufacturing techniques are the last steps in the continuous polymerization process.
In a continuous process, feeding of the ingredients and removal of polymer latex are continuous this requires a pressure-control valve to control the discharge of latex from the reactor. The aqueous emulsion polymerization is conducted by either batch or by continuous processes. Typical manufacturing conditions involve temperature ranges from 30 ☌ to 125 ☌, and pressure ranges from 0.35 MPa to 10.4 MPa. Fluorinated acid soap is used as an emulsifying agent. Commonly used initiators include organic or inorganic peroxide compounds, such as ammonium persulfate. Most of the fluoroelastomers typically are prepared by high-pressure, free radical, aqueous emulsion polymerization ( Patil 1999, Schroeder 1987).
Patil, in Encyclopedia of Materials: Science and Technology, 2001 3 Manufacturing
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