Characteristic temperature scaled particle

Nuclealion and growth steps create particles under kinetics control following a reaction path of minimum activation energy under conditions imposed on the system (acidity, concentration, temperature), but the products are not necessarily tliermodynamically stable. Aging of the suspensions, which may take place over a very large time scale (hours, days or months), allows the system to tend towards or to reach stability) and this is why ageing is often associated with modifications of some physical or chemical characteristics of the particles. Some of the most frequently observed phenomena are described below. 

Third, a uniform temperature profile across the particle can be assumed considering the characteristic length scales and the heat transfer mechanisms. In support of this assumption, a typical Biot number, Bi = G- L k for a nanosized particle can be estimated to be on the order of 10 which means that the temperature variation within the particle is negligible. The characteristic length is... 

Glicksman and Farrell (1995) constructed a scale model of the Tidd 70 MWe pressurized fluidized bed combustor. The scale model was fluidized with air at atmospheric pressure and temperature. They used the simplified set of scaling relationships to construct a one-quarter length scale model of a section of the Tidd combustor shown in Fig. 34. Based on the results of Glicksman and McAndrews (1985), the bubble characteristics within a bank of horizontal tubes should be independent of wall effects at locations at least three to five bubble diameters away from the wall. Low density polyurethane beads were used to obtain a close fit with the solid-to-gas density ratio for the combustor as well as the particle sphericity and particle size distribution (Table 6). 

From the thermodynamic standpoint, the basic components of stars can be considered as photons, ions and electrons. The material particle gas (fermions) and the photon gas (bosons) react differently under compression and expansion. Put n photons and n material particles into a box. Let R be the size of the box (i.e. a characteristic dimension or scale factor). The relation between temperature and size is TR = constant for the photons and TR = constant for the particles. This difference of behaviour is very important in the Big Bang theory, for these equations show quite unmistakably that matter cools more quickly than radiation under the effects of expansion. Hence, a universe whose energy density is dominated by radiation cannot remain this way for long, in fact, no longer than 1 million years. 

---