Particles specific heat determination

Specific gravity is the most critical of the characteristics in Table 3. It is governed by ash content of the material, is the primary determinant of bulk density, along with particle size and shape, and is related to specific heat and other thermal properties. Specific gravity governs the porosity or fractional void volume of the waste material, ie,... 

Thus, it is not the absolute value of D, but its ratio with k that determines the character of the phenomena. Convection blurs the effect in convective motion the particles of gas which carry quantities of material and heat are in the ratio of the concentration to the product of the specific heat and temperature, which corresponds to equality of the effective (related to the gas motion) coefficients of diffusion and thermal diffusivity. In all cases radiation from the surface of the catalyst lowers its temperature Tr. 

Specific Heat—The specific heat of particles is determined by heating a given weight of a sample to nearly 100 deg C in a steam bath, and quickly stirring the hot particles into the water in a calorimeter. The temperature rise may thus be determined and the specific heat obtained from this observation and the known masses involved. Most soils, whether loams, sands, or clays, have specific heats ranging from 0.15 to 0.20 cal per g per deg C. 

Duration of a cycle of HHP operation is defined as time required for reaction hydrogenation/dehydrogenation in pair hydride system. This time determines heat capacity of HHP. Duration of a cycle depends on kinetics of hydrogenation reactions, a heat transfer between the heated up and cooling environment, heat conductivities of hydride beds. Rates of reactions are proportional to a difference of dynamic pressure of hydrogen in sorbers of HHP and to constants of chemical reaction of hydrogenation. The relation of dynamic pressure is adjusted by characteristics of a heat emission in beds of metal hydride particles (the heat emission of a hydride bed depends on its effective specific heat conductivity) and connected to total factor of a heat transfer of system a sorber-heat exchanger. The modified constant of speed, as function of temperature in isobaric process [1], can characterize kinetics of sorption reactions. In HHP it is not sense to use hydrides with a low kinetics of reactions. The basic condition of an acceptability of hydride for HHP is a condition of forward rate of chemical reactions in relation to rate of a heat transmission. 

According to Violle,1 the temperature of the positive carbon point and of the carbon particles in the voltaic arc equals the evaporation temperature of carbon. This was determined by breaking off the incandescent tip of the carbon and dropping it into a calorimeter. One gram carbon requires 1600 cal. to heat it from 0° up to its evaporation temperature. As 300 cal. are necessary to heat it from 0° to 1000°, 1300 cal. remain for raising the temperature from 1000° to x°, if x is the evaporation temperature of carbon. If we take the specific heat of carbon at 0.52, then 1300 cal. represent 2500° more, so that the evaporation temperature of carbon, x and the hottest parts of the luminous arc, equal 35000.2... 

Specific heats of metals and hydrides are easily determined and typically fall in the range of 0.1-0.2 cal/g°C. Thermal conductivity is a little more difficult to determine. The conductivity of the metal or hydride phase is not sufficient the effective conductivity of the bed must be determined. This depends on alloy, particle size, packing, void space, etc. Relatively little data of an engineering nature is now available and must be generated for container optimization. Techniques to improve thermal conductivity of hydride beds are needed. As pointed out earlier, good heat exchange is the most important factor in rapid cycling. 

The recommended method [29] for the determination of the thermal diffusivity of individual kernels is to calculate it from experimentally measured values of the thermal conductivity of kernel material, specific heat, and kernel (particle) density—the so-called indirect method. The method may lead to approximate results with a relative error, which is difficult to estimate in respect to a true (real) value, which can only be determined by direct measurements. The results of thermal properties for wheat and corn [44] and for single soybeans [59] confirm the above. 

The performance of an extruder is determined as much by the characteristics of the feedstock as it is by the machine. Feedstock properties that affect the extrusion process inciude buik properties, meit flow properties, and thermal properties. Important buik flow properties are the buik density, compressibility, particle size, particle shape, external and internal coefficient of friction, and agglomeration tendency. Important melt flow properties are the shear and eiongational viscosity as a function of strain rate and temperature. The commonly used melt indexer provides only limited information on the meit viscosity. Important thermal properties include the specific heat, the glass transition temperature, the crystalline melting point, the latent heat of fusion, the thermal conductivity, the density, the degradation temperature, and the induction time as a function of temperature. 

In a similar way, the mechnical reactor configuration can be specified, or built in specifications for various types of reactors can be sued. With the sued of optional data groups it is possible to specify interbed cooling, to include calculation of lower (feed effluent) heat exchanger, to carry out an optimization of inlet temperature(s) to the catalyst bed(s), to calculate required catalyst volume to obtain a specified conversion, etc. As a further important feature it is possible to include -by specifying an optional data group- calculation of diffusion restrictions in the catalyst particles and to determine the effectiveness factor at each point in the catalyst bed. 

Generally, a particle in a particle—fluid flow system can have two types of motion translational and rotational, which are determined by Newton s second law of motion. The corresponding governing equations for particle i with radius R, mass m moment of inertia I and specific heat capacity Cp j can be written as ... 

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