Temperature effects specific heat

Fig. 11. Effective specific heat v. Temperature in a two-bed regenerative cycle...

A new circumstance arises in the transition from one residence time to another. The accompanying change in the effective specific heat will lead to a change in the maximum temperature achievable for complete consumption, i.e., will be equivalent to a continuous change in the heat effect. 

Efficiency of starch dispersion can be further improved when an excess quantity of steam is used97 or when the starch is held under pressure in a retention device (tank or coil) before discharge to the atmosphere. Both processes require a flash chamber (cyclone) to remove excess steam and steam relieved by the pressure drop. Excess steam refers to a multiple of the quantity required to reach target temperature and pressure. The quantity of saturated steam to reach a target temperature can be calculated from its heat content, the slurry temperature, the specific heats of starch and water, and the enthalpy of starch gelatinization. The action of excess steam in the dispersion zone between the jet and back-pressure valve causes a shear effect that enhances disintegration of the starch granules. In many applications, a three-fold excess of steam is used. 

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. 

In concluding this section, we emphasize an amazing fact that the internal mathematical structure of the JT center determines the magnitude of the polaron effective mass. This implies that there will be an intrinsic difference in w between the manganese oxides Lai- Sr MnOs with eg electrons and the titanium ones Lai xSr cTi03 with t2g electrons, as may be observed by the difference in the transport mass or the T-linear coefficient in the low-temperature electronic specific heat Cv(T) [101]. The experimental result on Cv(T) obtained by Tokura s group [106] may be relevant to this issue. 

The DSC is widely used to measure the glass-rubber transition temperature (Tg-value), which is an important parameter for polymer characterisation. The Tg-value represents the temperature region at which the (amorphous phase) of a polymer is transformed from a brittle, glassy material into a tough rubberlike liquid. This effect is accompanied by a step-wise increase of the DSC heat flow/temperature or specific heat/ temperature curve. Enthalpy relaxation effects can hamper the... 

FIGURE 27.1 Schematic diagram of calorimeter. (From Viranichai, S., Effect of moisture content and temperature on specific heat of wheat, MSc dissertation (unpublished). Department of Agricultural Engineering, University of Manitoba, Winnipeg, Manitoba, Canada, 1971. With permission.)... 

Figure 4.17 Effective specific heat capacity of virgin and char materials as a function of temperature (normalized with respect to initial mass of sample) from DSC and modeling [21]. (With permission from Elsevier.)...

Researches of Eucken and his co-workers on ethylene have in fact afforded very striking confirmation of this concept. They deduce from the effect of temperature on specific heat a torsional or turning oscillation of fairly high frequency (750 cm - 10 per sec.) so that the molecule represents a highly impeded one dimensional oscillator whose properties have been studied by Teller and Weigert. Comparison of measurement and theory shows that the barrier of potential which has to be scaled in the transition from cis- to trans-form, lies far above kT] on this depends the stability of the two isomers and the possibility of isolating them by the methods of synthetic organic chemistry. 

The experimental values for the low-temperature electronic specific heat coefficient 7 and equivalently the thermal effective mass mt are usually lai er than the theoretical values of... 

The method of DSC is based on measuring the very small thermal effects produced during thermal processes and is recommended as well suited for determining the effect of temperature on specific heat [38,42]. In the DSC method, any gain or loss of thermal energy is recorded as the equipment warms the... 

The other class of formulations of the FEM is based on the definition of an effective specific heat. This results in the inclusion of the latent heat effect in the capacitance matrix. There are a number of ways in which this can be provided for. Each of these methods makes use of an enthalpy temperature curve, for example. 

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