Specific heat dielectrics Table

Table I. AT Values of Two Homologous Series, vith Specific Heat and Dielectric Constants...

Table VI summarizes the effect of heating medium on the loss of acids after 3 minutes of microwave heating. Loss of volatile acids varied widely dependent on the microwave medium. Acetic and caproic acids had losses ranging from 20-80% and 0-73%, respectively, depending on medium composition. The dielectric property, specific heat, or other physical/chemical properties of individual flavor compounds can provide valuable insight into the potential behavior of these compounds during the microwave process. The dielectric property of the total food system and the affinity of the flavor compound for the microwave medium, however, were primarily responsible for the behavior of these flavor compounds during microwave heating.

This table summarizes the best available values of the density, specific heat capacity at constant pressure (Cp, vapor pressure, viscosity, thermal conductivity, dielectric constant, and surface tension for liquid water in the range 0 — 100 °C. All values (except vapor pressure) refer to a pressure of 100 kPa (1 bar). The temperature scale is IPTS-68. 

The dielectric constant and thermal conductivity decrease with increasing temperature, whereas the specific heat increases. The thermal conductivities, cubic expansion coefficients, dielectric constants, and electrical conductivities of various solvents are listed in Table 11. Critical data of solvents and the technical use of supercritical liquids are described in [14.82]. 

In equations (5)-(8), i is the molecule s moment of Inertia, v the flow velocity, K is the appropriate elastic constant, e the dielectric anisotropy, 8 is the angle between the optical field and the nematic liquid crystal director axis y the viscosity coefficient, the tensorial order parameter (for isotropic phase), the optical electric field, T the nematic-isotropic phase transition temperature, S the order parameter (for liquid-crystal phase), the thermal conductivity, a the absorption constant, pj the density, C the specific heat, B the bulk modulus, v, the velocity of sound, y the electrostrictive coefficient. Table 1 summarizes these optical nonlinearities, their magnitudes and typical relaxation time constants. Also included in Table 1 is the extraordinary large optical nonlinearity we recently observed in excited dye-molecules doped liquid... 

The thermal and dielectric properties of several composite systems are shown in Table 4. Note that the thermal expansion, conductivity, and specific heat all vary by approximately a factor of two over the range of temperature from 23°C to 1000°C. 

This book contains tables of the properties of water and steam from 0 to 800 and from 0 to 1000 bar which have been calculated using a set of equations accepted by the members of the Sixth International Conference on the Properties of Steam in 1967. Properties which are tabulated include the pressure, specific volume, density, specific enthalpy, specific heat of evaporation, specific entropy, specific isobaric heat capacity, dynamic viscosity, thermal conductivity, the Prandtl number, the ion-product of water, the dielectric constant, the isentropic exponent, the surface tension and Laplace coefficient. Also see items [43] and [70]. 

ELDAR contains data for more than 2000 electrolytes in more than 750 different solvents with a total of 56,000 chemical systems, 15,000 hterature references, 45,730 data tables, and 595,000 data points. ELDAR contains data on physical properties such as densities, dielectric coefficients, thermal expansion, compressibihty, p-V-T data, state diagrams and critical data. The thermodynamic properties include solvation and dilution heats, phase transition values (enthalpies, entropies and Gibbs free energies), phase equilibrium data, solubilities, vapor pressures, solvation data, standard and reference values, activities and activity coefficients, excess values, osmotic coefficients, specific heats, partial molar values and apparent partial molar values. Transport properties such as electrical conductivities, transference numbers, single ion conductivities, viscosities, thermal conductivities, and diffusion coefficients are also included. 

The differences between the main types of polysulphone are quite small. The polyethersulphones (Type III in Table 21.3) have markedly better creep resistance at elevated temperatures, e.g. 150°C, significantly higher heat distortion temperatures and marginally superior room temperature meehanical properties than the Type II materials. They also exhibit higher water absotption, dielectric constant and specific gravity. 

The energy quantum (0.0016 eV) of the microwave irradiation is totally inadequate for exciting atom-atom bonds or specific parts of a molecule and hence cannot induce chemical reactions, as opposed to ultraviolet or infrared radiation (Table 25.1). When molecules rotate in a matrix, they generate heat by friction. The amount of heat generated by a given reaction mixture is a complex function of its dielectric property, volume, geometry, concentration, viscosity, and temperature. Thus, two samples irradiated at the same power level for the same period of time will most likely end up with rather different final temperatures. 

The chemical and therefore structural nature of the polymer determines Tg. For most commercial polymers, values lie in the range — 100 °C to 250 °C as illustrated in Table 1.1. The value can be >250°C (e.g. in thermosets) but decomposition often occurs before it is reached. Tg can be determined by any technique which shows a change in a particular property of the polymer with temperature, e.g. density, modulus, heat capacity, refractive index, dielectric loss, X- and j8-ray adsorption, gas permeability, proton and NMR. The value of Tg can be obtained from plots of the magnitude of this property against temperature and is indicated by a break in linearity. Figure 1.4 shows modulus (i.e. strength) v. temperature and Figure 1.5 specific volume v. temperature for a typical polymer. 

It heis long been established that a dielectric material, such as many types of ceramics, can be heated with energy in the form of high frequency electromagnetic waves. The frequency range used for microwave heating lies between 400 MHz and 40 GHz, however the allowed frequencies are restricted to distinct bands which have been allocated for Industrial, Scientific and Medical (ISM) use, as shown in Table 1. The principal frequencies are centred at 433 MHz, 915 MHz (896 MHz in the UK) and 2450 MHz since specific industrial equipment can be readily purchased. 

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