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Specific heat pressure dependence

Comparing this with equation (A.2.2), it is seen to predict exactly the same dependence of che effusion rate on pressure and temperature. Furthermore, Che ratio of specific heats y depends relatively weakly on che nature of the gas, through its molecularity, so che prediction chat dV/dt 1/M, which follows from equation (A-2.2) and agrees with Graham s results, is not markedly inconsistent with equation (A.2.3) either. [Pg.188]

The specific heat represents the amount of energy required to raise a unit mass one unit in temperature. For gases, the specific heat differs depending on whether the gas is allowed to do work by expanding against an atmosphere (constant pressure definition, c, ) or is constrained within a volume (constant volume definition, c ). Examples of units of c, and are J/g K or Btu/lbm °F. If we wish to express this on a molar basis we shall use the upper case that is, or Q having units of J/mol K or Btu/lbmol °F. [Pg.78]

Although there have been few data collected, postshock temperatures are very sensitive to the models which specify y and its volume dependence, in the case of the Gruneisen equation of state (Boslough, 1988 Raikes and Ahrens, 1979a Raikes and Ahrens, 1979b). In contrast, the absolute values of shock temperatures are sensitive to the phase transition energy Ejp of Eq. (4.55), whereas the slope of the versus pressure curve is sensitive to the specific heat (see, e.g.. Fig. 4.28). [Pg.105]

Equivalent hydrostatic pressure Pressure dependence of Curie temperature Change in compressibility Change in specific heat Change in thermal expansion... [Pg.121]

Compressibility and pressure dependence of Curie temperature are directly measured changes in specific heat and thermal expansion are calculated from the Ehrenfest relation. [Pg.121]

Whereas heat capacity is a measure of energy, thermal diffusivity is a measure of the rate at which energy is transmitted through a given plastic. It relates directly to processability. In contrast, metals have values hundreds of times larger than those of plastics. Thermal diffusivity determines plastics rate of change with time. Although this function depends on thermal conductivity, specific heat at constant pressure, and density, all of which vary with temperature, thermal diffusivity is relatively constant. [Pg.398]

The specific heat of a substance must always be defined relatively to a particular set of conditions under which heat is imparted, and it is here that the fluid analogy is very liable to lead to error. The number of heat units required to produce unit rise of temperature in a body depends in fact on the manner in which the heat is communicated. In particular, it is different according as the volume or the pressure is kept constant during the rise of temperature, and we have to distinguish between specific heats (and also heat capacities) at constant volume and those at constant pressure, as well as other kinds to be considered later. [Pg.7]

The dependence of gas specific heats on temperature was discussed in Chapter 3, Section 3.5. For a gas in the ideal state the specific heat capacity at constant pressure is given by ... [Pg.325]

The simplicity and accuracy of such models for the hydration of small molecule solutes has been surprising, as well as extensively scrutinized (Pratt, 2002). In the context of biophysical applications, these models can be viewed as providing a basis for considering specific physical mechanisms that contribute to hydrophobicity in more complex systems. For example, a natural explanation of entropy convergence in the temperature dependence of hydrophobic hydration and the heat denaturation of proteins emerges from this model (Garde et al., 1996), as well as a mechanistic description of the pressure dependence of hydrophobic... [Pg.316]

The expansion factor Y depends on the pressure drop X, the dimensions (clearance) in the valve, the gas specific heat ratio k, and the Reynolds number (the effect of which is often negligible). It has been found from measurements (Hutchison, 1971) that the expansion factor for a given valve can be represented, to within about 2%, by the expression... [Pg.328]

Hence the heat transport, in this case, depends on the dimension and shape of the liquid container. As we can see in Fig. 2.13, the thermal conductivity (and the specific heat) of liquid 4He decreases when pressure increases and scales with the tube diameter. At temperatures below 0.4 K, the data of thermal conductivity (eq. 2.7) follow the temperature dependence of the Debye specific heat. At higher temperatures, the thermal conductivity increases more steeply because of the viscous flow of the phonons and because of the contribution of the rotons. [Pg.68]

The heat capacity of a substance can differ, depending on which are the variables held constant, with the quantity being held constant usually being denoted with a subscript. For example, the specific heat at constant pressure is commonly denoted cP, while the specific heat at constant volume is commonly denoted cv ... [Pg.71]

A special care is to be devoted to the control that all the parts of the apparatus have reached the desired temperature when parts remain at higher temperature, due to the high value of the specific heat, the cooling only by radiative exchange is usually impossible. To open a gas heat switch, several hours of pumping are usually necessary to reduce the pressure to a value suitable for the thermal isolation. An insufficient pumping leads to a time-dependent heat leak due to desorption and condensation of the residual gas at the coldest surfaces. [Pg.107]

The temperature profile of a planetary atmosphere depends both on the composition and some simple thermodynamics. The temperature decreases with altitude at a rate called the lapse rate. As a parcel of air rises, the pressure falls as we have seen, which means that the volume will increase as a result of an adiabatic expansion. The change in enthalpy H coupled with the definition of the specific heat capacity... [Pg.212]

Any characteristic of a system is called a property. The essential feature of a property is that it has a unique value when a system is in a particular state. Properties are considered to be either intensive or extensive. Intensive properties are those that are independent of the size of a system, such as temperature T and pressure p. Extensive properties are those that are dependent on the size of a system, such as volume V, internal energy U, and entropy S. Extensive properties per unit mass are called specific properties such as specific volume v, specific internal energy u, and specific entropy. s. Properties can be either measurable such as temperature T, volume V, pressure p, specific heat at constant pressure process Cp, and specific heat at constant volume process c, or non-measurable such as internal energy U and entropy S. A relatively small number of independent properties suffice to fix all other properties and thus the state of the system. If the system is composed of a single phase, free from magnetic, electrical, chemical, and surface effects, the state is fixed when any two independent intensive properties are fixed. [Pg.17]

It is most important to know in this connection the compressibility of the substances concerned, at various temperatures, and in both the liquid and the crystalline state, with its dependent constants such as change of. melting-point with pressure, and effect of pressure upon solubility. Other important data are the existence of new pol3miorphic forms of substances the effect of pressure upon rigidity and its related elastic moduli the effect of pressure upon diathermancy, thermal conductivity, specific heat capacity, and magnetic susceptibility and the effect of pressure in modif dng equilibrium in homogeneous as well as heterogeneous systems. [Pg.8]

This maximum velocity depends on the molecular mass Mg, the specific heat y, and the stagnation temperature Tg. The velocity increases as y and Mg decrease, and as To increases. Based on Eq. (1.52), a simplified expression for mass flow rate in terms of the nozzle throat area Aj (= A ) and the chamber pressure (= pg) is given by... [Pg.14]

Experiments indicate that the smooth variations of thermodynamic properties (e.g., V, Ky, and the specific heat at constant pressure Cp) with temperature are intermpted by the kinetic process of glass formation, leading to cooling rate dependent kinks in these properties as a function of temperature. In our view, these kinks cannot be described by an equilibrium statistical mechanical theory, but rather are a challenge for a nonequilibrium theory of glass formation. Nonetheless, some insight into the origin of these kinks and the qualitative... [Pg.181]

Specific heat of evaporation. Defined as the quantity of heat in joules required to evaporate 1 kg of a liquid at boiling temperature. The specific heat of evaporation is dependent upon pressure. [Pg.355]

All known gases, called real gases, are nonideal, which means that they do not obey the fundamental gas laws and the equation pv =RT [See under "Detonation (and Explosion), Equations of State , in this Volume]. Specific heats of "real gases vary with temperature and the product composition depends upon both temperature and pressure. [Pg.351]


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See also in sourсe #XX -- [ Pg.382 ]




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