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Adiabatic process calculation

In this chapter, we look at the techniques known as direct, or on-the-fly, molecular dynamics and their application to non-adiabatic processes in photochemistry. In contrast to standard techniques that require a predefined potential energy surface (PES) over which the nuclei move, the PES is provided here by explicit evaluation of the electronic wave function for the states of interest. This makes the method very general and powerful, particularly for the study of polyatomic systems where the calculation of a multidimensional potential function is an impossible task. For a recent review of standard non-adiabatic dynamics methods using analytical PES functions see [1]. [Pg.251]

In an ambitious study, the AIMS method was used to calculate the absorption and resonance Raman spectra of ethylene [221]. In this, sets starting with 10 functions were calculated. To cope with the huge resources required for these calculations the code was parallelized. The spectra, obtained from the autocorrelation function, compare well with the experimental ones. It was also found that the non-adiabatic processes described above do not influence the spectra, as their profiles are formed in the time before the packet reaches the intersection, that is, the observed dynamic is dominated by the torsional motion. Calculations using the Condon approximation were also compared to calculations implicitly including the transition dipole, and little difference was seen. [Pg.309]

We have seen how to calculate q for the isochoric and isobaric processes. We indicated in Chapter 1 that q = 0 for an adiabatic process (by definition). For an isothermal process, the calculation of q requires the application of other thermodynamic equations. For example, q can be obtained from equation (2.3) if AC and w can be calculated. The result is... [Pg.56]

The conditions existing during the adiabatic flow in a pipe may be calculated using the approximate expression Pi/ = a constant to give the relation between the pressure and the specific volume of the fluid. In general, however, the value of the index k may not be known for an irreversible adiabatic process. An alternative approach to the problem is therefore desirable.(2,3)... [Pg.170]

For multicomponent systems with boiling range greater than 80°C, a single adiabatic flash calculation to 80 to 90 percent of the inlet pressure P0 yields the two-phase specific volume oI at pressure P1 and co is calculated from (Nazario and Leung, Sizing Pressure Relief Valves in Flashing and Two-Phase Service An Alternative Procedure, J. Loss Prev. Process lnd. 5(5), pp. 263-269, 1992)... [Pg.79]

Adiabatic cracking reactor, 10 617-618 Adiabatic decomposition, of hydrogen peroxide, 14 61-62 Adiabatic dehydrogenation, 23 337 Adiabatic dehydrogenation unit, 23 339 Adiabatic evaporation, general separation heuristics for, 22 319 Adiabatic flame temperature, 12 322 Adiabatic flash calculation, 24 681 Adiabatic nitration process, 17 253—255 Adiabatic pressure-reducing valve,... [Pg.17]

Detonation (and Explosion), Temperature Developed On. It may be defined as the maximum temperatures developed on detonation and explosion and must not be confused with Detonation (and Explosion) Temperature described in previous item A. Calculation of Temperature of Detonation (or Explosion). The oldest and simplest method is based on the assumption that expln is an adiabatic process taking place at constant volume and that the heat evolved (Qv), is used exclusively for heating the products of expln. Another assumption is that temp can be calcd by. dividing the heat of expln by specific heats of the products of expln ... [Pg.589]

The entropy, Spontaneous vs non-spontaneous, Reversible and irreversible processes, Calculation of entropy changes (Isothermal, isobaric, isochoric, adiabatic), Phase changes at equilibrium, Trouton s rule, Calculation for irreversible processes... [Pg.297]

We have therefore shown that adiabatic surfaces can be said to cross off the real coordinate axes, and indeed if the classical equations of motion are solved in complex coordinate space then it is possible to simulate non-adiabatic processes. This can be considered as the basis of the Stuckelberg semi-classical approach to non-adiabatic transitions in atom-atom collisions (64) and it has been recently extended to more degrees of freedom (65). Moreover the actual form of potential surfaces in the complex plane has been obtained by direct calculation (66). [Pg.118]

Step 3 Guess Ml and find AH3 solution from Figure 12.14. Calculate AH for process. Continue to guess Ml until AH =0 for adiabatic process. [Pg.454]

Thus, the model incorporating the direct hole trapping by adsorbed dichloroacetate molecules, which has been proposed by Bahnemann and co-workers, appears to be probable [7]. Moreover, calculations using the Marcus electron transfer theory for adiabatic processes which result in a reorientation energy of 0.64 eV suggest that also in the case of SCN- the hole transfer occurs in the adsorbed state [7]. [Pg.194]

A design for purifying helium consists of an adiabatic process that splits a helium stream containing 30-mole-percent methane into two product streams, one containing 97-mole-percent helium and the other 90-mole-percent methane. The feed enters at 10 bar and 117 C the methane-rich product leaves at 1 bar and 27 C the helium-rich product leaves at 50°C and IS bar. Moreover, wort is produced by the process. Assuming helium an ideal gas with CP = (5/2)1 and methane an ideal gas with CP = (9/2)/ , calculate the total entropy change of the process on the basis of 1 mol of feed to confirm that the process does not violate the second law. [Pg.169]

Consequently, the electronic transition probabilities can be interpreted as relative weights of the individual branches of a system point trajectory. The final weights of trajectories terminating in the product asymptote can then serve for calculating the reaction attributes in the same manner as the numbers of trajectories in case of adiabatic processes (7,49). [Pg.259]

The First Law contains an important corollary Since for an adiabatic process AE - Wa - 0, one can compute AE for such processes from a measurement or calculation of Wa. If this same... [Pg.52]

Adiabatic processes. Ratio of the specific heats. If the gas is contained in st vessel, the walls of which are impermeable to heat or adiabatic so that no interchange of heat with the surroundings is possible, the energy of the gas diminishes by the amount of the work done against the external pressure. On the other hand, if the gas is compressed, its energy increases by the amount of the work done in the compression. In the first case there is a fall, in the second a rise in the temperature of the gas. The magnitude of the change in temperature may be calculated from equation (2) as follows ... [Pg.91]

Finally, we may calculate the relation between the temperature and pressure in an adiabatic process. We have... [Pg.92]

In the integral, A and B represent, respectively, the initial and final equilibrium states for the process. The calculation must be conducted along a reversible path connecting A and B. For a reversible adiabatic process, q = 0 and, therefore, AS = 0. Such a process is also called isentropic (that is, the entropy is constant). [Pg.545]

To calculate the adiabatic reaction temperature, you assume that all the energy liberated from the reaction at the reference temperature plus that brought in by the entering stream (relative to the same base temperature) is available to raise the temperature of the products. We assume that the products leave at the temperature of the reaction, and thus if you know the temperature of the products, you automatically know the temperature of the reaction. In effect, for this adiabatic process we can apply Eq. (4.40). [Pg.464]

The adiabatic cooling lines are lines of almost constant enthalpy for the entering air-water mixture, and you can use them as such without much error (1 or 2%). However, if you want to correct a saturated enthalpy value for the deviation which exists for a less-than-saturated air-water vapor mixture, you can employ the enthalpy deviation lines which appear on the chart and which can be used as illustrated in the examples below. Any process that is not a wet-bulb process or an adiabatic process with recirculated water can be treated by the usual material and energy balances, taking the basic data for the calculation from the humidity charts. If there is any increase or decrease in the moisture content of the air in a psychrometric process, the small enthalpy effect of the moisture added to the air or lost by the air may be included in the energy balance for the process to make it more exact as illustrated in Examples 4.47 and 4.49. [Pg.487]

In Section 4.1.1, Eqs. [4-1] and [4-2] were used to estimate the relationship between air pressure and altitude, assuming temperature to be constant with height. When combined with a third equation, Eqs. [4-1] and [4-2] also can be used to calculate the dry adiabatic lapse rate. The third equation, presented as the following Eq. [4-7], is based on an adiabatic process for air that rises and expands due to a decrease in pressure. By definition for an adiabatic process, heat flow into the rising air is assumed to be zero. Therefore, conser-... [Pg.298]

While the SHS process has high reaction rate and short duration, it can be regarded as an adiabatic process in our calculation ... [Pg.302]


See other pages where Adiabatic process calculation is mentioned: [Pg.770]    [Pg.484]    [Pg.233]    [Pg.62]    [Pg.5]    [Pg.6]    [Pg.8]    [Pg.53]    [Pg.61]    [Pg.188]    [Pg.850]    [Pg.158]    [Pg.464]    [Pg.379]    [Pg.158]    [Pg.123]    [Pg.376]    [Pg.107]    [Pg.83]    [Pg.34]    [Pg.280]    [Pg.44]    [Pg.509]    [Pg.517]   
See also in sourсe #XX -- [ Pg.67 , Pg.68 , Pg.68 , Pg.69 , Pg.70 ]




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