Adiabatic measured curve

Fig. 8 shows respective simulation results. The estimate using adiabatic exciton states (see the subsequent section) coincides with the LRT absorbance. Although the electrostatic coupling to solvent molecules has been included the achieved broadening is insufficient to meet the measured curve. An additional broadening due to the inclusion of intra chromophore vibrations removes this discrepancy. 

The heat capacity of solids and melts can be determined by adiabatic calorimetry and various methods of DSC and MTDSC, where with modem methods, the latter may reach a precision equal or better than the adiabatic measurement, so that curves like in Figures 4.1 and 4.2 are available for an... 

Figure 6.7 Exothermic process involving constant heat generation with the corresponding measured curve obtained with an ideal adiabatic calorimeter.

IS An air-water-vapor mixture, 1 std atm, 180 C, flows in a duct (wall temperature 180 Q at 3 m/s average velocity. A wet-bulb temperature, measured with an ordinary, unshielded thermometer covered with a wetted wick (9.5 mm outside diameter) and inserted in the duct at right angles to the duct axis, is-52 C. Under these conditions, the adiabatic-saturation curves of the psychromctric chart do not approximate wet-bulb lines, radiation to the wet bulb and the effect of mass transfer on heat transfer are not negligible, and the k-type (rather than F) mass-transfer coefficients should not be used. 

In the ARC (Figure 12-9), the sample of approximately 5 g or 4 ml is placed in a one-inch diameter metal sphere (bomb) and situated in a heated oven under adiabatic conditions. Tliese conditions are achieved by heating the chamber surrounding the bomb to the same temperature as the bomb. The thermocouple attached to the sample bomb is used to measure the sample temperature. A heat-wait-search mode of operation is used to detect an exotherm. If the temperature of the bomb increases due to an exotherm, the temperature of the surrounding chamber increases accordingly. The rate of temperature increase (selfheat rate) and bomb pressure are also tracked. Adiabatic conditions of the sample and the bomb are both maintained for self-heat rates up to 10°C/min. If the self-heat rate exceeds a predetermined value ( 0.02°C/min), an exotherm is registered. Figure 12-10 shows the temperature versus time curve of a reaction sample in the ARC test. 

Eable 4.7)Draw in the Mollier diagram at the 14 °C point of the saturation curve (a) the state change line of the adiabatic humidification and (b) an auxiliary line, associated with the wet bulb temperature measurement, by means of which the state can be defined. The pressure of air is p = 1 bar. 

Adiabatic calorimetry. Dewar tests are carried out at atmospheric and elevated pressure. Sealed ampoules, Dewars with mixing, isothermal calorimeters, etc. can be used. Temperature and pressure are measured as a function of time. From these data rates of temperature and pressure rises as well as the adiabatic temperature ri.se may be determined. If the log p versus UT graph is a straight line, this is likely to be the vapour pressure. If the graph is curved, decomposition reactions should be considered. Typical temperature-time curves obtained from Dewar flask experiments are shown in Fig. 5.4-60. The adiabatic induction time can be evaluated as a function of the initial temperature and as a function of the temperature at which the induction time, tmi, exceeds a specified value. 

Before beginning the series of runs to determine the relief size, the physical property and kinetic data need to be correlated in the form required, by the code. In some cases, the code may already have the components required on a database. In all other cases, physical property data must be found, estimated or measured and correlated in the appropriate form. Some codes have a front-end program for curve fitting of data. For tempered systems, the vapour/ liquid equilibrium models are of critical importance since errors will cause the code to open the relief system at the wrong temperature and reaction rate. It is therefore worthwhile to spend time to ensure reasonable behaviour of the vapour pressure predictions. Check that all correlations behave sensibly over the entire temperature range of relevance for relief sizing. A good test for the physical property and kinetic data supplied to the code is to first model the (unrelieved) adiabatic calorimetric test which was used to obtain the kinetic data.. . ... 

TITRATION (Thermometric). This technique consists of the detection and measurement of the change in temperature of a solution as the titrant is added to it, under as near adiabatic conditions as possible. Experimentally, the titrant is added from a constant-delivery burette into die titrate (solution to be titrated) which is contained in an insulated container such as a Dewar flask. The resultant temperature-volume (or time) curve thus obtained is similar to odier titration curves, e.g., acid-base, in that the end point of the reaction can be readily ascertained. Since all reactions involve a detectable... 

Here the last equality relates the cumulant to the adiabatic magnetic susceptibility xf 1 at the frequency fcco. Thus, the desired equation reduces to = 0. In a real system the adiabatic susceptibility xf 1 is a directly measurable quantity. Therefore, comparing the measured dimensional bias fields in the branching points with the theoretical numbers c0/i one can, for example, evaluate the particle volume. Table II lists the calculated values of the branchoff points for the limiting cases e oc and s = 0, that is, for both families of lines shown in Figure 4.28. For intermediate values of s, one finds that for every k and j the contours pt-( 0, e) fill in uniformly the area between the respective limiting curves. 

The evaluation of chemical reaction hazards involves establishing exothermic activity and/or gas evolution that could give rise to incidents. However, such evaluation cannot be carried out in isolation or by some simple sequence of testing. The techniques employed and the results obtained need to simulate large-scale plant behavior. Adiabatic calorimeters can be used to measure the temperature time curve of selfheating and the induction time of thermal explosions. The pertinent experimental parameters, which allow the data to be determined under specified conditions, can be used to simulate plant situations. 

One reason for interest in more accurate calculations on HF has been the measured dissociation energy Z)o(HF), which can be obtained from photoionization or photoelectron spectra. Since HF+ dissociates correctly within the Hartree-Fock approximation to H+ and F(2P) in both the X2Tl and 2S+ states, PE curves were calculated by Julienne et a/.,203 and later by Bondybey et a/.,187 both of whom obtained values of Do in good agreement with experiment for the SCF calculation. The bond length in HF+ of 1.000 bohr is less than the experimental result, which the authors call into question. Julienne et al. give a detailed discussion of the adiabatic dissociation process. HF+ was also considered in the calculations of ref. 198. Richards and co-workers have reported several calculations of the PE curves of HF+, including the A2E+ state, which is correctly predicted to be bound.204... 

Ll Cl" " (Figure 12) was the most abundant species, and hence the easiest to measure. A reasonably linear segment is apparent over ca. one decade, although this curve is less steep than in the case of Li. This may reflect the more complex Boltzmann population of states for this tetratomic molecule, where a pre-exponential factor is necessary. The departure from linearity is also less abrupt, and occurs at ca. 10.20 eV. We take this to be the adiabatic I.P. of Li2Cl2. Our earlier photoelectron spectroscopic studies (18) yielded 10.22 and 10.17 eV for this quantity, employing two alternative methods of extrapolation. Hence, the inference seems quite plausible that departure from linearity on the semi-logarithmic plot yields a value very close to the adiabatic ionization potential. 

Increasing the sample diameter (D) increases the ratio of volumetric heat generation to surface heat loss The dependence of U on D, for different systems, is shown in Fig. 54. By increasing the diameter above a critical value, the combustion temperature approaches the adiabatic value, and U becomes constant. This behavior has been observed for the solid flame Ta-C system (curve 1), the Ti-C system (curve 2) where one reactant melts, and in Ni-Al (curve 3) where both reactants melt. The maximum measured temperature as a function of radial position in a cylindrical pellet with a diameter of 2 cm for the Mo+2Si system is presented in Fig. 55. The data show significant heat losses from the specimen. For this reason, incomplete combustion often occurs for samples with small diameter and may lead to an undesirable product phase composition (Martynenko and Borovinskaya, 1975 Bratchikov et al., 1980). 

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