Energy release curve

Fig. 9. Stored energy release curves for CSF graphite irradiated at 30°C in the Hanford K reactor cooled test hole [64], Note, the rate (with temperature) of stored energy release (J/Kg-K) exceeds the specific heat and thus under adiabatic conditions self sustained heating will occur.

However, the characteristics of point b with regard to temperature fluctuations are quite different. At this point the slope of the energy release curve is greater than the slope of the energy loss curve. If a small positive temperature fluctuation were to occur, one would be in a... 

Figure 5. Kinetic energy release curve for 0+ atoms formed from (2 + 1) REM PI of 02 at 225 nm. The inset is a plot of the measured (FWHM) width of the stronger peaks versus the square root (sqrt) of their kinetic energy. Many of the measured peaks are actually two or more overlapped peaks, thus the width is often an upper limit. With this set of peaks the apparatus function W shows a 35-meV peak width at 1 eV, i.e., W = 35 /KE. With nonoverlapped peaks a value of 25V/KE is expected.

Other reactions will have somewhat different forms for the curve of Qq versus T. For example, in the case of a reversible exothermic reaction, the equilibrium yield decreases with increasing temperature. Since one cannot expect to exceed the equilibrium yield within a reactor, the fraction conversion obtained at high temperatures may be less than a subequilibrium value obtained at lower temperatures. Since the rate of energy release by reaction depends only on the fraction conversion attained and not on the position of equilibrium, the value of Qg will thus be lower at the higher temperature than it was at a lower temperature. Figure 10.2 indicates the general shape of a Qg versus T plot for a reversible exothermic reaction. For other reaction networks, different shaped plots of Qg versus T will exist. 

Energy release and energy loss curves for an irreversible reaction in a flow reactor. 

U-shaped curve, we have mixtures that can be ignited for a sufficiently high spark energy. From Equation (4.25) and the dependence of the kinetics on both temperatures and reactant concentrations, it is possible to see why the experimental curve may have this shape. The lowest spark energy occurs near the stoichiometric mixture of XCUi =9.5%. In principle, it should be possible to use Equation (4.25) and data from Table 4.1 to compute these ignitability limits, but the complexities of temperature gradients and induced flows due to buoyancy tend to make such analysis only qualitative. From the theory described, it is possible to illustrate the process as a quasi-steady state (dT/dt = 0). From Equation (4.21) the energy release term represented as... 

In DSC instruments, heat production (q) can be determined directly as a function of temperature. The shape of the heat production curve is also important for hazard identification. A sharp rise in energy release rate (i.e., a steep slope of the exotherm), whether due to a rapid increase of the rate constant with temperature or to a large enthalpy of reaction, indicates that the substance or reaction mixture may be hazardous. Figure 2.14 illustrates an example of a DSC curve with a gradual exothermic reaction, while Figure 2.15 is an example of a steep exothermic rise. 

The element may enter the wave in the state corresponding to the initial point and move directly to the C-J point. However, this path demands that this reaction occur everywhere along the path. Since there is little compression along this path, there cannot be sufficient temperature to initiate any reaction. Thus, there is no energy release to sustain the wave. If on another path a jump is made to the upper point (1 ), the pressure and temperature conditions for initiation of reaction are met. In proceeding from 1 to 1, the pressure does not follow the points along the shock Hugoniot curve. 

All of the sonic disturbances in question take the form of progressive (forward moving) waves in air, in the manner of sine curves whose characteristics are governed by the laws of physics. The wave motion commences at the source of the energy release, i.e. the exploding firework, and is caused by the sequential disturbance (i.e. vibration) of the individual particles in the air. 

The strong influence exerted by many. of these factors, especially degree of confinement and charge diameter, shows that the energy release which is initiated in the deton front does not occur instantaneously. Hence, any theory (such as "curved-front or "nozzle ) must take into consideration the lateral expansion (See Ref 61, pp 188-201). This expansion (if at all appreciable during time t, where reaction zone thickness is a-Dt) will modify the deton process because a) part of the energy released is used in the expansion (See Ref 61, p 201), hence does not contribute to propaga tion of rhe wave front, and b) peak temp and pressure are lower than when lateral expansion... 

Fig 13 Critical acceleration and energy release rate curves determined from long-duration pulse experiments, as functions of shock amplitude v in PBX 9404. Energy rate shown is the net result of mechanical dissipation and exothermic chemical reaction. Following thermochemical convention, energy release rate due to exothermic reaction is denoted as a negative value of H ... 

We present a preliminary study on the structural dynamics of photo-excited iodine in methanol. At early time delays after dissociation, 1 - 10 ns, the change in the diffracted intensity AS(q, t) is oscillatory and the high-q part 4 -8 A 1 is assigned to free iodine atoms. At later times, 10-100 ns, expansive motion is seen in the bulk liquid. The expansion is driven by energy released from the recombination of iodine atoms. The AS(q, t) curves between 0.1 and 5 (is coincide with the temperature differential dS/dT for static methanol with a temperature rise of 2.5 K. However, this temperature is five times greater than the temperature deduced from the energy of dissociated atoms at 1 ns. The discrepancy is ascribed to a short-lived state that recombines on the sub-nanosecond time scale. 

Equilibrium Vaporization. The cesium release results presented in this chapter may also be used to demonstrate our earlier conclusion that equilbirium vaporization represents the upper limit for the fractional fission-product release as a function of sodium vaporization. Figure 6 shows three cesium release curves. Curve A was calculated from the Rayleigh Equation in conjunction with the partial molar excess free energy of mixing of infinitely dilute cesium—sodium solutions reported... 

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