Temperature sensitivity of the condensed phase

From Eq. (3.78), it can be seen that the temperature sensitivity depends on two par-ameters,[iil O and W O is the so-called temperature sensitivity of the gas phase , which is determined by the parameters of the gas phase, and W is the so-called temperature sensitivity of the condensed phase , which is determined by the parameters of the condensed phase. 

The relationship between temperature sensitivity and burning rate is shown in Fig. 7.21 as a function of AP particle size and burning rate catalyst (BEFP).li31 The temperature sensitivity decreases when the burning rate is increased, either by the addition of fine AP particles or by the addition of BEFP. The results of the temperature sensitivity analysis shown in Fig. 7.22 indicate that the temperature sensitivity of the condensed phase, W, defined in Eq. (3.80), is higher than that of the gas phase, 5), defined in Eq. (3.79). In addition, 4> becomes very small when the propel-... 

The temperature sensitivity of gas phase 4> defined in Eq. (3.79) and the temperature sensitivity of the condensed phase V defined in Eq. (3.80) are obtained from the data of the burning surface temperature Ts, the temperature in the fizz zone Tg, the activation energy in the fizz zone Eg, the heat of reaction at the burning surface Qj, the temperature gradient in the fizz zone (f>, and the burning rate r. Figure 7-43 shows the temperature sensitivity of the burning rate of HMX-CMDB propellants as... 

Fig. 7.22 Temperature sensitivities of the gas phase and the condensed phase of AP-HTPB composite propellants.

The temperature sensitivity stays around 0.0028 fC for most cases. At elevated pressures, the heat feedback from the gas phase to the condensed phase is higher, and thus the effect of initial temperature on the interfacial energy balance becomes less important. A numerical analysis on the temperature sensitivity for low-pressure conditions was further performed by Beckstead and co-workers [35]. The predicted temperature sensitivity was determined to be too low compared to the measurements, mostly due to the uncertainties associated with the treatment of the condensed phase in the model. 

The condensed phases also are important to the physical processes of the atmosphere however, their role in climate poses an almost entirely open set of scientific questions. The highest sensitivity of physical processes to atmospheric composition lies within the process of cloud nucleation. In turn, the albedo (or reflectivity for solar light) of clouds is sensitive to the number population and properties of CCN (Twomey, 1977). At this time, it appears impossible to predict how much the temperature of the Earth might be expected to increase (or decrease in some places) due to known changes in the concentrations of gases because aerosol and cloud effects cannot yet be predicted. In addition, since secular trends in the appropriate aerosol properties are not monitored very extensively there is no way to know... 

These equations are commonly called pyrolysis relations, in reference to the thermal (as opposed to a possibly chemical or photonic) nature of the initiating step(s) in the condensed phase decomposition process. It can be seen that while the second, simpler pyrolysis expression with constant coefficient As) preserves the important Arrhenius exponential temperature dependent term, it ignores the effect of the initial temperature, condensed phase heat release and thermal radiation parameters present in the more comprehensive zero-order pyrolysis relation. These terms To, Qc, and qr) make a significant difference when it comes to sensitivity parameter and unsteady combustion considerations. It is also important to note the factor of 2, which relates the apparent "surface" activation energy Es to the actual "bulk" activation energy Ec, Es- E /1. Failure to recognize this factor of two hindered progress in some cases as attempts were... 

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