Amplitudes of temperatures

The amplitude of temperature fluctuations was controlled in a feedback loop by adjusting the relative phase between the primary and secondary forced air flows. A demonstration of the closed-loop performance is illustrated in Fig. 24.12. The controller converged on the optimum phase with a 1/e rise time of approximately 30 control steps (Fig. 24.12a). Figure 24.126 illustrates the difference between the power spectra with control off (i.e., neither primary nor secondary drivers) and control optimized. The response time necessary to reach the optimum phase was slowed by the large variations in the measured coherence (examples shown in Fig. 24.12a) which are attributed to the complex interactions between the inlet mode, the combustor modes, and the preferred mode of the jet. 

The solution to Equation (4.32) enables us to trace temperature variations Tw(z, t) and suggests the conclusion that in this case these variations weakly depend on TW(Q, t). Even if 7V(0, /) increases by 2°C, then according to (4.32), the amplitude of temperature changes with depth will rapidly decrease to 0.97°C, 0.33°C, and 0.01°C at depths 40cm, 2m, and 3m, respectively. Hence, with a 2°C increase in the average global atmospheric temperature, flux FlCH4 will increase by no more than 1.4%. 

Donhowe and Hartel (1996) also compared recrystallization rates of ice crystals in ice cream at different amplitudes of temperature fluctuations. Above temperature fluctuations of 0.50 °C, significantly faster recrystallization occurred, as compared to constant temperature conditions. Recrystallization rates were about twice as fast with temperature fluctuations of 1.00°C compared to 0.010 °C. The shape of the crystals after recrystallization at fluctuating temperatures was more jagged and uneven, whereas recrystallization at constant temperature produced a rounding effect. This was evidence that melt-refreeze and accretion were the main mechanisms of recrystallization under fluctuating temperatures. 

Under quasi-isothermal conditions and at steady state, the solution of Eq. (20) can be written with constants An = Aa/No and A-c = Asj/(RT ), where A is the amplitude of temperature modulation. 

If it is additionally assumed that the amplitude of temperature oscillations e(t) around the average temperature Tav is negligibly small, we can put... 

Table II Comparison of some representative amplitudes of temperature...

Dimensionless time Amplitude of velocity disturbance Amplitude of concentration disturbance Amplitude of temperature disturbance Density, kg m ... 

Thus, as can be seen in Eq. (5), the heat flow signal will contain a cyclic component which is dependent on amplitude of kinetic response (C), amplitude of temperature B), and fi equency (w). 

The unique Joule-Thomson characteristics associated with supercritical carbon dioxide have been first investigated. The amplitude of temperature drop eaused by Joule-Thomson effect has been estimated and presented as a funetion of the temperature of supercritical carbon dioxide. 

Although thermal expansion compatibility [1-6] is usually assessed by the differences between thermal expansion coefficients, the magnitude of stresses also depends on elastic constants and on the amplitude of temperature changes, from sintering or deposition/bonding conditions to operation temperatures, and down to room temperature due to discontinuous operation or for maintenance. Excessive thermal expansion of individual materials also implies greater risks of thermal shock or failure under temperature gradients. 

---