Oscillation temperature

These studies have indicated that the independent parameters controlling the postulated solid-phase reactions significantly affect the resulting acoustic admittance of the combustion zone, even though these reactions were assumed to be independent of the pressure in the combustion zone. In this combustion model, the pressure oscillations cause the flame zone to move with respect to the solid surface. This effect, in turn, causes oscillations in the rate of heat transfer from the gaseous-combustion zone back to the solid surface, and hence produces oscillations in the temperature of the solid surface. The solid-phase reactions respond to these temperature oscillations, producing significant contributions to the acoustical response of the combustion zone. 

Gas density Propellant density Boltzmann constant A factor to account for temperature oscillations ignition delay time Diffusion time... 

At the CISE Laboratories in Milan, where the phenomenon of fast and slow burn-out was first noted, the onset of random temperature oscillations has in itself been assumed to signify burn-out, the implication being that temperature oscillations always occur [Bertoletti et ah (BI9) and Alessandrini et al. (A5)]. However, the CISE experiments have in the past been carried out with preformed mixtures of steam and water at entry to a heated test channel, and it is possible that this feature, which is known to produce flow disturbances (see Section III), may be the reason for the fact that temperature oscillations always occur. 

In the study by Hetsroni et al. (2006b) the test module was made from a squareshaped silicon substrate 15 x 15 mm, 530 pm thick, and utilized a Pyrex cover, 500 pm thick, which served as both an insulator and a transparent cover through which flow in the micro-channels could be observed. The Pyrex cover was anod-ically bonded to the silicon chip, in order to seal the channels. In the silicon substrate parallel micro-channels were etched, the cross-section of each channel was an isosceles triangle. The main parameters that affect the explosive boiling oscillations (EBO) in an individual channel of the heat sink such as hydraulic diameter, mass flux, and heat flux were studied. During EBO the pressure drop oscillations were always accompanied by wall temperature oscillations. The period of these oscillations was very short and the oscillation amplitude increased with an increase in heat input. This type of oscillation was found to occur at low vapor quality. 

The solution of Eqs. (11.15-11.17), subject to the conditions (11.24-11.26), determines the displacement of the interface in time, as well as the evolution of the velocity, pressure and temperature oscillations. 

When the temperature Ts of the interface is constant, and wall heat flux is also constant, temperature oscillations are the result of the meniscus displacement along micro-channel axis. They are expressed as... 

Assuming that the temperature oscillations that are due to the displacement of the interface decrease far from Xf, the sign in front of Eq. (11.53) is positive for phase L and negative for phase G. 

Since the reaction rate is proporhonal to the density, p, it is clear that the heat release rate will increase with pressure. However, since acoushc waves are adiabatic, they are also accompanied by a temperature oscillation... 

These three numerical experiments show how the waters of an evaporating lagoon respond differently to the different seasonal perturbations that might affect them. Some record of these perturbations might, in principle, be preserved in the carbonate sediments precipitated in the lagoon. All three perturbations—productivity, temperature, and evaporation rate— cause seasonal fluctuations in the saturation state of the water and in the rate of carbonate precipitation. Temperature oscillations have little effect on the carbon isotopes. Although seasonally varying evaporation rates affect 14C, they have little effect on 13C. Productivity fluctuations affect both of the carbon isotopes. 

Self-sustained Oscillations. Under certain conditions, isothermal limit cycles in gaseous concentrations over catalysts are observed. These are probably caused by interaction of steps on the surface. Sometimes heat and mass transfer effects intervene, leading to temperature oscillations also. Since this subject has recently been reviewed (42, 43) only a few recent papers will be mentioned here. 

Recently, such a temperature oscillation was also observed by Zhang et al (27,28) with nickel foils. Furthermore, Basile et al (29) used IR thermography to monitor the surface temperature of the nickel foil during the methane partial oxidation reaction by following its changes with the residence time and reactant concentration. Their results demonstrate that the surface temperature profile was strongly dependent on the catalyst composition and the tendency of nickel to be oxidized. Simulations of the kinetics (30) indicated that the effective thermal conductivity of the catalyst bed influences the hot-spot temperature. 

Exothermic reaction parameters of, 27 63 temperature oscillations, 27 65-67 Explosion, petovskite preparation, 36 250 Extended Hiickel treatment, 34 136, 147, 154, 156, 166, 173... 

Fig. 3. Filtered signal (solid line) and measured time series (dotted line) for the first experiment E.l (see text for details). Temperature oscillation were induced by recycle between heat exchanger and biological reactor. The filtered signal remains the oscillatory behavior of the system.

This was also done in order to attribute the temperature oscillations only to the interconnection. Time series were filtered (see solid lines in Figures 3 and 4) by low-pass filter in order to eliminate noise effects in temperature measurements (in Figures 3 and 4, the dotted line and the solid line correspond, respectively, to the temperature measurements and the filtered temperature). 

Figure 12.8 Heating and cooling system on the barrel a) schematic of the original configuration that created the temperature oscillations in Fig. 12.7 and b) a better configuration that minimized the temperature oscillations...

In order to reduce the cooling level to the barrel zone, a metering valve was placed in the water line upstream of the solenoid valve as shown in Fig. 12.8(b). Now when the controller opens the solenoid valve, a much lower quantity of water and thus cooling is available to the barrel zone. Prior to this modification, the barrel temperatures oscillated 10 °C about the set point temperature. After the modification, the temperature oscillations were reduced to about 3 °C, and the profitability of the process was improved due to the minimization of resin consumption. 

Kokushkin, N. V. 1958. A study of combustion of a homogeneous mixture in a turbulent flow by means of recording temperature oscillations. Jzv. Academy Science USSR, Technical science ser. 3. 

The outputs of the sensors were used in two closed-loop control strategies developed for combustor performance optimization [7]. The objective of the first strategy, based on an adaptive least-mean squares (LMS) algorithm, was to maximize the magnitude and coherence of temperature oscillations at the forcing frequency /o in the measured region. The LMS algorithm was used to determine... 

Elliot M, Labeyrie L, Duplessy JC (2002) Changes in North Atlantic deep-water formation associated with the Dansgaard-Oeschger temperature oscillations (60-10 ka). Quat Sci Rev 21 1153-1165... 

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