Temperature transient behavior

Fig. 13.17 (a) transmission spectrum of MLR used as a temperature sensor. Transient behavior of MRL periodically heated by C02 laser at wavelength of (b) 1550.4 nm (flat spectrum) and (c)... 

One of the first models to examine transients in polymer-electrolyte fuel cells was a stack-level model by Amphlett et al. Their model is mainly empirical and examines temperature and gas flow rates. They showed that transient behavior lasts for a few minutes in a stack before a new steady state is reached. In a similar stack-level analysis, Yerramalla et al.2 9 used a slightly more complicated single-cell model and examined the shape of the transients. They noticed voltage behavior that had oscillations in it and some leakage current. Their overall analysis was geared to the development of a controller for the stack. 

What equations would have to be solved to determine transient behavior in a tubular reactor How would you guess that temperatures might vary with time for step changes in Tf, Tco, or flow rates ... 

It is common that the absorption bands are normally dependent on temperature, and most of them show red shift at elevated temperatures. These behaviors are closely related to the solvation and the formation of hydrogen bonds between transients and water molecules. Precise theoretical consideration is not made yet. 

Figure 3.4 Typical transient response characteristic for hole carrier transport in a-As2Sc3 at room temperature. The behavior is displayed with both linear (a) and logarithmic (b) axes of current and time.

D. Hardacre, C. Seddon, K. R. Compton, R. G. Voltammetry of oxygen in the room-temperature ionic liquids l-ethyl-3-methylimida-zolium bis(triflyl)imide and HexEt3N+ TfiN one-electron reduction to form superoxide. Steady-state and transient behavior in the same cyclic voltammogram resulting from widely different diffusion coefficients of oxygen and superoxide. J. Phys. Chem. A 2003,... 

The transient behavior of the particle temperature is defined by the energy balance... 

Consider the cases where very hot particles are suddenly exposed to a cold environment. Derive an expression to account for the transient behavior of the particle temperature using Eq. (4.62). Assume that Tf 3> Tw and the cooling is dominated by thermal radiation. 

Figure 6. Transient behavior during ramp changes in feed temperature. Key to ramp increase O,t = 0 , 10 min and A 25 min oo. Key to ramp decrease A, t — 0 and X 20 min oo.

Figure 7. Transient behavior during ramp changes in the salt bath temperature. Key X. t = 0 V, 10 min A 17min and 0,29 min oo.

Solids temperatures were measured at different levels by intercepting receptacles, each with a bare fine-wired thermocouple at its center. When in the upright position, the receptacle collected the falling solids, and its thermocouple measured the solids temperature. When the receptacle was turned to dump the solids, the thermocouple was exposed to the surrounding gas and thus measured the gas temperature. The transient behavior of the collected solids in heating the thermocouple was carefully analyzed (Liu and Tai, 1965) to justify the accuracy of the measurement. 

For problems where the fluid behavior is steady and the final solution is independent of the initial conditions, calculations can usually be carried out in a steady-state fashion. For problems that describe transient behavior or that require a time-marching solution technique, initial conditions must be supplied in addition to boundary conditions. These include the state of the flow field, concentration fields, and temperature fields at time zero at all locations in the domain. 

The transient behavior and temperature overshoot in a stirred tank was first discussed in ... 

Ionic polarization and electron injection under bias result in a time-dependent, non-uniform electric field within the films. If complete discharge of the space-charge is not permitted between measurements, apparently non-reproducible transient behavior results from the space-charge field. Reproducibility is restored by high temperature discharge before each measurement. 

A variety of additional measurements have been made on the photolysis behavior of myoglobin and the related protein, hemoglobin. These include room-temperature transient electronic absorption studies in the nanosecond range,521 nanosecond-to-picosecond resonance Raman spectroscopy,522,523 and low-temperature transient electronic absorption measurements in regions other than the Soret band.524... 

Figure 2 depicts the analytical transient behavior of the dimensionless temperature distribution along the capillary. The circles represent the position of the droplet in this space-time coordinate system. The liquid droplet is predicted to accelerate first and then slow down when it moves out of the temperature field. 

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