Temperature measurement transient

Distance-Velocity Lag (Dead-Time Element) The dead-time element, commonly called a distance-velocity lag, is often encountered in process systems. For example, if a temperature-measuring element is located downstream from a heat exchanger, a time delay occurs before the heated fluid leaving the exchanger arrives at the temperature measurement point. If some element of a system produces a dead-time of 0 time units, then an input to that unit,/(t), will be reproduced at the output a.s f t — 0). The transfer function for a pure dead-time element is shown in Fig. 8-17, and the transient response of the element is shown in Fig. 8-18. 

For capacity measurements, several techniques are applicable. Impedance spectroscopy, lock-in technique or pulse measurements can be used, and the advantages and disadvantages of the various techniques are the same as for room temperature measurements. An important factor is the temperature dependent time constant of the system which shifts e.g. the capacitive branch in an impedance-frequency diagram with decreasing temperature to lower frequencies. Comparable changes with temperature are also observed in the potential transients due to galvanostatic pulses. 

Summary of Published C(t) Measurements. Transient solvation dynamics of a variety of excited state probe molecules have been studied in the last few years. Table 1 summarizes the measurements that have been made at room temperature. Table 2 gives a brief summary of the low temperature results. 

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. 

Figure 26 Results of the decomposition of the measured transient spectra the peak positions (a), spectral widths (FWHM) (b), and reorientation times (c) of three prominent spectral components I—in, attributed to different local structures of water, as a function of temperature experimental points the lines are drawn as a guide for the eye.

Haghi,A.K. and Rondot, D., may 2000.A Thermal Imaging Technique for Measuring Transient Temperature Field, 5th DAS Int. Conf. Proc., 80-87, Romania. 

Borsenberger et al. (1993a) measured hole mobilities of TAPC doped poly(styrene)s with different dipole moments poly(styrene) (PS-1), poly(4-f-butylstyrene) (PS-2), and poly(4-chlorostyrene) (PS-3). The dipole moments of PS-1, PS-2, and PS-3 are f 1.0, and 1.7 Debye, respectively. Figure 32 shows a series of room temperature photocurrent transients for 40% TAPC doped PS. ... 

The measurement system developed, as shown in Figure 5, is introduced into the furnace on level SCCo i so that the ceramic tip is in the gas flow. The key elements of the measurement equipment are a suction pyrometer for the temperature measurement, a wide-range oxygen sensor (BOSCH LSU4) for the fast oxygen measurement, and a thermal conductivity detector (TCD) to measure the transient response of the Helium tracer concentration. For the determination of the transient response of the TCD measurement system itself Helium tracer was injected Just at the inlet of the suction pyrometer. In Figure 7 a typical transient response of the TCD measurement system is shown (curve with index SCCi . 

In Table VII are listed the average catalyst bed temperatures during two of the hot cycles of the FTP. Cycle 11 is a long (96 sec), relatively constant speed portion of the FTP with mild accelerations and decelerations. A moderate acceleration, a brief cruise, and a normal deceleration constitute cycle 16. Temperatures measured during these cycles are thus representative of hot steady state and transient operations respectively. The very high conversions attained with the platinum catalysts are reflected by these temperatures, which were maximum at a converter... 

In order to estimate the stability of triplet carbenes (19) under ambient conditions, laser flash photolysis ( LFP) [26] was carried out on the precursor diazomethanes (18) in solution at room temperature. The transient absorption bands formed upon the flash were recorded by a multi-channel detector. These bands were assigned to the triplet carbenes (19) by comparison with those obtained in matrix at low temperature. The kinetic information was then available by monitoring the decay of the transient absorption with oscillographic tracer. When triplet carbenes decayed unimolecularly, which is often so, lifetime (x) can be determined. However when the decay did not follow a single exponential, which is sometimes the case, x cannot be determined. In this case, a half-life (ti/2) is estimated from the decay curve as a rough measure of the stability. 

Richards CD, Richards RE (1998) Transient temperature measurement in a convectively cooled droplet. Exp Huids 25 392-400... 

The test facility needs to be established to test the heat transfer performance and heat transport limitations. Both transient and steady-state tests should be conducted for a micro heat pipe. For low-temperamre heat pipes, however, the steady-state test is of most concerned. A typical experimental system for low-temperature heat pipes similar to the one shown in Fig. 3 would normally be used. The test facility shown in Fig. 3 consists of the heat pipe, a heat power supply and measuring unit, a cooling unit, and a data acquisition unit for the temperature measurements. The operating temperature of a heat pipe can be controlled by a cooling block connected to a cooling bath, where the temperature of the coolant is maintained at a constant temperature based on the designed operating temperature. The heat source is directly connected to the evaporator. 

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