Thermocouple axial

Since the higher thermal conduc tivity material (copper or bronze) is a much better bearing material than the conventional steel backing, it is possible to reduce the babbitt thickness to. 010-030 inch. Embedded thermocouples and RTDs will signal distress in the bearing if properly positioned. Temperature-monitoring systems have been found to be more accurate than axial-position indicators, which tend to have linearity problems at high temperatures. 

A schematic view of an extruder is shown in figure 1. The extruder barrel is essentially a ferrous alloy cylinder, with aluminum block heaters attached to the outside. There are several temperature control zones along the length of the extruder. Measurement thermocouples are installed in the extruder barrel itself. Barrel temperature is used to control the temperature of the polymer melt. Energy from the heaters is conducted both radially and axially in the barrel. Below, figure 2 shows a sketch of the extruder barrel, with the heaters and the temperature measurement points used in this paper marked. 

Fig. 21. Comparison of time-average temperature reading from thermocouples located at different axial points on the periphery of the carbon bed for periodic flow interruption and steady-state operation. Time-average u = 1.65 mm/s for flow interruption, r = 60 min and s = 0.5. Gas and liquid inlet temperature is about 26.5°C. (Figure from Haure et al., 1989, with permission, 1989 American Institute of Chemical Engineers.)...

A number of issues relative to the prediction of solids conveying in smooth bore single-screw extruders are exposed from the theoretical fits to the data in Fig. 5.32. First, the data needed to carry out an effective simulation is difficult to take and is very time consuming, and only a few labs have the proper equipment that is, bulk density measurement, dynamic friction data, lateral stress, and solids conveying data. Moreover, care must be taken to develop an accurate representation of the surface temperature for the barrel and screw as a function of the axial position. This would be quite difficult in a traditional extruder with only a control thermocouple to measure the temperature at the midpoint of the barrel thickness. Second... 

The temperature of the screw was measured by several investigators [29-32]. The measurements were performed by mounting thermocouples in an axial hole bored in the center of the screw or by protruding the thermocouples into the melt flow. The sensor signals were then transmitted to a chart recorder using an electrical rotary union. The technology available at the time of these measurements limited the number of sensors in the screw and the quality of the data. 

Figure 17.8 shows the probe, which consists of a 1-millimeter diameter t3rpe K thermocouple centered between two 1-millimeter diameter pressure taps. Each of the pressure tubes was bent 90° and sheared at the bend. To obtain a measurement, the tube is rotated until the pressure difference between the two taps is maximized. This is the position at which one tube is directed into the oncoming flow and the other is parallel to it. The approach flow thus observes an approximately 1-millimeter thick planar obstruction. The pressure difference and temperature are then recorded. The pressure difference is related to the approach velocity, and the angle determines the tangential and axial velocity components in this case. The local mass flux is then determined from the axial velocity component and the temperature (necessary to compute the flow density), and... 

It can also identify texture of the semi coke formed as illustrated in Figure 6. If a binder is used with a coal, the Plastofrost technique can determine the coal-binder interaction and the texture of coke formed from the binder phase. Although not considered in studies undertaken at Waterloo, the axial location of the thermocouples in the sample holder makes the Plastofrost procedure capable of measuring coal-coke conductivity as a function of coal, temperature and compaction pressure, with just a modest redesign of the heating slab. 

The catalytic bed (70 cm ), supported by a metallic gauze, is located in the reforming section. Water is fed to the reactor at the bottom of the metallic gauze. The temperature inside the reactor is monitored by four thermocouples one (Tcomb) is located on the SiC foam and the other three (T ref L, T ref M, T ref H) are located at 25, 50 and 75%, respectively, of the catalytic bed height to provide the reactor temperature axial profile. Moreover, additional thermocouples monitor... 

Finally, predicted and simulated catalyst temperatures are compared in Fig. 23. These temperatures were measured by a thermocouple inserted into the catalyst 25 mm from the front face, as measured in the axial direction. The agreement between measurement and prediction is good, indicating that the thermal properties used in the model for the catalyst/substrate are reasonable. 

Fig. 10.50 Location of the pressure gauge (P) and the thermocouples (7) at the five axial barrel positions. The three cross sections A-A, B-B and C-C are used for contour plots of the numerical results. [Reprinted by permission from T. Ishikawa, S. Kihara, K. Funatsu, T. Amaiwa, and K. Yano, Numerical Simulation and Experimental Verification of Nonisothermal Flow in Counterrotating Nonintermeshing Continuous Mixers, Polym. Eng. Sci., 40, 365 (2000).]...

Figure 2. Locations of axial and radial measuring devices in reactor. Key , catalyst bed , inert packing 1-23, thermocouples and sampling to gas analyzer and 30, 31, sampling to gas chromatograph.

This time instead of having one thermocouple movable inside an axial ceramic tube as in [11,18] the thermocouples were fixed inside of catalyst pellets. 

The catalytic CO oxidation by pure oxygen was selected as a model reaction. The Pt/alumina catalyst In the form of 3.4 mm spherical pellets was used. The CO used In this study was obtained by a thermal decomposition of formic acid In a hot sulphuric acid. The reactor was constructed by three coaxial glass tubes. Through the outer jacket silicon oil was pumped, while air was blown through the inner jacket as a cooling medium. The catalyst was placed in the central part of the tube. The axial temperature profiles were measured by a thermocouple moving axially in a thermowell. Gas analysis was performed by an infrared analyzer or by a thermal conductivity cell. [7]. 

A detailed experimental study of operating conditions in a nonadiabatic fixed bed reactor revealed that for certain inlet conditions oscillatory or erratic behavior of temperature profiles can be observed [23]. To follow this phenomenon local thermocouple temperature reading and axial temperature profiles were monitored. The results of measurements are reported in Fig. 3. 

Although two reactors are shown in Figure 1, they were not used simultaneously. The reactor shown in the center was the fixed bed reactor which is of primary interest in this contribution. It consisted of a 12.7 mm diameter X 250 mm long steel tube packed with 40/50 mesh catalyst (0.3 mm average particle diameter). The reactor was heated by a nichrome wire coil and was well insulated. The coil spacing was adjusted and was packed in insulation with the intent of making the reactor crudely adiabatic. A variac controlled heater on the reactor inlet and a thermocouple sensor kept the feed to the reactor at the nominal reaction (or feed inlet) temperature of 400°C. The tube of the fixed-bed, reactor was fitted with 12 thermocouples to record the axial temperature profile in the bed (Figure 1). 

Steady-State Behaviour The dashed line in Figure 2 shows a typical experimental axial temperature profile for conditions listed in Table I. The banded region in the vicinity of the hot spot includes those points (labelled a, b and c) in which radial temperature profiles were also measured using moving thermocouples. There, the upper and lower lines represent the highest measured temperature and the wall temperature, respectively, at those axial points. 

Figure 9.2 Schematic of radial thermal conductivity apparatus. Specimen dimensions are 2.75 cm in radial thickness and 56 cm in length. Not shown are thermocouples placed axially along the central heater and voltage taps 5 cm apart. Inner and outer thermocouple junctions extend out radially, centered axially between the voltage taps.

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