Thermocouples installations

A typical thermocouple installation for an industrial application is shown in Fig. 6.23. Instead of placing the reference junction in a temperature controlled environment (which is often inconvenient), an automatic reference junction compensation circuit is fitted. This provides a second source of emf Sj,° in series with the thermocouple emf E. The meter thus measures 0 = E 0 where E%-0... 

Fig. 6.23. Thermocouple installation with automatic reference junction compensation...

In our previous study, a supercritical biomass conversion system was developed with a bath-type reaction vessel to hydrolyze woody biomass resources and to convert them into useflil chemicals and fuel. This system can cover a range of up to 280MPa in pressure and up to 500 C in temperature, measured with the pressure gauge and thermocouple installed. 

To start a treatment of the sample in supercritical water, the reaction vessel was quickly heated by immersing it in the tin hath preheated at SOO C and maintained at supercritical temperature between 380 and 400and pressure between 140 and 200MPa for about 5 sec unless otherwise indicated. To quench the reaction, the reaction vessel was moved in the water bath. During this treatment, the temperature of the reaction vessel was monitored by a thermocouple installed into the reaction vessel. At the same time, the pressure was also measured by the pressure gauge attached to reaction vessel. 

Wiring Diagrams of Thermocouple Installations.— Figure 11 illustrates a simple thermoelectric installation for a rare-metal couple. The couple is properly protected by a porcelain or quartz tube and if necessary by an outer tube of iron, chromel, fireclay, etc. From the head of the couple compensating lead wires are carried to the bottom of a pipe driven 10 ft. under ground. From the bottom of the pipe copper lead wires are carried to the indicator. 

Figure 13 illustrates a multiple thermocouple installation connected to a single indicator. Compensating lead wires are carried from the couples to a conveniently located cold-junction box. The temperature of this box is thermostatically controlled. From the cold-junction box copper wires are carried to the terminal block and selective switch illustrated. A common return has been employed between the cold-junction box and the switchboard. In general it is preferable to use individual return wires for each couple. The switchboard illustrated is designed for six couples. By pressing one of the buttons shown any desired couple is connected directly to the indicator. 

The gasifier is equipped with 8 ports for thermocouple installation and 4 ports for pressure sensing. Two sets of ports at 180 degrees to each and capped with tempered glass are provided for the fuel height optical sensors. 

The sintering temperature was controlled with a thermocouple installed in a hole with a large diameter. 

Thermocouple installation is important to ensure the proper temperature will be measured. Figure 5.3 shows a thermocouple located at the top of the radiant section in a process heater used to measure the temperature of fhe heater. As will be discussed later, this type of fhermocouple measurement needs to be corrected to get the actual temperature. The location of this thermocouple is important because if it is located too close to the wall, then the temperature will be lower due to the lower temperature tubes that are cooled by process fluid. That lower temperature would not be representative of the average heater temperature. Figure 5.4 shows a photo of the thermocouples used to measure the water outlet temperatures from calorimeters in a flame impingement heating study [17]. The thermocouples were positioned so that water would have to flow over the junctions, regardless of the flow rate. If the thermocouples were positioned, for example, perpendicular to a vertically downward flow of water, there is a good chance the junction would not... 

Aspirated thermocouple installed (a) aspirator design sketch, (b) thermocouple/aspirator assembly, (c) at the test chimney. (GTI Applied Combustion Research Facility, Des Plaines, IL)... 

In one application, the TRC/TRC cascade control was used with four thermocouples installed, in parallel, in the convection section of the heater which was installed in thermowells. The thermowells were inserted in the heater wall between the tubes. Because the thermocouples receive the same heat as the convection section tubes, an instantaneous detection of furnace temperature was made. 

CHORDAL THERMOCOUPLE - A thermocouple installed in furnace tubes, designed to measure the effectiveness of water treatment within the boiler. 

Oil temperature of the Tank YW Room temperature Thermocouple Thermocouple Installation of the tank... 

Whether corrosive atmosphere will be encountered by the thermocouple. In that case, protective sheath (SS-304, SS-316, SS-310, HRS or ceramic) is required. The response time of thermocouple installed in the ceramic sheath is lower, however. 

The barrel is made of a steel cylinder that contains a reciprocating screw. Heating media, usually electrical heaters, are fitted around the barrel as the heat source. Temperatures are measured by thermocouples installed within the different zones of the barrel. Barrel temperature should be controlled within a small variation of the set-point. The barrel has three zones. 

There are aeven replaceable themocouple stringers which run from side to side through the core. Each stringer has five thermocouples along its length. There are also 98 non-replaceable thermocouples installed in the active core. Eighty-four of these are distributed in cooled filler blocks at five elevations in three vertical support planes parallel to the front face of the reactor. These planes are at the quarter points from front to rear. The other 14 non-replaceable thermocouples are in cooled and Uncooled cells typical of the packing In filler block cones. 

Tests were done on two barrel segment sizes using an array of twelve (12) thermocouples installed on the length-wise centerline of each barrel. Pairs of these thermocouples were installed at six (6) incremental depths, progressing from the outside surface to the bore. Both MICA-style and ceramie-style band-heaters were tested on each barrel size, as follows ... 

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