Thermometers insertion type

An Omega model HH22 type J-K digital thermometer, connected to a type K thermocouple probe inserted directly into the flask, was used to measure the temperature. 

Distillation heads (or still-heads) are shown in Fig. 2.13 (a)-(c). Type (a) is a bend ( knee-tube ) which is frequently employed for those distillations which merely require the removal of solvent. Type (b) is a simple distillation head when fitted into a flask with a ground glass socket, the assembly is virtually a distillation flask. For some purposes, a thermometer may be fitted into a one-hole rubber stopper of correct taper and then inserted into the socket the area of rubber which is exposed to the organic vapour is relatively so small that the amount of contamination thus introduced is negligible. If, however, all rubber stoppers must be absent because of the highly corrosive nature of the vapour, a thermometer fitted with an appropriate size cone is employed. Alternatively the... 

For both type of microwave reactors, if the reactor is not supplied with a temperature sensor or more likely accurate temperature measurment is prerequisited during an experiment, the fiber-optic temperature sensor is directly applied to the reaction mixture. In order to secure the sensor from harsh chemicals, the sensor is inserted into a capillary that in turn is inserted into the reaction mixture. In such a case, it is strongly advocated to use capillaries that are made of quartz glass and are transparent to microwave irradiation. Any capillary that is made of glass or even borosilicate glass can always slightly absorb microwave energy, in particular, while the reaction mixture does not absorb microwaves efficiently, and in turn lead to failures of fiber-optic thermometer performance. 

A special type of calorimeter, a bomb calorimeter, is useful for the measurement of the fuel value (Calories) of foods. Such a device is illustrated in Figure 8.6. Its design is similar, in principle, to that of the "coffee cup" calorimeter discussed earlier. It incorporates the insulation from the surroundings, solution pool, reaction chamber, and thermometer. Oxygen gas is added as one of the reactants, and an electrical igniter is inserted to initiate the reaction. However, it is not open to the atmosphere. In the sealed container the reaction continues until the sample is completely oxidized. All of the heat energy released during the reaction is captured in the water. 

These can be used over a very wide range. Their principle of operation is based on the large temperature coefficient of electrical resistance of Pt and Ni (for example, the resistance of Pt changes by 0.4% per degree). These thermometers are among the most accurate temperature measuring instruments. It is not difficult to make a resistance thermometer in the laboratory, but the commercial instruments are preferable. The high-temperature type consists of a mica cross inserted in a thin-wall quartz tube. A fine double Pt filament is wound around the mica cross. 

A round-bottomed multinecked flask is a common approach when a sealed cell is required. Fig. 2(a). The multiple ports allow for insertion of tubes for deaeration, thermometers, and the various electrodes. As mentioned above, cells that press the sample against a window are called flat cells. Flat cells are easily sealed and convenient to use. Fig. 2(b). A clamp-on cell is a type of flat cell commonly used for coated samples. Fig. 2(c). Large areas are typically needed for clamp-on cells, and crevice corrosion is not a problem. The clamp-on cell uses a common glassware... 

IS An air-water-vapor mixture, 1 std atm, 180 C, flows in a duct (wall temperature 180 Q at 3 m/s average velocity. A wet-bulb temperature, measured with an ordinary, unshielded thermometer covered with a wetted wick (9.5 mm outside diameter) and inserted in the duct at right angles to the duct axis, is-52 C. Under these conditions, the adiabatic-saturation curves of the psychromctric chart do not approximate wet-bulb lines, radiation to the wet bulb and the effect of mass transfer on heat transfer are not negligible, and the k-type (rather than F) mass-transfer coefficients should not be used. 

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