Thermostatic control

Several plants employ cooled-belt flakers. These consist of flexible steel belts, ca 1-m wide and up to 50-m long, that have short mbber skirting at the edges. Molten pitch flows from a thermostatically controlled tank over a weir to give a flat thin sheet on the belt, which is cooled from below by water sprays. At the end of the belt, the solid pitch is broken up by rotating tines. The pitch flakes are drained and transported to a covered storage silo by belt conveyor, during which time the surface moisture evaporates. 

Tremendous advances have been made in the design and efficiency of roU refiners. The methods currently used for casting the roUs have resulted in machines capable of very high output and consistent performance. The efficiency of the newer refiners has also been improved by hydrauHc control of the pressure between the roUs and thermostatic control of cooling water to the roUs. 

The electrolytes are non-corrosive and the electrodes do not corrode with time. This feature is of special significance when compared with an ordinary liquid resistance starter used commonly for slip-ring motors. Electrolytes do not deteriorate and therefore do not require replacement. The evaporated liquid can be replenished with drinking water when the level of the electrolyte falls as a result of evaporation. In Europe such starters have been used for over 15-20 years. Electrolyte switching is a costlier proposition compared to direct on-line or star/delta switching due to additional shorting contactor and timer, and the cost of electrolyte, its tank and thermostatic control etc. The cost may. 

Thermostatic control of the gas supply to the heater is required so that the air-off temperature can be controlled. This is achieved by a two-stage control that opens a valve partly on low rate and fully on high rate. 

Room air conditioner (self-contained) A rcxjm air conditioner complete with a direct expansion (dx) system condenser and evaporator fans, filtration, and thermostatic control. 

Storage tanks can be heated with thermostatically controlled steam coils, hot-water coils, electric immersion heaters or a combination of these. The elements and their... 

Automatic thermostatic control (single or multiple stage) ... 

Air-cooled condensers having two or more fans (Figure 6.2) may have a pressure switch or thermostatic control to stop the fans one by one. This method is simple, cheap, and effective. 

Where evaporative condensers and water cooling towers have only one fan (or fan drive motor), coarse control can he effected hy on-off switching. The time lag will then depend on the mass of water in the circuit, and the sensing element needs to have a wide differential to prevent frequent motor starts. Towers should have thermostatic control of the fan to prevent water freezing on the packing in winter. 

Low-voltage electric resistance heater cables fixed to the structural floor slab and then protected within a 50 mm thickness of cement and sand to give a suitable surface on which the floor vapour barrier can be laid. The heating is thermostatically controlled, and it is usual to include a distance reading or recording thermometer to give visual indication of the temperature of the floor at several locations below the insulation. 

Direct injection of liquid nitrogen is also used on the larger vehicles. This is carried in metal vacuum flasks and the vehicle will he reliant on depots where the liquid nitrogen flask can he refilled. The only mechanical equipment will he a thermostatically controlled solenoid injection valve. 

In the first of these methods, the reduction in air mass flow is limited by considerations of distribution velocities within the rooms, so at light load more air may need to be used, together with more re-heat, to keep air speeds up. Within this constraint, any proportion of sensible and latent heat can be satisfied, to attain correct room conditions. However, full humidity control would be very wasteful in energy and a simple thermostatic control is preferred. 

The blending of cold and warm air will be thermostatically controlled, so that the humidity in each zone must be allowed to float, being lowest in the zones with the highest sensible heat ratio. 

Electric ovens. The most convenient type is an electrically heated, thermostatically controlled drying oven having a temperature range from room temperature to about 250-300 °C the temperature can be controlled to within 1 -2 °C. They are used principally for drying precipitates or solids at comparatively low controlled temperatures, and have virtually superseded the steam oven. 

The column is enclosed in a thermostatically controlled oven so that its temperature is held constant to within 0.5 °C, thus ensuring reproducible conditions. The operating temperature may range from ambient to over 400 °C and for isothermal operation is kept constant during the separation process. 

A large number of the results presented in this review were obtained with the device presented in Fig. 26 and its operating principle will be explained in some detail. The basic set-up consists essentially of a stainless steel syringue closed at one end by a narrow circular orifice and surrounded by a thermostatically controlled jacket. Apart from minor mechanical details used to improve flow field uniformity, the degradation apparatus is similar to the device described by Merrill... 

The agitation studies for PET depolymerization were performed in the Atlas Launder-ometer. The Launder-ometer is a device for rotating closed containers in a thermostatically controlled water bath. The procedure used in these experiments was adapted from an American Association of Textile Chemists and Colorists (AATCC) standard test method. The 5% sodium hydroxide solution (250 mL) was preheated to 80°C in a 1-pint stainless steel jar. The catalysts were added in the following amounts in separate experiments TOMAC (0.04 g, 0.0001 mol) TOMAB (0.045 g, 0.0001 mol) and HTMAB (0.045 g, 0.0001 mol). The PET fiber specimens (1.98 g, 0.01 mol) were placed in the containers along with ten -in. stainless steel balls to aid in the agitation process. The jars were sealed in the Launder-ometer, whose bath was at the desired temperature (80°C). The machine was allowed to run for the allowed treatment times (i.e., 30, 60, 90, 150, and 240 min) at 42 rpm. Upon decanting, any residual fibers... 

A convenient thermostat control for a beaker is simply a small bulb filled with toluene to which a U-tube full of mercury is attached (Figure 73, IV). This can be made with 8 mm and 15 mm tubing. The bulb may be filled by successive heating and cooling, with the head in toluene. 

Fluorescence spectra were recorded using an SLM 4800 spectrofluorimeter (Bioritech, Chamarande, France) fitted with a thermostat-controlled (30°C) front-surface accessory. The incidence angle of the excitation radiation was 60°. Coagulation kinetics were performed in a quartz cuvette 1 cm x 1cm. All spectra were corrected for instrumental distortions in excitation using a rhodamine cell in the reference channel. 

The oven temperature always drops a few degrees, owing to the cooling effect of the cold acid and the evaporation of a relatively large quantity of water. This drop in temperature is much less noticeable in a large oven than in a small one, and in one having thermostatic control in contrast to manual control. 

A mixture of 2-iodotoluene (8.78 g, 0.04 mol) and trimethyl phosphite (24.8 g, 0.20 mol) was placed in a 45-ml, double-jacketed silica reaction vessel. The mixture was degassed by flushing with dry nitrogen for 5 min and irradiated with a 450-watt Hanovia (Model 679A-10) high-pressure quartz mercury vapor lamp fitted with an aluminum reflector head. The lamp was placed 5 cm from the inner portion of the reaction vessel. The reaction temperature was maintained at 0°C by the circulation of coolant from a thermostatically controlled refrigeration unit. Irradiation was continued at this temperature for 24 h. At the end of this time, the volatile materials were removed with a water aspirator, and the residue was vacuum distilled (96 to 97°C/0.25 torr) to give the dimethyl 2-methylphenylphosphonate (7.28 g, 91%). 

To ensure operation under reproducible conditions, the column is enclosed in a thermostatically controlled oven whose temperature can be held constant to within 0.1°C. Operating temperatures range from ambient to over 400°C and may remain constant during a separation - isothermal operation - or automatically increased at a predetermined rate to speed the elution process - temperature programming (p. 106). The latter is a form of gradient elution. Rapid temperature equili-... 

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