Electric resistance heating coil

ELECTRIC DEFROSTING - Use of electric resistance heating coils to melt ice and frost off evaporators during defrosting. 

Electric Furnace - An air heater in which air is blown over electric resistance heating coils. 

The most advantageous application of the heat pump in the UK at the present time is where air cooling is required in the summer and air heating from the same piece of equipment in the winter. The alternatives will be electric resistance heating, with a higher fuel cost, or the provision of a hot water coil, at extra capital cost. 

The top lid also carries stainless steel cooling coils, through which air may be circulated, to control top temperatures and prevent loss of ZrCU vapor in gases discharged from the furnace. The furnace is provided with three external electric resistance heating elements to provide the heat of sublimation of ZrCLi and control temperature distribution. 

Another method for maintaining this pressure is by the use of electrical energy. This electrical energy is used in the form of heat which can be introduced directly into the liquid as shown on the left side of Figure 3. This heat can also be introduced into the build-up circuit, which eliminates the resistance heating coil within the container. The pressure for this system is maintained by an electrical pressure switch which alternates the flow of electrical energy at the predetermined pressure. 

The generally very good electrical insulation properties coupled with heat resistance and non-burning behaviour indicate usage in coil bobbins, printed circuit boards (which resist heat of soldering), lamp bulb bases and TV... 

Winter heating items fitted within room air-conditioners may be electric resistance elements, hot water or steam coils, or reverse cycle (heat pump). One model of water-cooled unit operates with a condenser water temperature high enough to be used also in the heating coil. 

A type of boiler that produces heat via electric resistance coils or electrodes. 

These measure the change in thermal conductivity of a gas due to variations in pressure—usually in the range 0.75 torr (100 N/m2) to 7.5 x 10"4 torr (0.1 N/m2). At low pressures the relation between pressure and thermal conductivity of a gas is linear and can be predicted from the kinetic theory of gases. A coiled wire filament is heated by a current and forms one arm of a Wheatstone bridge network (Fig. 6.21). Any increase in vacuum will reduce the conduction of heat away from the filament and thus the temperature of the filament will rise so altering its electrical resistance. Temperature variations in the filament are monitored by means of a thermocouple placed at the centre of the coil. A similar filament which is maintained at standard conditions is inserted in another arm of the bridge as a reference. This type of sensor is often termed a Pirani gauge. 

For determining the heat capacity, a dc electric current of about 1.5 A is passed through a heating coil of 6Q. resistance during a known time interval. The magnitude of the current is measured as a function of time by determining the potential difference developed across a standard resistance in series with the coil. The electrical circuit is shown in Fig. 2. 

Procedure. It is advisable to cany out a test of the electrical heating procedure in advance of the actual runs. This will also provide a chance to check on the heating-coil resistance under actual operating conditions (i.e., when the coil is hot). Place roughly... 

Electrical heating circuit for solution calorimeter. The standard resistor should be a wire-wound resistor with a low temperature coefficient and rated for 2 W. If a heating coil of higher resistance (say, 60 2 is to be used, the current can be reduced to 0.5 A and a 1-H standard resistor can be used. 

A coil of wire wound round an iron core was made to rotate in a calorimeter between the poles of a horse-shoe magnet. Electric currents are produced in the wire, and are in turn converted into heat owing to the electrical resistance of the coil. The conversion of work into heat takes place indirectly by means of the electric current. By this method Joule obtained the mean value J = 459-62 kgm. for the mechanical equivalent of heat. 

The bath temperature may be controlled by heating with an immersed loop of Nichrome resistance coil, such as the heating element from an electrical appliance. The coil is connected to a 110-volt line in series with a 27-ohm 5-ampere variable resistor and a 600-watt heater element, which may be cut out of the circuit to lower the fixed resistance. An ammeter in the circuit helps to determine the proper adjustment of the sliding contact of the resistor. To avoid an excessive load on the coil,... 

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