Heat engines come in two types: internal combustion engines and external combustion engines.
Furnaces come under the classification of external combustion.
In external combustion, the air fuel mixer is allowed to ignite inside a chamber that is not sealed away from external air.
The ignition is followed by flame in the presence of oxygen to support combustion and flame is established which radiates the heat.
Proper receivers should absorb this and transfer to a medium, which gets the process heat for further transmission.
In the furnace, a tall chimney is installed that also creates a natural draft, creating a suction effect in the combustion chamber.
With the controlled spray of liquid fuel, the maximum atomization takes place as the fuel is blown through a nozzle that enables optimum air and fuel mixer.
This helps to establish the flame because of the natural air draft created that acts as the negative pressure to direct the flame towards the object to receive and absorb heat.
Thus, hot gases heated by the flame is passed through the heat exchangers that absorbs the heat from the hot gases, following which the gases cool as they have already transferred the heat goes out through the chimney by virtue of the draft that is there continuously acting upon complemented by the air blown by the blower.
The stack temperature is about 350 to 450 degrees centigrade depending upon the efficiency of the furnace.
In high efficiency furnaces these hot gases are passed through a suction arrangement which are lead into another set of columns to absorb the heat that is still present in the effluent gases and then leave the residual heat out which will be about 120 to 150 degrees centigrade maximum.
The residual heat in the flue gases are recovered thus.
The heat exchangers are metal walled enclosed tubes containing a medium.
This metal has the high conductive ability to absorb the heat from the hot gases and transfer instantly to the medium.
Copper and aluminum, known for their high conductive nature, are these metals normally used in heat exchangers.
Sometimes if air only is needed for heating purpose, the hot gases are directly passed through conduits to heat the area and then will be lead to an induced draft at the end to expel the hot gases out through venting column.
Here also these conduits are made of highly conductive metal to distribute the heat to the place needed.
Thermostat, switches off the valve, when the heat exceeds the set level arresting the heating process and switches on when the temperature comes down.
Other controls are gas valve, ignition control, igniter, transformer, limit control, photocell to sense the flame, blower control board etc.
In automation, the controls are regulated by a commanding center called sequence controller, which stream lines the overall sequence of operation.
Thus, the mechanism of a furnace is controlled to operate safely to supply the process heat to suit the function it is meant for.
Furnace is a great power center and regulating this is like controlling an elephant that obeys a man to discharge the duties at his command; so is the furnace.
Furnaces come under the classification of external combustion.
In external combustion, the air fuel mixer is allowed to ignite inside a chamber that is not sealed away from external air.
The ignition is followed by flame in the presence of oxygen to support combustion and flame is established which radiates the heat.
Proper receivers should absorb this and transfer to a medium, which gets the process heat for further transmission.
In the furnace, a tall chimney is installed that also creates a natural draft, creating a suction effect in the combustion chamber.
With the controlled spray of liquid fuel, the maximum atomization takes place as the fuel is blown through a nozzle that enables optimum air and fuel mixer.
This helps to establish the flame because of the natural air draft created that acts as the negative pressure to direct the flame towards the object to receive and absorb heat.
Thus, hot gases heated by the flame is passed through the heat exchangers that absorbs the heat from the hot gases, following which the gases cool as they have already transferred the heat goes out through the chimney by virtue of the draft that is there continuously acting upon complemented by the air blown by the blower.
The stack temperature is about 350 to 450 degrees centigrade depending upon the efficiency of the furnace.
In high efficiency furnaces these hot gases are passed through a suction arrangement which are lead into another set of columns to absorb the heat that is still present in the effluent gases and then leave the residual heat out which will be about 120 to 150 degrees centigrade maximum.
The residual heat in the flue gases are recovered thus.
The heat exchangers are metal walled enclosed tubes containing a medium.
This metal has the high conductive ability to absorb the heat from the hot gases and transfer instantly to the medium.
Copper and aluminum, known for their high conductive nature, are these metals normally used in heat exchangers.
Sometimes if air only is needed for heating purpose, the hot gases are directly passed through conduits to heat the area and then will be lead to an induced draft at the end to expel the hot gases out through venting column.
Here also these conduits are made of highly conductive metal to distribute the heat to the place needed.
Thermostat, switches off the valve, when the heat exceeds the set level arresting the heating process and switches on when the temperature comes down.
Other controls are gas valve, ignition control, igniter, transformer, limit control, photocell to sense the flame, blower control board etc.
In automation, the controls are regulated by a commanding center called sequence controller, which stream lines the overall sequence of operation.
Thus, the mechanism of a furnace is controlled to operate safely to supply the process heat to suit the function it is meant for.
Furnace is a great power center and regulating this is like controlling an elephant that obeys a man to discharge the duties at his command; so is the furnace.