Ads
related to: induced draft fan
Search results
Results From The WOW.Com Content Network
Forced draft: When air or flue gases are maintained above atmospheric pressure. Normally it is done with the help of a forced draft fan. [2] Induced draft: When air or flue gases flow under the effect of a gradually decreasing pressure below atmospheric pressure. In this case, the system is said to operate under induced draft.
Induced draft – A mechanical draft tower with a fan at the discharge (at the top) which pulls air up through the tower. The fan induces hot moist air out the discharge. This produces low entering and high exiting air velocities, reducing the possibility of recirculation in which discharged air flows back into the air intake.
As a result it can be more easily routed through walls or floors. However, the condensing furnace is more expensive initially because of the extra induced-draft fan and condensate pump required, and the extra heat exchanger in the firebox. The heat exchangers may be damaged by corrosion or metal fatigue from many heating and cooling cycles.
The third method is by simply using an induced draught fan (ID fan) which sucks flue gases out of the furnace and up the stack. Almost all induced draught furnaces have a negative pressure. Forced draught: draught is obtained by forcing air into the furnace by means of a fan (FD fan) and duct-work.
The axial fan is often contained within a short section of cylindrical ductwork, to which inlet and outlet ducting can be connected. Axial fan types have fan wheels with diameters that usually range from less than a foot (0.3 meters) to over 30 feet (9.1 m), although axial cooling tower fan wheels may exceed 82 feet (25 m) in diameter.
The induced draft fan assists the FD fan by drawing out combustible gases from the furnace, maintaining slightly below atmospheric pressure in the furnace to avoid leakage of combustion products from the boiler casing.