Forced Draft Type vs Induced Draft Type

CHARATERISTICS OF INDUCED DRAFT TYPE

   Advantages

       Better distribution of air across the bundle.
       Less possibility of hot effluent air recirculating into the intake.
       Better process control and stability because the plenum covers 60% of the bundle face area,           reducing the effects of sun, rain, and hall.
       Increased capacity in the fan-off or fan failure condition, since the natural draft stack effect is           much greater.

   Disadvantages

       Higher horsepower requirements if the effluent air is very hot.
       Effluent air temperature should be limited to prevent damage to fan blades, bearings, or          other mechanical equipment in the hot air stream. When the process inlet terature exceed the          maximum temperature, forced draft design should be considered because high effluent air          temperatures may occur during fan-off or low air flow operation.
       Fans are less accessible for maintenance, and maintenance may have to be done in the hot air          generated by natural convection.
       Plenums must be removed to replace bundles.


CHARATERISTICS OF FORCED DRAFT TYPE

   Advantages

      Lower horsepower requirements if the effluent air is very hot.
      Better accessibility of fans and upper bearings for maintenance.
      Better accessibility of bundles for replacement.
      Accommodates higher process inlet temperatures.

   Disadvantages

      Less uniform distribution of air over the bundle.
      Increased possibility of hot air recirculation, resulting from low discharge velocity from the bundles,          high intake velocity to the fan ring, and no stack.
      Low natural draft capability on fan failure.
      Complete exposure of the finned tubes to sun, rain, and hail, which results in poor process control          and stability.
 

Production Capacity for Air cooled heat exchanger