Posted by Tarzan on June 11, 2001 at 09:13:36:
You asked to know what "accelerated circulation" was because the board of examiners always ask...You can tell them this:
An "accelerated circulation" type W/T boiler is one where the generating tubes and downcomers are slanted at a steep angle, more so than a regular natural circulation boiler. Both are still natural circulation boilers, but the accelerated type is used where higher firing rates are required. Most accelerated circulation boilers will have large downcomer tubes located away from the combustion area of the furnace so that the water in them remains relatively cool in relation to the water in the generating tubes. This design still relies on the fact that water will circulate naturally due to the difference in density of the boiling water in the generating tubes and the cooler water in the downcomer tubes.
Don't confuse this with "controlled circulation" of "forced circulation" type boilers. These types of boilers use pumps to force the water thru the tubes.
Good luck with the board!