Why is the boiler chimney thin at the top and thick at the bottom?
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Suddenly one day, a colleague asked me: Do you see why the stove chimney is thin at the top and thick at the bottom? I asked a few old employees who burned the stoves but they didn't know. I just knew that it was designed that way. I'm not a boiler guy, so I'm taking the liberty to ask.
The size of the chimney's suction force is related to the difference in temperature between the flue gas and the outside air, as well as the height of the chimney. The higher the temperature difference between the flue gas and the outside air, the greater the chimney suction force. In order to ensure that the chimney has appropriate suction force, the diameter and height of the chimney need to be calculated based on the flue gas volume, the average temperature of the flue gas, and the flow rate of the flue gas. The purpose of gradually reducing the diameter of the chimney from bottom to top is to increase the flow rate of flue gas to increase the chimney suction force and maintain the negative pressure in the furnace.
1． The flue gas flows inside it and its volume decreases due to heat dissipation. By using thin ones at the top and thick ones at the bottom, the flue gas circulation area is reduced, and the flue gas flow rate remains unchanged or even increases, which can prevent the backflow of flue gas. 2. The center of gravity of the chimney is at the bottom, with a large supporting area and good stability.
You can also build a chimney with a small bottom and a large top and see how it works. ha
There are many discussions on this issue in the forum. You can check the old posts. http://bbs.hcbbs.com/viewthread.php?tid=443794&highlight=%D1%CC%B4%D1
Mainly to reduce the flue gas flow and increase the suction force, and also to enhance the stability of the chimney