Chimney flue temperature

[Ian PParticipant @ianp]

Posted by Bazyle on 20/01/2017 09:01:20:

Sounds interesting and though not model engineering it is 'making stuff'.

I'm curious why you would think to mention that its 'not model engineering'?

This forum is related to two periodicals, one is aimed fully at model engineers and one is definitely engineering in general (but I do accept it has 'model' in its title) so whilst there might be two groups of forum users I regard each member and each post as being equally relevant to the forum.

Ian P

[Ian PParticipant @ianp]

Rather than measure the temperature at the outlet of the stack, why not measure the flue temperature at the outlet of the 'heat exchanger'?

Better would be to measure the inlet and outlet temperatures so you can see just how much energy you are taking out of the available heat.

Even if you knew the gas temperature at the top of the chimney, I'm unsure how it will help to decide how much to lengthen the heat exchanger by.

Ian P

[Gordon WParticipant @gordonw]

From practical experience of stoves – The temperature can vary , depending on fuel type and weather conditions. I've seen stove pipes dull red at the top when the air inlet was left open after lighting. Taking hot air off the flue can even stop the flue gas going up the flue. Too cold and a tar etc. deposit sets to the inside. I used to advise having a blaze-up once a week to stop large build up, esp. on wood burners.

[SandgrounderParticipant @sandgrounder]

Posted by Gordon W on 20/01/2017 12:12:38:

From practical experience of stoves – The temperature can vary , depending on fuel type and weather conditions. I've seen stove pipes dull red at the top when the air inlet was left open after lighting.

When I worked with some heat treatment furnaces 'dull red' was about 600C in a dimly lit room.

John

[Ian S CParticipant @iansc]

Thirty odd years ago Mum and Dad had problems with a fire place in a new home. The fire was available with either of two chimneys, one for burning coal, and the other for wood. Wood was the fuel of choice, but they soon found that the chimney required cleaning nearly every week, after Dad died, and Mum moved out of the house, someone did some investigations and found that the wrong chimney had been fitted, the one for coal fires was designed to run at a higher temperature, and when using wood the chimney did not get hot enough to burn the rubbish that went up the chimney, so it got stuck inside, so EGT seems to be important.

Ian S C

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