Boiler metal temperature

[Rebecca Hannah]

Hi all,

I have a question.

In a power boiler, if we know the saturation temperature or superheated steam temperature, can we estimate the metal temperature?

Thanks very much

Rebecca

 

[davefitz]

Sure, that is how the boiler mfr designs the individual components. Using complex computer programs , the local fluegas temperature and heat flux is computed, and once the heat flux and bomponent fluid temperature is known, thne it is stragihtforward to compute the metl temperature. The complicated part is adding safety factors for unbalances, such as fluegas flow and temperature unbalances, working fluid flow and temperature unbalances, and dynamic effects .

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[davefitz]

Remenber, the boiler is made of thousands of individual tubes, and it only takes the failure of one tiny tube to force the entire boiler to be shutdown. Therefore the governing deisgn philosphy is to design all tubes to be adequate to survive the "worst tube" operating conditions, given that there will be unbalances in flow and temperature of fluid and gases .

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

And eventually surface contamination and thickening oxide scale will have the effect of increasing metal temperature.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[JStephen]

Note that Davefitz' answer assumes you have more information than what you stated. If you assume heat is being transferred across a surface, you can't assume average temperature is equal to the cool side, which is what it sounds like you were hoping to do.

 

[Rebecca Hannah]

Thanks everyone for the effort.

Maybe if I give a couple of examples, it could be easier to answer.

Let's say a 60-barg boiler with a superheated steam of 540 deg.C, and the feedwater temperature is 107 deg. C.

The saturation temperature would be 277 deg. C. In the furnace, the waterwall tubes and the platen superheaters are exposed to radiant heat, so what would be the estimated metal temperature? In the case of convective tubes, it would be subjected to lower temperatures, so what would be the metal temperature, and the economizer, what would be the estimated temperature?

If someone has a way to figure out these estimates, I appreciate it very much.

Best regards

Rebecca