Heat Loss of Hot Air: Get the Facts on Temperature & Insulation

[RayJalaly]

Hi everyone

I'm new around here and I wonder if anyone can help please. I'm taking hot air off the chimney stack inside a factory at a temperature ranging between 700 and 400 degrees going through a 4 inch stainless steel pipe with 3mm wall thickness. This pipe line will be about 35 meters long in total carrying the hot air to a holding tank in order to keep it warm. I like to know what the temperature of the air would be once its traveled about 35 meters of pipeline totally lagged. About 10 meters of the pipe line will be outside but will be insulated. If we assume the temperatures outside could get as low as say -5 degrees in the winter in the worst case scenario, I'd like to know what the air temperature inside the pipe would be once its delivered to the tank outside if the input temperature at source ranges between 400 and 700 degrees. I'd like to thank anyone who can help in advance. Cheers

 

[haruspex]

totally lagged

Need to know the thickness and conductivity of the lagging.

 

[russ_watters]

...and flow rate of the air. Also, a sketch would help visualize this.

If the entire run is insulated, then it is an easy problem because you don't have to try tackling the convective heat loss.