Bare Pipe Heat Loss in Steam System

Med618

I have about 30 feet of 3 inch in diameter steam pipe which needs to be insulated. I am able to calculate the heat loss in BTU's per hour from a bare pipe, however I am having trouble estimating the number of hours that steam is being lost through the pipe.



A lot of people simply say, "assume a seven month heating season with the boiler on 12 hours a day, 30 days a month". The problem is I think this is a huge over estimation. If you look at the heat timer settings, and the length of a boiler cycle at different temperatures, there is no way the boiler is running for that long over the course of the year.



But am I wrong to figure this just based upon boiler run time? Is steam in the system, and heat being lost even when the burner isn't firing? How would you recommend estimating the number of hours.



Any help would be much apprecaited.

Jamie Hall

Could I ask

just why it is necessary to determine the annual heat loss from this pipe?  Seems an odd question.



However... there will be heat loss from the pipe any time the boiler is making steam, but relatively little when it is not (the amount is related to the stored heat and heat capacity of the pipe, which really isn't all that great).  Therefore, what you need is the number of hours the boiler actually is running, as you suggest.



As is normal, however, the pipe should be insulated -- not so much to prevent the heat loss, but to enable more even and much faster and controlled steam distribution to the system.

gerry gill

Could always

install a temperature data logger on the pipe for a season. Or short period of time and extrapolate the data you desire.

ChrisJ

Temp

Wouldn't the air temperature around the pipe also make a huge difference?  For example I'm sure a bare steam pipe in a 40F crawl space kills far more steam than one in an 80F basement.



Please let us know the results you come up with as I am curious.