Boiler Heat Xfer Area


Old 01-13-19, 03:27 PM
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Join Date: Oct 2008
Location: USA
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Boiler Heat Xfer Area

Older hot-water or steam boilers often, on their nameplate, listed the heat transfer area, in sq ft. The simplest example may be a fire-tube boiler: the heat transfer area is just the total surface of the fire tubes. A "figure of merit" was often cited, Btu/sq ft - the lower the better. Nowadays, heat xfer area is very seldom even mentioned. What happened? Maybe that explains why older boiler are so much physically larger than the modern ones, of similar ratings?

Modern boiler specs do list net and gross Btu/hr ratings. Maybe that covers it all? On the other hand, for an internal combustion engine, I want to know not just the horsepower but also the displacement. Engine horsepower and boiler efficiency specs may be susceptible to some monkey business, but Btu/hr input and heat xfer area are pretty much verifiable by DIYers.
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Old 01-14-19, 04:19 AM
Join Date: Jan 2017
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I see that you have been around a while and maybe you have gray hair like I do. Years ago, the steam boilers that were produced were large enough that they could in most cases store all the water the system would use without the need for a separate condensate storage tank system or having the boiler flood in the off cycle. Today that would cost too many $ so contractors have to compensate. I won't go into details but the company I worked for made a lot of money fixing other contractors short comings, (adding condensate feed systems and the like). We did a lot of work on 1 pipe 2 pipe steam, high and low pressure steam boilers fired with gas, both natural and sewer, #1, #2, #6, fuel oil, Hard and soft coal, and wood chips and saw dust. I saw a lot of stuff. I see the stuff they make today and I cry. Wow have the times change. I will probably get chastised for my "rant" but WHO CARES!
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