Insulation

JohnNY

I'm consulting for a 120-unit building in Brooklyn and found this steam header absurdly close to the make-up air intake louvres. I'm not going to suggest they repipe the header, rather, I'd appreciate some solid numbers on what size insulation might eliminate undue condensing in the header on a 10° day.
Many thanks.

JohnNY

Code only calls for ½" wall thickness. I'm thinking 1.5", but I hate to guess when the right math is probably pretty simple.

Abracadabra

Can't help you on the math, but imho directing the incoming flow of air down to the floor will help as well.

ChrisJ

10 degree air blowing on it is rough.
I'd do 2" at a minimum for that immediate area. 1.5" would probably do pretty decent as well.

I've never been good at calculating the loss of insulated pipes and I've tried a few times.

KC_Jones

Try this and see if that helps.
http://www.engineersedge.com/heat_transfer/heatlossinsulatedpipe/heat_loss_insulated_pipe_equation_and_calculator_13169.htm

Zman

@JohnNY,
It is not perfect, but I plugged a 3" pipe with 212 degree water and 10 degree air into Siggy's software.
The bare pipe lost 334 BTU/hr per foot, with 1/2" fiberglass it lost 67 BTU/hr per foot and 1" fiberglass it lost 42 BTU/hr per foot.
For a short run like that I would think the numbers are close enough.
Carl

Quercus

Assuming those numbers are good, condensation depends on the rate you are putting steam through the pipes. Whether removing 334 BTU/hr/ft will lower your energy to saturation is what you are worried about. I suspect not if you are looking at a 10 foot section. That would be like having a radiator added to the system.

Your heat loss will be higher than those examples because there is more heat in the pipe to lose. I don't recall the scale of the difference with steam vs water, plus it depends on the steam conditions. If you are very superheated you will lose heat but not necessarily condense. Closer to saturation and it may be an issue. Either way, the heat is lost.

Slowing or diverting the cold stream will weaken it's ability to cool convectively.

I thought I could help with solid numbers but I am too rusty for that. Mark's handbook is too obtuse for me to relearn in 15 minutes so I think I will explain my approach to your question without numbers.

Steve

ChrisJ

Please, correct me if I'm wrong but 212F steam should dissipate the same exact heat through X amount of surface as 212F water.

The only difference would be when determining how much water you need to pump to keep the temperature up. No? The Delta T is still the same?

Zman

ChrisJ said:

Please, correct me if I'm wrong but 212F steam should dissipate the same exact heat through X amount of surface as 212F water.

The only difference would be when determining how much water you need to pump to keep the temperature up. No? The Delta T is still the same?

Chris,
That is my thinking.
Although the 10 degree air will take the heat away faster than 70 air, the relationship is linear.
At 70 degree air,
Bare pipe 217 BTU/hr per foot
1/2" 50 BTU/hr per foot
1" 31 BTU/hr per foot
Carl

Quercus

ChrisJ said:

Please, correct me if I'm wrong but 212F steam should dissipate the same exact heat through X amount of surface as 212F water.

The only difference would be when determining how much water you need to pump to keep the temperature up. No? The Delta T is still the same?

Heat dissipation would be the same but the effect of the heat loss would be different depending on the saturation level. If the 212 steam is mostly saturated you can condense easier than "dry" 212 steam. Once you go above the 212 you would have much more heat to lose to become water again.

In a big building near the boiler I would expect hotter steam. I am not a steam boiler operator, so I'm relying on distantly past training.

Where would the condensate typically start falling out in a system like this?

JohnNY

Zman said:

@JohnNY,
It is not perfect, but I plugged a 3" pipe with 212 degree water and 10 degree air into Siggy's software.
The bare pipe lost 334 BTU/hr per foot, with 1/2" fiberglass it lost 67 BTU/hr per foot and 1" fiberglass it lost 42 BTU/hr per foot.
For a short run like that I would think the numbers are close enough.
Carl

I feel like this tells the story right here. Adding another ½" to pipe losing 42 BTU/ft is going to bring us to a pretty happy place.

JUGHNE

If you closed the vent up, would a "Fan in a Can" take care of the combustion air? But do you still need "ventilation" for the room.

You would want to insulate everything possible then or have a pretty hot room in there and surrounding areas.

JohnNY

Fan in a Can instead of insulation just isn't my thing. I hate fans. I also hate pumps. Granted, these are two of life's necessary evils, but I avoid when possible.

ChrisJ

JohnNY said:

Fan in a Can instead of insulation just isn't my thing. I hate fans. I also hate pumps. Granted, these are two of life's necessary evils, but I avoid when possible.

Can I interest you in a monitor top?
No fans! I too, avoid them when I can.

Abracadabra

JUGHNE said:

If you closed the vent up, would a "Fan in a Can" take care of the combustion air? But do you still need "ventilation" for the room.

You would want to insulate everything possible then or have a pretty hot room in there and surrounding areas.

I have a feeling that size boiler would need multiple fan-in-a-cans.

RobG

Fans=Late night emergency calls!

Answerman

JohnNY said:

Code only calls for ½" wall thickness. I'm thinking 1.5", but I hate to guess when the right math is probably pretty simple.

@JohnNY I beleive the NYC Energy Conservation Code requires 2.5" thick insulation for steam pipes ≤4", and 3" insulation for pipes 4" and larger.

But if I'm missing something, or that doesn't apply for some reason, please let me know..