Heat loss from buried pipe in "concrete conduit"
Heat loss from buried pipe in "concrete conduit"
(OP)
looking to figure the heat loss from steam and condensate piping in a buried "concrete conduit." the conduit is a concrete tunnel about 1' tall by about 1' wide that is buried at a depth from 3' to 10' - hilly terrain. the conduit is open at both ends to the steam pits or buildings. the steam piping is 3" at 100 psi with 2" of mineral wool, the condensate is 2" with 1" mineral wool.
if it was a buried insulated pipe i use the simple method of assuming the earth is at a relativley constant temperature and cipher it from that. i try to be conservative and the number are good enough.
any thought on the best way to approach this? i am thinking of including the space between the outside of the insulation and the inside of the concrete and the concrete as more insulation and figure the heat loss from there. among other things this basically ignores any convection in the conduit space.
the actual situation is much more complicated and messier than i describe.
if it was a buried insulated pipe i use the simple method of assuming the earth is at a relativley constant temperature and cipher it from that. i try to be conservative and the number are good enough.
any thought on the best way to approach this? i am thinking of including the space between the outside of the insulation and the inside of the concrete and the concrete as more insulation and figure the heat loss from there. among other things this basically ignores any convection in the conduit space.
the actual situation is much more complicated and messier than i describe.





RE: Heat loss from buried pipe in "concrete conduit"
RE: Heat loss from buried pipe in "concrete conduit"
the length is hundreds of feet and in reality varies between 8" to 2" and to make it more complicated the conduit in areas is crushed, missing insulation, leaky steam pits, steam pits fill with water and run down the conduits ruiing insulation. Just wanted to keep it simple for now.
i can get the outside temp of insulation thru calculations.
i agree with surrounding air temp between steam or outer insulaiton temp and ground temp.
i agree about still air - for all practical purposes it is.
yes trial and error - will probably use a high number or "average" to give all involved a conservative number.
i do not have my ASHRAE with me but will look it up. lots on the web.
i agree about the air temp stabilizing around the conduit.
Thank you
RE: Heat loss from buried pipe in "concrete conduit"
Actually, you didn't, ostensibly, since you are including the air as a layer of insulation.
It does not necessarily need to be iterative, the solution solves a bunch of simultaneous equations, so programs that have systems of equations solvers can do it directly. You just have to balance the heat flows, since the energy is conserved.
TTFN
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RE: Heat loss from buried pipe in "concrete conduit"
Here's one:
http://www.crrel.usace.army.mil/library/crrelrepor...