Client in trouble
Client in trouble
(OP)
I need a bit of help calculating something for a client who has gotten into a bit of bother. He has installed heating into a site of 60 houses. Each house has an 8 port manifold with each port distributing to an individual radiator. The problem lies with the pipe running from the manifold to the radiator. This pipe runs below the insulating layer and therefore according to building regulations (Ireland) should be insulated, but instead he has simply run the pipe through a corrugated plastic sleeve. I need to calculate what heat is being lost into the ground through this 'pipe-in-pipe'. The information i have is:
-water inlet temperature
-radiator size in KW
-pipe inner and outer diameter
-thermal conductivity value of PEX pipe and plastic sleeve
I'm not certain what temperature i will assume for the surrounding concrete but i also need to know:
-Mass Flow Rate (for formula- Q=M*A*(T1-T2)
-U-value for the pipe and plastic sleeve (it's been 25 years since i've studied this and am struggling to remember the correct formulae and also the diameter of the corrugated plastic sleeve has a max and min- should i take an average)
Any advice would be greatly appreciated as it looks like this client will be getting sued by the developer.
Thanks
-water inlet temperature
-radiator size in KW
-pipe inner and outer diameter
-thermal conductivity value of PEX pipe and plastic sleeve
I'm not certain what temperature i will assume for the surrounding concrete but i also need to know:
-Mass Flow Rate (for formula- Q=M*A*(T1-T2)
-U-value for the pipe and plastic sleeve (it's been 25 years since i've studied this and am struggling to remember the correct formulae and also the diameter of the corrugated plastic sleeve has a max and min- should i take an average)
Any advice would be greatly appreciated as it looks like this client will be getting sued by the developer.
Thanks





RE: Client in trouble
David
RE: Client in trouble
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Client in trouble
RE: Client in trouble
The other option is to enter the structure into a thermal analysis program.
I doubt that any ad hoc hand calculation will adequately capture the behavior of this structure.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Client in trouble
Why do it right, when you can do it twice.
RE: Client in trouble
i cannot help with the building code issues or with the details of the required input values for this particular problem.
and i'll spare your client my tedious lecture on "do it right or don't do it".
but the basic equations for addressing this type of problem are here:
http://myweb.wit.edu/leod1/MECH594/Texit.html
you no doubt will have to make assumptions and tweak input values to fit your problem.
i hope this is helpful
regards
magicme
------------------------------------
there's no place like gnome.
RE: Client in trouble
500*(T1-T2)*gpm = BTUH, where T1 is temp before, and T2 is temp after.
Flow rate can be accurately measured by a strap on magnetic flow meter.