Simple Pipe Heat Loss Calculation

[steve300]

Thanks in advance..

What is the heat loss per meter of 32mm copper pipe (1.63mm thick)with 40C water flowing through it, if ambient temperature is 10C, 20, 30C?

Thanks,
steve.

 

[IRstuff]

You can use Newton's law of cooling:
Q = htc*area*(deltaT)

TTFN

FAQ731-376

 

[steve300]

How do I work out htc for my copper pipe?

 

[IRstuff]

Lots of heat transfer information floating around, like:

http://web.mit.edu/lienhard/

http://www/ahtt.html

TTFN

FAQ731-376

 

[athomas236]

try ASTM-C680-82

Regards,

athomas236

 

[jmiles]

Steve,

For a problem like yours i usually develop a thermal circuit.

I typically set the length to 1m and then use that as the heat transfer per meter of pipe, but the equation is of the form:

q = inside temperature - outside temperature / sum of thermal resistances

The thermal resistances are as follows

For the internal convection you have 1/(2*Pi*r1*L*h1)

Where r1 is the internal radius in meters, L is the Length in meters, and h is the internal convection coefficient

ln(r2/r1)/(2*Pi*k*L)

This is the heat transfer throught he wall of your copper pipe, where r2 is the external radius, and k is the thermal conductivity of copper

if there is insulation or cladding or anyhtign around the pipe like that you will add more terms like the last, if there is not though your last term will be your external convection which is again of the form

1/(2*Pi*r2*L*h2)

where h2 is your external convection coefficient.

Now if you need to calculate your convection coefficients things get a bit trickier, but it can still be done.

i hope this helps somewhat.

q will give you a result in watts, but if you set all the L's to 1 then the answer will really be in w/m length of pipe.