# Exit Temp / Heat Loss in External Pipework

• sam...wise

#### sam...wise

I have been trying to establish what the heat loss and exit temp (in deg C) for 100ml of water traveling down a pipe located externally to a building and subjected to -10degC air temperatures will be if:

The pipe has an internal diameter of 19mm and a length of 3m.
100ml of water with initial temp of 20degC is traveling in the pipe at approximately 0.5m/s. (The pipe is not full of water).
The 100ml water is being released from a siphon, which takes approximately 7seconds. Flow rate = approx. 14.3ml/s.
Assuming material is temp of external air and thickness is negligible.

Both conduction and convection heat losses will be occurring, but I am not sure which is the greater.

Using, the below for water at 20degC:
density = 998kg/m^3
thermal conductivity = 0.598 W/m.degC
Dynamic viscosity = 1.002 kg/m.s
Kinematic viscosity = 1.004 x10-6
Cp = 4182 J/kg.degC
Pr = 7.01

For convection calcs I have been trying to use Texit = (Tsurface - Tin)e^-(h.A/mdot.Cp) but I could do with clarification of my results, as I am not sure they are correct.

Thank you for any assistance. Please let me know if additional information is required.

I have solved this problem. This thread can be deleted.