calculation of heat loss from a hot water ppr80 pipe

[etchyHA]

hi all

how can i calculate the heat loss from a polyproplane pipe conveyed hot water to radiators ? the eqn. of the overall heat transfer is

1/u= (1/hiAi)+ (1/hoAo)+ thick./k

which thick.=0.3 mm , ho= h air at 23c ,
hi= h water at 75c k= thermal conductivity of ppr80 pipe

i want these values
i dont know if i should add the radiation loss or not??

 

[corus]

Radiation tends to be less significant at lower temperatures so you could exclude it. For h to air you need the value using natural convection. It's about 10 W/m^2 C but you'd be better looking at the full formula. For heat loss to the fluid there are simplified equations in MacAdams Heat Transfer book. Alternatively use the Engineer's toolbox

http://www.engineerstoolbox.com/

corus