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## Homework Statement

A thick wall cylinder having a thermal conductivity of 60W/mK has a 75mm inner diameter and is 2.5mm thick. The pipe carries water at 90 degrees celsius inside and the outside is surrounded by air at 20 degrees celsius.

The heat transfer coefficients inside and outside the hot water pipe are 500W m2 K and 35 W m2 K respectively. Natural convection can be ignored.

Calculate the heat loss in W per unit length of the pipe

## Homework Equations

q= K Delta U T1-T2/r1-r2 = T1-T2/r2-r/Kal

Alm = 2Pie Lr2- 2Pie Lr1/Ln(2(2{PieLr2/2pieLr1 [/B]

**= A2-A1/ln(A2/A1)**

## The Attempt at a Solution

q = 90-20/0.03875-0.037

60 * (2Pie x 1 x 0.03875- 2Pie x 1 x 0.03875)/

ln (2Pie x 1 x0.3875/2Pie x 1 x0.3875/2Pie x 0.3875