A 7-cm-external-diameter, 18-m-long hot-water pipe at 80°C is losing heat to the surrounding air at 5°C by natural convection with a heat transfer coefficient of 25 W/m2·°C. Determine the rate of heat loss from the pipe by natural convection, in kW.

Question

Physics

Sammy

22 September, 19:41

A 7-cm-external-diameter, 18-m-long hot-water pipe at 80°C is losing heat to the surrounding air at 5°C by natural convection with a heat transfer coefficient of 25 W/m2·°C. Determine the rate of heat loss from the pipe by natural convection, in kW.

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Answers (1)

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Thomas Eaton · Answer 1

Given:

D = 7 cm

= 0.07 m

A = pi * r ^2

= pi * (0.07/2) ^2

= 0.00385 m2

T1 = 80°C

T2 = 5°C

h = 25 W/m2·°C

Q = A * h * delta T

= 0.00385 * 25 * (80 - 5)

= 7.22 W

= 7.22 * 10^-3 kW.