Thermodynamics HW Solutions 847

# Thermodynamics HW Solutions 847 - Chapter 10 Boiling and...

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Chapter 10 Boiling and Condensation 10-70 A 40-cm long cylindrical heat pipe dissipates heat at a rate of 150 W. The diameter and mass of a 40-cm long copper rod that can conduct heat at the same rate are to be determined. Assumptions Steady operating conditions exist. Properties The properties of copper at room temperature are ρ = 2702 kg/m 3 and k = 237 W/m. ° C. Analysis The rate of heat transfer through the aluminum rod can be expressed as & Qk A T L = Δ Solving for the cross-sectional area A and the diameter D gives 150 W Δ T = 4 ° C L = 40 cm Heat pipe D = 0.5 cm 150 W cm 28.4 = = = ⎯→ = = ° ° = Δ = π ) cm 9 . 632 ( 4 4 4 cm 9 . 632 m 0.06329 = W) 150 ( C) C)(4 W/m. (237 m 0.4 2 2 2 2 A D D A Q T k L A & The mass of this aluminum rod is mV A L == = ρρ (2702 kg / m )(0.06329 m )(0.4 m) =
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