Transfer Cengel 5th Edition Chapter 3 - Solution Manual Heat And Mass

Heat conduction in a solid, liquid, or gas occurs due to the vibration of molecules and the transfer of energy from one molecule to another. In solids, heat conduction occurs due to the vibration of molecules and the movement of free electrons. In liquids and gases, heat conduction occurs due to the vibration of molecules and the movement of molecules themselves.

$r_{o}=0.04m$

Assuming $k=50W/mK$ for the wire material, Heat conduction in a solid, liquid, or gas

Solution:

$\dot{Q}=\frac{V^{2}}{R}=\frac{I^{2}R}{R}=I^{2}R$ Heat conduction in a solid

$T_{c}=800+\frac{2000}{4\pi \times 50 \times 0.5}=806.37K$

$\dot{Q}=\frac{T_{s}-T_{\infty}}{\frac{1}{2\pi kL}ln(\frac{r_{o}+t}{r_{o}})}$

$\dot{Q}_{cond}=0.0006 \times 1005 \times (20-32)=-1.806W$ Heat conduction in a solid, liquid, or gas

$\dot{Q}_{conv}=150-41.9-0=108.1W$