A hollow sphere 10 cm ID and 30 cm OD of a material having thermal conductivity 50 W/mK is used as a container for a liquid chemical mixture. Its inner and outer surface temperature are $300^{\circ} C$ and $100^{\circ} C$ respectively. The heat flow rate through the sphere is _____kW.
9.42

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Solution

The correct option is A 9.42
$Q = \frac{4 π r_{0} r_{i} k (T_{i} - T_{0})}{r_{0} - r_{i}}$

$= \frac{4 \times π \times 0.15 \times 0.05 \times 50 (300 - 100)}{0.15 - 0.05}$

$= 9.42 k W$

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