Sum

A steel frame (K = 45 W m^{−1}°C^{−1}) of total length 60 cm and cross sectional area 0.20 cm^{2}, forms three sides of a square. The free ends are maintained at 20°C and 40°C. Find the rate of heat flow through a cross section of the frame.

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#### Solution

Thermal conductivity*, K* = 45 W m^{–1} °C^{–1}

Length*, l* = 60 cm = 0.6 m

Area of cross section, *A* = 0.2 cm^{2} = 0.2 × 10^{−4} m^{2}

Initial temperature*, **T*_{1} = 40°C

Final temperature*, **T*_{2} = 20°C

Rate of flow of heat = `"Tempreature diffrences"/ "thermal resistance"`

`(DeltaQ)/(Deltat) = (KA ( T_1 - T_2 ))/ ( l )`}

`(DeltaQ)/(Deltat) = (45 xx 0.2 xx 10^-4 ( 40 - 20))/(0.6)`

`= 0.03 W`

Concept: Heat Transfer - Conduction

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