Question

A hot plate 1 m × 1.5 m is maintained at 300°C. Air at 25°C blows over the plate. If the convective heat transfer coefficient is 20 W/m²°C, calculate the rate of heat transfer.

Answer 1

Area of the plate exposed to heat transfer, A = 1 × 1.5 = 1.5 m² 

Plate surface temperature, t_s = 300°C 

Temperature of air (fluid), t_f = 20°C 

Convective heat-transfer coeffficient, h = 20 W/m²°C 

Rate of heat transfer, Q : 

From Netwon’s law of cooling, 

Q = hA (t_s – t_f ) 

= 20 × 1.5(300 – 20) = 8400 W or 8.4 kW.