Air at 20°C blows over a plate of 50 cm x 75cm maintained at 250°C. If the convection heat transfer coefficient is 25W/m$^2$°C, the heat transfer rate is
- A. 2.156kW
- B. 2156kW
- C. 215.6kW
- D. 21.56kW
Answer: A. 2.156kW
Explanation: $Q = h A \Delta T = 25 \times (0.5 \times 0.75) \times (250-20) = 25 \times 0.375 \times 230 = 2156.25$ W.