The change in plate temp with time dT/dt = –0.02K/s, is

Question

The average heat transfer coefficient on a thin hot vertical plate suspended in still air can be determined from observations of the change in plate temperature with time as it cools. Assume the plate temp to be uniform at any instant of time and radiation heat exchange with the surroundings is negligible. The ambient temperature is 25⁰C, the plate has a total surface area of 0.1m²  and a mass of 4 kg.

The specific heat of the plate material is 2.5Kj/KgK. The convective heat transfer coefficient in W/m²K, at instant when the plate temp is 225⁰C and the change in plate temp with time dT/dt = –0.02K/s, is

      (a) 200                                                                (b) 20

      (c) 15                                                                  (d) 10