A wood box [k = 0.16 W/(m degree C) ] is kept at a constant temperature of 20 degrees C by an electric heater. The box is 0.4 x 0.4 x 0.4 m, and its walls are 2.5 cm thick. If the temperature outside the box is 4 degrees C, how much power will the heater use?
Are the dimensions correct on k W/m-C or should they be W / m2- K ?
The bos has six sides 6 * .4 * .4 = .96 m^2
watts = .96 m^2 * .16 W / m2-K * ( 293.15 - 277.15 K ) = I do not know if this is correct......I am unfamiliar with the 'k' units in your question...
if the units are correct it MIGHT be
watts = .96 m2 / (.025m) * .16 W /m -C * ( 20 - 4 C ) = ........... W