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Kqwert
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Homework Statement
An impenetrable flat horizontal plate is radiated with 3000 W/m^2, where 500 W/m^2 is reflected. The surface temperature of the plate is 200 °C and it emits 500 W/m^2. Air with temperature 25 °C flows over the plate, and the heat transfer coefficient due to this is 20 W/m^2*K.
Calculate the (i) emissivity, (ii) absorptivity
Homework Equations
The Attempt at a Solution
(i) A black body absorbs all incoming radiation, and all absorbed radiation is emitted. Therefore, I would say that a black plate would emit 3000 W/m^2, and the emissivity of my plate would be 500/3000 = 0.166. This is wrong, could anyone please explain me what is wrong?(ii) Using Kirchoff's law I would assume that emissivity = absorptivity, but this is also wrong according to the solutions manual. Could anyone correct my thinking?