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sbaw88

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- Top plate - Ceramic Porcelain material - 2.65in x 4.8in x 0.06in - carries a small heater (2in x 0.125in x 0.01in) on top of it which generates 18W of heat.

- Bottom heater - 5.8in x 3.65in x 0.03in - Stainless steel plate

- Air gap between the two heaters - 0.01in

The top small heater power runs constantly for 4.5 minutes and the plate has a convection coefficient of 30 W/m

^{2}C. The bottom heater start running 30 seconds after the top heater starts and goes from ambient temperature (24.85 C) to 400C.

I am including radiation effect between the bottom layer of top plate and upper layer of bottom plate. I am mainly concerned about the convection coefficient to be used for air. I am unable to get a proper value of the coefficient to be used. Can someone help me with the calculations? Am I missing something very basic?

Thanks!