A small oven with a surface area of 0.28 m2 is located in a room in which the walls and the air are at a temperature of 27°C. The exterior surface of the oven is at 150°C and the net heat transfer by radiation between the oven’s surface and the surroundings is 586 W. If the average convective heat transfer coefficient between the oven and the surrounding air is 11 W/(m2 K), calculate: (a) the net heat transfer between the oven and the surroundings in W, (b) the thermal resistance at the surface for radiation and convection, respectively, in K/W, and (c) the combined heat transfer coefficient in W/(m2 K).
GIVEN
FIND
ASSUMPTIONS
- Steady state prevails
SKETCH
(a) The net heat transfer is the sum of the convective heat transfer, the net
radiative heat transfer
(b) The radiative resistance is
The convective resistance is
These two resistances are in parallel, therefore the total resistance is given by
(c) The combined heat transfer coefficient can be calculated from
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