Question

Hot air at 80°C is blown over a 2-m by> on0 4-m flat surface at 30°C. If the average? convection heat transfer coefficient varies between 20 W/m2 °C and 100 W/m °C, draw a relation between the rate of heat transfer from the air to the 80°C Air 30°C plate.(nm kW) and the convection heat transfer coefficient

Answer 1

Step-by-step explanation:

The given data is as follows.

`T_(air) = 80 ^(o)C`,
`T_(surface) = 30 ^(o)C`

Area of the flat plate is 2 × 4 = 8
`m^(2)`.

Average convection heat transfer coefficient
`(h_(avg))` =
`((20 + 100) W/m^(2) ^(o)C)/(2)` =
`60 W/m^(2) ^(o)C}`.

Hence, formula to calculate heat transfer through convection from air to the water is given as follows.

q =
`h_(avg) * A_(surface) * (T_(air) - T_(surface))`

=
`60 W/m^(2) ^(o)C} * 8 m^(2) * [(80 - 30)]^(o)C`

= 24000 W

or, = 24 kW

Hence, the direction of heat flow is from air to the surface.

Thus, we can conclude that transfer of heat is 24 kW.