Question

The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature and approximate the human body by a rectangular block with a height of 1.57 m, a width of 41.5 cm and a length of 21.0 cm. Calculate the power emitted by the human body.

Fortunately our environment radiates too. The human body absorbs this radiation with an absorbance of 97.0 percent, so we don't lose our internal energy so quickly. How much power do we absorb when we are in a room where the temperature is 22.0 °C?

How much energy does our body lose in one second?

Answer 1

The emissivity of the human skin e = 97.0%
                                                     = 0.97
Temperature T = 35.0 °C
                        = 35 + 273
                       = 308 K
Height h = 1.57 m
Width w = 41.5 cm
              = 0.415 m
Length L = 21 cm
               = 0.21 m
Total area A = 2( Lh+Lw+wh)
                     =2.1368 ²
The power emitted by the human body E = eAσ T ⁴

Where σ = Stefan constant

              = 5.67 x 10 ^-8 W/ m ² K ⁴

Subsitute values we get E = 1.6123 x 10 ³ watt