Question

A person with skin temperature 28o
C is present in a room at temperature
22o
C.Assuming the emissivity of skin to be unity and surface area of the
person as 1.9 m2
, compute the radiant power of this person

Answer 1

use the formula,

P = σeA[T1⁴ - T2⁴] , where T1 > T2

where P is radiant power, e is emissivity, A is surface area , T1 and T2 are temperatures of skin and room respectively.

here given,

σ = 5.672 × 10^-8 J/(s.m².k⁴)

e = 0.5

A = 1.9 m²

T1 = 28°C = 28 + 273 = 301K

T2 = 22°C = 22 + 273 = 295K

so, P = 5.672 × 10^-8 × 0.5 × 1.9 [301⁴ - 295⁴]

= 34.226 W

hence, power radiant of this person is 34.226 W (approximately)