Question

What is the rate of loss from an unclothed person standing in air at 23 degree celsius if skin temperature is 34 degree celsius and surface of body is 1.5 m^2. e=0.70 sigma=5.7×10^-8 W/m^2K^4?
A. 156 W
B. 72.2 W
C. 96.4 W
D. 57.07 W

Answer 1

(B) 72.2 W would be the the rate of loss from an unclothed person

Explanation:

The heat loss is given by : (Stefan–Boltzmann law  )

Q = ε σ Α (T₂⁴ - T₁⁴ )

23 °c = 296 k

34°c = 307k

ε = emissivity   in our case = 0.7

σ = constant given 5.7 * 10 ⁻⁸

Α =  area of the body

using value in eq 1 . we get

Q = 0.7 *  5.7 * 10 ⁻⁸  * 1.5 * (307⁴- 296⁴ )

   = 0.7 * 5.7 * 1.5 * 12.1

    = 72 .2