Question

For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 175-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 35 . If the rate of heat loss from this man to the environment at is 336 W, determine the rate of entropy transfer from the body of this person accompanying heat transfer, in W/K.

Answer 1

Answer:

Sgen = 0.0366 W/K

Explanation:

for the body:

∴ Q = - 336 W...rate of heat loss

∴ T surface = 35°C ≅ 308 K

the rate of entropy transfer from the body:

⇒ ΔS = - Q/Ts

for the enviroment:

⇒ ΔS = Q/Te

∴ assuming: T = Tenv = 25°C ≅ 298 K

resulting in a net variation in the universe:

⇒ Sgen = ΔS = Q/Tenviroment - Q/Tsurface = Q(Ts - Te)/Ts*Te

⇒ Sgen = (336( 308-298))/(308×298) = 3360 WK/91784 K² = 0.0366 W/K