Question

A spherical pot of hot coffee contains 0.75 L of liquid (essentially water) at an initial temperature of 100°C. The pot has an emissivity of 0.60, and the surroundings are at a temperature of 20.0°C. Part A Calculate the coffee's rate of heat loss by radiation. Express your answer with the appropriate units. ? T HÅ Value o 2 Units H = Submit Request Answer

Answer 1

let r is the radius of the pot.

given

V = 0.75 L

= 0.75*10^-3 m^3

use, V = (4/3)*pi*r^3

0.75*10^-3 = (4/3)*pi*r^3

==> r = 0.05636 m

surface area, A = 4*pi*r^2

= 4*pi*0.05636^2

= 0.03992 m^2

T1 = 100 C = 100 + 273 = 373 K
T2 = 20 C = 20 + 273 = 293 K
e = 0.6

using stefan-Boltzman's law
The rate of heat loss by radiation,

H = sigma*A*e*(T1^4 - T2^4)

= 5.67*10^-8*0.03992*0.6*(373^4 - 293^4)

= 16.3 W <<<<<<<<------------------------Answer