The cooling time can be calculated applying the principles of radiation only as in Equation 1. The energy radiated to the black body can be expressed as:
Q = Total heat energy radiated (BTU)
A = Area of the radiating surface (ft2)
t = Time (hours)
T1 = Absolute temperature of the hot surface (°F)
T2 = Absolute temperature of the cool body of air (°F)
e = Emissivity or absorption factor of the metal surface
For a very small increment of time, dt there will be radiated a very small heat energy, dQ, and Equation 1 is transformed into Equation 2a or 2b.
t2 = Metal temperature (°F) minus room temperature.
tr = Room temperature or metal temperature (°F) when the metal is placed into the cooling chamber or room.
G = Metal weight (pounds)
c = Specific heat of the metal (BTU/pound-°F)
dt1 = Average decrease of metal temperature (°F)
Due to its complex nature, this discussion will conclude next week.