Calculate the time required to heat 40,000 pounds of a fluid
from 68 degrees to 260 degrees Fahrenheit.
The fluid is stored in a tank that is equipped with a heating coil
having 80 square feet surface. Heat
transfer coefficient through that coil is 150 BTUs per hour per square foot per
degree Fahrenheit. Specific heat of the
fluid is 0.55 BTUs per pound per degree Fahrenheit.
Solution:
This is very specific case where tank contents are being
heated by an isothermal heating medium.
Equation18.5, of Kern addresses this case. In that equation, M is mass of the batch, c is specific heat, U,
heat transfer coefficient, and A heat transfer area. T1 is the temperature of the condensing fluid (steam). For our situation, steam is condensing at
320 degrees Fahrenheit.
Plugging in the data, theta, time required to increase the
temperature from 68 degrees to 260 degrees is found to be 2.63 hours.