E5.14 Isothermal Heating Medium

Example 5.14: Calculate the time required to heat the 40000 lb tank contents from 68 °F to 260 °F with saturated steam condensing at 320 °F flowing in a 80 ft² coil having an overall heat transfer coefficient of 150 Btu/(h·ft²°F). Specific heat of the fluid is 0.55 Btu/(lb·°F)

Solution: This is a situation where tank contents are heated by an internal coil, which receives heating medium at isothermal conditions.

Heat transfer coefficient of internal coil, U = 150 Btu/(h·ft²·°F)

Mass of the tank contents, M = 40000 lb

Initial temperature of tank fluid, t₁ = 68 °F

Final temperature of tank fluid, t₂ = 240 °F

Temperature of isothermal heating medium, T₁ = 320 °F

Heat transfer area, A = 80 ft²

Specific heat of the tank fluid, c = 0.55 Btu/(lb·°F)

Time required to achieve this heating can be found as