Agitated Vessel: This is another application of heat transfer from a coil that is immersed in an agitated vessel. The governing equation is given in Table 5.10 as Equation 6.
Example 5.17: Calculate the heat transfer from a coil immersed in an agitated vessel. The agitator is a turbine that at 150 r/min.
The fluid has the following properties:
Density, ρ = 45 lb/ft3, absolute viscosity, μ = 10 lb/(ft·h)
Specific heat, c = 0.7 Btu/(lb·°F); thermal conductivity of fluid, k = 0.10 Btu/(h·ft·°F)
The system has the following properties:
Vessel diameter, D = 8 ft, agitator diameter, L = 3 ft;
Viscosity correction factor, φ = 1.
Solution: The heat transfer correlation for agitation of the fluids depends upon the type of the impeller. In general, it is given as
Where constant a is 1.5 and viscosity correction factor is 1.
The agitator speed is 150 rpm = 9000 rph.
The Reynolds number, Re, can be found as
And the Prandtl number, Pr = cμ/k = 70.
We can now calculate the Nusselt number, Nu, to be
And the heat transfer coefficient, h, can be found to be