Heat Transfer Coefficients Inside Agitated Vessels

In order to complete the overall heat transfer coefficient calculation, an estimate must also be made inside the process vessel. The following estimate should yield reasonable results:

Eq. (11)

Where:

A_d = agitator diameter
N = agitator speed, rev/s
All other variables as previously defined
a is defined by the table below:

Calculating the Overall Heat Transfer Coefficient

When calculating the overall heat transfer coefficient for a system, the vessel wall resistance and any jacket fouling must be taken into account:

Eq. (12)

Notice that the thermal conducitivity of the vessel wall and the wall thickness are included in the calculation. A typical jacket fouling factor is around 0.001 h ft² °F/Btu. When calculating the overall heat transfer coefficient, use a "common sense" analysis of the final value. The tables below will give some guidance to reasonable final values:

Table 2: Estimated Overall Heat Transfer Coefficients for Jacketed Tank Systems (Imperial Units)		Table 3: Estimated Overall Heat Transfer Coefficients for Jacketed Tank Systems (Metric Units)

References

1. Heat Transfer Design Methods by 'John J. McKetta'
2. Hand Book of chemical Engineering Calculation 3rd Edition by 'Micclas P. Chopey'.
3. Applied Process Design for Chemical and Petrochemical Plants by 'Ludwig' Volume 3.
4. Estimate Heat Transfer and Friction in Dimple Jackets, 'John Garvin', CEP Magazine, April 2001, p. 73
5. Heat Transfer in Agitated Jacketed Vessels, 'Robert Dream', Chemical Engineering, January 1999, p. 90
6. Encyclopedia of Pharmaceutical Technology, 'James Swarbrick', p. 217
7. Tranter Plate Coil Product Manual