Date of Award
Master of Science in Chemical Engineering - (M.S.)
George C. Keeffe
Four papers have been published which correlate variables affecting heat transfer through a jacket in a kettle agitated by a paddle type agitator. There are differences in the equations resulting from each of these papers. In none of these papers was variation of the stirrer diameter or stirrer width considered.
It is the purpose of this paper to show that all published data in such a system can be correlated by a single equation which differs from those previously presented. Preliminary recalculation of published data indicated that a relationship exists which involves the stirrer width and diameter. Experimental work was undertaken to provide data for determining this relationship.
As a result of this work, the following equation is proposed to correlate heat transfer coefficients on the wall of a jacketed kettle agitated by a paddle type agitator with the fluid and geometric variables:
hT/k = 0.112(cμ/k).44 (D2Np/μ).75 (μ/μw).25(T/D).40 (D/Dw).13
It is believed that this best expresses the data observed by the author. It is further believed to express adequately all previously published data. Without the two groups (T/D) and (Dw/D), equations having coefficients ranging from 0.097 to 0.176 were derived. These varying coefficients result from the use of different agitators having different ratios of T/D and Dw/D. Without these correlating groups, the limiting equations vary in coefficient by a factor of two. For a given system at any Reynolds number, heat transfer coefficients derived from the limiting equations also would vary by a factor of two.
This is the first paper on this subject to include the terms (T/D) and (Dw/D) in such a correlation. This is the first paper to suggest an exponent other than 2/3 for the Reynolds number. This is the first paper to suggest the 0.44 power of the Prandtl number. Brown, Scott and Toyne (22) suggested that this exponent should be 1/4. Uhl (151), however, suggested that it might be greater than 1/3. The -1/4 exponent chosen for the ratio (μw/μ) is essentially the same as that (-0.24) proposed by Uhl (151).
Pursell, Herbert Palfrey, "Jacket heat transfer coefficients in an agitated vessel, the paddle agitator" (1954). Theses. 2270.