Prediction of batch heat transfer coefficients for pseudoplastic fluids ...

Prediction of batch heat transfer coefficients for pseudoplastic fluids ... Prediction of batch heat transfer coefficients for pseudoplastic fluids ...

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108 optimum impeller heights were used in all the subsequent 1.Jork; hO'IJ.!6ver, '.Ihen the more viscous fluids ,.rere in the vessel the wall temperature differences could not be eliminated .. Impeller fIeight In addition to af:fecting the uniformity of \-1all tem£)­ ex'ature, the impeller height also influenced the heat trans:fer rate. In general, the greater the impeller distance from the vessel bottom" the greater the heat trans:fer rate (1r-Jithin the limits tested, up to 1/2 the vessel height) .. This phenomenon is pl""obably closely related to the large wall temperature variations which are present Hhen the Lmpeller is very close to the bottom of the vessel, (ie. as the impeller is raised, the agitation of the batch is more uni:form and thus the wall temperature variations are reduced and the heat transfer rates increased). Since the amount of data measuring these effects is limited the results are only qualitative. They are shown graphically for the anchor, propeller" and turbine in Figures 5-1, 2 and 3. As can be seen on these curves, a two inch vertical displacement of the impeller changes the heat transfer coefficient by almost ten percent .. There 1.

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