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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

ON THE BEHAVIOUR OF NON-NEWTONIAN LIQUIDS IN COLLINEAR OHMIC HEATERS

Get access (open in a dialog) DOI: 10.1615/IHTC10.2910
pages 285-290

Sinopsis

The food industry is moving towards continuous production. Heaters that generate heat within the liquid, and for which capacity is determined by volume rather than exchange arca are ideal for food processing. Ohmic or direct electrical heating is such a volumetric heating process. This work attempts to model a collinear Ohmic heater by solving simultaneously the equations of Laplace, Fourier and Navier-Stokes. Results show that the maximum temperature lies close to the wall. Wall cooling is therefore a necessary part of a volumetric heater. For food processes the heater performance is mainly determined by the liquids activation energy. The heater design (liquid throughput, tube length and radius) is best characterised by the number of Graetz; lower numbers indicate a better, more homogeneous temperature distribution.