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Heat transfer and fluid flow experiments were made in narrow vertical enclosures of varying aspect ratio (5 ≤ H/W ≤ 40) filled with non-Newtonian fluids whose consistencies ranged from near that of water to several orders of magnitude more. Temperature and velocity profiles were obtained for thermal conditions of low convection augmentation to fully developed turbulent flow. The tests were run over periods of as much as 60 days, during which time the flow index and the consistency of the fluids changed markedly according to their thermal histories. Local hot and cold wall and average enclosure heat transfer rates and wall shear stresses were evaluated. For all the fluids, including the abnormal fluids (those which thickened with increasing temperature) the heat transfer could be correlated by Nu=CRab although the constant C differed for the two classes of fluids. These correlations were valid over the entire flow regimes studied even in the presence of multiple boundary layers and secondary vortices.