Experiments and computations have been performed for turbulent air flow in a circular duct in which uniform heating is applied over a 60 deg arc of the circumference. The results are compared to those for both a uniform heat flux around the full circumference of the duct and for a uniform heat flux around half the circumference. The flow was hydrodynamically fully developed at the start of heating and there were negligible buoyancy effects. Both the experimental results and the computations show that the local heat transfer coefficients for the narrow strip (60 deg wide) are less than the values for uniform heating around the full circumference but greater than the values for uniform heating around half the circumference (180 deg). This rather surprising result is a consequence of the temperature distribution in the fluid and the definition of the local heat transfer coefficient, which is based on the bulk temperature.

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