Combined Free and Forced Convection in a Constant-Temperature Vertical Tube
- 1 April 1958
- journal article
- research article
- Published by ASME International in Transactions of the American Society of Mechanical Engineers
- Vol. 80 (3) , 739-745
- https://doi.org/10.1115/1.4012500
Abstract
An experimental study of superposed free and forced convection for air in a vertical tube is examined. The Nusselt modulus, based on the log-mean-temperature difference, ranged from 15.0 to 57.1; the Graetz modulus, based on the bulk or average temperature of the air, ranged from 40.2 to 1710; and the Grashof-Prandtl D/L modulus, based on properties of air at the wall temperature, ranged from 1.05 × 105 to 1.30 × 106. The Martinelli equation for heating fluids flowing vertically upward does not correlate the data satisfactorily. An analysis of the system from a macroscopic viewpoint leads to the derivation of an equation which fits the experimental data.Keywords
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