SOME ASPECTS OF THE HEAT TRANSFER FOR BANKS OF TUBES IN CROSS-FLOW FOR THE LOW RANGE OF REYNOLDS NUMBERS
Experimental and analytical results are reported for staggered and in-line tanks, each of 1.25 × 1.25, 1.50 × 1.50 and 2.0 × 2.0 pitch ratios, of 30 mm diam tubes in cross-flows of transformer oil and aviation oil, to cover the ranges of Re from 1 to 2·104 and Pr from 100 to 14,000. Effects of the physical fluid properties are evaluated for laminar flows lay Pr in the power of 0.36.
Local perimetric values of the heat transfer coefficient are determined on tubes in the first row and in an inner row within the banks, to illustrate the specific flow features in the banks, for different tube locations, bank geometries and bank arrangements.
Criterial relations are suggested for the mean heat transfer in the first row and in the inner rows of the banks studied with factor-and exponent values determined experimentally.
A technique is also suggested to locate flow direction changes within a bank. Measured local velocities and temperatures are applied in a calculation of the laminar boundary layer, for either favourable or adverse pressure gradients at high values of Pr (over 2,000). A semi-empirical calculation technique is applied in a double-structure model of the boundary layer, and the results are found in a satisfactory-agreement with the experimental values.