Effect of turbulence length scale on heat transfer from a cylinder in crossflow

Date

1979-12

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Abstract

This study describes overall mass transfer measurements made 'from cylinders exposed to a turbulent air stream. The test portion of the cylinder was coated with a shell of naphthalene. The relevant heat transfer data were obtained by the application of theheat-~asstransfer analogy. Tests were conducted for a Reyaolds number range from 24,242 to 25,044 and mainly 22,058, the turbulence intensity from 0.60 to 7.40 percent, and the ratio of turJulence length scale to cylinder diameter from 0.410 to 2.373. Data are discussed and the effect of turbulence length scale on overall heat transfer i~ investigated. Atta~pts to obtain a correlation equation that predicts the ratio Q~ turbulent ~usselt number to laminar ~usselt number as a function o: tur~ulence intensity, length scale, and Reynolds number were made. T~e resulting correlation equations are presented. For constant Reynolds number and turbulence length scale, an increase in heat transfer rates with increased turbulence intensity was observed. For constant Reynolds number and turbulence intensity, the heat transfer rate was found to decrease monotonically with increased value of the ratio of turbulence lengtn scale to cylinder diameter. ~o "optim.um11 effect of turbulence length scale for L/d equal to 1.6 was observed.

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Keywords

Heat -- Transmission, Cylinders, Turbulence -- Measurement, Mass transfer

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