Library Subscription: Guest

ISSN Online: 2377-424X

ISBN Print: 0-89116-909-1

International Heat Transfer Conference 9
August, 19-24, 1990 , Jerusalem, Israel

EFFECTS OF THE VELOCITY DISTRIBUTION BEHIND GRIDS ON THE LOCAL HEAT AND MASS TRANSFER IN STAGNATION FLOWS

Get access (open in a dialog) DOI: 10.1615/IHTC9.2590
pages 309-314

Abstract

Turbulence originates in velocity differences upstream. Therefore downstream of a turbulence generator the turbulent flow field contains more or less regular velocity variations. Depending on the actual velocity distribution and its interference with the downstream boundary layer flows at the tested object the heat and mass transfer can strongly be influenced. In a systematic study the local and integral heat transfer is analyzed in stagnation flows behind planar and biplanar grids with different orientation of the grid wires and hence the corresponding velocity distribution to the stagnation line. The new results prove, that the turbulence parameters, as turbulence intensity and integral length scales, fail to predict the heat and mass transfer as soon as velocity defects exist. Not the length scales of the turbulence but the wavelength of the regular velocity distributions can strongly influence the flow field, heat and mass transfer.