Modelling turbulent heat transfer in rough channels using phenomenological theory

Rough walls are often encountered in industrial heat transfer equipment. Even though it is well known that a rough wall affects velocity fields and thermal fields differently (and therefore also skin friction factors and Stanton or Nusselt numbers), predicting the effect of rough walls on turbulent heat transfer remains difficult. A relation between the scalar spectrum and the Stanton number is derived for channels with both smooth and rough walls. It is shown that the new relation agrees reasonably well with recent DNS experiments for wall roughness sizes of k + < 150 and when Pr = 0.7 − 1.0. Under these conditions, a thermal analogue of Moody’s diagram can be created using the newly developed relation.

DEVELOPMENT OF BIFUNCTIONAL ADDITIVES TO DIESEL FUELS ON THE BASIS OF PETROCHEMICAL PRODUCTS

The developed method of determining the theoretical calculated hydraulic resistance and heat transfer for round pipes with rough walls based on multilayer models of turbulent boundary layer, mainly different from existing theories by taking into account the share volume of cavities in the sublayer, and the rough and smooth surfaces of the channel that can lead to a reduction of heat transfer of about 15%, it is necessary to consider the mode of developed roughness.