DETERMINATION OF HEAT TRANSFER COEFFICIENTS DURING THE FLOW OF NON-NEWTONIAN FLUIDS IN PIPES AND CHANNELS OF CHEMICAL PROCESS EQUIPMENT

Abstract

The problem of heat transfer of non-Newtonian fluids in the channels of chemical-technological equipment is considered. A mathematical model is proposed for determining heat transfer characteristics during the flow of Bingham fluids, generalized displaced fluids and power fluids in channels of different geometries. During the Bingham fluid flow, for the calculation of heat transfer coefficients, the convective temperature transfer equation is given in the approximation of the thermal boundary layer so that only the transverse derivative with respect to y is stored on the right side, and the x coordinate is assumed to be aligned along the tangent component of the fluid flow velocity. Nusselt numbers are determined by the derivatives of the tangent velocity on the walls of the channels and at the boundaries of the solid core. If the tangent of the fluid velocity on the wall has two components, then the velocity, the derivative of the Nusselt number, is determined through these components in accordance with the Pythagorean theorem. When a generalized shear fluid is used to calculate the Nusselt numbers, it must be taken into account that in a flat channel with longitudinal and longitudinal-transverse flows there are two heat transfer coefficients, and in a rectangular channel there are four heat transfer coefficients. The determination of the heat transfer coefficients of a power-law fluid is considered only for longitudinal flow in a flat channel and is carried out similarly to the calculation procedure for Bingham and generalized-shear fluids. The obtained expressions, when carrying out engineering calculations, allow us to calculate the corresponding heat transfer and heat transfer coefficients during the flow of non-Newtonian fluids in the channels and with the environment.