Substantiation of a New Calculation and Selection Algorithm of Optimal Heat Exchangers with Nanofluid Heat Carriers Taking into Account Surface Forces

Abstract

The article examines the problem of correct, accurate calculation and optimization of the choice of heat exchange equipment when using nanofluid heat carriers for heat treatment of liquid food products using milk as an example. To solve this problem, the motion of a metal nanoparticle in a turbulent flow of the main coolant was simulated using the methods of similarity theory, taking into account the action of surface forces in the laminar boundary layer. New formulas are obtained for a qualitative assessment of the average thickness of the laminar boundary layer that appears around a turbulently moving metal nanoparticle. A number of qualitative correlations with other literature sources that explain the behavior of nanoparticles in a turbulent liquid medium are shown. A new approach to heat transfer processes is considered taking into account the theory of J. Boussinesq, which gives an idea of turbulent viscosity and thermal conductivity, as well as a comparison of the resistance forces to the surface forces. The physical meaning of the previously obtained by us new similarity numbers Bl and Blturb. and their application in our new numerical equation for calculating heat exchangers is considered, and a new express method for evaluating the efficiency of using nanofluid heat carriers is proposed. The proposed method of express calculation shows that the mixture H2O + EG (60:40) improves the heat exchange properties of water by + 12.86%, and the mixture (H2O + EG (60:40) + 1.5% TiO2) and (milk + 0.5% pumpkin seed oil) - by + 16.75%, which corresponds to the experiments and our calculations, and the well-known express method based on classical numerical equations shows a deterioration by - 4.5% and, accordingly, by – 1.2%.