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Received: 13 December 2017 Accepted: 5 March 2018 The sources of the literature are analyzed in the article on the influence of the average thickness of the laminar boundary layer (LBL) on the heat transfer coefficient of the various heat-conducting systems. Different authors at different times established the explicit correlation dependence of the increase in heat transfer coefficients with a decrease in the average thickness of the LBL. The average thickness of the LBL according to the literature data was reduced in the various ways (using electric or magnetic field for the flow of the liquid, using the nanoparticles in the flow and various of the metallic spiral inserts, etc.). Applying the similarity theory and using dimensionless Euler, Froude and Reynolds numbers in the LBL, and also applying a new surface number, we previously derived the formula for the calculation of the average thickness of the LBL, which in this paper is used to the calculation the overall heat transfer coefficient of the shell-and-tube heat exchanger. We brought out new number of the turbulent thermal conductivity in the LBL transitional zone by the dimensional analysis method. The relations have also been obtained for the calculating of the transitional viscosity and of the transitional thermal conductivity in the transitional zone of the LBL. The article provides the examples the calculation of the shell-and-tube heat exchanger using the classical method and the proposed formulas. The calculation of the resistance of the LBL and the turbulent zones of the refrigerant flows is carried out the taking into account the coefficients of the turbulent thermal conductivity, as well as the coefficients of the surface tension of the liquids. We proposed the calculation of the shell-and-tube heat exchanger using of the refrigerant with an optimum concentration of the propylene glycol in the water (47%). The increase of the overall heat transfer coefficient of the heat exchanger is about 10%.

heat and technology

Specific features of heat exchangers calculation considering the laminar boundary layer, the transitional and turbulent thermal conductivity of heat carriers