Comparison of Technical and Economical Characteristics of Various Types of the Surface of Convective Heat Transfer

摘要

The results of numerical and computational studies of the technical and economic characteristics of one of the promising types of tube finning - transverse punched spiral-tape are presented. As a result of a numerical study, the share of all sections of the tube surface with a punched spiral finning in heat transfer with the change of all geometric dimensions of the finning were determined. It was established that heat transfer occurs mainly through the surface of the fins - the proportion of the surface of the fins in heat transfer and specific heat perception is 82 … 96%. The surface of the punched part of the fins at the maximum acceptable height of the petals transfers up to 80 … 84% of the heat. The average surface heat transfer coefficient of the punched part of the fins is much higher than the solid part. In a numerical experiment, it is 2 times higher (120 $mathrm{w} /mathbf{m}^{2}{}^{circ}mathbf{C}$ versus 60 $mathbf{W}/mathbf{m}^{2}{}^{circ}mathbf{C}$). Consequently, the required value of the heating surface and its metal consumption and cost are reduced. As a result of a computational study, seven parameters that characterize the technical and economic efficiency of the five options for the heating surface of the P-83 boiler-utilizer were compared. Staggered banks with a punched spiral finning have the best values of all the compared parameters, except for aerodynamic resistance. This variant of the heating surface provides the greatest metal savings of 26.7^%. The staggered banks with continuous finning and in-line banks with punched finning have approximately identical values of the majority of the compared parameters are, but the aerodynamic resistance of the in-line banks is much lower (1882 Pa against 2597.4 Pa). Therefore, their use is preferable. The staggered smooth tube banks have the worst values of all compared parameters.