Calculation and experimental analysis of heat transfer of assemblies of ribbed heat exchange elements

Abstract

The results of thermal-hydraulic and strength tests of finned tube assemblies welded from KP 20 elements of four sizes are presented. The elements are representing by steel plate 0.4 mm in thickness, covered with a copper film 0.025 mm in thickness. One or two conical necks 17 mm long are extended in the plates. A set of placed in each other cones form a welded finned tube 23/20 mm with a toothed inner surface. As a result of the tests: high strength characteristics of these assemblies were demonstrated (internal pressure of burst under normal conditions is 40 MPa, resistance to sudden changes in temperature and freezing of water in “pipes”); a high average coefficient of thermal conductivity in the thickness of the ribs was confirmed at the level of 75 W/(m×K); the increase in the intensity of the heat transfer process is 2.15 times with the help of technological protrusions on the inner surface of the “pipe” to a turbulent single-phase flow in comparison with the calculated values for “smooth” pipes with a moderate increase in hydraulic resistance; the method of heat-hydraulic calculation of heat exchangers consisting of such “pipes” is proposed. The method is based on the ratios set out in the regulatory document “RD 24.035.05-89”. Thermal and hydraulic calculation of NPP heat exchanging equipment”, with amendments considering the high degree of finning of the tested “pipes” and the asymmetry of the edges of the ribs relative to the axis of the “pipes” bearing pressure, as well as the change in the value of the correction for the smallness of the tube bundle — we also identified areas of effective use of assemblies tested sizes of elements KP 20.