Authors & Affiliations
Grabezhnaya V.A., Parfenov A.S., Mikheev A.S.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia
Parfenov A.S. – Research engineer, A.I. Leypunsky Institute for Physics and Power Engineering.
Mikheev A.S. – Head of laboratory, A.I. Leypunsky Institute for Physics and Power Engineering.
The study of turbulent flow in helical coiled tubes is of great interest in view of the widespread use of such heat exchange channels in engineering practice, in particular in the nuclear industry in the form of steam generators for nuclear power plants and research reactors. In the designed reactor facility BREST-OD-300 is planned to use a steam generator with helical tubes.
To date, accumulated a large amount of both experimental and theoretical works devoted to the convective heat transfer in helical coiled tubes.
Experimental study the convective heat transfer in helical tubes is mainly conducted on test sections electrically heated by, and air was used as the working fluid. In recent years appeared a number of works, which presents the results of investigation of convective heat transfer in in the coiled tubes, heated by the coolant. But there are no works, which considered the convective heat transfer in a tube of small diameter, but the large winding diameter.
The steam generator model, which was tested, consisted of two identical three-tube sections (modules). The three-tube bundle winding diameter was 1600 mm, the outer diameter of steam generating tube was 18 mm. Heating of the three-tube bundle was with the lead coolant. The experimental model was well equipped with thermocouples.
With the temperature profiles Heat transfer coefficients of water convection (economizer zone) and vapor convection (superheated vapor zone) were determined from temperature distributions of the three-tube model shell. The subject of consideration were only modes where the Reynolds number was above Re = 2.2· 104. For comparison data about convective heat transfer obtained in experiments with the design recommendations were selected formulas.
On the basis of performed analysis it is concluded that there is no reliable guidelines for calculation of convective heat transfer in a helically coiled tubes of steam generators at present. At first, this applies to superheated vapor zone, where a strong change in thermodynamic properties of steam takes place in the beginning of this zone. All existing correlations for calculation convective heat transfer were obtained on test sections in which the geometry and operating parameters is far from the operating conditions of steam generator plants.
Recommended in Governing Technical Material correlations for calculation the convective heat transfer in the developed turbulent flow in a helically coiled steam generator tubes gives a lower (20–30 %) the values of heat transfer coefficients and leads to the notoriously conservative results.
reactor, steam generator, heavy liquid coolant, lead, water, helical coiled tubes, convective heat transfer, superheat vapor, model of steam generator, experiment, adiabatic wall, the temperature profile
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