Forced convection of water in rod-bundles

Abstract

Heat transfer of water in rod-bundles is of particular importance in many engineering applications. Although numerous experimental studies have been conducted to develop heat transfer correlations for forced convection in rod-bundles, with either a square or a triangular lattice, most data was taken at high Reynolds numbers (Re > 6,000); only a few data points had been reported at lower Reynolds number [1-5]. Recently, El Genk and co-workers have performed a series of heat transfer experiments of forced convection of water at the low and high Reynolds numbers as well as of natural and combined convection in uniformly heated, triangularly and square arrayed rod-bundles with P/D = 1.25, 1.38, and 1.5 [6-10]. Like all other investigators, they correlated the heat transfer data for square lattice and triangular lattice separately, with P/D as a parameter. This paper shows that forced convection data for both square and triangularly arrayed rod-bundles, when expressed in terms of the bundle porosity, can be represented by a single correlation, one each for forced turbulent convection land forced laminar convection. Also, the experimental values of the Reynolds number at the transition between these two convection regimes is expressed in terms of the bundle porosity, regardless of themore » lattice type and rod diameter. This approach reduces the number and simplifies the form of the forced convection correlations, making them easy to use in potential engineering applications. Although the effect of the rod diameter and the type of lattice in the bundles is implicit in the expressions of the bundle porosity, it is explicit in the definition of the heated equivalent diameter in both Re and Nu, and hence will influence the heat transfer coefficient.« less