Numerical Solution of an Open Cavity, Natural Convection Heat Exchanger

An “open-cavity” natural convection heat exchanger is one in which the flow on one side is driven by buoyancy forces and in which the effect of associated piping, valves, and fittings on that side can be ignored, since the exchanger is effectively exposed there to an extensive fluid of uniform temperature. This paper reports a finite volume numerical solution of the full set of equations governing the flow on the natural convection side of such a heat exchanger. The exchanger’s dimensionless performance is shown to depend on five dimensionless groups: a modified Rayleigh number Ra*, a flow number F describing the forced convection heat capacity, a Biot number Bi describing the effect of forced convection side heat transfer coefficient, an aspect ratio A_R, and the Prandtl number Pr. A parametric study is performed for suitable ranges of Ra*, F, and Bi, and for Pr = 6 and AR = 0.1. The results are presented in terms of a Nusselt number, a dimensionless flow rate, and the exchanger effectiveness as a function of these variables.