Heat Transfer and Friction Loss in Laminar Radial Flows through Rotating Annular Disks

Abstract

Heat transfer and pressure drop performance are experimentally studied for laminar radial flow through a stack of corotating annular disks. The disk surfaces are heated by condensing steam to create constant surface temperature condition. The traditionally defined friction factor is modified to include the effect of centrifugal force induced by the rotation of the heat transfer surface on core pressure drop. Empirical equations are derived for the heat transfer and friction factors at zero rotational speed. Test results are obtained for various rotational speeds. It is disclosed that (1) The transition in the radial flow through rotating parallel disk passages occurs at the Reynolds number (based on the hydraulic diameter of the flow passage) of 3000 at which stall propagation occurs in the rotor. (2) In the laminar flow regime, its heat transfer performance at zero rotational speed is superior to forced convection in the triangular, square, annular, rectangular and parallel-plane geometries. (3) The effects of disk surface rotation are twofold: a significant augmentation in heat transfer accompanied by a very substantial reduction in friction loss. (4) These rotational effects decrease with an increase in the fluid flow rate until the transition Reynolds number where the effects of centrifugal and Coriolis forces diminish is reached. (5) Heat transfer performance at low through flows is superior to that of high-performance surfaces for compact heat exchangers.