Numerical Evaluation of Heat Transfer from Rotating Discs Separated by Sealing Elements

Abstract

Process waste heat recovery has been gaining attention in last decades in order to use resourcesefficiently. Even though the mechanisms of heat transfer in static systems such as cross flow heatexchangers are well understood, the situation is totally different for the heat transfer mechanisms insystems consisting of parallel, rotating discs. The situation becomes even more complex when sealingelements prevent fluid from following the natural path in rotational direction. In this work ReynoldsAveraged Navier-Stokes (RANS) simulations using the k-omega-SST turbulence model were performedfor various disc radii, rotational and cross flow velocities as well as disc spacings. Simulations wereexecuted for rotational Reynolds numbers Re! ranging from 94,094 to 435,623 and cross flow Reynoldsnumbers ReU between 3,993 and 36,052. In this paper we show the correlation of resultingflow structures, temperature distribution and resulting heat transfer from multiple rotating discs. Resultsfrom simulations of several different geometrical setups of the discs for various operating pointsshow a maximum of convective heat transfer at a given point that is dependent on the cross flowvelocity, disc diameter, disc spacing and rotational velocity. An increase in air cross flow velocity aswell as larger disc spacing show positive effects on the convective heat transfer in contrast to higherrotational velocity and larger discs. Even though the simulations show some limitations of classicalmeans to increase heat transfer from rotating discs, the influence of sealing elements and resultingflow structures in the gap have not been investigated. It is very likely that the thermal performancecan be further increased by optimizing shape and arrangement of these elements which is subject tofurther research.