BUOYANCY-INDUCED CONVECTION IN A NARROW OPEN-ENDED ANNULUS

Results from a combined experimental and numerical investigation of bu oyancy driven flow and heat transfer in a narrow annular gap between c o-axial, horizontal cylinders are presented in this work. The annulus is open at both ends through which the ambient fluid can interact with the fluid inside the gay. In the experimental study, a constant heat flux was utilized to simulate buoyancy induced convection in an open e nded annular cavity with a low gap to inner cylinder radius ratio; loc al surface temperature measurements were made to determine heat transf er characteristics of the convective flow. The heat transfer results a re correlated by <(Nu)over bar> = 0.134(Ra)(0.264) for the range of R ayleigh numbers considered (7.09 x 10(8) less than or equal to Ra les s than or equal to 4.76 x 10(9)) in the experiments. In the numerical investigation, solutions to the three-dimensional time-averaged (Reyno lds) steady-state equations of fluid motion and hear transfer were obt ained using a finite element analysis. Results of the conjugate study including the local temperature distributions, heat transfer-coefficie nts, and the flow field showing the interactions between the ambient a nd cavity flow fields agree favorably with experimental results. An in vestigation was also carried out to study the effect of axial length a nd the gap width of the annulus. A correlation for the average Nusselt number as a function of Rayleigh number, axial length and gap width h as been obtained The present work provides, for the first lime, an exp erimental and numerical study of turbulent buoyancy induced flows in a narrow open-ended annulus.