HEAT-TRANSFER AND FLOW STABILITY IN A ROTATING-DISK STAGNATION FLOW CHEMICAL-VAPOR-DEPOSITION REACTOR

The flow and heat transfer in a vertical high-speed rotating disk/stag nation flow chemical vapor deposition (CVD) reactor is studied with pa rticular emphasis on the effects of the spacing (H) over bar between t he stationary gas inlet and the rotating disk. In both one- and two-di mensional (1-D and 2-D) analyses the Navier-Stokes and energy equation s are soh,ed for hydrogen to determine the effects of (H) over bar, fl ow rate, disk spin rate, buoyancy, and finite geometry on the gas flow patterns and the heat transfer from Be disk. The I-D results show tha t the heat transfer from the rotating disk, Nu(1D), depends on the flo w parameter (SP = \<(mu)over bar>(in)\/root<(omega)over bar><(nu)over bar>(in)) and the disk Reynolds number (Re-omega = (r) over bar(d)(2)< (omega)over bar>/<(nu)over bar>(in)) to a much greater extent at small er spacings A = (H) over bar/(r) over bar(d) = 0.54) than at larger sp acings (A = 2.16). For SP values of 0.92 and 4.5 and for both spacings studied, Nu(1D) approaches the value for an infinite rotating disk in a semi-infinite medium for Re-omega > 450 approximately, except for t he case at SP = 4.5 and A = 0.54, where Nu(1D) is significantly larger . The 2-D results show a larger effect of Sp on the radial variation o f Nu(2D) for larger values of A (the uniformity of Nu(2D) is improved significantly at the larger A when the inlet velocity matches the asym ptotic value for an infinite rotating disk). For both values of A ther e is greater nonuniformity of Nu(2D) at the larger value of SP; when t he disk is ''starved'' (SP = 0.23, Re-omega = 456), there is gas recir culation above the rotating disk. The results are only slightly affect ed when (r) over bar(0)/(r) over bar(d) is varied by approximately 30% (from 1.1 to 1.4) for the conditions SP = 0.23, A = 0.54, and Re-omeg a = 456.