The three dimensional mixed convection heat transfer characteristics in an idealized horizontal CVD reactor with a tilted susceptor is investigated numerically. The governing equations are transformed into a general curvilinear systems. For computing fluid flow and heat transfer in a irregular shaped domain, the SIMPLE algorithm is extended to the present curvilinear coordinate, and a nonstaggered grid system is adopted. The Cartesian velocity components are used as the dependent variables in the momentum equations. The effects on heat transfer rate uniformity of the susecptor are investigated for various input flow rate and channel height. Furthermore the formation of return flow induced by transversal rolls is studied as a function of dimensionaless parameters