Heat transfer and fluid flow phenomena occurring in an annulus with an inner rotating cylinder have been studied numerically. A computer program was developed using a finite difference technique to study the effect of parameters such as gap width, length of rotor, axial flow velocity, rotational speed and fluid properties on heat transfer. Computer plots were obtained for the parameters such as tangential velocity, radial velocity, duct temperature, axial velocity, etc. The information obtained can be used in the estimation of the coefficients of heat transfer from a rotating surface. © 1989.