Heat transfer and friction for laminar flow of gas in a circular tube at high heating rate: Solutions for hydrodynamically developed flow by a finite-difference method

Abstract An implicit finite difference scheme is developed for solving the problem of laminar flow of gases in heated (or cooled) circular tubes with an unheated entrance section, under conditions where large variations of gas properties occur. The solution is based on the boundary-layer equations, the validity of which for the present problem has been verified from the numerical solutions. Numerical examples are worked out for air including (i) pure forced convection with different rates of uniform heating; (ii) pure forced convection with uniform wall temperature with heating as well as cooling of the gas ; and (iii) superimposed forced and natural convection with uniform heat flux. For pure forced convection approximate expressions for the local Nusselt number and the friction factor are given.