Heat transfer and friction for laminar flow of helium and carbon dioxide in a circular tube at high heating rate

Abstract

Using an implicit finite-difference scheme described previously [1], solutions have been worked out for hydrodynamically developed laminar flow of helium and carbon dioxide with uniform heating rates so high that appreciable variations of gas properties occur. Whereas the results for helium closely approximate those previously found for air, both the Nusselt numbers and the friction factors for carbon dioxide come out considerably higher. For the Nusselt number with pure forced convection improved empirical expressions, based on the local Graetz number, are given. The local friction factors can be estimated from the wall-to-bulk temperature ratio.