LAMINAR FORCED-CONVECTION IN A CIRCULAR TUBE WITH CONSTANT HEAT-FLUX AND SLIP-FLOW

An analytical solution to the problem of laminar gas flow in microtube s with a constant heat flux boundary condition at the wall is presente d. The microtube diameter is small enough that the Knudsen number beco mes an important parameter; thus, both a slip flow hydrodynamic condit ion and a temperature jump thermal condition are assumed at the wall. The fluid is assumed to be hydrodynamically fully developed at the tub e entrance. An indirect solution method utilizes the solution for a pr eviously reported isothermal wad problem. The results indicate that th e fully developed Nusselt number decreases with Knudsen number. For in stance, with a Knudsen number of 0.04, the Nusselt number for fully de veloped flow is reduced 14% over that obtained for a nonslip boundary condition. The reduction is strongly influenced by the increased tempe rature jump as Knudsen number increases.