Determination of two-phase friction factors for void fraction and boiling heat transfer evaluation

Visual and photographic observations of the boiling processes undergone by refrigerants in a cylindrical tube under both stationary and rotating conditions show that there are no bubbles generated for refrigerants heated on the tube surface. This indicates that the transfer of heat is always enhanced by increasing the centrifugal acceleration. The laminar flow in a cylindrical porous tube with uniform mass injection through the porous wall was studied both theoretically and experimentally. The full Navier-Stokes equations are solved numerically by employing some finite difference schemes. Solutions for velocity profiles and frictional pressure drops were obtained by the use of vorticity and stream function approach. An experimental apparatus for measuring velocity profiles and static pressure drops was set up which uses Pitot tubes to measure the velocities in terms of dynamic pressures. The device is sensitive to pressure differentials of 0.1 micron of water.