Bottom Of Annulus Research Articles

CFD simulation of nanofluid forced convection inside a three-dimensional annulus by two-phase mixture approach: Heat transfer and entropy generation analyses

The behavior of water–Al2O3 nanofluid inside the three-dimensional horizontal concentric annulus is investigated by the two-phase mixture procedure regarding the first and second laws of thermodynamics. The annulus walls are subjected to constant temperature boundary condition. Heat transfer and entropy generation rates, nanoparticle distribution, skin friction coefficient, and temperature distribution are evaluated at different concentrations and Reynolds numbers. The results show that nanoparticle concentration at the bottom of annulus and the upper side of inner cylinder is greater than other regions. In addition, the heat transfer and thermal entropy generation rates increase with increment of concentration and Reynolds number. Moreover, the lowest and highest thermal entropy generation rates happen in the annulus central part and near the walls, respectively. Bejan number is very close to 1 at all cases under study, which shows the dominance of thermal entropy generation.

An analytical prediction on the pump-induced pressure pulsation in a pressurized water reactor

Pump-induced pressure pulsation in the reactor vessel annulus and inlet pipe of a pressurized water reactor is analyzed. Two systems of the inlet pipe and annulus are coupled, and a new intermediate boundary condition adopting impedance concept is imposed at the bottom of annulus. The pump forcings for each frequency are obtained using the measured pump discharge pressures. The open boundary condition at the bottom of annulus is found to be appropriate. An analytical solution for pressure distributions is obtained and found to be in good agreement with the measurements.