This article presents two dimensional (2D) and three-dimensional (3D) computational analysis of rotating detonation combustion (RDC) in annular chambers using the commercial computational fluid dynamics (CFD) solver ANSYS-Fluent V13. The applicability of ANSYS-Fluent to predict the predominant phenomena taking place in the combustion chamber of a rotating detonation combustor is assessed. Simulations are performed for stoichiometric Hydrogen-Air combustion using two different chemical mechanisms. First, a widely used one-step reaction mechanism that uses mass fraction of the reactant as a progress variable, then a reduced chemical mechanism for H2-Air combustion including NOx chemistry was employed. Time dependent 2D and 3D simulations are carried out by solving Euler equations for compressible flows coupled with chemical reactions. Fluent user defined functions (UDF) were constructed and integrated into the commercial CFD solver in order to model the micro nozzle and slot injection system for fuel and oxidizer, respectively. Predicted pressure and temperature fields and detonation wave velocities are compared for the two reaction mechanisms. Curvature effects on the properties of transverse detonation waves are studied by comparing the 2D and 3D simulations. The effects of diffusion terms on RDC phenomena are assessed by solving full Navier-Stokes equations and comparing the results with those from Euler equations. Computational results are compared with experimentally measured pressure data obtained from the literature. Results show that the detonation wave velocity is over predicted in all the simulations. However, good agreement between computational and experimental data for the pressure field and transverse detonation wave structure proves adequate capabilities of ANSYS-Fluent to predict the main physical characteristics of RDC operation. Finally, various improvements for RDC modeling are postulated, particularly for better prediction of wave velocity.

The increasing addition of hot components on a single module comes with the challenge to cool the module. The cooling challenges are due to the presence of hot spots and the reduce space for attaching heat sinks to each component. The proposed cooling solution for a multi-chip module is a single vapor chamber shared amongst the multiple heat sources. Designing an application-optimized vapor chamber requires detailed understanding of the different processes occurring, including heat transfer by conduction, two-phase heat transfer, and fluid mechanics in porous media. In this work, a relatively large module with many heat sources is considered. We present a case of two 100W heat sources surrounded by eight heat sources of 10W each. We explore different configurations and their capillary limitations for a vapor chamber (110 mm × 110 mm). We present the comparison of numerical results using two point flux approximation method, CFD model, and a simplified model using potential flow theory to represent flow in the porous media. Results are used to analyze the capillarity limitation of the large vapor chamber in delivering liquid flow to heat source locations for steady state.

A combined particle image velocimetry (PIV) and particle image thermometry (PIT) method was applied to visualize and measure simultaneously the 2-D velocity and temperature fields in a crystallizer. The 2-D supersaturation field can be also determined before nucleation or seeding takes place. The hydrodynamic behavior in an internal loop airlift crystallizer was studied for different air flow rates, sparger types, and crystal holdups to get insight in the optimal process conditions for this crystallizer, i.e. uniform temperatures and particle concentration. The 2-D velocity and temperature gradients showed that in a 2 L crystallizer the mixing is sufficient to ensure uniform supersaturation profiles at an overall superficial air velocity higher than 2.3 mm/s. Suspension tests showed that a superficial air velocity of 7 mm/s was sufficient to avoid settling of the crystals. This air flow rate assured the lifting of the solids from the bottom of the crystallizer for crystals with a mean size of 1.5 mm and holdups up to 10 wt %. Both the circulation velocity and the crystal holdup which could be totally suspended increased with the air flow rate. For the ammonium sulfate−water system, the crystal growth behavior, which is also influenced by the mixing, was theoretically studied. The growth of the crystals in an airlift crystallizer behaves comparable to that in a suspension stirred crystallizer, and no evidence for mass transfer limitation of the crystal growth was found.