M. A. Habib

Calculation of turbulent flow andheat transfer in periodicallyconverging–diverging channels

Abstract A numerical study of flow in a sinusoidally varying, periodic converging–diverging channel is performed to examine turbulent flow and heat transfer characteristics. The method is based on the fully conserved control-volume representation of fully elliptic Navier–Stokes, and energy equations in body-fitted orthogonal curvilinear coordinate system. Turbulence is simulated via two-equation (k–ϵ) model. The study comprises computed velocity and streamline distributions, the kinetic energy of turbulence, pressure drop, friction factor, and local, average and maximum Nusselt number distribution. Systematic variations are made in Reynolds number (40 000–100 000) and the aspect ratio (2a/λ=0.27 and 0.34). The present study is further extended to flows with different ranges of inlet swirl.

Turbulent natural convection flow in partitioned enclosure

Abstract This study represents the numerical solutions of the buoyancy driven turbulent flows in an inclined two-dimensional rectangular enclosure in which one of the inclined walls is heated and the other is cooled. The low Reynolds number k -ϵ model is used to model the turbulent flow. The effect of various parameters such as the angle of inclination, the Rayleigh number and the number of partitions on the flow field and the average Nusselt number have been investigated and presented.

Vortex shedding-free strainers

The subject of the periodic vortex shedding behind bluff bodies, which exhibits oscillatory behaviour, is of direct relevance to many practical applications, e.g. pipelines and heat exchangers. Repetitive failures were occurring in associated piping components on the suction of a sales gas compressor. Available experimental investigations indicated the occurrences of vibrations at the predominant frequencies of 1500 and 3000 Hz in the compressor strainer pipes. Hence, this study is aimed at identifying the source of such high vibration levels. The study investigated the flow-induced vibrations in the compressor strainer pipe through numerical simulation of the flow in the pipe including the strainer, as well as structural modal analysis calculations for the strainer at steady-state conditions. Three different geometrical configurations were considered. The first strainer has a truncated-cone geometry with uniform size holes. The second is witch-hat geometry with uniform holes, while the third is a modified witch-hat configuration with non-uniform holes. The results obtained from the frequency analysis of the flow field downstream of strainers with the first two geometries indicated dominant amplitudes at 1500 Hz and appreciable excitations at its second harmonic. However, the results demonstrated that the dominant vibration amplitudes have been appreciably reduced for the third case of the modified witch-hat configuration with non-uniform holes.

Use of Nanofluids for Enhanced Natural Cooling of Discretely Heated Enclosures

Natural convection heat transfer from discrete heat sources to nanofluids is of great importance because of its application in the cooling of electronic components. The presence of the nanoparticles in the fluids increases appreciably the effective thermal conductivity of the fluid and consequently enhances the heat transfer characteristics. The present study is aimed to investigate numerically the natural convection heat transfer from discrete heat sources to nanofluids. The behavior of nanofluids was investigated numerically inside a heated cavity to gain insight into convective recirculation and flow processes induced by a nanofluid. A computational model was developed to analyze heat transfer performance of nanofluids inside a cavity taking into account the solid particle dispersion. The model was validated through the comparison with available experimental data. The results showed good agreement. The influence of the solid volume fraction on the flow pattern and heat transfer inside the cavity was investigated. The results show that the intensity of the streamlines increases with the volume fraction. It is also indicated that higher velocities along the centerline of the enclosure are achieved as the volume of nanoparticles increases. The influence of the loading factor is more distinguished at the upper heaters and in particular at the highest heater. The heat transfer increases as the volume fraction of the nanoparticles increases from 2 to 10%.