ادریس ترشیزی

This paper deals with the injection of twin oblique nanofluid jets into a channel with water cross-flow. In this regard, the effects of different geometric and physical parameters including the velocity, distance, and angles of the jets as well as the nanoparticles volume fraction therein are studied. The Eulerian-Eulerian two-phase model is employed to analyze the present problem. By solving separate equation sets for water and the nanoparticles, this approach provides the possibility of behavior prediction for each of the phases inside the flow field, separately. The accuracy of the current simulations is confirmed by comparing the obtained results with available experimental data. The results show that replacement of a single jet with twin jets increases the heat exchange from the target surface and makes its distribution more uniform along the surface. In addition, it is found that rise in the velocity and distance of the jets leads to heat transfer improvement. However, the effect of the nanoparticles volume fraction in the injected nanofluid on the heat transfer rate of the target surface is strongly dependent to the nanoparticles penetration into the water cross-flow. Closer scrutiny of the results reveals that the injection angles of the twin jets play an important role in the nanoparticles penetration as well as their distribution pattern inside the flow field and thereby, by adjusting these angles, the heat exchange from the target surface can be improved.

This paper deals with heat transfer in jet impingement of nanofluids. Attention is focused to compare single-phase and two-phase nanofluid models and to study separate behaviors of the base fluid and the nanoparticles through the Eulerian-Eulerian two-phase model. For this purpose, jet impingement of Al2O3/water nanofluid in different conditions is simulated adopting the single-phase, two-phase mixture and Eulerian-Eulerian models and the corresponding results are discussed. For the solution of the governing equations of the three models, the control-volume approach is used. The accuracy of the current simulations is demonstrated by comparing the obtained results with those of open literature. The results indicate that in all of the approaches, increase in the Reynolds number as well as nanoparticle fraction leads to heat transfer improvement. During the current computations, the two-phase models predict higher heat transfer as compared to the single-phase model. Closer scrutiny of the two-phase approaches indicates that heat transfer of the Eulerian-Eulerian model is higher than the mixture model. However, it is found that with increase in the Reynolds number and decrease in the nanoparticle fraction, results of the two approaches become closer. Finally, the Eulerian-Eulerian model demonstrates that temperature distribution in the base fluid and the nanoparticles are similar but the corresponding velocity distributions are distinct.

This paper deals with water flow in a backward-facing step with blowing of different nanofluids. The objective is to evaluate the effect of nanofluid blowing on the heat transfer rate. For this purpose, the Eulerian-Eulerian two-phase model is employed. The accuracy of the current simulations is demonstrated by comparing the obtained results with those of open literature. The results show that increasing the nanofluid blowing as well as nanoparticles fraction therein improve heat exchange from different surfaces of the channel. Comparing the results of different nanofluids leads one to conclude that the bottom wall heat transfer attains its maximum value when the blowed nanofluid contains nanoparticles with the highest thermal conductivity. However, it is found that maximum heat transfer in the top wall is achieved during blowing of a nanofluid with the highest nanoparticle penetration into the channel flow. Moreover, it is observed that discrepancies appearing between the results of different nanofluids become more remarkable as one increases the nanofluid blowing or nanoparticles fraction therein. Finally, the Eulerian-Eulerian model demonstrates that among the interphase forces, the effects of virtual mass and particle-particle interaction forces are negligible in such a way that they can be ignored.