This work describes the recent progress in the improvement of heat transfer through microscale facing steps. This analysis includes previous studies that aimed to improve heat transfer with and without hybrid nanofluids. This review presents the experimental and numerical results on the usage of hybrid nanofluids. Furthermore, this work introduces the use of backward-facing step (BFS), forward-facing step (FFS) and microscale steps with different flow regimes and working fluids. This study reveals an increase in heat transfer by utilizing hybrid nanofluids as a working fluid and an improvement in the coefficient of heat transfer when the nanoparticle volumes and concentrations of hybrid nanofluids increase. This work points out the studies on hybrid nanofluids over BFS and FFS, describes various nanoparticles used on the basis of thermal conductivity and shows the improvement in the rate of heat transfer. This study also outlines the discussion and future direction of the current review.
Experimental research was presented in this paper to illustrate the heat transmission and flow characteristics of nanofluid on a microscale backward-facing step channel. Except for the downstream wall, which was applied with uniform heat flow, the channel side walls were deemed adiabatic. Water was used as the base fluid and mixed with 30 nm diameter CuO nanoparticles with a volume fraction in the range of 0-0.04. The experiment was conducted at a Reynolds number range of 5,000–10,000. The results showed that the Nusselt number increases as the volume fraction increases. However, the increase in the nanoparticle volume fraction leads to an increment in the friction factor. Furthermore, the results indicated that increasing the Reynolds number lead to the volume fraction decreasing. It was found that there is an improvement of heat transfer by applying the CuO/water nanofluid with a 0.03 volume fraction of CuO nanoparticles with a significant performance evaluation criterion (PEC>1).
A physical model was designed and constructed with a scale of 1:50 to simulate Mandali Dam spillway and its approaches. Twenty six measuring were carried out with different discharges that cover the range of expected discharges. Analysis of the collected data showed that the discharge coefficient, Cd, of the spillway was 1.7 at low discharges and it was 2.05 in case of high discharges. The model showed that the relative losses of energy dissipated through the stilling basin were varied inversely with the discharge between 71.7% and 64.6%. The measurements of the three piezometers sets located on the spillway indicated that all the measured pressures along the weir surface are positive for full range of discharges. The hydraulic model confirmed that the approach flow to the spillway inlet was generally smooth and without disturbances.
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