Experimental Investigation of Ice Accretion on Horizontal Axis Wind Turbines

Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.In this paper, ice accretion on a wind turbine blade with a NACA 63415 airfoil is investigated with experimental techniques. Several different angles of attack, from 0° to 90°, and wind velocities, 3 m/s, 4 m/s and 5 m/s are studied. Tests are conducted in a climatic wind chamber with a fan and two spray nozzles. The largest quantity of ice accumulation on the blade was 7.2 kg, at an angle of attack of 90°. The results of this paper provide valuable new experimental data for ice accretion on wind turbine blades

Preparation and Properties of Nanoparticle-enhanced Composite Phase Change Material with Ceramic Porous Media

Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Nanoparticle-enhanced tailing-paraffin composite phase change material (NCPCM) is fabricated by spontaneous melt infiltration. Industrial waste-iron tailing is used as raw material to prepare ceramic porous carrier with a foam-gel casting method. By adjusting the fabrication parameters, optimal NCPCM properties are obtained with paraffin content of 70%~88% and thermal conductivity of 0.351~0.490 W/(m·K), which is nearly 200% the thermal conductivity of paraffin wax. After 25 melting/solidification cycles, the nanoparticles remain well dispersion with overall stability in the composite phase change material, and the thermal conductivity slightly decreased from 0.349 to 0.317 W/ m·K. With multiple melting and solidification cycles, a low weight loss of 2.3~7.8 wt.% is demonstrated. The strength of ceramic frame is found to have a direct effect on the weight loss. Compared with exisiting nanoparticle-enhanced phase change material, the new NCPCM shows significantly improved thermal conductivity and better nanoparticle stability due to its ability to prevent nanoparticles from disposition

Feasibility Study of Synthetic Oil Based Nanofluids for Use in Thermal Oil Heaters

Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Thermal oil heaters can be considered as an alternative to steam boilers for process heating use. Instead of boiling water, thermal oil heaters use heat transfer oils with high boiling points which allows operation at low pressures. To increase thermal oil heater efficiency, a nanofluid consisting of a common heat transfer oil, the synthetic TH66, and copper nanoparticles has been proposed. Based on existing correlations for nanofluids, a figure of merit (FOM) was created to evaluate heat transfer performance while factoring in pumping power increases. A maximum FOM increase of 13% was found for a thermal oil heater using the nanofluid when compared to one that uses the base fluid oil

Droplet Impact, Spreading and Freezing on Metallic Surfaces of varying Wettability

Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Ice formation and accumulation can lead to operational failure and risks for structures, including power transmission lines, aircraft, offshore platforms, marine vessels, and wind turbines. Liquid repellent and icephobic surfaces can reduce ice accretion and improve asset integrity and safety in harsh environments. There are significant needs to probe how wettability affects the droplet impact, ice nucleation and ice accretion processes on different kinds of micro-structured surfaces. This paper presents experimental results of droplet impact, icing delay time and ice accumulation on metallic surfaces with varying wettability. Several different designs of the hydrophobic surfaces are considered. A commercial hydrophobic coating is also used to enhance liquid repellent features and reduce ice accumulation. The results demonstrated that when the static contact angle increases, the total icing time increases, suggesting desirable icing delays. The total icing time decreases with lower surface temperature, higher impact velocity or smaller droplet diameter

Evolution of Air Plastron Thickness and Slip Length over Superhydrophobic Surfaces in Taylor Couette Flows

Drag reduction (DR) using superhydrophobic surfaces (SHSs) has received intensive interest due to the emergence of SH coating technology. The air layer (plastron “δ”) trapped between the SHS and the water controls the flow slip over the SHSs. We demonstrate slippage over three fabricated SHSs in laminar and low turbulent Taylor–Couette flows. We experimentally investigate how the slip length increases with a higher Reynolds number (Re) over the tested SHSs; simultaneously, the air plastron thickness investigates using a viscous model. The mean skin friction coefficient (Cf) can be fitted to a modified semi-empirical logarithmic law expressed in the Prandtl–von Kármán coordinate. An effective slip length is estimated in the 35–41 µm range with an achieved 7–11% DR for the tested surfaces. Statistical analysis is used to develop a regression model from the experimental data. The model shows an R2 of 0.87 and good agreement with the experimental data. This shows the relation between the dimensionless slip length (b+), the dimensionless plastron thickness (δ+), and the Reynolds number, which is directly proportional. The regression model shows that b+ and Reynolds numbers have a higher impact on the δ+ than the surface wettability, which attribute to the small difference in the wetting degree between the three tested surfaces. The practical importance of the work lies in its ability to provide a deep understanding of the reduction in viscous drag in numerous industrial applications. Furthermore, this research serves as a groundwork for future studies on hydrophobic applications in internal flows

Nanosecond Laser Fabrication of Hydrophobic Stainless Steel Surfaces: The Impact on Microstructure and Corrosion Resistance

Creation of hydrophobic and superhydrophobic surfaces has attracted broad attention as a promising solution for protection of metal surfaces from corrosive environments. This work investigates the capability of nanosecond fiber laser surface texturing followed by a low energy coating in the fabrication of hydrophobic 17-4 PH stainless steel surfaces as an alternative to the ultrashort lasers previously utilized for hydrophobic surfaces production. Laser texturing of the surface followed by applying the hydrophobic coating resulted in steady-state contact angles of up to 145°, while the non-textured coated base metal exhibited the contact angle of 121°. The microstructure and compositional analysis results confirmed that the laser texturing process neither affects the microstructure of the base metal nor causes elemental loss from the melted regions during the ultrafast melting process. However, the electrochemical measurements demonstrated that the water-repelling property of the surface did not contribute to the anticorrosion capability of the substrate. The resultant higher corrosion current density, lower corrosion potential, and higher corrosion rate of the laser textured surfaces were ascribed to the size of fabricated surface micro-grooves, which cannot retain the entrapped air inside the hierarchical structure when fully immersed in a corrosive medium, thus degrading the material's corrosion performance

Cooperation-based sperm clusters mediate sperm oviduct entry and fertilization

Sperm cooperation has been observed in multiple species, yet its existence and benefit for reproductive success in mammals remains underexplored. Here, combining tissue-clearing with deep three-dimensional imaging, we demonstrate that postcopulatory mouse sperm congregate into unidirectional sperm cooperative clusters at the utero-tubal junction (UTJ), a key physical barrier for passage into the oviduct. Reducing sperm number in male mice by unilateral vasoligation or busulfan-treatment impairs sperm cluster formation and oviduct entry. Interestingly, sperm derived from Tex101-/- mouse has normal number, motility and morphology, yet they cannot form sperm cluster and fail to pass through the UTJ, which is at least in part due to the altered tail beating pattern of the Tex101-/- sperm. Moreover, Tex101-/- sperm's defect in oviduct entry cannot be rescued by the presence of wild-type (WT) sperm in the same uteri by sequential mating, suggesting sperm cooperative cluster as an essential behavior contributing to male fertility, which could be related to human infertility or subfertility

Experimental and Theoretical Modelling of Concentrating Photovoltaic Thermal System with Ge-Based Multi-Junction Solar Cells

Climate change is one of the biggest environmental, political, economic, technological, and social challenges of the 21st century. Due to ever-increasing fossil fuels costs. The world energy system should be transitioned to renewable energy sources to mitigate greenhouse gas emissions. Solar energy is one of the suitable alternatives to fossil fuel usage. Currently, the most widely available solar technologies are solar photovoltaic (PV) and solar thermal. The integration of these two techniques enables the exploitation of the most significant amount of solar radiation. This combination has led to a hybrid photovoltaic/thermal system (PV/T). Concentrated solar radiation on PV cells, known as concentrated photovoltaic (CPV), effectively decreases PV receivers’ area and harnesses the same quantity of solar radiation. However, the main problem with CPV is the elevated PV surface temperature, which often requires active cooling. This issue can be solved by introducing a Concentrating Photovoltaic Thermal (CPVT) system. In this article, a new CPVT hybrid system based on Point Focus Fresnel Lens (PFFL) and embedded Multi Junction Photovoltaic (MJPV) (GaInP/InGaAs/Ge) cells has been experimentally investigated and numerically modelled under indoor conditions. Experiments and simulations were carried out at different heat transfer fluid (HTF) flow rates and under constant irradiation emitted from a sun simulator. The results indicate that the thermal and electrical performance of the CPVT system improves under the testing conditions, where the total efficiency was 68.7% and 73.5% for the experimental and CFD models, respectively. At the same time, the highest thermal efficiency of the experimental and CFD models was 49.5% and 55.4%, respectively. In contrast, the highest electrical efficiency was 36.5% and 37.1%. Therefore, the CPVT system has an excellent possibility of being competitive with conventional power generation systems