Experimental Investigation of Runner Design Parameters on the Performance of Vortex Turbine

The vortex turbine (VT) is a micro-hydro turbine that extracts power from a water vortex that is artificially generated in a conical or cylindrical cross-section basin. The former cross-section gives rise to a stronger vortex than the latter, meaning it has more potential for power generation. For this reason, the present study experimentally analyzed the effect of sensitive geometric parameters on the VT performance, i.e., the rotor to basin diameter ratio (RB) and runner’s position in the conical basin (CB). The results show that the ideal runner in terms of RB for the best performance of VT is a runner with RB = 0.6, which has a maximum potential for the utilization of the forced vortex region of the Rankine vortex. Moreover, the best position for the installation of a VT runner is the location at the bottom near the orifice, as the strong vortex tangential velocity and maximum head drop at the mid-position is not a feasible option. Blades with a tilt in the vertical plane are suggested for use in the power extraction at the bottom of CB whereas crossflow blades suit the rotational flow region near the top of CB, i.e., the surface vortex

Energy Efficiency Ratio Analysis of Half Cycle Air-Conditioners Using Liquified Petroleum Gas

Alternative fuels have proven to be an effective means of reducing the environmental impact of road transportation. On the other hand, the increasing use of air conditioning has declined the fuel economy of passenger vehicles. Half-cycle air conditioning systems (HCACSs) can address this concern of the declining fuel economy by using the fuel as a refrigerant. One of the candidates to be considered as refrigerants in HCACSs is liquefied petroleum gas (LPG). Under various conditions, LPG in the liquid state is injected into the evaporator of an HCACS. At the end of the evaporation process, LPG vapors can be directed for the combustion taking place in devices such as generators, automobiles, and cooking stoves. The present study investigates the performance of three in-housed manufactured evaporators having staggered and/or aligned tube arrangements with variable tube sizes, numbers of fins, fin spacings, and fin materials. As a refrigerant, LPG, having 65% propane and 35% butane, was passed through three evaporators. The energy efficiency ratios (EERs) were indirectly measured for evaporative pressures of 132, 168, and 201 kPa, with mass flow rates of 0.6, 0.75, and 0.9 g/s, respectively, when the fan speed interacting with the evaporators was varied. The results revealed that the aligned configuration with the same tube and fin material performed better even at low fan speeds

Determination of the Structural Characteristics of Microalgal Cells Walls under the Influence of Turbulent Mixing Energy in Open Raceway Ponds

Turbulent flow mixing is essential in optimizing microalgal cultivation in raceway ponds. Microalgal cells are however highly sensitive to hydrodynamic stresses produced by turbulent mixing because of their small size. The mechanical properties (wall deformation and von Misses stress) of the microalgal cell wall structure under the influence of turbulent mixing are yet to be explored. High turbulence magnitudes damage microalgal cell walls by adversely affecting their mechanical properties which consequently destroy the microalgal cells and reduce the biofuel production. Therefore, such a study is required to improve the biofuel productivity of microalgal cells before their cell wall damage in raceway pond. This study developed a novel fluid–structure interaction (FSI)-based numerical model to investigate the effects of turbulent mixing on the cell wall damage of microalgal cells in raceway ponds. The study investigated microalgal cell wall damage at four different locations in a raceway pond in consideration of the effects of pond’s hydrodynamic and geometric properties. An experiment was conducted with a laboratory-scale raceway pond to compare and validate the numerical results by using time-dependent water velocities. Microalgal cell wall shear stress, cell wall deformation, and von Misses stress in the raceway pond were investigated by considering the effects of aspect ratios, water depths, and paddle wheel rotational speeds. Results showed that the proposed numerical model can be used as a prerequisite method for the selection of appropriate turbulent mixing. Microalgal cell wall damage is high in shallow and narrow raceway ponds with high paddle rotational speeds

Analytical and Experimental Investigation of a Triangular-Channeled Solar Water Heater

Utilization of solar energy is increasing in different states of the world, and the sun is regarded as the largest source of continuous and coherent energy. In the present study, a novel configuration of a v-corrugated solar collector with triangular channels for domestic water heating has been analytically investigated. A mathematical model based on effectiveness-NTU method is established to thermally examine the collector. Additionally, the heat losses from the body of the collector, useful energy from the collector and solar efficiency have been calculated analytically over different operating parameters. The effects of mass flow rate and solar heat flux on water outlet temperature are evaluated analytically and compared with the experimental results. Moreover, the study includes the experimental and theoretical investigation of the heat exchange effectiveness and thermal efficiency of the proposed absorber. The study shows that high temperature and high performance can be obtained from this collector as more heat energy can be collected by using triangular channels because all the three sides of these channels are exposed to solar radiations at the same time. Therefore, these channels will enhance the collector exposed surface area and thereby increase the solar efficiency and overall performance of the system

Analysis of Passive Mixing in a Serpentine Microchannel with Sinusoidal Side Walls

Sample mixing is difficult in microfluidic devices because of laminar flow. Micromixers are designed to ensure the optimal use of miniaturized devices. The present study aims to design a chaotic-advection-based passive micromixer with enhanced mixing efficiency. A serpentine-shaped microchannel with sinusoidal side walls was designed, and three cases, with amplitude to wavelength (A/λ) ratios of 0.1, 0.15, and 0.2 were investigated. Numerical simulations were conducted using the Navier–Stokes equations, to determine the flow field. The flow was then coupled with the convection–diffusion equation to obtain the species concentration distribution. The mixing performance of sinusoidal walled channels was compared with that of a simple serpentine channel for Reynolds numbers ranging from 0.1 to 50. Secondary flows were observed at high Reynolds numbers that mixed the fluid streams. These flows were dominant in the proposed sinusoidal walled channels, thereby showing better mixing performance than the simple serpentine channel at similar or less mixing cost. Higher mixing efficiency was obtained by increasing the A/λ ratio

Refrigeration Potential Investigation of Liquefied Petroleum Gas under Atmospheric Conditions

One of the potential refrigerants for refrigeration systems is liquefied petroleum gas (LPG) that can absorb latent heat from the surrounding and provide cooling, if introduced in liquid state. The present study determines the cooling effect produced in flowing water in coils after exchanging heat with liquid LPG, coming from an inverted cylinder. In an insulated box with a copper coil, the water flow rates were varied while maintaining the amount of surrounding liquid LPG. The results reveal that the cooling effect is proportional to the rate at which water flows, but the time for liquid LPG to evaporate decreases. For smallest water flow rates, the temperature differential across the water inlet and outlet was found to be the largest

Three dimensional numerical investigations for the effects of gas diffusion layer on PEM fuel cell performance

Gas diffusion layer (GDL) is an important component of a proton exchange membrane fuel cell (PEMFC) to take part in the interplay of the transport of different species. It has been found that the performance of a PEMFC depends upon the morphology of the GDL. The performance of PEM fuel cell varies with different porosity and thickness of the GDL. Hence, a three dimensional model is simulated to find out the effects of porosity and thickness of GDL on PEMFC performance using a commercial code CFD-ACE+. It was observed that high porosity gave high current density by allowing more reactants to reach the reaction site. Similarly greater thickness of the GDL gives reactant species to increase the consumption rate at the GDL/catalyst layer interface. The simulation results showed that the connection of bipolar plate with the GDL played an important role for reducing the amount of reactants to reach the catalyst layer especially under the land area of the bipolar plate. However, this effect seems to decrease with an increase of overall porosity and the thickness of the GDL

Rheological investigation of neonatal double-lumen cannula with and without deformable erythrocytes

The double-lumen cannula (DLC) is the most critical component of extracorporeal membrane oxygenation (ECMO) because of its narrow cross-section, thereby developing the highest shear stress in the entire ECMO circuit. To measure blood damage in a DLC, the Eulerian approach is generally used without contemplating exposure time or history of blood exposure to shear stresses. Alternatively, Lagrangian approach has also been recently employed for a Newtonian blood flow through a DLC, thereby leaving a research gap on the impact of variable shear rate in case of non-Newtonian blood flow. In the present study, the hemodynamic performance of DLC is investigated using different non-Newtonian models by applying Lagrangian approach. Moreover, the motion of RBC was tracked inside the cannula to predict its behavior during the motion. The results showed that the return lumen had higher pressure, velocity, and shear stress values than other parts of the DLC. In addition, recirculation was observed due to the mixing of blood coming from different inlets and found increase with increasing flow rate of blood. Moreover, it was found that the blood damage increased with increasing flow rate. There was more blood damage in the Newtonian model than in the other non-Newtonian models at higher flow rates. However, the Carreau model showed more blood damage at lower flow rates than the other models. The Cross model showed DLC's higher efficacy in delivering oxygenated blood to the tricuspid outlet because it showed the least blood damage among all other models. It was also concluded that the efficacy of the DLC to deliver oxygenated blood to the tricuspid outlet decreases with increasing blood flow rate

Fabrication of Low-Cost Resistance Temperature Detectors and Micro-Heaters by Electrohydrodynamic Printing

EHD printing is an advanced deposition technology that is commonly utilized for the direct manufacture of electrical devices. In this study, meander-type resistive electrodes consisting of silver nanoparticles were printed directly on rigid glass and flexible polyethylene terephthalate (PET) substrates. High-resolution patterns of ≈50 µm linewidth were successfully printed on untreated surfaces utilizing a bigger nozzle of 100 µm inner diameter after improving the experimental settings. The manufactured electrodes were evaluated and used as Resistance Temperature Detectors (RTDs) and micro-heaters in a systematic manner. The temperature sensors performed well, with a Temperature Coefficient of Resistivity (TCRs) of 11.5 ×10−3/°C and 13.3 ×10−3/°C, for glass and PET substrates, respectively, throughout a wide temperature range of 100 °C and 90 °C. Furthermore, the RTDs had a quick response and recovery time, as well as minimal hysteresis. The electrodes’ measured sensitivities as micro-heaters were 3.3 °C/V for glass and 6.8 °C/V for PET substrates, respectively. The RTDs were utilized for signal conditioning in a Wheatstone bridge circuit with a self-heating temperature of less than 1 °C as a practical demonstration. The micro-heaters have a lot of potential in the field of soft wearable electronics for biomedical applications, while the extremely sensitive RTDs have a lot of potential in industrial situations for temperature monitoring

Thermo-Fluid Performance Enhancement Using NACA Aerofoil Cross-Sectional Tubes

Industrial heat exchange applications encounter flow across a bank of tubes in an aligned or staggered configuration. The former arrangement causes boundary layer separation and wake formation in the trailing part of the first tube leading to poor heat exchange. Alternatively, the staggered arrangement is used for heat transfer improvement, accompanied by a rise in the pressure drop. The present study uses tubes of NACA airfoil cross-sections as an alternative solution. The pressure drop and heat transfer rates in aligned aero tubes are improved by 36% and 3% more than in the circular tubes with a staggered arrangement, respectively