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This research involves an experimental study of vapour compression refrigeration system (VCRS) with hybrid-nanofluids zeotropic blends of (23%-R32/25%-R125/52%-R134a) in the ratio of (0.03 - 0.15 %.Vol.) with elven samples as thus: 001, 010, 100, 011, 111, 211, 121, 112, 221, 212 and 122 gram). A morphology characterization test was conducted using scanning electron microscope (SEM) and X-ray Diffraction (XRD) amongst the selected ratios using compressor work efficiency, power consummation rate and Coefficient of performance (COP) as the core enhancement parameters. The most favorable blend produced the optimum COP in three different fraction ratios (011, 111 and112). The outcome indicated that thermo-physical and vapor compression properties of hybrid-nanofluids zeotropic (011) zero gram-TiO2, 7.5g-Al2O3/CuO; (112) 3.75 g-TiO2/Al2O3, 7.5 g-/CuO and (111) 5.0g-TiO2/Al2O3/CuO produced the best optimum performance of 3.1%, 1.41% and 1.21% respectively. The COP was found to be highest at (011) blend by about 3.1% at refrigerant temperature of -7 oC. The maximum compressor power coefficient, volumetric cooling capacity and TEGWI were found to increase by 13.51%, 5.78 % and 1.06 kg/sec CO2. The study also revealed that nanoparticles mixed in the base fluid increased the heat transfer coefficient even with a smaller particle portion of 0.003%, with optimum improvement of 0.0075 Vol % application. The calculated values of exergy destruction in each component at various % fractions are presented in Appendix I. Outcome of the study confirmed that hybrid-nanofluids zeotropic blend is energy efficient and environmentally friendly with good characteristics healthier than CFCs and HCFCs, and can offer healthier compressor/refrigerator working fluid substitute to be adopted in VCRS and air conditioning operations. [ABSTRACT FROM AUTHOR]

Renault internal combustion engines have complex, expensive, and challenging experimentally computed in-cylinder flow dynamics. The current study employed computational fluid dynamics to simulate the in-cylinder charge behavior at various valve lift opening clearance in a four-stroke spark-ignition internal combustion engine. The governing equations for an unstable, three-dimensional and compressible turbulent flow were computed using the continuity equations (for mass conservation), Navier-Stokes equations (for momentum conservation), and RNG k-turbulence model. The engine was modelled using SolidWorks 2019 while the in-cylinder charge behavior was simulated using ANSYS Fluent 14.5 model. The thermal characteristics and parameters with respect to air-fuel mixtures were observed to improve with higher temperature (with respect to the cylinder) during combustion. The volumetric and mechanical efficiency of the cycle significantly improved as a result of the increased valve lift opening clearance, which caused more charge to be ingested into the cylinder. Additionally, it was found that at lower valve lift, which may be characterized by minimal or zero losses, the rate of heat retention in the cylinder was at its peak, but very high cylinder charge temperatures was predisposed to a decrease in the intake charge density. From the Particle Image Velocimetry (PIV) obtained in this study, increasing valve lift opening clearance led to increase in-cylinder velocity vectors, vorticity magnitudes, and distributions of turbulence kinetic energy (TKE), which signified improvement in combustion efficiency, increased torque and power output for efficient engine performance. [ABSTRACT FROM AUTHOR]

Cooling refrigeration systems ingest prime energy and contribute to universal negative impact due to ecologically unfavorable working fluids used. Hence, the quest to improve the performance of Vapour Compression Refrigeration System (VCRS) with more efficient and eco-friendly refrigerant such as nanoparticles becomes imperative. In this study, performance analysis of hybrid nanofluids-zeotropic mixtures in a VCRS were experimentally investigated to determine the best operating optimum performance using exergy based approach. To achieve this, varying concentrated mixtures were selected using ternary graph. The results revealed that all the designated ratios of the mixed refrigerant with different fractions achieved good performance improvement with optimum values obtained at (011) zero gram of TiO2, 7.5g-Al2O3/CuO. All the selected hybrid mixtures led to an improved outcome in terms of Coefficient of Performance (COP), less power consumption and high performance exergetic efficiency, with COP values ranging from 0.31% to 3.10% and exergetic efficiency from 0.32 to 1.43%. The value for thermal conductivity, dynamic viscosity, density and specific heat were found to be highest (0.0958 W/m.K; 0.00164 W/m.K; 686.82 kg/m³ and 359.82 kJ/kg.K) at the same concentration of zero grams TiO2 in the mixture. Comparison made from the performance characteristics curve (with global parameters) indicated that maximum power coefficient and cooling capacity for the various concentrations were found at (001) 7.5g-TiO2, zero grams Al2O3/CuO equal to 2.2 kW, and the minimum value at concentration of 5 was 0.61% at (111) 5g-TiO2/Al2O3/CuO, and 0.87% for (121). An increase was observed in the maximum power coefficient, cooling capacity and COP increased by 13.51%, 5.78% and 10.33%. It was also observed that hybrid nanofluid-zeotropic refrigerant worked seamlessly with VRCS, making it a sustainable, green and clean as well as eco-friendly alternative with near-zero to zero negative effects on public health safety and environment. [ABSTRACT FROM AUTHOR]

In this paper, the performance characteristics of a fabricated Horizontal Axis Wind Turbine (HAWT) with and without flanged diffusers were studied using wind tunnel experiment. Measurements of global parameters (power, torque, rotational speed efficiency, etc.) were carried out at wind speed regime between 3-7 m/s. Flanged diffusers of five different inlet-outlet diameter ratios were employed. The results showed minimum mean increments in Tip-Speed Ratios (TSRs) of about 45% with the smallest diffuser and a maximum of 80% with the largest diffuser. Increments in the torque even at modest wind speed of 4 m/s were as much as 65, 70 and 76% for the largest three diffusers and about 33% for the smaller diffuser. The power output (with and without diffuser) gradually increased from 3-7 m/s wind speed, while the power coefficient (Cp) increased from 3-5.5 m/s, and thereafter began to fluctuate as the wind speed approached 7 m/s. Comparatively, maximum Cp of the turbine without diffuser was 0.22 for λ = 0.534 at a wind speed of 7 m/s, while the maximum average value of Cp for turbine with flanged diffuser 3 was 0.34 for λ = 0.706 at the same wind speed. As a result of the flanged diffuser attachment, the maximum Cp increased by 36%. The results showed mean incremental values of 52 and 57% with the greater value obtained from the second largest diffuser (Di/Do = 0.70) and the least value from the largest diffuser (Di/Do = 0.80), while the first three diffusers achieved near identical increments of 55%. This consequently implies that increments in the extracted power (i.e., Cp) above 5 m/s wind speed declined with indications of separation and turbulence in the flows beyond the rotor. [ABSTRACT FROM AUTHOR]

Fluid flow models developed for pipe flow in gasoline port fuel injection system with different number of injectors working under steady state condition was simulated in this study using FLOWMASTER Software. Using existing equations, theoretical analysis were computed for the same flow parameters and results obtained for each parameter for both the simulation and theoretical approach were compared accordingly. Results obtained for the theoretical approach and that of simulation had not shown much correlation due to the assumptions and computational errors. The pipe flow was simulated under steady state condition and the inlet pressure flowing across the circular pipe was observed to increase per unit time while fluctuations characterised by sinusoidal pattern were observed on the plot of total pressure at bends against time. The normal pressure while flowing along the pipe duct increased proportionally with the pipe length but suddenly experienced a decline and pick-up again as it encountered bends. The mass flow rate of gasoline was observed to increase gradually as the simulation time progressed. For the three simulated outcomes, decrease were observed as the flow approached bends along the circular pipe. Hence, the use of FLOWMASTER software in Computational Fluid Dynamics (CFDs) helped in predicting flow characteristics along the rail pipes in gasoline port fuel injection system. [ABSTRACT FROM AUTHOR]