Impact of Thermal Dissipation on the Lighting Performance and Useful Life of LED Luminaires Applied to Urban Lighting: A Case Study

Currently, LED technology is an established form of lighting in our cities and homes. Its lighting performance, durability, energy efficiency and light, together with the economic savings that its use implies, are displacing other classic forms of lighting. However, some problems associated with the durability of the equipment related to the problems of thermal dissipation and high temperature have begun to be detected, which end up affecting their luminous intensity and the useful life. There are many studies that show a direct relationship between the low quality of LED lighting and the aging of the equipment or its overheating, observing the depreciation of the intensity of the light and the visual chromaticity performance that can affect the health of users by altering circadian rhythms. On the other hand, the shortened useful life of the luminaires due to thermal stress has a direct impact on the LCA (Life Cycle Analysis) and its environmental impact, which indirectly affects human health. The purpose of this article is to compare the results previously obtained, at different contour temperatures, by theoretical thermal simulation of the 3D model of LED street lighting luminaires through the ANSYS Fluent simulation software. Contrasting these results with the practical results obtained with a thermal imaging camera, the study shows how the phenomenon of thermal dissipation plays a fundamental role in the lighting performance of LED technology. The parameter studied in this work is junction temperature (Tj), and how it can be used to predict the luminous properties in the design phase of luminaires in order to increase their useful life.

Influence of Waterside Buildings’ Layout on Wind Environment and the Relation with Design Based on a Case Study of the She Kou Residential District

It is important to improve residential thermal comfort in the high dense cities, in which wind environment is crucial. Waterside buildings take an advantage of micro-hydrological-climate in summer that should be used to enhance residential thermal comfort especially in the subtropical region. In order to propose design approaches according to the outdoor thermal comfort of the waterside residential, a case study of Shenzhen She Kou residential district has been made. It focused on various factors that could have influence on wind environment for improving thermal comfort. Using wind velocity ratio (ΔRi) criterion, factors of building development volume, building direction and layout pattern, open space arrangement etc. have been broadly explored using FLUENT simulation. To planning parameters, the Floor Area Ratio (FAR) is significantly influence wind environment, the smaller FAR is better. To the vertical layout of the buildings, multi-storey layout and multi-storey & sub high-rise mixed layout would provide better wind environment. To the horizontal layout, the determinant is better than the peripheral. Other factors such as the buildings’ direction towards the road, buildings’ height, and open space setting, have influence on wind environment yet. In general, the more benefit of design layout for wind breezing, the better wind environment it could get

Radical Reduction of Aircraft Fuel Consumption by Optimizing Aerofoil by New Evolutionary Algorithms

This work deals with aerofoil aerodynamic features optimization, not only to improve flight features, but also to improve economy, ecology and safety of parameters of flight technique. In cruise mission, occupying the most flight time, the most important parameter is aerodynamic drag, which directly influences the aeroplane operational economy of transportation. Drag reduction is adequately reflected in the fuel consumption reduction. Consumption reduction is also adequately reflected in the flight ecology. In take-off and landing mission, the safety is priority and directly influences the aerofoil geometry. For cruise mission the new modified evolutionary algorithms (EA) are used to parameters incoming to Bezier-PARSEC 3434 parametrization. Such aerofoil is processed and evaluated by the Xfoil program. The change of model parameters results to optimal aerofoil shape. The DCAG (Direct Control Aerofoil Geometry) is unique developed mechanical device, makes possible the change of curvature of aerofoil, and also aerofoil geometry. DCAG is based on the rotary principle, which makes it possible to define the curvature of aerofoil for every roll as well as defining the geometry in the variable parts of aerofoil. For take-off and landing mission the best combination of slots and flaps is choosed. To improve of laminarity and reduce turbulent flow the DCAG is used. The work results to optimization, which is 50 times faster in comparison to ordinary optimization, with minimum of input parameters (flight speed, chord length, range of angles of attack and fitness function). The optimized aerofoil can achieve savings in fuel consumption up to 44% in comparison with unoptimized aerofoil, the aerodynamic drag reduction up to 44%. The output was checked by ANSYS Fluent simulation.

Radical Reduction of Aircraft Fuel Consumption by Optimizing Aerofoil by New Evolutionary Algorithms

This work deals with aerofoil aerodynamic features optimization, not only to improve flight features, but also to improve economy, ecology and safety of parameters of flight technique.In cruise mission, occupying the most flight time, the most important parameter is aerodynamic drag, which directly influences the aeroplane operational economy of transportation. Drag reduction is adequately reflected in the fuel consumption reduction. Consumption reduction is also adequately reflected in the flight ecology. In take-off and landing mission, the safety is priority and directly influences the aerofoil geometry.For cruise mission the new modified evolutionary algorithms (EA) are used to parameters incoming to Bezier-PARSEC 3434 parametrization. Such aerofoil is processed and evaluated by the Xfoil program. The change of model parameters results to optimal aerofoil shape.The DCAG (Direct Control Aerofoil Geometry) is unique developed mechanical device, makes possible the change of curvature of aerofoil, and also aerofoil geometry. DCAG is based on the rotary principle, which makes it possible to define the curvature of aerofoil for every roll as well as defining the geometry in the variable parts of aerofoil.For take-off and landing mission the best combination of slots and flaps is choosed. To improve of laminarity and reduce turbulent flow the DCAG is used.The work results to optimization, which is 50 times faster in comparison to ordinary optimization, with minimum of input parameters (flight speed, chord length, range of angles of attack and fitness function).The optimized aerofoil can achieve savings in fuel consumption up to 44% in comparison with unoptimized aerofoil, the aerodynamic drag reduction up to 44%.The output was checked by ANSYS Fluent simulation.

Design of Internal Flow Passage of Internal Chip Removal Drill for Suction Type Internal Chip Removal System

Aiming at the current problem that the cutting chips cannot be automatically recovered in the hole-making process of carbon fiber reinforced resin matrix composites, This article first introduces a new type of drilling chip removal technology system-suction type internal chip removal system, which can timely and effectively discharge the powdery chips generated in CFRP hole processing during cutting; Secondly, in view of the problem of the internal runner design of the internal chip removal drill used in the system, this article conducted the following research: 1) Based on cutting experiments and statistical methods, classify the chips produced in CFRP hole making, and give the chip distribution rules; 2) Secondly, on the basis of fluid mechanics, using FLUENT simulation method, on the basis of defining the center distance and center angle of the inner runner for the design of the internal chip removal drill bit, the center distance and the center angle of the inner runner are given. The influence law of the chip removal center angle and the cross-sectional shape of the internal runner on the chip removal effect of the tool internal runner; 2) Based on fluid mechanics, using FLUENT simulation method, on the basis of defining the center distance of the inner runner and the center angle of the inner runner, the center distance of the inner runner, the center angle and the cross-sectional shape of the inner runner are given to the tool The influence law of the chip removal effect of the internal runner; Finally, a suction type internal chip removal system was built, and the experimental method was used to verify the correctness of the internal runner design of the internal chip removal tool.

Effects of Fin Arrangements on Thermal Hydraulic Performance of Supercritical Nitrogen in Printed Circuit Heat Exchanger

The printed circuit heat exchanger (PCHE) with discontinuous fins is a novel type of compact and highly efficient plate heat exchanger, which has superior thermal hydraulic performance. The morphology and characteristics of the flow channel greatly affect the performance of the PCHE. The discontinuous airfoil fins are used in PCHE channel design because they can affect the flow and heat transfer by increasing the heat transfer area and the disturbance in the channel. In this paper, the effects of different staggered distance (Ls) and transverse distance (Lv) of airfoil fin arrangements on the heat transfer and flow of supercritical nitrogen in the PCHE are numerically simulated using ANSYS Fluent. Simulation results and subsequent analysis show that the appropriate decrease in Ls and reduction in Lv between the two rows of fins can improve the convective heat transfer of the PCHE. A fully staggered arrangement of fins (Ls = 1.2) and an appropriate increase in the Lv can mitigate pressure drop. The comprehensive performance of different channel geometries is compared by the performance evaluation criteria (PEC) in this study. It is shown that considering flow resistance and heat transfer, the comprehensive heat transfer performance can be enhanced by properly increasing the staggered distance and the vertical distance between fins. When Ls = 1.2 mm and Lv = 1.25 mm, the PEC value of the staggered channel is the highest, which is 11.6% higher than that of the parallel channel on average.

Hydrodynamic characteristics of marine composite propeller blade using a numerical approach

<p>The aim of the present research work is to investigate the hydrodynamic characteristics (pressure distribution, rotational speed, thrust and torque) of the conventional B-series composite propeller blade. The open water efficiency for the scaled model of composite propeller blade is computed using computational fluid dynamics (CFD) fluent simulation tool. The obtained numerical results show that the propeller will operate at optimum efficiency for the given speed condition and perform with reduced efficiency at other operational speeds. The computed responses are also validated with the standard B-series data which verifies the accuracy and robustness of the present numerical approach in analyzing the performance characteristics of propellers. The deviation in solution ranges from 5 to 15% in the case of thrust, 10-20% in case of torque. Pressure estimation is usually quite accurate with a 5-8% variation. The tabular data of pressure distribution over the propeller blade may be used for further structural analysis</p>

The effect of printing velocity on the temperature and viscosity of the polymer thread at the nozzle exit in 3D printers

Fused Deposition Modelling (FDM) is a powerful method for advanced additive manufacturing of polymeric materials, due to its simplicity and low cost. However, the process implies complex phenomena which are not fully understood yet. In particular, the effect of viscosity on the printed thread is a key parameter to control if good quality products are to be obtained. Experimental data of two grades of acrylonitrile-butadiene- styrene copolymer (ABS) was employed to analyse, by using ANSYS Fluent simulation package, six printing velocities at a temperature of 230°C. A drastic temperature change was observed as the printing velocity increases, confirming the effect of viscosity on the shear created on the wall of the nozzle transversal to the printing bed. The polymers analysed present different viscosity behavior even under the same angular frequency range (0.1 to 100 rad/s), and testing temperature (230°C), which could lead to inhomogeneities. Our results allow taking into account these parameters as part of the design criteria.