Research and Modelling on Electrical and Thermal Mode of LEDs Operation in the Luminaire

2018 ◽  
pp. 155-162 ◽  
Author(s):  
Sergei S. Kapitonov ◽  
Anastasia V. Kapitonova ◽  
Sergei Yu. Grigorovich ◽  
Sergei A. Medvedev ◽  
Taher Sobhy
Keyword(s):  
Thermal Conditions ◽  
Operating Mode ◽  
Thermal Processes ◽  
Thermal Mode ◽  
Crystal Temperature ◽  
Premature Failure ◽  
Model Based

In the article, the electrical and thermal processes in the LED lamp with varied parameters are investigated. Voltage and current measurements on all LEDs of the luminaire are carried out in the nominal operating mode. The power allocated to each LED is determined. The calculation of the LED crystal temperature was carried out using the developed thermal LED model based on the results of the measurements and by using “Multisim” program. It has been established that the temperature of the crystals of individual LEDs in the luminaire differ significantly, which leads to unfavourable thermal conditions for them and an increased likelihood of premature failure.

New Model of a Basin-Type Solar Still

2002 ◽  
Vol 124 (3) ◽  
pp. 311-314 ◽  
Author(s):  
Irene De Paul
Keyword(s):  
Flow Visualization ◽  
Physical Model ◽  
Thermal Inertia ◽  
Thermal Conditions ◽  
Salt Deposit ◽  
Solar Still ◽  
New Model ◽  
Model Based ◽  
Productivity Measurements ◽  
Real Scale

Thermal and productivity measurements and flow visualization experiences were performed on a real scale module of a basin type solar still, whose geometry and thermal conditions could be changed in a controlled way. The convective stage was studied with the aim of acquiring information about the nature of the medium inside it and the influence of different parameters over the productivity. Literature shows a great number of experimental and numerical works dealing with different aspects of the performance of solar stills: thermal losses, vapor losses, salt deposit on the tray, geometry, thermal inertia, etc. Few works are reported that take into account convective phenomena and the fluiddynamic characteristics of the medium inside the still. Most of these works are based on Dunkle’s and Copper’s models of the still that does not take into account the characteristics of the environment. A new physical model based on these experiments is presented.

Theoretical and Experimental Study of Led Luminaire

2015 ◽  
Vol 756 ◽  
pp. 453-458
Author(s):  
S.Yu. Gurin ◽  
B.V. Akimov ◽  
B.P. Gritsenko
Keyword(s):  
Energy Efficient ◽  
Cooling System ◽  
Light Output ◽  
Flow Simulation ◽  
Thermal Conditions ◽  
Operating Mode ◽  
Luminous Flux ◽  
Effective Work ◽  
Software Application ◽  
Special Software

Today, the LED illumination takes one of the leading positions in the segment of lighting equipment. This is due to the lighting market demanding energy-efficient and ecologically safe sources of light. The purpose of this project was to investigate the temperature conditions of Сree LEDs, depending on impressed current. The basic idea was to obtain dependencies that could be used to select the optimal operating mode for getting the most LED lamp efficiency. Calculation of thermal conditions was held with the help of a special software application SolidWorks Flow Simulation. In the course of research 5 PCBs mounted on the aluminum housing of the designed luminaire were calculated. On each board different current from 0.35A to 1.5A was impressed. LED quantity on PCBs was chosen so that the luminous flux was the same on all the boards - 5klm. After the calculations the graphs and experiments, reflecting energy efficient characteristics of the luminaire were obtained. The analysis of obtained results elucidates that the operating heat regimes at LED supply currents varying from 0.35 A to 0.7 A are most suitable for the effective work of a lamp. At currents higher than 1 A, there is a considerable drop of the light output. The calculation of LEDs thermal condition (especially, powerful) and the choice of a suitable cooling system is one of the main criteria in the design of a reliable and durable LED lighting system.

scholarly journals Energy efficiency of cogeneration utilization of residual heat of flue gases during the drying of coal concentrate in pipe-dryers

2019 ◽  
Vol 109 ◽  
pp. 00065
Author(s):  
Yurii Oksen ◽  
Maksym Radiuk ◽  
Yurii Komissarov ◽  
Mykhailo Kirsanov
Keyword(s):  
Power Generation ◽  
Electric Energy ◽  
Thermal Conditions ◽  
Hot Water ◽  
Flue Gases ◽  
Thermal Mode ◽  
Heat Power ◽  
Heat Potential ◽  
Power Generation Unit ◽  
Generation Unit

The possibility of increasing the efficiency of drying coal concentrate unit on the basis of pipe-dryers has been investigated by converting the heat of flue gases outlet into electrical energy and the heat potential of hot water supply system with a heat power generation unit operating on low-boiling working fluids. A method and an algorithm for calculating the thermal mode of the unit under the conditions of specified limitations on temperature pressures in heat exchangers have been developed. On the basis of mathematical modeling of thermal conditions, it has been found that under the conditions of PD-11 pipe-dryers, when the heat power generation unit operates with butane-pentane mixture, 204 kW of electricity can be generated with the condensation cycle, and 1780 kW of heat and 65 kW of electric energy can be generated with the heating cycle.

scholarly journals The PMV and PPD indices in the selected boiler room

2018 ◽  
Vol 44 ◽  
pp. 00021 ◽  
Author(s):  
Robert Cichowicz ◽  
Artur Stelęgowski
Keyword(s):  
Indoor Environment ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Thermal Conditions ◽  
Thermal Processes ◽  
Technological Equipment ◽  
Work Area ◽  
Boiler Room ◽  
Industrial Boiler ◽  
Made In

Thermal microclimate in a boiler room is formed by factors resulting from thermal processes that are taking place in combustion units. These factors are negatively affecting the indoor environment by worsening the air quality, and therefore it is crucial to maintain adequate air parameters in the room. It is a consequence of the fact that in the boiler room the operation of technological equipment results in an exposure of workers to adverse effects caused by thermal factors. Therefore, the evaluation of thermal conditions in the work area of people was made for the selected industrial boiler room using PMV and PPD indices (which allow to determine the thermal sensation of employees, regarding their surrounding thermal environment, based on the methodology of ISO 7730 standard). The analysis was based on own experimental measurements and numerical calculations made in the DesignBuilder program.

The Effect of Chaotic Mixing on Heat Transfer in Continuous Thermal Processes at Low Peclet Numbers

2010 ◽  
Author(s):  
M. F. M. Speetjens
Keyword(s):  
Heat Transfer ◽  
Electronics Cooling ◽  
Thermal Conditions ◽  
Laminar Flows ◽  
Chaotic Mixing ◽  
Asymptotic State ◽  
Thermal Processes ◽  
Driven Cavity ◽  
Transfer Rates

Chaotic fluid mixing is generally considered to enhance fluid-wall heat transfer and thermal homogenisation in laminar flows. However, this essentially concerns the transient stage towards a fully-developed (thermally-homogeneous) asymptotic state and then specifically for high Pe´clet numbers numbers Pe (convective heat transfer dominates). The role of chaos at lower Pe under both transient and asymptotic conditions, relevant to continuous thermal processes as e.g. micro-electronics cooling, remains largely unexplored to date. The present study seeks to gain first insight into this matter by the analysis of a representative model problem: heat transfer in the 2D time-periodic lid-driven cavity flow induced via non-adiabatic walls. Transient and asymptotic states are investigated in terms of both the temperature field and the thermal transport routes. This combined Eulerian-Lagrangian approach enables fundamental investigation of the connection between heat transfer and chaotic mixing and its ramifications for temperature distributions and heat-transfer rates. The analysis exposes a very different role of chaos in that its effectiveness for thermal homogenisation and heat-transfer enhancement is in low-Pe transient and asymptotic states marginal at best. Here chaos may in fact locally amplify temperature fluctuations and thus hamper instead of promote thermal homogeneity. These findings reveal that optimal thermal conditions are at lower Pe not automatic with chaotic mixing and may depend on a delicate interplay between flow and heat-transfer mechanisms.

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