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Design and investigation of cooling system for high-power LED luminaire
摘要： This paper is concerned with development of cooling system for high-power LED luminaire, including design, simulation, production and investigation. Dimension, shape, and topology optimization algorithms and their program realization are developed with the use of MathCad. Thermal design by Comsol Multiphysics showed that the system on the base of heat pipes is the most effective system for cooling of high-power LED luminaire. The numerical simulation was employed to valid the designed-in engineering solution of cooling system for high-power LED luminaire under elevated temperature operating conditions and different orientation in space. In accordance to simulation data cooling system on the base of heat pipes is designed. Theoretical results are well validated by experimental data and numerical simulation and can be widely utilized for designing of cooling system related to various LED products.
关键词： Cooling system,Heat pipe,Thermal design,High-power LED luminaire
更新于2025-09-23 15:21:01
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Performance enhancement of graphene-coated micro heat pipes for light-emitting diode cooling
摘要： The rate of water transport through graphene nanocapillaries is profoundly enhanced compared to that in microscale capillaries due to the prevalence of exceptionally high capillary pressures and large slip lengths. As an inaugural study, we integrate graphene nanocapillaries into a micro heat pipe (MHP) for enhanced light-emitting diode (LED) cooling. With the use of graphene nanocapillaries, the ultrafast water transport synergically enhances the water circulation and evaporation process in the microfluidic device. The graphene-coated MHP achieves more than 45% enhancement in the overall performance compared to the uncoated counterpart. In turn, the experiments demonstrate a drastic reduction of LED’s operating temperature (more than 25 °C) which translates into a significantly prolonged lifespan of LED. The molecular dynamics simulations reveal that the oxygenated functional groups attached on graphene further increase the capillary pressure (~1000 bar) and effective velocity (~20 m/s) of the nanoconfined water, compared to those (~500 bar and ~10 m/s) in a pristine graphene nanochannel. The ultrafast water transport in graphene nanocapillary is justified. This study provides a holistic analysis and important insight into the phenomenon of ultrafast water transport in graphene nanocapillaries that exhibits an enormous potential in thermal energy management applications for LED cooling.
关键词： Electronics cooling,Micro heat pipe,Graphene nanocapillaries,Ultrafast water transport
更新于2025-09-23 15:19:57
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Measurement of photoionization cross-section of Li (2p, 3d) excited states using thermionic diode detector
摘要： Studies on photoionization cross-section measurement of lithium 2p and 3d excited states selectively populated by single and two photons are reported. The photoionization is carried out in a heat-pipe cum thermionic diode detector using nitrogen laser pumped pulsed dye laser. Rhodamine perchlorate (Rh-640) dye is used to generate the desired tunable laser output in the range of 635 to 675 nm. Both, the thermionic diode detector and dye laser are developed in-house. A negative space charge region formed around diode cathode filament is illuminated by dye laser exciting pulse followed by ionizing UV radiation from nitrogen laser. The effect of ionizing laser pulse energy and precise tuning of dye laser on photoionization signal, across 670.780 nm (2S1/2 → 2P1/2,3/2) single-photon transition and 639.145 nm (2S1/2 → 2D3/2,5/2) two-photon transition are studied. The results obtained are compared with model calculations of photoionization signal saturation curve. The ionization cross-section for both the states (2P1/2, 2D5/2) are determined as 15.40 ± 2.8 Mb and 8.04 ± 1.6 Mb, respectively and atomic number density N ～ 5.6 × 10^8 (cm^?3).
关键词： Dye laser,Photoionization cross-section,Thermionic diode,Heat-pipe,Lithium
更新于2025-09-19 17:15:36
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Assessment of the cost reduction potential of a novel loop-heat-pipe solar photovoltaic/thermal system by employing the distributed parameter model
摘要： A novel micro-channel loop-heat-pipe solar photovoltaic/thermal (LHP- PV/T) system is developed employing the co-axial tubular heat exchanger as the condenser and upper-end liquid header with tiny holes as the liquid feeder. The design facilitates an easier connection among the solar modules. It creates the improved condensation and separate evaporation effects within the LHP. A reduced evaporator area will thereby have a minor impact on the overall heat transfer performance, leading to significant potential for cost reduction. A distributed parameter model is established and validated by experimental data. The model is then applied to analyze the cost reduction potential of the LHP- PV/T via the optimization of geometrical and structural parameters. The impact of the area reduction on the LHP evaporator differs from that on the traditional integral heat pipe PV/T. The decrements in thermal and electrical efficiencies of the LHP- PV/T are 2.47% and 0.03% respectively when the width of heat pipes in the evaporator decreases from 26 to 10 mm. When the number of heat pipes decreases from 30 to 6, the decrements in thermal and electrical efficiencies are 4.63% and 0.12%, whilst the overall system cost drops by 28.58%, thus the cost-effectiveness of the system can be improved.
关键词： Co-axial tubular heat exchanger,Photovoltaic/thermal,Cost,Loop-heat-pipe,Micro-channel
更新于2025-09-19 17:13:59
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Thermal characteristics of a compact LED luminaire with a cooling system based on heat pipes
摘要： To increase the compactness of a LED luminaire, in this work it has been suggested to use 8 radial thermal pipes as a heat sink from a COB (Chip-on-Board) matrix to the heat-transfer surface, while the latter should be rings of heat exchanger located concentrically around the light source. These rings are cooled utilizing natural convection of ambient air. The used computer modelling enabled us to evaluate the possibility of the suggested cooling system to provide the normal thermal regime for a power COB matrix. It has been shown that for the power 500 W, as the LED light source, provided that all electric power is converted into thermal power, the temperature of the luminaire base frame in the place of contact with the light source does not exceed 85.5 °С. When using the heat-conducting paste of Arctiс Silver 5 type with the heat conductivity coefficient 8.7 W/(m·°С) in the contact zone and the paste layer thickness 0.1·10-3 m, it corresponds to the temperature of the LED light source case 89.5 °С. With account of the thermal resistance inherent to the COB matrix, the temperature of its semiconductor crystals reaches 139.5 °С, which does not exceed the acceptable value of operation temperature for these crystals 140 °С. At lower values (from 50 to 80%) of the consumed electric power, which is converted into thermal energy, depending on the type of COB, the value of the working temperature of the semiconductor crystal is from 112.5 to 128.7 °C.
关键词： Velocity distribution,Temperature distribution,Heat pipe,Ring,LED luminaire,СОВ matrix
更新于2025-09-19 17:13:59
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Experimental study and exergy analysis of photovoltaic-thermoelectric with flat plate micro-channel heat pipe
摘要： Effective cooling of the photovoltaic can enhance electrical conversion efficiency of a photovoltaic system. The combination of photovoltaic and thermoelectric generator provides unique advantages because of their complementary characteristics. In addition, hybrid photovoltaic-thermoelectric can utilize a wider solar spectrum thereby harvesting more energy from the sun. Heat pipes are passive devices that can transfer heat efficiently over a long distance. Therefore, this study presents an experimental investigation and exergy analysis of a photovoltaic-thermoelectric with flat plate micro-channel heat pipe. The experiment is performed in a laboratory using a solar simulator and water-cooling is used for the thermoelectric generator. The effect of thermoelectric load resistance, micro-channel heat pipe back insulation and solar radiation on the performance of the hybrid system is presented and a comparison with a photovoltaic only system is provided. Results show that the hybrid system provides an enhanced performance compared to the photovoltaic only system and absence of insulation behind the micro-channel heat pipe enhances electrical performance of the hybrid system. Furthermore, results show the feasibility of the hybrid system for generating electricity and small hot water. This study will provide valuable guidance for design of photovoltaic-thermoelectric systems with heat pipe and verifies the feasibility of such systems.
关键词： Thermal management,Power generation,Exergy,Micro-channel heat pipe,Photovoltaic-thermoelectric
更新于2025-09-16 10:30:52
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A Heat Pipe Cooler for High Power LED’s Cooling in Harsh Conditions
摘要： The paper presents an innovative method for High Power LEDs cooling in harsh conditions. To take full advantage of the benefits of LEDs, proper thermal management must be realized. This paper describes the limits of the cooling solution based on heat pipe, to maintain the junction temperature close to the nominal value, to avoid the color shift, recoverable light output reduction, voltage decreases. The most important, the reliability of any LED is a direct function of junction temperature, knowing that the higher the junction temperature, the shorter the lifetime of the LED.
关键词： LED Cooling,Energy Efficiency.,Heat-Trap,Heat Pipe
更新于2025-09-12 10:27:22
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Preliminary experiment on a novel photovoltaic-thermoelectric system in summer
摘要： Compared with the PV electricity generation, the hybrid Photovoltaic-thermoelectric (PV-TE) can generate more electricity due to its ability to utilize a wider solar spectrum than the PV. The PV-TE employing micro-channel heat pipe array is a novel PV-TE-MCHP system which is capable of providing high cost performance compared to the traditional PV-TE due to the use of the micro-channel heat pipe array. In this paper, the experimental investigation of this new system in summer in Hefei city, China is presented for the first time. The comparison between this system and PV alone is made, and the details are presented. The power output, PV temperature, and the hot and cold sides temperatures of the TE are all tested. The results show that the novel system has a higher electrical output than the PV alone. The electrical efficiencies of this system during the test are all higher than 14.0% and the PV temperatures are about 20 (cid:1)C higher than the ambient temperature. Based on this experiment, the results also verify the feasibility of the new system, which will give a valuable reference for the PV-TE design.
关键词： Micro-channel heat pipe,Power output,Experimental investigation,Photovoltaic-thermoelectric
更新于2025-09-11 14:15:04
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Energy performance analysis of a novel solar PVT loop heat pipe employing a microchannel heat pipe evaporator and a PCM triple heat exchanger
摘要： This study presents a numerical analysis of the energy efficiency for a novel solar PVT Loop Heat Pipe (PVT-LHP) employing a novel Micro-channel evaporator and a novel PCM heat storage exchanger. It presents a description of the different sub-models in the PVT-LHP system (the PVT model, the microchannel heat collector model and the novel PCM triple heat exchanger model) and the integrated model of the system. The integrated model of the system was solved by ensuring a heat balance at the condenser and the evaporator. A parametric analysis has been performed in order to assess the influence of the environmental parameters (i.e. solar radiation, air temperature, wind velocity), structural parameters (i.e. glazing cover, the number of absorbing microchannel heat pipes, PV cell packing factor), the circulating fluid variables (i.e. cold-water inlet temperature and water mass flow rate) on the energy performance of the system. The novel PVT-LHP has been compared with a conventional Solar PVT-LHP system. It was found that lower solar radiation, lower ambient air temperature, higher wind speed, higher packing factor, lower cold-water inlet temperature and a smaller cover number led to an enhanced electrical efficiency, but a reduced thermal efficiency of the module; whereas a higher cold-water mass flow rate and a greater number of microchannel heat pipes gave rise to both thermal and electrical efficiencies of the module. It was also found that an increase of solar radiation, ambient temperature, cover number, microchannel heat pipe number and packing factor are favourable factors for the overall COP (Coefficient Of Performance) of the system, whereas an increase of wind velocity and cold water mass flow rate are unfavourable. The study indicated the existence of an optimal cover number, number of microchannel heat pipes and mass flowrate. Under the given design conditions, the electrical, thermal and overall efficiency of the PV/LHP module were 12.2 %, 55.6 % and 67.8% respectively and the novel system can achieve 28% higher overall energy efficiency and 2.2 times higher COP compared to a conventional system. The integrated computer model developed in this study can be used to design and optimize the novel PVT-LHP heating system.
关键词： microchannel,power supply,PVT,Loop Heat Pipe,PCM triple heat exchanger,heating
更新于2025-09-10 09:29:36