共查询到10条相似文献,搜索用时 187 毫秒
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The effect of SiO2 particles on heat transfer performance of a pulsating heat pipe(PHP) was investigated experimentally.DI water was used as the base fluid and contrast medium for the PHP.In order to study and measure the character,there are SiO2 /H2 O nanofluids with different concentration and applying with various heating powers during the experiment investigation.According to the experimental result,the high fraction of SiO2 /H2 O will deteriorate the performance of PHP compared with DI water,i.e.the thermal resistance and the temperature of evaporation section increases.It is in contrary in the case of low fraction of SiO2 /H2 O.Finally,the comparison of the thermal performances between the normal operation system and the static settlement system is given.It is found that both the thermal resistance of nanofluid PHP and the temperature of the evaporation section increase after standing for a period,and it is the same trend for the temperature fluctuation at the identical heating power for PHP. 相似文献
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Closed-loop pulsating heat pipe 总被引:15,自引:0,他引:15
Flow visualization was conducted for the closed-loop pulsating heat pipe (PHP) using a charge coupled device (CCD). It was observed that during the start-up period, the working fluid oscillates with large amplitude, however, at steady operating state, the working fluid circulates. The direction of circulation for the working fluid is consistent once circulation is attained, but the direction of circulation can be different for the same experimental run. Phenomena such as nucleation boiling, coalescence of bubbles, formation of slug and propagation of inertia wave were observed in the closed-loop PHP. The findings showed that the meandering bends, uneven slug and plug distribution and non-concurrent boiling at the evaporator contributed to the driving and restoring forces for fluid circulation and oscillations. 相似文献
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C. I. Ezekwe 《Energy Conversion and Management》1990,30(4):403-408
A passive radiative cooling system was designed, constructed and tested under clear skies. This refrigerator operates by losing heat to the night sky through infrared (i.r.) radiation emission. It consists of a radiator, an array of heat pipe elements and a cold chamber. The heat pipe elements are so arranged that they act as thermal diodes, transferring heat from the cold chamber to the radiator. Performance tests show that the system has a cooling capacity of 628 kJ/m2 per night with a sky coefficient of performance of 0.26. The lowest temperature attained in the cold chamber was 12.8°C for an ambient temperature of 20°C. The overall results indicate that the system has a great potential for providing a cold storage facility in developing countries and in remote areas. 相似文献
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A rack cooling system based on a large scale flat plate pulsating heat pipe is proposed. The heat generated from IT equipment in a closed rack is transferred by the rear door pulsating heat pipe to the chilled air passage and is avoided to release into the room. The influence of the start-up performance of the heat pipe, the load of the rack and the load dissipation to the temperature and the velocity distribution in the rack are discussed. It is found that the temperature would be lower and the temperature distribution would be more uniform in the rack when the pulsating heat pipe is in operation. Also, the effect of rack electricity load on temperature distribution is analyzed. It is indicated that higher velocity of chilled air will improve heat transfer of the rack. 相似文献
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A study on the new separate heat pipe refrigerator and heat pump 总被引:2,自引:0,他引:2
A new separate heat pipe refrigerator and heat pump is suggested based on the general three temperature thermal jet refrigerator and heat pump cycle. Sub-cooled hot water or other appropriate liquid heated by low grade heat sources forms the hot end and another heat pipe containing evaporator and condenser ends, adiabatic section of two-phase ejector and throttling tube is as the cold end of the separate heat pipe system. Performance relations for the thermal jet refrigerator and heat pump of such system is analyzed and a method of thermodynamic performance analysis is recommended. Primary prediction shows the feasibility of such heat pipe system for cold and warm water supply. 相似文献
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Shung-Wen Kang Wei-Chiang Wei Sheng-Hong Tsai Shih-Yu Yang 《Applied Thermal Engineering》2006,26(17-18):2377-2382
Nano-fluid is employed as the working medium for a conventional 211 μm wide × 217 μm deep grooved circular heat pipe. The nano-fluid used in this study is an aqueous solution of 35 nm diameter silver nano-particles. The experiment was performed to measure the temperature distribution and to compare the heat pipe thermal resistance using nano-fluid and DI-water. The tested nano-particle concentrations ranged from 1 mg/l to 100 mg/l. The condenser section of the heat pipe was attached to a heat sink that was cooled by water supplied from a constant-temperature bath maintained at 40 °C.At a same charge volume, the measured nano-fluid filled heat pipe temperature distribution demonstrated that the thermal resistance decreased 10–80% compared to DI-water at an input power of 30–60 W. The measured results also show that the thermal resistances of the heat pipe decrease as the silver nano-particle size and concentration increase. 相似文献
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Mostafa Keshavarz Moraveji Sina Razvarz 《International Communications in Heat and Mass Transfer》2012
In this research, the effect of using aluminum oxide nanofluid (pure water mixed with Al2O3 nanoparticle with 35 nm diameter) on the thermal efficiency enhancement of a heat pipe on the different operating state was investigated. 相似文献
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Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fall ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters. 相似文献