The effect of working fluid on the start-up and thermal performance in terms of thermal resistance and heat transfer coefficient of a pulsating heat pipe have been studied in the present paper. Methanol and de-ionized...The effect of working fluid on the start-up and thermal performance in terms of thermal resistance and heat transfer coefficient of a pulsating heat pipe have been studied in the present paper. Methanol and de-ionized water has been selected as the working fluid. The minimum startup power for DI water was obtained at 50% filling ratio and for methanol at 40%. The optimum filling ratio in terms of minimum startup power and minimum thermal resistance was 50% for DI water and 40% for methanol. The minimum thermal resistances for DI water and methanol were observed at vertical orientation. The evaporator side heat transfer coefficient for water was slightly more, while the condenser side heat transfer coefficient was appreciably more than that of methanol. Studies were also conducted for start-up time and temperature at different orientations and it was found that the PHP charged with methanol worked efficiently at all orientations.展开更多
Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying fi...Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%-70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs- the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer( dry burning) limit. With filling ratio of 70% and inclination of 75°, oscillating heat pipe with acetone started up with heating input of just 24 W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.展开更多
Micro heat pipes(MHP) cooling is one of the most efficient solutions to radiate heat for high heat flux electronic components in data centers. It is necessary to improve heat transfer performance of microgroove back p...Micro heat pipes(MHP) cooling is one of the most efficient solutions to radiate heat for high heat flux electronic components in data centers. It is necessary to improve heat transfer performance of microgroove back plate heat pipes. This paper discusses about influence on thermal resistance through experiments and numerical simulation with different working fluids, filling ratio and heat power. Thermal resistance of the CO2 filled heat pipe is 14.8% lower than the acetone filled heat pipe. In the meantime, at the best filling ratio of 40%, the CO2 filled heat pipe has the optimal heat transfer behavior with the smallest thermal resistance of 0.123 K/W. The thermal resistance continues to decline but the magnitude of decreases is going to be minor. In addition, this paper illustrates methods about how to enhance heat pipe performance from working fluids, filling ratio and heat power, which provides a theoretical basis for practical applications.展开更多
热管冷却反应堆采用非能动传热技术,热响应速度快,可避免堆芯单点失效,具有功率密度大、寿命长、环境适应性强、工作性能稳定等特点,是目前空间核反应堆研究的热点。基于清华大学开发的反应堆蒙特卡洛中子输运程序RMC(reactor Monte Car...热管冷却反应堆采用非能动传热技术,热响应速度快,可避免堆芯单点失效,具有功率密度大、寿命长、环境适应性强、工作性能稳定等特点,是目前空间核反应堆研究的热点。基于清华大学开发的反应堆蒙特卡洛中子输运程序RMC(reactor Monte Carlo code),以美国爱荷华国家实验室(Idaho National Laboratory,INL)设计的热管冷却反应堆INL Design A为研究对象,选取3种热管工质开展热管冷却反应堆堆芯物理计算。计算结果表明:锂热管工质不仅拥有很好的热物性参数,并且使用锂热管工质的热管冷却反应堆缓发中子有效份额最大、中子能谱较硬、燃耗反应性损失最小、增殖性能最佳,有利于热管冷却反应堆堆芯小型化与长寿命。因此,推荐锂为热管冷却反应堆的热管工质。展开更多
文摘The effect of working fluid on the start-up and thermal performance in terms of thermal resistance and heat transfer coefficient of a pulsating heat pipe have been studied in the present paper. Methanol and de-ionized water has been selected as the working fluid. The minimum startup power for DI water was obtained at 50% filling ratio and for methanol at 40%. The optimum filling ratio in terms of minimum startup power and minimum thermal resistance was 50% for DI water and 40% for methanol. The minimum thermal resistances for DI water and methanol were observed at vertical orientation. The evaporator side heat transfer coefficient for water was slightly more, while the condenser side heat transfer coefficient was appreciably more than that of methanol. Studies were also conducted for start-up time and temperature at different orientations and it was found that the PHP charged with methanol worked efficiently at all orientations.
基金Project 51306198 supported by National Natural Science Foundation of ChinaProject 00921915023 supported by Organization Department of Beijing+1 种基金Project NR2013K07 supported by Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning EngineeringProject 331614013 supported by Beijing University of Civil Engineering and Architecture
文摘Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%-70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs- the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer( dry burning) limit. With filling ratio of 70% and inclination of 75°, oscillating heat pipe with acetone started up with heating input of just 24 W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.
基金financial support for this research through the Beijing Natural Science Foundation(No.8202034)the USTB-NTUT Joint Research Program.
文摘Micro heat pipes(MHP) cooling is one of the most efficient solutions to radiate heat for high heat flux electronic components in data centers. It is necessary to improve heat transfer performance of microgroove back plate heat pipes. This paper discusses about influence on thermal resistance through experiments and numerical simulation with different working fluids, filling ratio and heat power. Thermal resistance of the CO2 filled heat pipe is 14.8% lower than the acetone filled heat pipe. In the meantime, at the best filling ratio of 40%, the CO2 filled heat pipe has the optimal heat transfer behavior with the smallest thermal resistance of 0.123 K/W. The thermal resistance continues to decline but the magnitude of decreases is going to be minor. In addition, this paper illustrates methods about how to enhance heat pipe performance from working fluids, filling ratio and heat power, which provides a theoretical basis for practical applications.
文摘热管冷却反应堆采用非能动传热技术,热响应速度快,可避免堆芯单点失效,具有功率密度大、寿命长、环境适应性强、工作性能稳定等特点,是目前空间核反应堆研究的热点。基于清华大学开发的反应堆蒙特卡洛中子输运程序RMC(reactor Monte Carlo code),以美国爱荷华国家实验室(Idaho National Laboratory,INL)设计的热管冷却反应堆INL Design A为研究对象,选取3种热管工质开展热管冷却反应堆堆芯物理计算。计算结果表明:锂热管工质不仅拥有很好的热物性参数,并且使用锂热管工质的热管冷却反应堆缓发中子有效份额最大、中子能谱较硬、燃耗反应性损失最小、增殖性能最佳,有利于热管冷却反应堆堆芯小型化与长寿命。因此,推荐锂为热管冷却反应堆的热管工质。
