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Evaporating Temperature Uniformity of the pulsating heat pipe with Surfactant Solutions at Different Concentrations

Journal of Thermal Science 2023年第1期32卷 183-191页

作者： BAO Kangli WANG Xuehui ZHANG Peng-E HAN Xiaohong TAN Jianming State Key Laboratory of Air-Conditioning Equipment and System Energy Conservation GREE Electric Appliances Inc.of ZhuhaiZhuhai 519070China Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province Institute of Refrigeration and CryogenicsZhejiang UniversityHangzhou 310027China

The evaporating section of the pulsating heat pipe(PHP)is in direct contact with the electronics when it is used for heat dissipation,and thus the evaporating temperature uniformity has an important effect on the safe and reliable operation of electronic equipment.On the basis of these conditions,an experimental study on the evaporating temperature uniformity of the PHP with surfactant solutions at different concentrations was conducted at the heat fluxes of(1911–19427)W/m^(2).Sodium stearate was utilized for the solute;the surfactant solutions were prepared with the concentrations of 0.001 wt%,0.002 wt%,and 0.004 wt%,respectively,and the filling ratios of the PHP were 0.31,0.44 and 0.57,respectively.The experimental results revealed that under all tested working conditions,the highest temperature always appeared in the intermediate zone of the evaporating section.As the heat flux increased,the temperature differences among different zones rose initially and then reduced due to the change of the flow motion and the flow pattern.The evaporating temperature uniformity of the sodium stearate solutions-PHP was better than that of the deionized water-PHP,which suggested that the evaporating temperature uniformity might be improved through decreasing the surface tension.Furthermore,combined with the effect of surface tension and viscosity,for different filling ratios,the required concentration was different when the best evaporating temperature uniformity was achieved.To be specific,when the filling ratio were 0.31 and 0.44,the best evaporating temperature uniformity was achieved at the concentration of 0.004 wt%,while at the filling ratio of 0.57,the best evaporating temperature uniformity was attained at the concentration of 0.002 wt%.

关键词： pulsating heat pipe surface tension evaporating temperature uniformity heat transfer

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Performance Evaluation of Small-channel pulsating heat pipe Based on Dimensional Analysis and ANN Model

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Energy Engineering 2022年第2期119卷 801-814页

作者： Xuehui Wang Edward Wright Zeyu Liu Neng Gao Ying Li Fluids and Thermal Engineering Research Group Faculty of EngineeringUniversity of NottinghamNottinghamNG72RDUK Ningbo Tech University Ningbo315100China Research Centre for Fluids and Thermal Engineering University of Nottingham Ningbo ChinaNingbo315100China

The pulsating heat pipe is a very promising heat dissipation device to address the challenge of higher heat-flux electronic chips,as it is characterised by excellent heat transfer ability and flexibility for miniaturisation.To boost the application of PHP,reliable heat transfer performance evaluationmodels are especially important.In this paper,a heat transfer correlation was firstly proposed for closed PHP with various working fluids(water,ethanol,methanol,R123,acetone)based on collected experimental data.Dimensional analysis was used to group the parameters.It was shown that the average absolute deviation(AAD)and correlation coefficient(r)of the correlation were 40.67%and 0.7556,respectively.For 95%of the data,the prediction of thermal resistance and the temperature difference between evaporation and condensation section fell within 1.13K/Wand 40.76K,respectively.Meanwhile,an artificial neural networkmodelwas also proposed.The ANN model showed a better prediction accuracy with a mean square error(MSE)and correlation coefficient(r)of 7.88e-7 and 0.9821,respectively.

关键词： pulsating heat pipe oscillation heat transfer correlation ANN model

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Finite time thermodynamics analysis and research of pulsating heat pipe cold storage device

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Energy Storage and Saving 2022年第1期1卷 33-43页

作者： Xiaofeng Xu Xuelai Zhang Merchant Marine College Shanghai Maritime UniversityShanghai 201306China

Phase change energy storage technology can effectively solve the energy mismatch in space and time.There are many disadvantages of phase change materials(PCMs),such as high supercooling,phase separation and poor heat transfer performance.As a new type of heat exchange structure,pulsating heat pipe has the advantages of simple structure,high heat transfer coefficient and good economic behavior.The system efficiency can be greatly improved by using pulsating heat pipe combined with cold storage technology.A set of pulsating heat pipe type cold storage device is developed,the finite time thermodynamic analysis is carried out,and the correlation between heat pipe efficiency and power is established.The three-dimensional physical model of pulsating heat pipe is simulated and verified by experiments.The experimental results show that in the cold storage stage,with the increase of the filling rate,the greater the pressure is,the better the heat transfer effect is;in the cold release stage,with the decrease of the filling rate,the smaller the pressure is,the better the heat transfer effect is.

关键词： Phase change energy storage pulsating heat pipe Finite time thermodynamics Liquid filling rate

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Full visualization and startup performance of an ammonia pulsating heat pipe

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Propulsion and Power Research 2013年第4期2卷 263-268页

作者： Zhihu Xue Wei Qu Minghui Xie China Academy of Aerospace Aerodynamics(CAAA) Beijing 100074China

In this paper,a novel study on full visualization and startup performances of pulsating heat pipe using ammonia as working fluid are experimented.The tested pulsating heat pipe,consisting of 6 turns,is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter.The filling ratio is 70%.Wall temperature fluctuations of several key positions are recorded under a series charge of heat inputs.The visualization investigation is conducted to observe the oscillations and circulation flows with the advantage of high quality digital video camera,by which the unique thermodynamic behaviors are able to recognize and analyze more easily.The experimental results show that the startup power required by the ammonia pulsating heat pipe(PHP)is very small,owing to particular identities of ammonia.It is observed that there are also some unevenly distributions in slug-train during initial and operating state.Phenomena such as circulation flows and local oscillations coupling breaking up of bubbles and formation of slugs are observed.

关键词： pulsating heat pipe Ammonia Visualization Startup performance Oscillation

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heat Leakage Numerical Investigation of a Compound Parabolic Concentratorpulsating heat pipe Solar Collector

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Journal of Thermal Science 2022年第5期31卷 1318-1326页

作者： XU Rongji CHEN Jingyan ZHANG Xiaohui WANG Ruixiang XU Shuhui Beijing Engineering Research Center of Sustainable Energy and Buildings Beijing University of Civil Engineering and ArchitectureBeijing100044China

As a new type of equipment for solar medium temperature utilization, the compound parabolic concentrator-pulsating heat pipe solar collector(CPC-PHPSC) uses pulsating heat pipe(PHP) as an endotherm, which can realize efficient energy conversion. The design of proper concentration ratio of compound parabolic concentrator(CPC) ensures that the incident sunlight can be concentrated on the evaporator section surface of PHP without solar tracking system. The objective of the present work is to study the influence of solar radiation intensity, air speed, material thickness(glass and insulation board) and tilt angle on the thermal performance of the new collector, which is difficult to control in the experiment. The heat leakage process and characteristics of the CPC-PHPSC were numerically studied by establishing a 3D numerical model of the collector unit. The results show that the theoretical collector efficiency of CPC-PHPSC reaches 74.5%, which is consistent with the experimental results. During operation, the heat collection performance is the best when the tilt angle is 45° and the solar radiation intensity is 1000 W/m^(2), while the excessive air speed will increase the convective heat loss. Increasing the thickness of insulation board and glass has little effect on the collector efficiency.

关键词： solar collector CPC(Compound Parabolic Concentrator) pulsating heat pipe solar irradiation intensity glass thickness

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