scholarly journals Influence of filling ratio and working fluid thermal properties on starting up and heat transferring performance of closed loop plate oscillating heat pipe with parallel channels

2017 ◽  
Vol 26 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Weixiu Shi ◽  
Lisheng Pan
Keyword(s):  
Thermal Properties ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Working Fluid ◽  
Oscillating Heat Pipe ◽  
Parallel Channels

scholarly journals Effect of Filling Ratio on Thermal Characteristics and Performance of a Pulsating Heat Pipe

2019 ◽  
Vol 9 (2) ◽  
pp. 3341-3345
Keyword(s):  
Heat Pipe ◽  
Thermal Characteristics ◽  
Filling Ratio ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Key Factors ◽  
Condenser Section ◽  
Oscillating Heat Pipe ◽  
Bottom Heat ◽  
And Performance

Pulsating heat pipes are complex devices for heat transfer and their optimal thermal performance depends mainly on different parameters. This work is about the thermal efficiency of a closed-loop oscillating heat pipe with a diameter of 2.0 mm and 3.0 copper tube inner and outer. For all experiments, the filling ratio (FR) was used 40%, 50 %,70%,80% and heat inputs of 20W, 40W, 60W, and 80W was provided to PHP. The position of the PHP was vertical bottom heat type. The length of evaporator, adiabatic and condenser section was maintained 52 mm,170mm,60mm. Water and benzene were selected as working fluids. From the available literature it is observed that working fluid and filling ratio are key factors in PHP's performance. The results show that the thermal resistance decreases rapidly with the increase in the heat input to 20 to 40 W., while it decreases gradually over 40 to 80W.Simulation is done in CFD and experimental data were equated to the results.

Visualization of an Oscillating Heat Pipe with Hydraulic Diameter Far Exceeding the Conventional Maximum Hydraulic Diameter

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Yulong Ji ◽  
Lilin Chu ◽  
Chunrong Yu ◽  
Zongyu Wang ◽  
Hongbin Ma
Keyword(s):  
Heat Pipe ◽  
Flow Pattern ◽  
Bubbly Flow ◽  
Research Work ◽  
Filling Ratio ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Oscillating Heat Pipe ◽  
Fundamental Research ◽  
Small Bubbles

Abstract For an oscillating heat pipe (OHP), the hydraulic diameter must be sufficiently small so that vapor plug and liquid slug can be formed by the capillary action. Therefore, the hydraulic diameter should not exceed a critical value named maximum hydraulic diameter (MHD). In the current research, a glass OHP with a hydraulic diameter of 6 mm was fabricated, and ethanol was used as the working fluid (Figs. 1 and 2). With a hydraulic diameter far exceeding the maximum hydraulic diameter (MHD) defined by dh,max≤{2σBo[(ρl−ρv)g]}1/2, the OHP can function. But the flow pattern is very different from that with a diameter smaller than the MHD, and depends on the filling ratio. When the OHP is charged with a higher filling ratio, the flow pattern is from the bubbly flow to the slug flow as shown in Fig, 3. When the charging ratio is low, the dispersed bubbly flow with many small bubbles generated on the surface was observed, and the dispersed bubbly flow was directly transformed into the annular flow as shown in Fig. 4. [This research work was supported by National Natural Science Foundation of China under Grant No. 51876019, the Preresearch of General Armament Department (6140922011310), LiaoNing Revitalization Talents Program (XLYC1807117), and the Fundamental Research Funds for the Central Universities of China under Grant No.3132019331.]

Corrosion mechanism in a closed-loop oscillating heat-pipe with check valves (CLOHP/CV)

2014 ◽  
Vol 61 (5) ◽  
pp. 293-299 ◽  
Author(s):  
S. Sangiamsuk ◽  
B. Bubphachot ◽  
O. Watanabe ◽  
S. Rittidech
Keyword(s):  
Heat Pipe ◽  
Closed Loop ◽  
Working Fluid ◽  
Future Research ◽  
Detailed Data ◽  
Content Type ◽  
Oscillating Heat Pipe ◽  
Copper Particles ◽  
Surface Corrosion ◽  
Inner Surface

Purpose – The purpose of this paper was to study the parameters affecting corrosion of the closed-loop oscillating heat-pipe with check valves (CLOHP/CV) in a system in clear that will be basic data to be used in future research. The majority of research focuses on the inner surface corrosion heat-pipe systems. The CLOHP/CV is commonly favored in cooling electronic devices, etc. Despite these common applications, limited reliable experimental research findings are available on the operation of the CLOHP/CV. Because of these reasons, the lack of detailed data, working fluids effect, working temperatures and duration of testing of the CLOHP/CV, this study focuses on determining the actual inner surface corrosion. Design/methodology/approach – Seven types of copper tubes used in the CLOHP/CV set were sectioned to observe their inner surfaces. Seven different specimens with tube corrosion were examined by a visual inspection, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The technique for detecting metals solution in samples is based on the fact that ground state metals absorb light at specific wavelengths. Metal ions in a solution are converted to atomic state by means of a flame. In this study, concentration of copper particle in the working fluid was found by flame atomic absorption spectroscopy (Flame-AAS) and elements that occurred on inner surface tube were analyzed by EDX. Findings – The analyses with SEM and EDX testing found that the character corrosion of inner surface of CLOHP/CV was pitting clearly. The analysis with Flame-AAS found that the concentration of copper particles in the distilled water and ethanol as working fluid is more than after 1,000 hours until 3,000 hours because of excess volume of oxygen in working fluid which causes many reactions at the beginning. When the oxygen decreases after 1,000 hours, it causes the reaction to decrease too and get the most concentration of copper particles, i.e. 18.57228 ppm or 0.40859 mg. Originality/value – Corrosion-dependant maintenance must also be factored into the design. Producing reliable equipment that will become standardized and fixing the time for proper maintenance will require individuals that are knowledgeable about the materials that are going to be used in the design of such equipment. Nowadays, the lack of detailed data of working fluids effect, working temperatures and duration of testing of the CLOHP/CV focuses on determining the actual inner surface corrosion. Therefore, this research aimed to study the parameters affecting corrosion of the CLOHP/CV in a system in clear that will be basic data to be used in future research.

Experimental Investigation on Operating Limitation of an Oscillating Heat Pipe

2013 ◽  
Author(s):  
Yulong Ji ◽  
Chao Chang ◽  
Gen Li ◽  
Hongbin Ma ◽  
Yuqing Sun
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Tilt Angle ◽  
Heat Transfer Performance ◽  
Input Power ◽  
Filling Ratio ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Al2o3 Nanofluid

This research represents an experimental investigation on the operating limitation of an oscillating heat pipe (OHP). The OHP has six turns and three sections: evaporator, condenser and adiabatic sections with lengths of 40 mm, 64 mm and 51 mm, respectively. Water or a mixture of water and alumina (Al2O3) making up a nanofluid served as the working fluid. Filling ratios ranging from 30% to 70%, and tilt angles (orientation) ranging from 0° to 90° were studied. The experimental results showed (1) the water/Al2O3 nanofluid can enhance the OHP heat transfer performance, i.e., the highest input power (operating limitation) increased when the OHP was charged with water/Al2O3 nanofluid; (2) the operating limitation increased as the filling ratio increased from 30% to 70%, but the optimum filling ratio of the OHP is 30% or 50% when the working power is lower or higher; and (3) the thermal resistance of the OHP decreased as the tilt angle increased, and the operating limitation increased as the tilt angle increased.

Heat Transfer Characteristics of Oscillating Heat Pipe With Water and Ethanol as Working Fluids

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Haizhen Xian ◽  
Yongping Yang ◽  
Dengying Liu ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Heat Transfer Performance ◽  
Filling Ratio ◽  
Working Fluid ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Oscillating Heat Pipe ◽  
Transfer Characteristics

In this paper, experiments were conducted to achieve a better understanding of the oscillating heat pipe (OHP) operating behavior with water and ethanol as working fluid. The experimental results showed that there existed a necessary temperature difference between the evaporator and the condenser section to keep the heat pipe working. The maximum effective conductivity of the water OHP reached up to 259 kW/m K, while that of the ethanol OHP is of 111 kW/m K. Not all the OHPs are operated in the horizontal operation mode. The heat transfer performance of the ethanol OHP was obviously affected by the filling ratio and the inclination angle but the influence law is irregular. The effect of the filling ratio and the inclination angle of the water OHP were smaller than that of the ethanol one. The heat transfer performance of the OHP was improved with increase of operating temperature. The startup characteristics of the OHP depended on the establishment of the integral oscillating process, which was determined by the operating factors. The startup temperature of the ethanol OHP varied from 40°C to 50°C and that of the water, OHP varied from 40°C to 60°C without considering the horizontal operating mode. The water OHP showed a better performance and more stable heat transfer characteristics than the ethanol OHP, which had no obvious advantages of the startup capability as well.

Theoretical Analysis on the Thermal Characteristics of Oscillating Heat Pipe

2010 ◽  
Author(s):  
Haizhen Xian ◽  
Yongping Yang ◽  
Dengying Liu ◽  
Xiaomin Liu ◽  
Xiaoze Du
Keyword(s):  
Theoretical Analysis ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Thermal Characteristics ◽  
Filling Ratio ◽  
Heating Power ◽  
Working Fluid ◽  
Oscillating Flow ◽  
Oscillating Heat Pipe ◽  
Oscillation Characteristics

Theoretical analysis on the thermal characteristics of the looped oscillating heat pipe was given to predict oscillation characteristics affected by filling ratio, inclination angle and heating power. The numerical results show that the alternative expansion and compression of vapors make the working fluid keep an oscillating flow in the heat pipe. This oscillating flow is affected by the inclination angle, filling ratio and heating power.

scholarly journals Effect of Working Fluid on Thermal Performance of Closed Loop Pulsating Heat Pipe

2019 ◽  
Vol 9 (2) ◽  
pp. 953-956
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Working Fluid ◽  
External Diameter ◽  
Pulsating Heat Pipe ◽  
Condenser Section ◽  
Heat Transfer Efficiency ◽  
Bottom Heat

The pulsing heat pipe (PHP) is an technology that is increasingly capable of applying many manufacturing areas, but a thorough knowledge of its thermo-hydrodynamic There's far from enough system. This research explored the features of oscillation and the heat transfer efficiency of a closed-loop PHP using an internal and external diameter copper tube with 2.0 and 3.0 mm respectively. For all experimentation, filling ratio (FR) was 40%, five turns and different heat inputs of 20 to 80 W was supplied to PHP. The position of the PHP was vertical bottom heat type. 52 mm, 170 mm,60 mm was retained for the duration of the evaporator, adiabatic and condenser section. Water, Ethanol are chosen as working liquids. To understand, thermal resistance features and median evaporator pressures for multiple operating liquids at distinct heat inputs. An significant consideration for the results of PHPs is the research on PHP stated operating fluid. The result demonstrates that, with the rise of the heating output from 20 to 80 W, where as steadily increases above 80W, the thermal resistance reduces faster. By comparing Water , Ethanol working fluids, Ethanol provides the highest heat performance . The simulation is performed in Mat lab and the results have been contrasted

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