scholarly journals Experimental Investigation of the Thermal Performance of a Wickless Heat Pipe Operating with Different Fluids: Water, Ethanol, and SES36. Analysis of Influences of Instability Processes at Working Operation Parameters

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 80 ◽  
Author(s):  
Rafal Andrzejczyk
Keyword(s):  
Heat Pipe ◽  
Input Power ◽  
Liquid Pool ◽  
Filling Ratio ◽  
Working Fluid ◽  
Operating Pressure ◽  
Two Phase ◽  
Condenser Section ◽  
Transfer Resistance ◽  
Working Fluids

In this study, the influences of different parameters on performance of a wickless heat pipe have been presented. Experiments have been carried out for an input power range from 50 W to 300 W, constant cooling water mass flow rate of 0.01 kg/s, and constant temperature at the inlet to condenser of 10 °C. Three working fluids have been tested: water, ethanol, and SES36 (1,1,1,3,3-Pentafluorobutane) with different filling ratios (0.32, 0.51, 1.0). The wall temperature in different locations (evaporation section, adiabatic section, and condenser section), as well as operating pressure inside two phase closed thermosyphon have been monitored. The wickless heat pipe was made of 0.01 m diameter copper tube, which consists of an evaporator, adiabatic, and condensation sections with the same length (0.4 m). For all working fluids, a dynamic start-up effect caused by heat conduction towards the liquid pool was observed. Only the thermosyphon filled with SES36 was observed to have operation limitation caused by achieving the boiling limit in TPCTs (two-phase closed thermosyphons). The geyser boiling effect has been observed only for thermosyphon filled with ethanol and for a high filling ratio. The performance of the thermosyphon determined the form of the heat transfer resistance of the TPCT and it was found to be dependent of input power and filling ratio, as well as the type of working fluid and AR (aspect ratio). Comparison with other authors would seem to indicate that lower AR results in higher resistance; however, the ratio of condenser section length to inside diameter of pipe is also a very important parameter. Generally, performance of the presented thermosyphon is comparable to other constructions.

Heat Transport Characteristics in Closed Loop Oscillating Heat Pipes

2005 ◽  
Author(s):  
Shuangfeng Wang ◽  
Shigefumi Nishio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Closed Loop ◽  
Flow Behavior ◽  
Working Fluid ◽  
Liquid Volume ◽  
High Heat Flux ◽  
Two Phase ◽  
Working Fluids ◽  
Inner Diameter

Heat transport rates of micro scale SEMOS (Self-Exciting Mode Oscillating) heat pipe with inner diameter of 1.5mm, 1.2mm and 0.9mm, were investigated by using R141b, ethanol and water as working fluids. The effects of inner diameter, liquid volume faction, and material properties of the working fluids are examined. It shows that the smaller the inner diameter, the higher the thermal transport density is. For removing high heat flux, the water is the most promising working fluid as it has the largest critical heat transfer rate and the widest operating range among the three kinds of working fluids. A one-dimensional numerical simulation is carried out to describe the heat transport characteristics and the two-phase flow behavior in the closed loop SEMOS heat pipe. The numerical prediction agrees with the experimental results fairly well, when the input heat through was not very high and the flow pattern was slug flow.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

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.

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.

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

Experiment Investigation on Heat Transfer Characteristics of a Novel Gravity-Assisted Heat Pipe Heat Exchanger

2011 ◽  
Vol 236-238 ◽  
pp. 689-693
Author(s):  
Xiao Lin Cao ◽  
Shuang Jun Cao ◽  
Xiao Jun Zhu ◽  
Wei Zeng ◽  
Fang Fang Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Filling Ratio ◽  
Heat Transfer Characteristics ◽  
Air Velocity ◽  
Condenser Section ◽  
Transfer Resistance ◽  
Transfer Characteristics ◽  
Minimum Heat

A novel gravity-assisted heat pipe with fins was developed. The influences of filling ratio, inclination angle and air velocity at condenser section on the heat transfer characteristics were investigated experimentally. The results show that heat power has an important effect on heat transfer characteristics while inclination angle has little effect on that. The minimum heat transfer resistance is got at the filling ratio equaling about 20%. The heat transfer thermal resistance decreases gradually as the air velocity at condenser section increases.

scholarly journals Study of Heat Pipe Thermal Performance with Internal Modified Geometry

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 231
Author(s):  
Alaa A. B. Temimy ◽  
Adnan A. Abdulrasool ◽  
F. A. Hamad
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Transit Time ◽  
Thermal Performance ◽  
Inclination Angle ◽  
Input Power ◽  
Filling Ratio ◽  
Lower Side ◽  
Condenser Section ◽  
Inner Diameter

The aim of this study was to investigate the effect of inserting a new internal tube packing (TP) on the thermal performance of a thermosyphon heat pipe (THP). The THP pipe was made from copper with an inner diameter of 17.4 mm and length of 600 mm. The new internal tube packing (TP) had a central copper disc with two copper tubes soldered onto both sides to transport vapor and condensate. The upper tube or riser had an inner diameter of 8.3 mm and was 300 mm long; it was connected to a hole in the disc from the upper side to transport the steam to the condenser section. The lower tube or downcomer had an inner diameter of 5 mm, was 225 mm long and was connected to the lower side of the disc to collect the condensate and transport it to the evaporator. The TP was inserted inside the THP to complete the design of the improved heat pipe (TPTHP). Experimental results showed that the TPTHP reduces the transit time from 16 to 11 min and the thermal resistance by 17–62% based on the input power and depending on the conditions of the THP. The results also showed that the inclination angle and filling ratio have no effect on the thermal resistance of the TPTHP.

Heat Transfer Characteristics of a 3-D Printed Pulsating Heat Pipe: Fundamental Experiments Using Water As a Working Fluid

2017 ◽  
Author(s):  
Yasushi Koito ◽  
Masahiro Kawaji
Keyword(s):  
Heat Pipe ◽  
Cooling Water ◽  
Experimental Results ◽  
Working Fluid ◽  
Transient Temperature ◽  
Pulsating Heat Pipe ◽  
Two Phase ◽  
Condenser Section ◽  
Heater Power ◽  
Cooling Water Temperature

This paper describes extended experiments on a pulsating heat pipe (PHP) fabricated by using a 3-D printer and a graphene-laden PLA (PolyLactic Acid) filament. Water was used as a working fluid. To maintain airtightness, the 3-D printed PHP was electroplated by copper since the graphene in the filament allows electric currents to pass through. The PHP had ten square channels. A cross section and a length of the square channel were 1.5 mm × 1.5 mm and 80 mm, respectively. Ends of each channel were connected to form a single serpentine channel. A filling ratio of the working fluid was 50%. In experiments, an evaporator section of the PHP was heated by a heater and a condenser section was cooled using a water-cooling jacket. The heater power was increased stepwise from 2.0 W to 7.0 W while the cooling water temperature and its flow rate were maintained at 4.0 °C and 0.25 LPM, respectively. Transient temperature distributions of the PHP were measured by K-type thermocouples. From the experimental results, steady-state two-phase heat transport operation of the PHP was confirmed for the heater power between 3.0 W and 6.0 W. Moreover, the present experimental results were compared with the previous ones, where ethanol was used as the working fluid. It was also confirmed that the thermal resistance of the PHP with ethanol was slightly smaller than that with water.

An Experimental Investigation of Heat Pipe Flat-Plate Solar Collector with Water-Ethanol Mixture as a Working Fluid

2014 ◽  
Vol 592-594 ◽  
pp. 1413-1417
Author(s):  
Pravin R. Harde ◽  
Ashok T. Pise ◽  
Balasao D. Kusure
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Flow Rate ◽  
Solar Collector ◽  
Filling Ratio ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Condenser Section ◽  
Ethanol Mixture ◽  
Flat Plate Solar Collector

The objective of the present study is to investigate the performance of solar collector with serpentine shape of heat pipe and water-ethanol as a working fluid. Serpentine shape is easy of manufacturing and also to reduce cost of manufacturing. In this work, heat pipe is made from copper tube having ID 10mm and OD 12mm.The tube is bent in serpentine manner and filled with Water-ethanol as a working fluid with 70% filling ratio. The length of evaporator, adiabatic and condenser section was 480mm, 50mm and 65mm respectively. The test is conducted for coolant flow rate 4.5 kg/hr different angle of collector 20°, 31.5°, 40°, 50°, 60°. Result shows that water-ethanol collector gives better performance than collector with water as a working fluid. Maximum efficiency is observed at 31.5° inclination.

Gravitational effects on electroosmotic flow in micro heat pipes

2019 ◽  
Vol 30 (2) ◽  
pp. 535-556
Author(s):  
Fun Liang Chang ◽  
Yew Mun Hung
Keyword(s):  
Heat Pipe ◽  
Electroosmotic Flow ◽  
Temperature Drop ◽  
Working Fluid ◽  
Vapor Flow ◽  
Two Phase ◽  
Condenser Section ◽  
Content Type ◽  
Micro Heat Pipe ◽  
Gravity Forces

Purpose This paper aims to investigate the coupled effects of electrohydrodynamic and gravity forces on the circulation effectiveness of working fluid in an inclined micro heat pipe driven by electroosmotic flow. The effects of the three competing forces, namely, the capillary, the gravitational and the electrohydrodyanamic forces, on the circulation effectiveness of a micro heat pipe are compared and delineated. Design/methodology/approach The numerical model is developed based on the conservations of mass, momentum and energy with the incorporation of the Young–Laplace equation for electroosmotic flow in an inclined micro heat pipe incorporating the gravity effects. Findings By inducing electroosmotic flow in a micro heat pipe, a significant increase in heat transport capacity can be attained at a reasonably low applied voltage, leading to a small temperature drop and a high thermal conductance. However, the favorably applied gravity forces pull the liquid toward the evaporator section where the onset of flooding occurs within the condenser section, generating a throat that shrinks the vapor flow passage and may lead to a complete failure on the operation of micro heat pipe. Therefore, the balance between the electrohydrodyanamic and the gravitational forces is of vital importance. Originality/value This study provides a detailed insight into the gravitational and electroosmotic effects on the thermal performance of an inclined micro heat pipe driven by electroosmotic flow and paves the way for the feasible practical application of electrohydrodynamic forces in a micro-scale two-phase cooling device.

Numerical Investigation of Regular and Hybrid Nanofluids Application as the Working Fluids on Thermal Performance of TPCT

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Roozbeh Vadi ◽  
Kamran Sepanloo
Keyword(s):  
Numerical Simulation ◽  
Thermal Resistance ◽  
Natural Circulation ◽  
Industrial Applications ◽  
Input Power ◽  
Working Fluid ◽  
Hybrid Nanofluid ◽  
Distilled Water ◽  
Two Phase ◽  
Working Fluids

Two-phase closed thermosyphon (TPCT) is a cost-effective heat transfer device with high thermal efficiency owing to extensive interphase heat and mass transfer. Thus, TPCT has found many industrial applications. Proper selection of the working fluid could further improve efficiency of TPCT, and nanofluids with superior thermal properties are suitable choices. Numerical simulation of boiling and condensation, natural circulation, and hybrid nanofluid modeling in a closed space is a notable challenge and current study is devoted to this subject. In this study, a novel methodology for incorporating the effects of compressibility and thermal expansion into all thermophysical properties of both phases is developed and programmed into a validated computational fluid dynamics (CFD) code. Distilled water, a regular nanofluid, Al2O3/water, and a hybrid nanofluid, TiSiO4/water are selected as the working fluids. Experimental data for wall thermal profile are employed to validate the numerical simulation. Then, overall thermal resistance is evaluated in terms of nanoparticles concentration and input power variations. Results indicate that the numerical methodology developed in this study could evaluate the optimum state of TPCT in an efficient and accurate manner and the optimum state for regular and hybrid nanofluid demonstrates 48% and 54% improvement over distilled water, respectively. Furthermore, a subtle relation between the thermal resistance and the height to which fluid column rises in TPCT has been discerned and quantified, which is used as a supplement to the conventional qualitative method of reasoning to justify the somewhat controversial behaviors of nanofluid application in TPCT.

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