Thermal Characteristics of a Circular Finned Thermosyphon Using Different Working Fluids

2014 ◽  
Vol 575 ◽  
pp. 322-328 ◽  
Author(s):  
Narayanan Alagappan ◽  
Narayanan Karunakaran
Keyword(s):  
Experimental Study ◽  
Ethylene Glycol ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Input ◽  
Base Fluid ◽  
Thermal Characteristics ◽  
Working Fluid ◽  
Two Phase ◽  
Evaporation And Condensation

The two-phase closed thermosyphon (TPCT), which is essentially a gravity-assisted wickless heat pipe, utilizes the evaporation and condensation of the working fluid inside the TPCT to transport heat. This experimental study was carried out to understand the thermal performance of circular finned thermosyphon using nanofluid with alcohol and was analyzed, compared with alcohol and base fluid DI water. The concentration of nanoparticle used in this setup was 110mg/lit of TiO2combined with 0.2 ml of ethylene glycol. The heat input (Q) were 10W, 12W, 14 W and 16 W and the orientation 30°, 45°, 60° and 90°.The results demonstrate that TiO2nanofluid with 0.2 ml of ethylene glycol improves the performance through reduction in thermal resistance by 85.86%.

scholarly journals Experimental study on heat transfer characteristics of a modified two-phase closed thermosyphon

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2481-2489 ◽  
Author(s):  
Babak Aghel ◽  
Masoud Rahimi ◽  
Saeed Almasi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Study ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics ◽  
Adiabatic Section

This study investigated the heat transfer characteristics of modified two-phase closed thermosyphon (TPCT) using water as the working fluid. In the modified TPCT, to reduce thermal resistance, a small TPCT was inserted inside the adiabatic section. For both the plain and modified thermosyphons the performances were determined at various heat inputs from 71-960 W. The results showed that the modified TPCT had less temperature difference between the evaporator and condenser sections than the plain one. According to the experimental data, in the modified TPCT, the thermal performance increased up to 20% over that of the unmodified one.

Investigation of the effects of base fluid type of the nanofluid on heat pipe performance

2020 ◽  
pp. 095765092091628 ◽  
Author(s):  
Duygu Yilmaz Aydin ◽  
Metin Gürü ◽  
Adnan Sözen ◽  
Erdem Çiftçi
Keyword(s):  
Ethylene Glycol ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Base Fluid ◽  
Sodium Dodecyl ◽  
Active Agent ◽  
Deionized Water ◽  
Working Fluid ◽  
Fluid Type ◽  
Surface Active

Most recently, an ascending tendency in nanoparticles containing working fluid utilization has been observed in such thermal systems as double pipe heat exchangers and thermosiphons in so far as its advantages upon the performance of such systems. In order to investigate how the type of the base fluid affects the nanofluid’s properties used for thermal applications, an experimental test rig was setup and two different nanofluid each of which involves different base fluid, but same nanoparticles and surface active agent were tested. During the nanofluid preparation process, bauxite nanoparticles as nanoparticle material and sodium dodecyl benzene sulfonate as surface active agents were used in volume fractions of 2% and 0.5%, respectively. As the base fluid type, ethylene glycol and deionized water were utilized. The tests were conducted under diverse working conditions and vacuum pressure. Distribution of temperature ahead the heat pipe wall, efficiency and heat pipe’s thermal resistance was experimentally investigated. It was observed from the experiments that each nanofluid improved the heat pipe performance significantly; however, deionized water/bauxite nanofluid gave the best results in terms of heat pipe’s thermal performance. For each nanofluid, the maximum increment in efficiency was observed under 200 W heating power and 10 g/s cooling water mass flow rate conditions, and improvement rates were 29.5% and 13.3% for ethylene glycol-based and deionized water-based nanofluids, respectively. At least 20% of decline in thermal resistance of the heat pipe was also recorded, when nanofluid was employed as working fluid.

A Comprehensive Experimental Investigation of the Performance of Closed-Loop Pulsating Heat Pipes

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
M. Halimi ◽  
A. Abbas Nejad ◽  
M. Norouzi
Keyword(s):  
Thermal Resistance ◽  
Flow Regime ◽  
Thermal Performance ◽  
Closed Loop ◽  
Heat Pipes ◽  
Filling Ratio ◽  
Working Fluid ◽  
Physical Parameters ◽  
Two Phase ◽  
Laboratory Conditions

Closed-loop pulsating heat pipes (CLPHPs) are a new type of two-phase heat transfer devices that can transfer considerable heat in a small space via two-phase vapor and liquid pulsating flow and work with various types of two-phase instabilities so the operating mechanism of CLPHP is not well understood. In this work, two CLPHPs, made of Pyrex, were manufactured to observe and investigate the flow regime that occurs during the operation of CLPHP and thermal performance of the device under different laboratory conditions. In general, various working fluids were used in filling ratios of 40%, 50%, and 60% in horizontal and vertical modes to investigate the effect of thermo-physical parameters, filling ratio, nanoparticles, gravity, CLPHP structure, and input heat flux on the thermal performance of CLPHP. The results indicate that three types of flow regime may be observed given laboratory conditions. Each flow regime exerts a different effect on the thermal performance of the device. There is an optimal filling ratio for each working fluid. The increased number of turns in CLPHP generally improves the thermal performance of the system reducing the effect of the type of the working fluid on the aforementioned performance. The adoption of copper nanoparticles, which positively affect fluid motion, decreases the thermal resistance of the system as much as 6.06–42.76% depending on laboratory conditions. Moreover, gravity brings about positive changes in the flow regime decreasing thermal resistance as much as 32.13–52.58%.

scholarly journals Thermal Performance of Micro-Pulsating Heat Pipe

2019 ◽  
Vol 8 (6) ◽  
pp. 2786-2791
Keyword(s):  
Thermal Resistance ◽  
Temperature Profile ◽  
Thermal Performance ◽  
Heat Input ◽  
Computational Study ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Ansys Fluent ◽  
Vof Model ◽  
Flow Circulation

In this study, thermal performance of MPHP is investigated computationally. A case with 0.7mm hydraulic diameter with 7 turns is considered for the study. Simulation is carried out using ANSYS-FLUENT® software by considering water as working fluid with the help of VOF model. Computational study shows the oscillation of fluid inside and formation of new vapor slugs. The heat input is varied from 1.2 W to 4.8 W in the step of 1.2. Flow circulation inside the MPHP is not unidirectional and frequently changes with the pressure disturbance created in the channels. The temperature profile from computational study shows the startup condition is changing with heat input. Thermal resistance of the MPHP decreases with increase in heat input and the corresponding thermal resistance found to be varied from 3.94 to 3.65 K/W.

Experimental Study of the Effects of Ferrofluid on Thermal Performance of a Pulsating Heat Pipe

2011 ◽  
Author(s):  
Maziar Mohammadi ◽  
Mohammad Mohammadi ◽  
Amir R. Ghahremani ◽  
M. B. Shafii
Keyword(s):  
Magnetic Field ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Input ◽  
Pure Water ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Water Based ◽  
The Magnetic Field

In this work, a four-turn Pulsating Heat Pipe (PHP) is fabricated and tested experimentally. The novelty of the present PHP is the capability of obtaining various thermal performances at a specific heat input by changing the magnetic field. The effects of working fluid (water and ferrofluid), charging ratio (25%, 40%, and 55%), heat input (25, 35, 45, 55, 65, 75, and 85 W), orientation (vertical and horizontal heat mode), and magnetic field on the thermal performance of PHPs are investigated. The results showed that applying the magnetic field on the water based ferrofluid reduced the thermal resistance of PHP by a factor of 40.5% and 38.3% in comparison with the pure water case for the vertical and horizontal mode, respectively. According to the experimental results, an optimum thermal resistance of 0.38 °C/W was achieved at the following conditions: water-based ferrofluid as the working fluid in the presence of magnetic field, vertical mode, charging ratio of 55%, 7% volumetric concentration, and 85 W heat input. This thermal resistance is 11.5 times better than that of the empty PHP.

An Experimental Study of Closed Loop Two-Phase Thermosyphon for Spent Fuel Pool Passive Cooling

2016 ◽  
Author(s):  
Minglu Wang ◽  
Mingguang Zheng ◽  
Cheng Ye ◽  
Zhongming Qiu ◽  
Zhenqin Xiong
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Closed Loop ◽  
Working Fluid ◽  
Spent Fuel ◽  
Two Phase ◽  
Spent Fuel Pool

The study reported here examined a closed loop two-phase thermosyphon (CLTPT) of evaporator length 7.6m and internal diameter 65mm used to cool the spent fuel pool. This experimental study investigates the thermal performances and heat and mass transfer characteristic of CLTPT by examining the thermodynamic cycles and overall thermal resistances with ammonia, R134a and water as the working fluid. Measurements of temperature and pressure distributions of the fluid around the loop were made under various conditions. Results show that this loop operates with low filling ratio, low mass flow rate, and high heat-transfer coefficient and the CLTPT has the ability to cool the spent fuel pool. The working fluid flowing through the heat pipe evaporator section generally experienced a subcooled zone, pool boiling zone and high gas quality two-phase region. The average heat transfer coefficient of evaporator reaches 450 W/m2•°C using R134a as working fluid. The thermal resistance of R134a is always smaller than ammonia but the thermal resistance of water is largest at small temperature difference while is smallest when temperature difference is large.

scholarly journals Thermal Performance Improvement of the Heat Pipe by Employing Dolomite/Ethylene Glycol Nanofluid

2020 ◽  
Vol 9 (1) ◽  
pp. 23-27 ◽  
Author(s):  
Duygu Yilmaz Aydin ◽  
Metin Gürü ◽  
Adnan Sözen ◽  
Erdem Çiftçi
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Sodium Dodecyl ◽  
Active Agent ◽  
Sodium Dodecyl Benzene Sulfonate ◽  
Working Fluid ◽  
Maintenance Cost

In heat transfer applications, heat pipes are widely- preferred because of some characteristics such as low cost, being able to be produced in any size and low maintenance cost make them superior. Moreover, the working fluid to be employed substantially affects the heat transfer characteristics of a heat pipe. In this paper, effects of nanoparticle addition into the ethylene glycol on heat pipe’s thermal performance were analysed experimentally. Every test was done using two variant working fluids, ethylene glycol and dolomite nanoparticles-doped ethylene glycol, respectively. Dolomite nanoparticles (2% by weight) and Sodium Dodecyl Benzene Sulfonate (0.5% by weight) were doped into the ethylene glycol while preparing the dolomite/ethylene glycol nanofluid. After filling in the heat pipe, experiments were realized under changing working conditions. Using experimental data, efficiency and thermal resistance of the heat pipe were examined. Viscosity of the each working fluid was determined. The contact angle –wettability measurements were also performed to specify the effects of surface active agent addition. The obtained findings revealed that nanoparticle inclusion inside the base fluid, i.e. ethylene glycol, improved the thermal performance (efficiency) and decreased the heat pipe’s thermal resistance substantially. ©2020. CBIORE-IJRED. All rights reserved

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

2020 ◽  
Vol 38 (1A) ◽  
pp. 88-104
Author(s):  
Anwar S. Barrak ◽  
Ahmed A. M. Saleh ◽  
Zainab H. Naji
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Maximum Deviation ◽  
Inlet Temperature ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Vof Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively.  Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input.  The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

Experimental Study of Thermal Performance of Nanofluid-Filled and Nanoparticles-Coated Mesh Wick Heat Pipes

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Naveen Kumar Gupta ◽  
Arun Kumar Tiwari ◽  
Subrata Kumar Ghosh
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Physical Vapor Deposition ◽  
Power Input ◽  
Working Fluid ◽  
Physical Vapor Deposition Method ◽  
The Stability ◽  
Stability Issues ◽  
Time Of Operation

The enhancements in thermal performance of mesh wick heat pipe (HP) using TiO2/H2O nanofluid (0.5, 1.0, and 1.5 vol %) as working fluid for different (50, 100, and 150 W) power input were investigated. Results showed maximum 17.2% reduction in thermal resistance and maximum 13.4% enhancement in thermal efficiency of HP using 1.0 vol % nanofluid as compared to water. The wick surface of the HP was then coated with TiO2 nanoparticles by physical vapor deposition method. The experimental investigation had been also carried out on coated wick HP using water as working fluid. Results showed 12.1% reduction in thermal resistance and 11.9% enhancement in thermal efficiency of the HP as compared to uncoated wick HP using water. Temporal deteriorations in thermal performance during prolonged working (2, 4, and 6 months) of HP were also studied. Temporal deterioration in thermal performance of HP filled with nanofluid depends upon the deterioration in thermophysical properties of nanofluids. The deterioration is due to the agglomeration and sedimentation of nanoparticles with respect to the time. Comparative study shows that after a certain time of operation, thermal performance of HP with nanoparticle coated wick superseded that of the HP filled with nanofluid. Therefore, nanoparticle coating might be a good substitute for nanofluid to avoid the stability issues. The present paper provides incentives for further research to develop nanofluids that avoid the encountered sedimentation or agglomeration.

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