Thermal Performance of a Compact Loop Heat Pipe with Silver-Water Nanofluid

2016 ◽  
Vol 852 ◽  
pp. 666-674 ◽  
Author(s):  
Emerald Ninolin ◽  
Godson Asirvatham Lazarus ◽  
K. Ramachandran
Keyword(s):  
Heat Transfer ◽  
Silver Nanoparticles ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Convective Heat Transfer Coefficient ◽  
Loop Heat Pipe ◽  
Volume Percentage

The thermal performance of a compact loop heat pipe is fabricated and tested for different heat inputs ranging from 30 W to 500 W using water and silver-water nanofluid with low volume concentrations of silver nanoparticles (0.03% and 0.09%) in vertical orientation. A flat square evaporator having a bottom area of 30 mm × 30 mm and a height of 15 mm is used in the present study. The effect of heat input on the thermal resistance, evaporation and condensation heat transfer coefficient is experimentally investigated. The results showed that a reduction in the evaporator thermal resistance of 26.45% is achieved with 0.09 volume percentage of silver nanoparticles when compared with that of water. Further an enhancement in the convective heat transfer coefficient of 25.23% has been observed with the same volume concentration of silver nanoparticles. Addition of small amount of nanoparticles enhanced the operating range of heat pipe beyond 500 W and without the occurrence of any dry out conditions. From the outcome of this study, it is concluded that the compact loop heat pipe with flat square evaporator can be used for thermal control of electronic equipments with limited space.

scholarly journals Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

2021 ◽  
pp. 199-199
Author(s):  
Lakshmi Reddy ◽  
Srinivasa Bayyapureddy Reddy ◽  
Kakumani Govindarajulu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Tilt Angle ◽  
Heat Load ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

Effect of Wick Characteristics on the Thermal Performance of the Miniature Loop Heat Pipe

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Randeep Singh ◽  
Aliakbar Akbarzadeh ◽  
Masataka Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Working Fluid ◽  
Vapor Flow ◽  
Loop Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Two phase heat transfer devices based on the miniature version of loop heat pipe (LHP) can provide very promising cooling solutions for the compact electronic devices due to their high heat flux management capability and long distance heat transfer with minimal temperature losses. This paper discusses the effect of the wick properties on the heat transfer characteristics of the miniature LHP. The miniature model of the LHP with disk-shaped evaporator, 10 mm thick and 30 mm disk diameter, was designed using copper containment vessel and water as the working fluid, which is the most acceptable combination in electronic cooling applications. In the investigation, wick structures with different physical properties including thermal conductivity, pore radius, porosity, and permeability and with different structural topology including monoporous or biporous evaporating face were used. It was experimentally observed that copper wicks are able to provide superior thermal performance than nickel wicks, particularly for low to moderate heat loads due to their low heat conducting resistance. With monoporous copper wick, maximum evaporator heat transfer coefficient (hev) of 26,270 W/m2 K and evaporator thermal resistance (Rev) of 0.06–0.10°C/W were achieved. For monoporous nickel wick, the corresponding values were 20,700 W/m2 K for hev and 0.08–0.21°C/W for Rev. Capillary structure with smaller pore size, high porosity, and high permeability showed better heat transfer characteristics due to sufficient capillary pumping capability, low heat leaks from evaporator to compensation chamber and larger surface area to volume ratio for heat exchange. In addition to this, biporous copper wick structure showed much higher heat transfer coefficient of 83,787 W/m2 K than monoporous copper wick due to improved evaporative heat transfer at wick wall interface and separated liquid and vapor flow pores. The present work was able to classify the importance of the wick properties in the improvement of the thermal characteristics for miniature loop heat pipes.

scholarly journals Development and Characterization of a Loop Heat Pipe With a Planar Evaporator and Condenser

2011 ◽  
Author(s):  
H. Arthur Kariya ◽  
Daniel F. Hanks ◽  
Teresa B. Peters ◽  
John G. Brisson ◽  
Evelyn N. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Convective Heat Transfer ◽  
Thermal Gradient ◽  
Convective Heat Transfer Coefficient ◽  
Planar Geometry ◽  
Loop Heat Pipe

We present the development and characterization of an air-cooled loop heat pipe with a planar evaporator and condenser. The condenser is mounted vertically above the evaporator, and impellers are integrated both sides of the condenser with tight clearance. The planar geometry allows for effective convective cooling by increasing the surface area and the convective heat transfer coefficient. To ensure condensation across the area of the condenser, a wicking structure is integrated in the condenser. The evaporator incorporates a multi-layer wicking structure to maintain a thermal gradient between the vapor and liquid regions, which is used to sustain the vapor and liquid pressures necessary for operation. The loop heat pipe was demonstrated to remove 140 W of heat at a temperature difference between the evaporator base and inlet air of 50 °C. This work is the first step towards the development of an air-cooled, multiple-condenser loop heat pipe.

Experimental and theoretical investigation of heat transfer characteristics of cylindrical heat pipe using Al2O3–SiO2/W-EG hybrid nanofluids by RSM modeling approach

2021 ◽  
Vol 68 (1) ◽  
Author(s):  
R. Vidhya ◽  
T. Balakrishnan ◽  
B. Suresh Kumar
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Diffraction Spectrum ◽  
Step Method ◽  
Ceramic Nanoparticles ◽  
Transfer Mechanisms

AbstractNanofluids are emerging two-phase thermal fluids that play a vital part in heat exchangers owing to its heat transfer features. Ceramic nanoparticles aluminium oxide (Al2O3) and silicon dioxide (SiO2) were produced by the sol-gel technique. Characterizations have been done through powder X-ray diffraction spectrum and scanning electron microscopy analysis. Subsequently, few volume concentrations (0.0125–0.1%) of hybrid Al2O3–SiO2 nanofluids were formulated via dispersing both ceramic nanoparticles considered at 50:50 ratio into base fluid combination of 60% distilled water (W) with 40% ethylene glycol (EG) using an ultrasonic-assisted two-step method. Thermal resistance besides heat transfer coefficient have been examined with cylindrical mesh heat pipe reveals that the rise of power input decreases the thermal resistance and inversely increases heat transfer coefficient about 5.54% and 43.16% respectively. Response surface methodology (RSM) has been employed for the investigation of heat pipe experimental data. The significant factors on the various convective heat transfer mechanisms have been identified using the analysis of variance (ANOVA) tool. Finally, the empirical models were developed to forecast the heat transfer mechanisms by regression analysis and validated with experimental data which exposed the models have the best agreement with experimental results.

Thermal Characteristics of a Cylindrical Heat Pipe using Multi-Layer Screen Mesh Wick

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
R. Sankar Rao ◽  
S. Bhanu Prakash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Wire Mesh ◽  
Working Fluid ◽  
Wick Structure ◽  
Screen Mesh

Heat pipe is the most widely used heat exchanging device in removal of heat from any given system at a faster rate. The thermal characteristics of heat pipe with single and multi-layered screen mesh wicks have been observed with two working fluids water and acetone. Heat pipe of length 250 mm and 12.7 mm outer diameter, made of copper material is used in all the trials of with and without wick structure. A 100 mesh stainless steel screen wire mesh is chosen as wick structure. Experiments were conducted at different heat loads and various inclinations with 100% fill ratio in evaporator. The performance is measured based on total thermal resistance and overall heat transfer coefficient. The heat pipe is found effective at 60o inclination with acetone as a working fluid and with four layered screen mesh wick. Uncertainty in thermal resistance and heat transfer coefficient is calculated for a heat input of 10W at 0 and 60 inclinations.

Experimental Investigation on the Performance of Naphthalene Heat Pipe in Half-Circumferential Heating Method

2010 ◽  
Author(s):  
Yun Liu ◽  
Hong Zhang ◽  
Dongdong Zhan ◽  
Caixia Yin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Carbon Steel ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Filling Ratio ◽  
Circumferential Direction ◽  
Temperature Uniformity ◽  
Heating Method

Based on the characteristics of a carbon steel-naphthalene heat pipe, a new type of medium temperature heat pipe solar receiver has been developed. According to Direct Steam Generation (DSG) with solar parabolic trough concentrators, a simulation experiment is founded which used a new half-circumferential heating method. At the working dip angles 4° and 8°, the working temperature of heat pipe is stabilized at 250°C, 300°C, 350°C, 380°C, respectively. In this article, the temperature uniformity in circumferential direction, thermal resistance and heat transfer coefficient of the carbon steel-naphthalene has been analyzed and studied. The results indicate: the temperature uniformity in circumferential direction is below 20°C. The optimum filling ratio is 30% and when used this filling ratio, the total thermal resistance basically maintained below 0.23°C/W. Heat transfer coefficient increased with the increase of the transfer power. This article serves as a reference to understanding the heat transfer performance of the carbon steel-naphthalene heat pipe in medium soar receiver.

Experimental Investigation and Performance Evaluation of a Multi Turn Closed Loop Pulsating Heat Pipe

2014 ◽  
Vol 592-594 ◽  
pp. 1554-1558 ◽  
Author(s):  
N. Narendra Babu ◽  
Rudra Naik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Closed Loop ◽  
Experimental Result ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids

Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

Solar Collectors with Tubes Partially Filled with Porous Substrates

1999 ◽  
Vol 121 (1) ◽  
pp. 20-24 ◽  
Author(s):  
M. K. Alkam ◽  
M. A. Al-Nimr
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Tube Wall ◽  
Convective Heat Transfer Coefficient ◽  
Porous Substrate ◽  
Collector Efficiency ◽  
Overall Heat Loss Coefficient ◽  
Porous Substrates

In this work, the thermal performance of a conventional collector is improved by inserting porous substrates at the inner walls of the collector tubes. The porous substrates improve the convective heat transfer coefficient between the tube wall and the fluid. This improvement is investigated numerically and its effects on the efficiency and the useful gain of the collector are evaluated. It is found that inserting the porous substrate may raise the collector efficiency considerably, especially at high values of the overall heat loss coefficient.

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