scholarly journals Characteristic of heat transfer nanofluid of Al2O3 improved by ZrO2 addition

2021 ◽  
Vol 882 (1) ◽  
pp. 012018
Author(s):  
Dani Gustaman Syarif ◽  
Jakaria Usman ◽  
Yofi Ike Pratiwi ◽  
Muhammad Yamin ◽  
Arie Hardian
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Crystallite Size ◽  
Xrd Analysis ◽  
Heat Transfer Efficiency ◽  
The World ◽  
Improve Heat Transfer ◽  
The Stability ◽  
Heat Transfers ◽  
The Heat Transfer Coefficient

Abstract Efforts to replace conventional fluids as coolants for heat transfers with new fluids are continuously being made to improve heat transfer efficiency. Nanofluids are currently widely studied around the world as candidates for conventional fluids substitutes. In this research, the synthesis of Al2O3-ZrO2 nanocomposites for heat transfer nanofluid applications was carried out. The synthesis of the nanoparticles was conducted by the hydrothermal method. Here, we used ZrO2 to improve the characteristics of Al2O3. The results of XRD analysis showed that the nanocomposite had an Al2O3 gamma structure. The Al2O3 nanoparticles and Al2O3-ZrO2 nanocomposite have a crystallite size of 7.41 nm and 6.84 nm, respectively. The addition of 0.1 % ZrO2 decreased the crystallite size and BET particle size and increased the zeta potential, hence the stability of the nanofluids. The increase of stability increased the heat transfer coefficient of the Al2O3 nanofluids, making them suitable for heat transfer.

Investigation of Heat Transfer Enhancement Effect on Normal and Nano Coated Wick Structure Heat Pipes-A Comparative Assessment

2020 ◽  
Vol 51 ◽  
pp. 191-198
Author(s):  
N. Manikanda Prabu ◽  
S. Nallusamy ◽  
G. Sureshkannan
Keyword(s):  
Heat Transfer ◽  
Electronic Devices ◽  
Research Work ◽  
Heat Pipes ◽  
Enhancement Effect ◽  
Heat Transfer Capacity ◽  
Wick Structure ◽  
Improve Heat Transfer ◽  
Super Conducting ◽  
The Stability

Removal of heat generation is an important characteristic needs to be considered in electromechanical and electronic devices which improve the stability and feasibility of system. Despite numerous cooling methods, heat pipes are recent updating in research line. Heat pipes are one of the super conducting medium of heat energy and it is being used as an equipment to absorb more heat through phase change process of cooling medium circulated in it. It ensures the direct enhancement in heat transfer capacity and characteristics. Nowadays, improvement of the thermal performance in heat pipes getting up with various technologies, especially combination of heat pipe and Nano fluids. It has been experimentally practiced and various results are observed by previous researches that wick structure also a part of reason in improvement. The aim of this research work is to analyze the influence of wick material to improve heat transfer characteristics in heat pipes. In addition, combination of nano coated wick material with heat pipes is comparatively analyzed. From the final observed results it was found that, the best combination of wick material is supporting the better cooling requirements in electronic devices.

Effect of By-Pass on the Heat Transfer Coefficient During Density Wave Oscillations in a Horizontal Mini-Channel

2018 ◽  
Author(s):  
Maria Fernandino ◽  
Carlos A. Dorao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Test Section ◽  
Density Wave ◽  
Two Phase ◽  
The Stability ◽  
Density Wave Oscillations ◽  
Cold Liquid ◽  
The Heat Transfer Coefficient

Two phase flow instabilities and in particular density wave oscillations, DWO, are strongly dependent on the internal and external characteristics of the system. Although significant work has been done investigating the characteristics of the stability of the oscillations, the effect of the oscillations on the heat transfer coefficient demands further research. In this work, the influence of a parallel bypass to the test section on the heat transfer coefficient during density wave oscillations is studied. It is observed that in the case of small amplitude DWO the influence of the bypass is negligible, while for the case of large amplitude DWO that reach conditions of flow reversal the heat transfer coefficient can be enhanced. This fact is attributed to cold liquid entering at the outlet of the test section from the bypass preventing the dryout of the wall at high qualities.

Investigation on Thermal-Hydraulic Parameters and Instability Under Two Different Heating Conditions Based on RELAP5 Code

2018 ◽  
Author(s):  
Zhaoyang Xia ◽  
Zhiwei Zhou ◽  
Tianji Peng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Thermal Power ◽  
Density Wave ◽  
Hydraulic Parameters ◽  
Heat Transfer Efficiency ◽  
The Subject ◽  
Heat Transfers ◽  
Relap5 Code

The subject of heat transfer behaviors of steam generator is of great interest for better heat transfer efficiency and safety in industry. On most previous study, the models of SG based on RELAP5 used heat structures as the power generation, which is different from heating by primary side. This paper investigates the distinctions of different heat transfer methods on the thermal-hydraulic parameters by RELAP5. Two different heat transfers are selected, case 1 is uniformly heated by heat structure and case 2 is heated by the primary side of SG. The results show that the onset position of critical heat flux for case 2 is ahead of that for case 1. Besides, the temperature of tube wall corresponding to position of critical heat flux increases abruptly in case 1, and the wall temperature in superheated region in case 1 increases faster than that in case 2 when the water becomes fully superheated vapor. Then instability distinctions for two heat transfer cases are studied in this investigation. It is detected the fluid flow heated by second method is more stable than the first one, and the system has a higher ultimate thermal power when density wave oscillation occurs for case 2.

scholarly journals A review on the thermal performance of nanofluid inside circular tube with twisted tape inserts

2020 ◽  
Vol 12 (6) ◽  
pp. 168781402092489
Author(s):  
Saadah Ahmad ◽  
Shahrir Abdullah ◽  
Kamaruzzaman Sopian
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Volume Fraction ◽  
Fluid Mixing ◽  
Transfer Efficiency ◽  
Working Fluid ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Heat Transfer Efficiency ◽  
Improve Heat Transfer

Working fluid with higher thermal conductivity and tube with better fluid mixing are two crucial elements for heat transfer enhancement in heat exchanger system. Hence, several methods and techniques have been explored to improve heat transfer efficiency, including dispersing nanoparticles into conventional heat transfer fluid and inserting instruments inside the tube of the heat exchanger. Studies have shown that nanofluid can improve heat transfer efficiency of the system due to its higher thermal conductivity and drastic Brownian motion of nanoparticles while inserts within tube can improve heat transfer efficiency by increasing axial velocity of working fluid for better fluid mixing. This article summarized 109 of journals from recent research on heat transfer enhancement of nanofluid flowing inside the tube with inserts as well as discussing the significant parameters that affected the system’s efficiency such as nanoparticles’ volume fraction, Reynolds number and types and configurations of inserts. Ultimately, analysis will be carried out to determine the most suitable modification of twisted tape inserts with the most optimum value of nanoparticle volume fraction for turbulence flow regime. Finally, some problems that need to be solved for future research such as agglomeration and pressure drop are discussed.

scholarly journals Analysis and Optimization of a Microchannel Heat Sink with V-Ribs Using Nanofluids for Micro Solar Cells

Micromachines ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 620 ◽  
Author(s):  
Ruijin Wang ◽  
Jiawei Wang ◽  
Weijia Yuan
Keyword(s):  
Heat Transfer ◽  
Solar Cells ◽  
Heat Sink ◽  
Physical Parameters ◽  
Microchannel Heat Sink ◽  
Power Intensity ◽  
Nusselt Numbers ◽  
Heat Transfer Efficiency ◽  
Chaotic Convection ◽  
Heat Transfers

It is crucial to control the temperature of solar cells for enhancing efficiency with the increasing power intensity of multiple photovoltaic systems. In order to improve the heat transfer efficiency, a microchannel heat sink (MCHS) with V-ribs using a water-based nanofluid as a coolant for micro solar cells was designed. Numerical simulations were carried out to investigate the flows and heat transfers in the MCHS when the Reynolds number ranges from 200 to 1000. The numerical results showed that the periodically arranged V-ribs can interrupt the thermal boundary, induce chaotic convection, increase heat transfer area, and subsequently improve the heat transfer performance of a MCHS. In addition, the preferential values of the geometric parameters of V-ribs and the physical parameters of the nanofluid were obtained on the basis of the Nusselt numbers at identical pump power. For MCHS with V-ribs on both the top and bottom wall, preferential values of V-rib are rib width d / W = 1 , flare angle α = 75 ° , rib height h r / H = 0.3 , and ratio of two slant sides b / a = 0.75 , respectively. This can provide sound foundations for the design of a MCHS in micro solar cells.

scholarly journals Critical Review on Nanofluids: Preparation, Characterization, and Applications

2016 ◽  
Vol 2016 ◽  
pp. 1-22 ◽  
Author(s):  
Mohamoud Jama ◽  
Tejvir Singh ◽  
Seifelislam Mahmoud Gamaleldin ◽  
Muammer Koc ◽  
Ayman Samara ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
High Performance ◽  
Two Phase ◽  
Heat Transfer Fluids ◽  
Thermal And Electrical Properties ◽  
Improve Heat Transfer ◽  
The Stability ◽  
New Generation

Heat transfer fluids are a crucial parameter that affects the size and costs of heat exchangers. However, the available coolants like water and oils have low thermal conductivities, which put many limitations to the development of heat transfer to achieve high performance cooling. The need for development of new classes of fluids which enhance the heat transfer capabilities attracted the attention of many researchers. In the last few decades, modern nanotechnology developed nanoparticles, which have unique thermal and electrical properties that could help improve heat transfer using nanofluids. A “nanofluid” is a fluid with suspended fine nanoparticles which increases the heat transfer properties compared with the original fluid. Nanofluids are considered a new generation of heat transfer fluids and are considered two-phase fluids of liquid solid mixtures. The efficiency of the fluid could be improved by enhancing its thermal properties, especially the thermal conductivity, and it is expected that the nanofluids will have a greater thermal conductivity than the base fluids. This paper reviews the preparation of metallic and nonmetallic nanofluids along with the stability of the produced nanofluids. Physical and thermal properties as well as a range of applications are also discussed in detail.

Research on Inner Cooling Apparatus Sets in the Mold of 700mm×700mm Bloom

2011 ◽  
Vol 328-330 ◽  
pp. 1623-1626
Author(s):  
Ming Hua Bai ◽  
Jing Jing Liu ◽  
Jun Li Ge ◽  
Zhi Qiang Liu ◽  
Zhi Ming Zhang
Keyword(s):  
Heat Transfer ◽  
Casting Speed ◽  
Empirical Formula ◽  
Liquid Core ◽  
Feasibility Analysis ◽  
Equiaxed Crystal ◽  
Heat Transfer Efficiency ◽  
Improve Heat Transfer ◽  
Segregation Level ◽  
The Impact

Based on the problems emerged from market, 700mm×700mm super-large billet has been advanced. This paper calculated the casting speed and the depth of liquid core according to empirical formula for 700mm×700mm super-large billet, based on calculate and feasibility analysis acquired the appropriate casting speed is 0.2 m/min. A new mold has been advance based on mold thermoanalysis that is complex mold. Theoretically analyzed the function of setting inner cooling and deflected SEN, indicate that complex mold can improve heat transfer efficiency and equiaxed crystal ratio, reducing center segregation; level rotary flow can uniform molten steel ingredient and growth of shell, reduce the impact depth, achieve the effect of E-EMS; calculation show that reduce the depth of liquid core by applying complex mold, finally, reduce infrastructure fee of caster.

Hydrothermal Synthesis of Nano ZrO2 Powders

2006 ◽  
Vol 317-318 ◽  
pp. 195-198 ◽  
Author(s):  
Cihangir Duran ◽  
Jia Yu ◽  
Kimiyasu Sato ◽  
Yuji Hotta ◽  
Koji Watari
Keyword(s):  
Particle Size ◽  
Reaction Time ◽  
Hydrothermal Synthesis ◽  
Crystallite Size ◽  
Xrd Analysis ◽  
Monoclinic Zro2 ◽  
Temperature Range ◽  
Mean Particle Size ◽  
Temperature And Precipitation ◽  
Solution Formation

Hydrothermal synthesis of nano ZrO2 powders were carried out at a temperature range of 100 to 200°C, using zirconium solution. Formation of ZrO2 formation was accelerated with temperature and precipitation of ZrO2 took place directly from the solution. XRD analysis revealed that monoclinic ZrO2 was formed at all conditions. Crystallite size was found to range from 2.6 to 4 nm. Mean particle size increased from 93 nm at 135°C to 125 nm at 200°C after reaction time of 2 h.

Analysis of Buoyancy Effect on Fully Developed Laminar Heat Transfer in a Rotating Tube

1985 ◽  
Vol 107 (2) ◽  
pp. 338-344 ◽  
Author(s):  
R. Siegel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Tube Wall ◽  
Perturbation Parameter ◽  
Axis Of Rotation ◽  
Wall Heating ◽  
Improve Heat Transfer ◽  
Radial Outflow ◽  
The Heat Transfer Coefficient

Laminar heat transfer is analyzed in a tube rotating about an axis perpendicular to the tube axis. The solution applies for flow that is either radially outward from the axis of rotation, or radially inward toward the axis of rotation. The conditions are fully developed, and there is uniform heat addition at the tube wall. The analysis is performed by expanding velocities and temperature in power series using the Taylor number as a perturbation parameter. Coriolis and buoyancy forces caused by tube rotation are included, and the solution is calculated through second-order terms. The secondary flow induced by the Coriolis terms always tends to increase the heat transfer coefficient; this effect can dominate for small wall heating. For radial inflow, buoyancy also tends to improve heat transfer. For radial outflow, however, buoyancy tends to reduce heat transfer; for large wall heating this effect can dominate, and there is a net reduction in heat transfer coefficient.

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