Advanced Coolant Research Articles

Significant properties of AA7075-methanol nanofluid flow through diverging channel with porous material: Differential Transform Method

The recent industrial needs for the production process depending upon heat transfer properties of the fluids. However, the utility of the nanofluid in comparison to the conventional fluid is widely used because of its advanced coolant efficiency. In particular cooling of electronic devices, drug delivery systems, operation theatre, etc. the use of nanofluid shows its influential characteristics. As a result, the contemporary study aims to inspect the heat transmission effects of alloy nanoparticles via the base fluid methanol is presented through a diverging channel. Particularly, the aluminium alloy of AA7075 containing base metal Aluminium (Al) about 87.1-91.4%, Zinc (Zn) up to 5.1-6.1%, Magnesium (Mg) about 2.1-2.9%, Copper (Cu) within the range of 1.2-2.0%, Chromium (Cr) amounts 0.18-0.28%, Silicon (Si) usually less than 0.4%, Iron (Fe) less than 0.5%, Manganese (Mn) up to 0.3%, and Titanium (Ti) usually less than 0.2%. However, the flow through a permeable medium, the interaction of Darcy dissipation energies the flow phenomena. An appropriate similarity transform rule is employed for the transformation of the basic equations and solved analytically via the differential transform method (DTM). Further, a comparative analysis with previously establish outputs is presented to ensure the accuracy of the adopted methodology. The impact of characterizing factors on the flow profiles are presented graphically and the important outcomes are; the velocity profile shows its dual characteristic for the variation of alloy nanoparticles whereas the fluid temperature enhances significantly. Further, heat transport feature enhances for the augmentation in the Eckert number which is exhibited for the inclusion of dissipative heat.

Performance Evaluation of the Electric Machine Cooling System Employing Nanofluid as an Advanced Coolant

In this paper, the overall performance of an electric machine cooling system was examined in terms of heat transfer and fluid flow. The structure of the cooling system was based on the cooling jacket method. The cooling jacket contains spiral channels surrounding the stator and end-windings of the electric machine. Al2O3-water nanofluid is used inside the channels as the cooling fluid. The concentration of nanoparticles and the geometric structure of the cooling system have special effects on both aspects of heat transfer and fluid flow. Therefore, in this paper, the overall performance of the cooling system was evaluated by considering these effects. This study compared the importance of heat transfer and fluid flow performances on the overall performance of the cooling system. Numerical analyses were performed by 3D computational fluid dynamics and 3D fluid motion analysis. The analyses were carried out based on the 3D finite element method using the pressure-based solver of the Ansys Fluent software in steady mode.

Graphene-silver alloyed quantum dots nanofluid: Synthesis and application in the cooling of a simulated electronic system

In this work, graphene-silver alloyed quantum dots were synthesized by an In-situ hydrothermal method for the preparation of nanofluid suspensions at various concentrations (200–1000 ppm) and to investigate their convective cooling performance in a simulated electronic system. The prepared nanofluid exhibits high dispersion stability at pH 7 and a maximum enhancement in thermal conductivity of 45.5% (±1%) was obtained for 1200 ppm nanofluid compared to water. The cooling studies show that the core temperature of the system gets decreases with an increase in Reynolds number and nanofluid concentration. The convective heat transfer coefficient and Nusselt number for 1000 ppm nanofluid enhances by 97% (±2%) and 37% (±1.5%) respectively compared to water. The maximum pumping power penalty of 6.2% (±0.5%) was obtained for 1000 ppm nanofluid at 10 ml/sec. The enhanced thermal transport properties of alloyed quantum dot nanofluid shows their inherent capability as an advanced coolant for heat-generating electronic systems.

Thermal–electrical–hydraulic properties of Al2O3–SiO2 hybrid nanofluids for advanced PEM fuel cell thermal management

Hybrid nanofluid is a new revolutionized cooling liquid with improved thermo-physical properties as compared to conventional coolant. This paper presents the feasibility of hybrid Al2O3–SiO2 nanofluids as an advanced coolant for PEM fuel cell application in terms of thermal–electrical–hydraulic thermo-physical properties. Nine mixture ratios of Al2O3–SiO2 were used in this experiment, ranging from 10:90 to 90:10 mixture ratios. The result demonstrated that both thermal conductivity and electrical conductivity decreased as the percentage of Al2O3 was increased in the mixture. In contrast, the dynamic viscosity property increased as the Al2O3 percentage ratio was increased. In summary, property enhancement ratio (PER) of thermo-hydraulic (PERt/v) and thermo-electrical (PERt/e) was established. Both PERt/v and PERt/e analyses favor 10:90 ratio of Al2O3–SiO2 hybrid as the most feasible ratio for the implementation in PEMFC. This is due to the dominant effect of thermal over viscosity and electrical conductivity.

Numerical Analysis of SiO2 Nanofluid Performance in Serpentine PEMFC Cooling Plate

Proton exchange membrane fuel cell (PEMFC) is among the potential substitute to current conventional internal combustion engine (ICE) in the automotive sector due to its efficient conversion efficiency and environmental friendly. However, thermal management issues in PEMFC needs to be addressed as excessive heat in PEMFC can deteriorate its performance as well as causing dehydration to the membrane. In this study, an advanced coolant of SiO2 nanofluids was numerically studied and effect in term of the heat transfer and fluid flow behavior in a single PEMFC cooling plate is investigated. The study simulated SiO2 nanofluids in a serpentine PEMFC cooling plate. The simulation is conducted at a low volume concentrations of 0.1, 0.3 and 0.5 % of SiO2 in water and water: Ethylene Glycol (W:EG) of 60:40 as base fluids. In this serpentine cooling plate design of PEMFC, a constant heat flux is applied to mimic the actual application of PEMFC. Upon completion of the study, heat transfer and fluid flow shows that the heat transfer coefficient of 0.5 vol. % of SiO2 nanofluids has improved by 3.5 % at Reynold (Re) number of 400 as compared to the base fluid of water with an acceptable pumping power increment.

Solar thermoelectric cooling using closed loop heat exchangers with macro channels

In this paper we describe the design, analysis and experimental study of an advanced coolant air conditioning system which cools or warms airflow using thermoelectric (TE) devices powered by solar cells. Both faces of the TE devices are directly connected to closed-loop highly efficient channels plates with macro scale channels and liquid-to-air heat exchangers. The hot side of the system consists of a pump that moves a coolant through the hot face of the TE modules, a radiator that drives heat away into the air, and a fan that transfer the heat over the radiator by forced convection. The cold side of the system consists also of a pump that moves coolant through the cold face of the TE modules, a radiator that drives cold away into the air, and a fan that blows cold air off the radiator. The system was integrated with solar panels, tested and its thermal performance was assessed. The experimental results verify the possibility of heating or cooling air using TE modules with a relatively high coefficient of performance (COP). The system was able to cool a closed space of 30 m3 by 14 °C below ambient within 90 min. The maximum COP of the whole system was 0.72 when the TE modules were running at 11.2 A and 12 V. This improvement in the system COP over the air cooled heat sink is due to the improvement of the system heat exchange by means of channels plates.

Thermodynamic modelling of liquid-vapour equilibrium and thermophysical properties of molten Pb–Bi systems

ABSTRACTA lead–bismuth alloy is an advanced coolant for nuclear power plants. The study of this alloy is of current importance. However, performing high-temperature experiments involves many problems. In this work, to study evaporation of a lead–bismuth alloy in the presence of intermetallic compounds in the condensed phase and dimers and trimers of metals in the vapour phase, a method of thermodynamic modelling was used. The investigations were carried out at temperatures from 400 to 3000 K with the lead content from 0.1 to 0.9 weight fractions in the lead–bismuth alloy. In the method of thermodynamic modelling a software package TERRA and a model of an ideal solution of interaction products were applied. Concentration and temperature dependencies of the content of components in the melt and in the gaseous phase over the melt were calculated. Temperatures, enthalpies, entropies of the melt–vapour transition and various thermophysical properties were defined.

Flow and Heat Transfer in Micro Pin Fin Heat Sinks With Nano-Encapsulated Phase Change Materials

In this paper, a 3D-conjugated heat transfer model for nano-encapsulated phase change materials (NEPCMs) cooled micro pin fin heat sink (MPFHS) is presented. The governing equations of flow and heat transfer are solved using a finite volume method based on collocated grid and the results are validated with the available data reported in the literature. The effect of nanoparticles volume fraction (C = 0.1, 0.2, and 0.3), inlet velocity (Vin = 0.015, 0.030, and 0.045 m/s), and bottom wall temperature (Twall = 299.15, 303.15, 315.15, and 350.15 K) is studied on Nusselt and Euler numbers as well as temperature contours in the system. The results indicate that significant heat transfer enhancement is achieved when using the NEPCM slurry as an advanced coolant. The maximum Nusselt number when NEPCM slurry (C = 0.3) with Vin = 0.015, 0.030, and 0.045 (m/s) is employed is 2.27, 1.81, and 1.56 times higher than the ones with base fluid, respectively. However, with increasing bottom wall temperature, the Nusselt number first increases then decreases. The former is due to higher heat transfer capability of coolant at temperatures over the melting range of phase change material (PCM) particles due to partial melting of nanoparticles in this range. However, the latter phenomenon is due to the lower capability of the NEPCM particles and consequently coolant in absorbing heat at coolant temperatures is higher than the temperature correspond to fully melted NEPCM. It was observed that the NEPCM slurry has a drastic effect on the Euler number, and with increasing volume fraction and decreasing inlet velocity, the Euler number increases accordingly.

Spectrophotometric Procedure for Fast Reactor Advanced Coolant Manufacture Control

The paper describes a spectrophotometric procedure for fast reactor advanced coolant manufacture control. The molar absorption coefficient of dimethyllead dibromide with dithizone was defined as equal to 68864 ± 795 l·mole-1·cm-1, limit of detection as equal to 0.583 · 10-6 g/ml. The spectrophotometric procedure application range was found to be equal to 37.88 - 196.3 g. of dimethyllead dibromide in the sample. The procedure was used within the framework of the development of the method of synthesis of the advanced coolant for fast reactors.

THERMAL CONDUCTIVITY COMPARISONS OF ORIGINAL AND OXIDIZED MULTIWALLED CARBON NANOTUBES-WATERBASED FLUIDS

Nanofluids are a new class of fluids engineered by dispersing nanoparticles in base fluids. The addition of small amount nanoparticles may enhance the thermo-physical properties of the original liquids. In this study, thermal conductivity of pristine and modified multiwalled carbon nanotubes (MWCNT) in water-based fluids was prepared and investigated at various temperatures ranging from 6OC to 45OC. Stable and homogeneous MWCNT nanofluids were successfully produced with an addition of polyvinylpyrrolidone (PVP) as the dispersing agent using physical agitation process. The addition of MWCNT into a fluid leads to the enhancement of its thermal conductivity. The prepared nanofluids, with good fluidity, stability, and high thermal conductivity, is a potential advanced coolant in thermal energy engineering and energy consumption saving.

Thermo-physical properties of water-based single-walled carbon nanotube nanofluid as advanced coolant

In this paper, the thermo-physical properties of water-based single-walled carbon nanotube nanofluids (SWCNTs-nanofluids) are experimentally studied. The effect of mass concentration, varying from 0.1 to 1 wt%, on the thermal conductivity, viscosity and density of nanofluids is investigated at the temperatures of 10–60 °C. The results show that the thermal conductivity, viscosity and density of nanofluids are higher than that of the base fluid, and increase with an increase in nanotubes concentration. The thermo-physical property variation of SWCNTs-nanofluids with temperature is similar to that of pure water, i.e. thermal conductivity increases, whereas the viscosity and density decrease with an increase in the temperature. When the concentration is 1 wt%, at 60 °C, the maximum thermal conductivity and viscosity enhancements increase by up to 16.2% and 35.9%, respectively. Furthermore, the heat transfer performance of SWCNTs-nanofluids as advanced coolants is evaluated in both laminar and turbulent flow regimes based on the measured data. The evaluated results indicate that SWCNTs-nanofluids have good heat transfer performance in laminar flow regime. For the case of turbulent flow regime, however, the viscosity increase worsens the heat transfer performance at the lower temperature and higher concentration.

Enhancement of the performance of a double layered microchannel heatsink using PCM slurry and nanofluid coolants

Advanced coolants such as nanofluids or PCM slurries are realized and reported as effective substitutions for conventional coolants in order to enhance the cooling performance of microchannel heatsinks. However, there are a number of disadvantages associated with using these advanced coolants that are always considered as their inevitable downsides including the increase of the needed pumping power of the system for both of the mentioned coolants and decrease of the fluid average thermal conductivity for PCM slurries. In this paper, a 3D conjugated heat transfer model of a double layer microchannel heatsink (MCHS) to investigate its thermal performance is presented and the effectiveness of simultaneous employing of both of these types of advanced coolants in a heatsink is assessed. Finite volume method (FVM) is used to solve the flow and heat governing equations simultaneously and the obtained results are validated with the experimental data. The assessed parameters in this study are: coolant type, coolant configurations, particle concentration, bottom surface temperature, and inlet fluid velocity. In order to investigate the flow and cooling efficiency of the heatsink, two dimensionless parameter, Nusselt and Euler numbers, are computed and compared between the considered configurations. The goal is to balance and optimize the desirable cooling enhancement that is obtained by using advanced coolants and is represented by associated Nusselt number from one side, and undesirable increase of the needed pumping power which is implied by relevant Euler number, from the other side. Results showed that using the proposed configurations, the cooling performance of the systems are enhanced and the disadvantages associated with advanced coolant are relieved, substantially.

Benchmarking of thermal hydraulic loop models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES), phase-I: Isothermal steady state forced convection

As highly promising coolant for new generation nuclear reactors, liquid Lead–Bismuth Eutectic has been extensively worldwide investigated. With high expectation about this advanced coolant, a multi-national systematic study on LBE was proposed in 2007, which covers benchmarking of thermal hydraulic prediction models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES). This international collaboration has been organized by OECD/NEA, and nine organizations – ENEA, ERSE, GIDROPRESS, IAEA, IPPE, KIT/IKET, KIT/INR, NUTRECK, and RRC KI – contribute their efforts to LACANES benchmarking. To produce experimental data for LACANES benchmarking, thermal–hydraulic tests were conducted by using a 12-m tall LBE integral test facility, named as Heavy Eutectic liquid metal loop for integral test of Operability and Safety of PEACER (HELIOS) which has been constructed in 2005 at the Seoul National University in the Republic of Korea. LACANES benchmark campaigns consist of a forced convection (phase-I) and a natural circulation (phase-II). In the forced convection case, the predictions of pressure losses based on handbook correlations and that obtained by Computational Fluid Dynamics code simulation were compared with the measured data for various components of the HELIOS test facility. Based on comparative analyses of the predictions and the measured data, recommendations for the prediction methods of a pressure loss in LACANES were obtained. In this paper, results for the forced convection case (phase-I) of LACANES benchmarking are described.