Nanofluids In Microchannel Heat Sink Research Articles

Numerical Investigation of Heat Transfer Enhancement of Al2O3 Nanofluid in Microchannel Heat Sink

This study focusses on using computational fluid dynamics (CFD) to study the enhancement of heat transfer from the use of AL2O3 nanofluid in a microchannel heat sink (MCHS) to develop a more efficient cooling device for high-power integrated circuits. The objective is to investigate the heat transfer performance, parameters, and enhancement rate using Ansys Fluent software, and to compare the results with experiments to show the effectiveness of this method. This study will also focus on the relationship between the friction fraction and nanoparticles volume fraction to improve the heat transfer enhancement in the MCHS. The temperature, pressure, heat transfer coefficient, Nusselt number, and friction coefficient are analysed in this study. The results showed that an increase in the volume fraction of the nanofluid leads to an increase in the average heat transfer coefficient. The results showed that for 4% nanofluid volume concentration, the Nusselt Number has improved by 10% compared to pure water. However, an increase in volume concentration also resulted in an increase in pressure drop.

Predicting entropy generation of a hybrid nanofluid in microchannel heat sink with porous fins integrated with high concentration photovoltaic module using artificial neural networks

This paper evaluates the characteristic of second law of thermodynamic, including Bejan number and entropy generation for hybrid nanofluid containing graphene-silver nanofluid through a MCHS whit porous fins. Finite-volume technique is utilized to solve the governing equations. To simulate the problem, different porous medium thicknesses, nanoparticle concentrations, and inlet mass flow rates are used while the heat flux remains constant. The minimum values of the frictional and thermal entropy generation are 5 × 10−4 and 6.25 × 10−2, while the maximum values are 3.2 × 10−4 and 9.75 × 10−2. With increasing nanoparticle concentration up to 0.06% wt at constant porous thickness tp=200 µm, frictional entropy generation rises up by 3 × 10−5 and heat transfer rate go up while, thermal entropy generation decreases by 1.5 × 10−2. In addition, by doubling the input mass flow rate and reaching 0.02% at constant nanoparticle concentration (0.06%), thermal entropy generation decreases by 2 × 10−2 while the frictional entropy generation increases by 2.4 × 10−4. The minimum magnitude of Bejan number is 0.994. This show that the irreversibility is derived significantly from thermal entropy generation rate. Finally, an artificial neural network is employed to obtain a model for entropy generation.

Numerical simulation of heat transfer and flow of Al2O3-water nanofluid in microchannel heat sink with cantor fractal structure based on genetic algorithm

The heat generated during operation of microelectronic devices often adversely affects product performance. A remedy for this problem can be through the incorporation of nanofluidic microchannel heat sinks. Advanced working fluids and channel structures can be used to improve the heat transfer performance of the microchannel heat sink. First, thermal resistance is treated as a single objective function, the geometry of the microchannel was optimized using a genetic algorithm. The flow and heat transfer characteristics of the optimized microchannel are analyzed. The effect of different nanofluid volume fractions and geometric parameters on the inlet and outlet pressure drop, flow resistance coefficient, substrate temperature, Nusselt number (Nu), and system thermal resistance in the fractal microchannel are investigated. The thermal resistance of Al2O3 nanofluid with a volume fraction of 5% is 12.5–14.7% lower than that of deionized water, and the microchannel substrate temperature is 6.26 °C lower than that of deionized water.

Experimental investigation of heat transfer of Al2O3 nanofluid in a microchannel heat sink

Microchannel heat sink (MCHS) with nanofluids has been widely utilized to improve heat transfer performance in micro-scale mechanical systems. Although various studies have demonstrated the heat transfer phenomena of Al2O3 nanofluid in MCHS, the flow and heat transfer characteristics have not been fully elucidated due to a insufficiency of experimental results. To investigate these heat transfer phenomena, measurements of the temperature and velocity fields in the MCHS are important because the flow characteristics influence the heat transfer performance. Therefore, in the present study, velocity and temperature fields of Al2O3 nanofluid and deionized(DI) water in a MCHS were systematically analyzed by employing the particle image velocimetry(PIV) and laser induced fluorescence(LIF) measurement techniques. The heat transfer characteristics were explained using flow behaviors and temperature distribution in the MCHS. Moreover, the entropy generation rate in the MCHS was also evaluated to demonstrate heat transfer performance. When the nanofluid was used as a working fluid in the MCHS, the generation rate of thermal entropy was 6.3% smaller than that of water. In conclusion, we experimentally demonstrated the heat transfer of nanofluid by using the velocity and temperature measurement technique. The results of this study will advance the study of heat transfer using Al2O3 nanofluids.

LBM simulation of thermo-hydrodynamic and irreversibility characteristics of a nanofluid in microchannel heat sink under affecting a magnetic field

ABSTRACT Understanding thermo-hydrodynamic characteristics of microchannels is of importance to fabricate efficient heat sinks, due to wide applications of cooling modules in microscales. In this work, water-alumina nanofluid heat transfer and laminar flow field of a microchannel under imposing a magnetic field is studied. The microchannel is partially heated by a constant heat flux. The effects of various values of Hartmann number, varying between 0 and 40, Reynolds number, increased from 10 to 500, and volume fraction of nanoparticles, which falls between 0 and 0.06, on the problem physics are investigated. Lattice-Boltzmann numerical method is applied to simulate the hydrodynamic and thermal field. Further, the energy loss due to thermal, frictional and magnetic mechanisms is also computed. It is shown that heat transfer is intensified by strengthening magnetic force, Reynolds number or concentration of nanoparticles. This is such that increasing Hartmann number from 0 to 40 or volume fraction of the nanofluid from 0 to 0.06 makes 150% increment in Nusselt number. Intensifying Reynolds number from 100 to 500 causes 200% rising in Nusselt number, as well. It is found that the thermal response of the microchannel to variation of pertinent parameters is nonlinear. Comparing the various sources of entropy generation shows that the thermal mechanism is most influential by the value of one order of magnitude larger than the other sources.

Entropy generation study of TiO2 nanofluid in microchannel heat sink for Electronic cooling application

Development of Micro-electro-mechanical systems (MEMS) in the recent years has motivated and necessitated the study of flows in micro-scale geometries such as microchannel. Thermal management in ultra-densely packed electronic devices is highly essential to increase the reliability of the component without compromising packaging. The present study provides an experimental and numerical investigation on laminar forced convection in parallel microchannel heat sink accompanied with integrated Aluminium bulk heat spreader and ultrafine TiO2 nanoparticle based nanofluid for different wt. % ranging from 0.1-0.35 under different power ratings. Numerical study is performed to understand the flow hydrodynamics in microchannel to investigate the temperature distribution in bulk heat spreader with increased flow rates by implementing the thermo-physical properties. Furthermore, a study on Exergy and entropy generation for different fluids is also discussed. The experimental studies reveal that parallel microchannel increases the effectiveness of integrated cooling with a marginal temperature deviation between the heat sink and Aluminium bulk for a distance of 1.5 mm. Implementation of TiO2 nanofluid registered as a better working fluid than the pure fluid for all the experimental settings.

Numerical investigation of laminar convective heat transfer and pressure drop of water-based Al2O3 nanofluids in a microchannel

The heat transfer and flow of nanofluids in microchannel heat sink is usually numerically investigated by the single-phase model. The thermal conductivity and viscosity of nanofluids are calculated in the whole computational region because the single-phase model, assumes the nanofluids is static and nanoparticles concentration is uniform. However for the actual forced flow process, the concentration distribution of the nanofluids is not uniform. So the thermal properties of the nanofluids vary within different computational regions. With the increase of the velocity of the nanofluids, the deviation between the prediction of single-phase model and experimental results increases. In this paper, a new simulation method is proposed to consider the inhomogeneous and dynamic thermophysical properties of the nanofluids by obtaining the nonuniformly distributed nanoparticle concentration in each numerical cell. At the same time, it takes into account the following factors: the interactions between the nanoparticles, the solid wall and the base fluid, the axial conduction, the slip boundary conditions and fluid-solid coupling. The results show that the proposed numerical simulation method further improve the simulation accuracy for the forced flow and heat transfer process of nanofluids in the microchannel in a wider range. The effects of the nanoparticles concentration, Reynolds number and axial heat transfer on the thermophysical properties of the nanofluilds, the flow and heat transfer characteristics of a rectangular microchannels with hydraulic dimensions of 341μm were analyzed using the proposed simulation model. The main results are as follows: the nanoparticles are enriched at the near wall for the fully developed region; the nonuniformity of the nanofluilds thermal conductivity coefficient distribution at the channel cross section increases with the increase of the mass flow rate and the inlet centration; under the same Reynolds number, the higher the nanofluids concentration the better the heat transfer characteristics, but there is no linear relationship between the enhancement amplitude and concentration; the heat transfer coefficient of nanofluid with 1% and 2% alumina nanoparticles concentration is about 5.86% and 8.49% higher than that of deionized water, respectively; the axial conduction effect cannot be ignored for the microchannel, which significantly affects the inlet and outlet region of the microchannel especially when the Reynolds number is low. The nanofluilds temperature in the microchannel increases with the curve and does not match the conventional linear growth hypothesis.

Fluid flow and heat transfer of nanofluids in microchannel heat sink with V-type inlet/outlet arrangement

The fluid flow and heat transfer characteristics of laminar nanofluid flow in microchannel heat sink (MCHS) with V-Type inlet/outlet arrangement are numerically studied. A constant heat flux boundary condition is applied on the base plate of MCHS and all the other surfaces of MCHS are insulated. Four different kinds of nanofluids are utilized as working fluids which are SiO2, Al2O3, ZnO and CuO dispersed in pure water as a base fluid. Three different volume fractions of 1%, 1.5% and 2% and three distinctive nanoparticle diameters of 30nm, 40nm and 60nm were employed. The results specify that the SiO2 nanofluid has the uppermost heat transfer rate compared to other tested nanofluids. Increasing the nanoparticles volume fraction together with decreasing the nanoparticles diameter enhances the Nusselt number value. The pressure drop coefficient did not change significantly by using nanofluid with various volume fractions and varied nanoparticle diameters. Moreover, the results indicate that nanofluid can enhance the performance of MCHS with V-shaped inlet/outlet arrangement.