scholarly journals Numerical Study of Heat Transfer Characteristics of Laminar Nanofluids Flow in Oblique Finned Microchannel Heat Sink: Effects of Different Base Fluids and Volume Fraction of Nanoparticles

2020 ◽  
Vol 76 (3) ◽  
pp. 25-37
Author(s):  
Choong Ji Ying ◽  
Yu Kok Hwa ◽  
Mohd Zulkifly Abdullah
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Volume Fraction ◽  
Numerical Study ◽  
Microchannel Heat Sink ◽  
Turbine Oil ◽  
The Heat Transfer Coefficient

This paper demonstrates a numerical study of heat transfer characteristics of laminar flow in oblique finned microchannel heat sink using nanofluid with nanoparticles added to various base fluids including water, ethylene glycol and turbine oil as coolant fluid. The width of the primary channel was 0.5 mm and the secondary channel was less than 0.15 mm in the oblique finned microchannel heat sink with an aspect ratio of 3. ANSYS Fluent was employed to model the flow in the geometry of microchannel. Single phase model and constant heat flux boundary condition were used in this numerical study. The modeling was validated by comparing the published data for conventional and enhanced microchannel heat sink. The base fluid acted as a comparison baseline to the nanofluid with volume fraction of 1.0% and 4.0%. Besides, the study was carried out in laminar flow regime, whereby the Reynold number ranged between 320 to 700. It was found that turbine oil based nanofluid had the highest Nusselt number among all fluids, followed by ethylene glycol and water to be the least. However, the heat transfer coefficient among all fluids were contrary to the Nusselt number where water achieved the highest heat transfer coefficient. The addition of nanoparticles increased the heat transfer coefficient of all fluids but it did not enhance their Nusselt number except water.

The effect of viscous dissipation on laminar nanofluid flow in a microchannel heat sink

2009 ◽  
Vol 223 (11) ◽  
pp. 2697-2706 ◽  
Author(s):  
M Ghazvini ◽  
M A Akhavan-Behabadi ◽  
M Esmaeili
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Viscous Dissipation ◽  
Heat Sink ◽  
Volume Fraction ◽  
Numerical Study ◽  
Microchannel Heat Sink ◽  
Fluid Temperature ◽  
Nanofluid Flow ◽  
Aspect Ratios

The present article focuses on analytical and numerical study on the effect of viscous dissipation when nanofluid is used as the coolant in a microchannel heat sink (MCHS). The nanofluid is made from CuO nanoparticles and water. To analyse the MCHS, a modified Darcy equation for the fluid and two-equation model for heat transfer between fluid and solid sections are employed in porous media approach. In addition, to deal with nanofluid heat transfer, a model based on the Brownian motion of nanoparticles is used. The model evaluates the thermal conductivity of nanofluid considering the thermal boundary resistance, nanoparticle diameter, volume fraction, and the fluid temperature. At first, the effects of particle volume fraction on temperature distribution and overall heat transfer coefficient are investigated with and without considering viscous dissipation. After that, the influence of different channel aspect ratios and porosities is studied. The results show that for nanofluid flow in microchannels, the viscous dissipation can be neglected for low volume fractions and aspect ratios only. Finally, the effect of porosity and Brinkman number on the overall Nusselt number is studied, where asymptotic behaviour of the Nusselt number is observed and discussed from the energy balance point of view.

Estimation of the Heat Transfer Coefficient of a Microchannel Heat Sink Using an Optimal Control Technique

2006 ◽  
Author(s):  
Florentina Simionescu ◽  
Daniel K. Harris
Keyword(s):  
Heat Transfer ◽  
Optimal Control ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Convective Heat Transfer Coefficient ◽  
Control Technique ◽  
Microchannel Heat Sink ◽  
Convective Boundary ◽  
The Heat Transfer Coefficient

Cooling of electronic devices requires the use of heat spreaders whose function is to allow the spreading of the heat flux lines in the 3-D space and to increase the exchange area with the coolant. The objective of this analysis is to estimate the convective heat transfer coefficient of a microchannel heat sink that corresponds to a maximum amount of heat removed from heat source placed on the top surface of the sink. This problem is solved using an optimal control technique in which we control the solution of the heat equation with the convective boundary condition, taking the heat transfer coefficient as the control. A conjugate gradient method is used to solve the optimal control problem. The results show that the temperature distributions corresponding to the controlled solution are lower than those corresponding to the uncontrolled solution. This study can provide guidance in designing micro heat pipe sinks, which have emerged as an effective technique for cooling electronic components.

Cooling Performance of Nanofluids in a Microchannel Heat Sink

2009 ◽  
Author(s):  
Y. Wang ◽  
S. J. Chung ◽  
J. P. Leonard ◽  
S. K. Cho ◽  
T. Phuoc ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Bottom Surface ◽  
Microchannel Heat Sink ◽  
Zno Nanoparticle ◽  
Microfabrication Technology ◽  
The Heat Transfer Coefficient

This paper describes an experimental study on microchannel heat sink performance where ZnO nanoparticle suspended fluids are used as coolant. The microchannel heat sink has 65 parallel microchannels branched out from an inlet reservoir and then collected into an outlet reservoir. Its fabrication process is based on the standard photolithographic microfabrication technology. A main feature of the heat sink has an array of on-chip temperature sensors on the channel bottom surface along the channel. Thus, the channel wall temperatures are directly measured. Heat transfer coefficient for the nanofluid is measured and compared with that of DI water as reference. The experiments show that the heat transfer coefficient of the ZnO nanofluid is 13% higher than that of the base fluid at the Reynolds number of 3.8, although it is comparable with that of DI water at lower Re numbers. The experiments also show that the heat transfer coefficient as well as the Nusselt number increases as the Reynolds number increases.

Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

2008 ◽  
Author(s):  
Ayman Megahed ◽  
Ibrahim Hassan ◽  
Tariq Ahmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Microchannel Heat Sink

The present study focuses on the experimental investigation of boiling heat transfer characteristics and pressure drop in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 295 μm, width of 254 μm, and a length of 16 mm. Un-encapsulated Thermochromic liquid Crystals (TLC) are used in the present work to enable nonintrusive and high spatial resolution temperature measurements. This measuring technique is used to provide accurate full and local surface-temperature and heat transfer coefficient measurements. Experiments are carried out for mass velocities ranging between 290 to 457 kg/m2.s and heat fluxes from 6.04 to 13.06 W/cm2 using FC-72 as the working fluid. Experimental results show that the pressure drop increases as the exit quality and the flow rate increase. High values of heat transfer coefficient can be obtained at low exit quality (xe < 0.2). However, the heat transfer coefficient decreases sharply and remains almost constant as the quality increases for an exit quality higher than 0.2.

scholarly journals Numerical analysis of heat transfer enhancement with the use of γ-Al2O3/water nanofluid and longitudinal ribs in a curved duct

2012 ◽  
Vol 16 (2) ◽  
pp. 469-480 ◽  
Author(s):  
Hosseinali Soltanipour ◽  
Parisa Choupani ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Base Fluid ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Transfer Enhancement ◽  
Dean Number ◽  
Particle Volume ◽  
The Heat Transfer Coefficient

This paper presents a numerical investigation of heat transfer augmentation using internal longitudinal ribs and ?-Al2O3/ water nanofluid in a stationary curved square duct. The flow is assumed 3D, steady, laminar, and incompressible with constant properties. Computations have been done by solving Navier-Stokes and energy equations utilizing finite volume method. Water has been selected as the base fluid and thermo- physical properties of ?- Al2o3/ water nanofluid have been calculated using available correlations in the literature. The effects of Dean number, rib size and particle volume fraction on the heat transfer coefficient and pressure drop have been examined. Results show that nanoparticles can increase the heat transfer coefficient considerably. For any fixed Dean number, relative heat transfer rate (The ratio of the heat transfer coefficient in case the of ?- Al2o3/ water nanofluid to the base fluid) increases as the particle volume fraction increases; however, the addition of nanoparticle to the base fluid is more useful for low Dean numbers. In the case of water flow, results indicate that the ratio of heat transfer rate of ribbed duct to smooth duct is nearly independent of Dean number. Noticeable heat transfer enhancement, compared to water flow in smooth duct, can be achieved when ?-Al2O3/ water nanofluid is used as the working fluid in ribbed duct.

Optimization Under Uncertainty of Manifold Microchannel Heat Sinks

2012 ◽  
Author(s):  
Suchismita Sarangi ◽  
Karthik K. Bodla ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Sinks ◽  
Optimization Under Uncertainty ◽  
Microchannel Heat Sink ◽  
Probabilistic Optimization ◽  
Manifold Microchannel

Conventional microchannel heat sinks provide good heat dissipation capability but are associated with high pressure drop and corresponding pumping power. The use of a manifold system that distributes the flow into the microchannels through multiple, alternating inlet and outlet pairs is investigated here. This manifold arrangement greatly reduces the pressure drop incurred due to the smaller flow paths, while simultaneously increasing the heat transfer coefficient by tripping the thermal boundary layers. A three-dimensional numerical model is developed and validated, to study the effect of various geometric parameters on the performance of the manifold microchannel heat sink. Apart from a deterministic analysis, a probabilistic optimization study is also performed. In the presence of uncertainties in the geometric and operating parameters of the system, this probabilistic optimization approach yields an optimal design that is also robust and reliable. Uncertainty-based optimization also yields auxiliary information regarding local and global sensitivities and helps identify the input parameters to which outputs are most sensitive. This information can be used to design improved experiments targeted at the most sensitive inputs. Optimization under uncertainty also provides a quantitative estimate of the allowable uncertainty in input parameters for an acceptable uncertainty in the relevant output parameters. The optimal geometric design parameters with uncertainties that maximize heat transfer coefficient while minimizing pressure drop for fixed input conditions are identified for a manifold microchannel heat sink. A comparison between the deterministic and probabilistic optimization results is also presented.

Numerical Study of Forced Convection of Nanofluids in a Microchannel Heat Sink

2008 ◽  
Author(s):  
Parisa Vaziee ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Volume Fraction ◽  
Numerical Study ◽  
Heat Removal ◽  
Al2o3 Nanoparticles ◽  
Microchannel Heat Sink ◽  
Particle Volume ◽  
Volume Fractions

Effectiveness of the microchannel heat sink cooled by nanofluids with various particle volume fractions is investigated numerically using the latest theoretical models for conductivity and viscosity of the nanofluids. Both laminar and turbulent flows are considered in this research. The model of conductivity used in this research accounts for the fundamental role of Brownian motion of the nanoparticles which is in good agreement with the experimental data. The changes in viscosity of the nanofluid due to temperature variation are considered also. Final results are compared with the experimental measurements for heat transfer coefficient and pressure drop in microchannel. Enhancement in heat transfer is achieved for laminar flow with increasing of volume fraction of Al2O3 nanoparticles. But for turbulent flow an enhancement of heat removal was not seen and using higher volume fractions of nanoparticles increases the maximum substrate temperature. Pressure drop is increased with using nanofluids because of the augmentation in the viscosity and this increase is more noticeable in higher Reynolds numbers.

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