Trapezoidal Microchannel Heat Sink Research Articles

The Effect of Geometric Parameters on Flow and Heat Transfer Characteristics of a Double-Layer Microchannel Heat Sink for High-Power Diode Laser.

The effect of the geometric parameters on the flow and heat transfer characteristics of a double-layer U-shape microchannel heat sink (DL-MCHS) for a high-power diode laser was investigated in this work. FLUENT 19.2 based on the finite volume method was employed to analyze the flow and heat transfer performance of DL-MCHS. A single variable approach was used to fully research the impact of different parameters (the number of channels, the channel cross-sectional shape, and the aspect ratio) on the temperature distribution, pressure drop, and thermal resistance of the DL-MCHS. The rectangular DL-MCHS heat transfer performance and pressure drop significantly increased with the rise in the channel's aspect ratio due to there being a larger wet perimeter and convective heat transfer area. By comparing the thermal resistance of the DL-MCHS at the same power consumption, it was found that the rectangular DL-MCHS with an aspect ratio in the range of 5.1180-6.389 had the best overall performance. With the same cross-sectional area and hydraulic diameter (AC = 0.36 mm, Dh = 0.417 mm), the thermal resistance of the trapezoidal microchannel heat sink was 32.14% and 42.42% lower than that of the triangular and rectangular ones, respectively, under the condition that the pumping power (Wpp) was 0.2 W. Additionally, the thermal resistance was reduced with the increment of the number of channels inside the DL-MCHS, but this would induce an increased pressure drop. Thus, the channel number has an optimal range, which is between 50 and 80 for the heat sinks in this study. Our study served as a simulation foundation for the semiconductor laser double-layer U-shaped MCHS optimization method using geometric parameters.

Effect of transverse and parallel magnetic fields on thermal and thermo-hydraulic performances of ferro-nanofluid flow in trapezoidal microchannel heat sink

Purpose This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under uniform heat flux and magnetic fields. Design/methodology/approach To investigate the effect of direction of Lorentz force the magnetic field has been applied: transversely in the x direction (Case I);transversely in the y direction (Case II); and parallel in the z direction (Case III). The three-dimensional governing equations with the associated boundary conditions for ferro-nanofluid flow and heat transfer have been solved by using an element-based finite volume method. The coupled algorithm has been used to solve the velocity and pressure fields. The convergence is reached when the accuracy of solutions attains 10–6 for the continuity and momentum equations and 10–9 for the energy equation. Findings According to thermal indicators the Case III has the best performance, but according to performance evaluation criterion (PEC) the Case II is the best. The simulation results show by increasing the Hartmann number from 0 to 12, there is an increase for PEC between 845.01% and 2997.39%, for thermal resistance between 155.91% and 262.35% and ratio of the maximum electronic chip temperature difference to heat flux between 155.16% and 289.59%. Also, the best thermo-hydraulic performance occurs at Hartmann number of 12, pressure drop of 10 kPa and volume fraction of 2%. Research limitations/implications The embedded electronic chip on the base plate generates heat flux of 60 kW/m2. Simulations have been performed for ferro-nanofluid with volume fractions of 1%, 2% and 3%, pressure drops of 10, 20 and 30 kPa and Hartmann numbers of 0, 3, 6, 9 and 12. Practical implications The authors obtained interesting results, which can be used as a design tool for magnetohydrodynamics micro pumps, microelectronic devices, micro heat exchanger and micro scale cooling systems. Originality/value Review of the literature indicated that there has been no study on the effects of magnetic field on thermal and thermo-hydraulic performances of ferro-nanofluid flow in a TMCHS, so far. In this three dimensional study, flow of ferro-nanofluid through a trapezoidal heat sink with five trapezoidal microchannels has been considered. In all of previous studies, in which the effect of magnetic field has been investigated, the magnetic field has been applied only in one direction. So as another innovation of the present research, the effect of applying magnetic field direction (transverse and parallel) on thermo-hydraulic behavior of TMCHS is investigated.

Numerical studies on the hydraulic and thermal performances of trapezoidal microchannel heat sink

The present work numerically studies the hydraulic and thermal performances of trapezoidal microchannel heat sink (TMCHS) with rectangular cross-sectional shape under the constant total channel volume. Considering the flow direction, channel arrangement direction and inlet location, TMCHSs with six different configurations are proposed to compare their hydraulic and thermal performances. The results demonstrate that the pressure drop of the six THCHSs always increases with the decreasing small-to-large end width ratio. For the thermal performance, only the two TMCHSs with Parallel Channel Parallel Flow Large Inlet (PCPFLI) and Reverse Channel Counter Flow Large Inlet (RCCFLI) configurations have improved thermal performances with the decreasing small-to-large end width ratio, including decreasing maximum temperature, decreasing thermal resistance and decreasing center zone temperature difference. On the basis of these, the effects of the channel height and inlet flowrate on the thermal performances of TMCHSs with PCPFLI and PCPFLI configurations are further studied. It is found that PCPFLI and RCCFLI configurations have lower thermal resistance and more uniform temperature distribution with increasing channel height and inlet flowrate. The TMCHS with RCCFLI configuration has the best thermal performances among the six TMCHSs. The findings reported in present work provide a simple method to improve the thermal performances of MCHS by changing the channel shape and configurations.

Numerical analysis on thermal performance of a trapezoidal micro-channel heat sink using an improved version of the augmented ε-constraint method

This work proposes the use of an improved version of the augmented ε-constraint method (AUGMENCON2) for the analysis of the thermal performance of a micro-channel heat sink. In order to highlight the strength and the effectiveness of this new approach, a trapezoidal micro-channel heat sink has been considered. The geometrical configuration namely the micro-channel widths and depth are the main variables considered in this study. Surrogate models based on the response surface methodology have been adopted to approximate the thermal resistance and the pumping power which provide an indication of the thermal performance of the micro-channel heat sink. A two-objective nonlinear problem have been formulated and implemented within the general algebraic modelling system. Global Pareto optimal solutions have been computed using the proposed method. Despite being a relatively straightforward method, the AUGMENCON2 provides a reasonable level of accuracy and shortens the required computational time in comparison to two existing approaches.

Numerical analysis on thermal performance of a trapezoidal micro-channel heat sink using an improved version of the augmented ε-constraint method

This work proposes the use of an improved version of the augmented e-constraint method (AUGMENCON2) for the analysis of the thermal performance of a micro-channel heat sink. In order to highlight the strength and the effectiveness of this new approach, a trapezoidal micro-channel heat sink has been considered. The geometrical configuration namely the micro-channel widths and depth are the main variables considered in this study. Surrogate models based on the response surface methodology have been adopted to approximate the thermal resistance and the pumping power which provide an indication of the thermal performance of the micro-channel heat sink. A two-objective nonlinear problem have been formulated and implemented within the general algebraic modelling system. Global Pareto optimal solutions have been computed using the proposed method. Despite being a relatively straightforward method, the AUGMENCON2 provides a reasonable level of accuracy and shortens the required computational time in comparison to two existing approaches.

Influence of Geometry and Magnetic Field on Convective Flow of Nanofluids in Trapezoidal Microchannel Heat Sink

The objective of the numerical study is to explore the effects of transverse magnetic field on heat transfer and fluid flow characteristics in a trapezoidal microchannel heat sink. The effects of the channel bottom width, channel top width, channel height and Hartmann number on heat transfer and fluid flow characteristics are widely investigated. In addition, effects of nanoparticles type (Al2O3, SiO2, CuO, ZnO), base fluid type (water and ethylene glycol) and its concentration (0–4%) under the influence of magnetic field are also investigated. The governing equations for three-dimensional steady, laminar flow and conjugate heat transfer of a microchannel are solved using the finite volume method. The acquired results are discussed in detail. The results reveal that the magnetic field can increase the thermal performance.

Performance Evaluation of a Trapezoidal Microchannel Heat Sink with Various Entry/Exit Configurations Utilizing Variable Properties

Most of numerical studies on microchannel heat sinks (MCHS) performed up to now are for a two-dimensional domain using constant properties of the coolant and solid part. In this study, laminar fluid flow and heat transfer of variable properties water in a trapezoidal MCHS, consisted of five trapezoidal microchannels, are studied. The three dimensional solution domains include both the flow field and the complete MCHS silicon made solid parts with variable conductivity. Four entry/exit configurations and three pressure drops of 5, 10 and 15 kPa are assumed. The results indicate that the A-type heat sink, for which the entry and exit are placed horizontally at the center of the north and the south walls, has a better heat transfer performance, smaller thermal resistance and provides more uniform solid temperature distribution. For pressure drop of 15 kPa, temperature-dependent properties of water increases the heat transfer between 2.73% and 3.33%, decreases the thermal resistance between 3.46% and 5.55 % and decreases the ratio of difference between the maximum and minimum substrate temperatures to the heat flux, θ, between 3.42% and 11.15%. Also by assuming temperature-dependent conductivity of silicon, the heat transfer increases between 0.75% and 2.58%, the thermal resistance decreases between 1.15% and 4.97 % and θ decreases between 2.41% and 6.49%.

Optimization of thermal performance of multi-nozzle trapezoidal microchannel heat sinks by using nanofluids of Al2O3 and TiO2

In this study, a new multi-nozzle trapezoidal microchannel heat sink (MNT-MCHS) was proposed. Five substrate materials, two nanofluids with nanoparticle volume fractions, 0.1% ≤ φ ≤ 1%, and channel hydraulic diameters, 157.7 µm ≤ Dh ≤ 248.2 µm, were numerically examined in detail. In addition, heat fluxes in the range of 100–1450 W/cm2 subject to inlet coolant temperature from 15 °C to 75 °C were examined in detail. A locally optimal MNT-MCHS was defined, and a novel equation was proposed for predicting the maximum temperature on the locally optimal MNT-MCHS depending on the heat flux, coolant inlet temperature, and the Reynolds number. It was found that at a Reynolds number of 900, the overall thermal resistance of a MNT-MCHS using copper as a substrate material is improved up to 76% as compared to that using stainless steel 304. The locally optimal MNT-MCHS, using TiO2-water nanofluid with φ=1%, could dissipate a heat flux up to 1450 W/cm2 at a Re of 900. A minimum thermal resistance in the present study is improved up to 11.6% and 36.6% in association with those of a multi-nozzle MCHS and a double-layer MCHS, respectively.

Numerical investigation of nanofluid heat transfer inside trapezoidal microchannels using a novel dispersion model

In the present work, steady state, laminar, hydrodynamically and thermally developing flow in a trapezoidal microchannel heat sink (MCHS) is investigated. Navier–Stokes equations are solved using finite volume method. A new correlation for the dispersion model is suggested to explain the heat transfer enhancement of nanofluids. Two kinds of nanofluids, Al2O3–water and CuO–water were considered and the results were validated using open literature data. It is shown that the proposed correlation gives the best result among other models. Furthermore, the effects of nanoparticle size and volume fraction on heat transfer are evaluated. The results show that the average Nusselt number increases rapidly with decrease of diameter of nanoparticles, but increasing nanoparticle size more than 60nm does not affect heat transfer considerably. Moreover, when the Reynolds number is low, adding more nanoparticles increases heat transfer slightly, so using nanofluid in applications where the Reynolds number is not commonly high (e.g. in microchannel fluid flow) sounds ineffective.

Numerical Optimization for Nanofluid Flow in Microchannels Using Entropy Generation Minimization

This study presents the numerical simulation of the three-dimensional incompressible steady and laminar fluid flow of a trapezoidal microchannel heat sink using nanofluids as a cooling fluid. Navier–Stokes equations with a conjugate energy equation are discretized by the finite-volume method. Numerical computations are performed for inlet velocity (W in = 4 m/s, 6 m/s, and 10 m/s), hydraulic diameter D h = 106.66 μm, and heat flux (q″ = 200 kW/m2. Numerical optimization is demonstrated as a trapezoidal microchannel heat sink design which uses the combination of a full factorial design and the genetic algorithm method. Three optimal design variables represent the ratio of upper width and lower width of the microchannel (1.2 ≤ α ≤ 3.6), the ratio of the height of the microchannel to the difference between the upper and lower width of the microchannel (0.5 ≤ β ≤ 1.866), and the volume fraction (0 ≤ φ ≤ 4%). The dimensionless entropy generation rate of a trapezoidal microchannel is minimized for fixed heat flux and inlet velocity. Numerical results for the system dimensionless entropy generation rate show that the system dimensionless friction entropy generation rate increases with Reynolds number; on the contrary, the higher the Reynolds number, the lower the system dimensionless thermal entropy generation rate. The results below show that the two-phase model gives higher enhancement than the single-phase model assuming a steadily developing laminar flow.

Investigating the effect of Brownian motion and viscous dissipation on the nanofluid heat transfer in a trapezoidal microchannel heat sink

In the present study, laminar forced convection of copper-oxide nanofluid in a trapezoidal microchannel-heat-sink (MCHS) is studied using the Eulerian–Eulerian two-phase approach. The incompressible, three dimensional and steady state conservation equations are solved using finite volume method. The substrate material is assumed to be silicon, mean diameter of spherical nanoparticles are considered 100nm and in the 1–4% volume concentration range. The effects of viscous dissipation, Brownian motion and geometry change on thermal performance of MCHS are evaluated. It is observed that the Brownian motion depends on three parameters, namely, nanofluid inlet temperature, nanoparticles diameter and volume fraction. Also, it is found that with the increase in aspect factor at constant Re, average Nusselt number and pressure drop reduce, while at a specified length of MCHS, average Nusselt number decreases. Finally, it is shown that considering the viscous dissipation, pressure drop varies very slowly, while with the increase in nanoparticles volume fraction and therefore increase in viscous dissipation, heat transfer reduces non-linearly.

Numerical study of microchannel heat sink performance using nanofluids

This study presents the numerical simulation of three-dimensional incompressible steady and laminar and turbulent fluid flow of a trapezoidal micro-channel heat sink (MCHS) using CuO/water nanofluid as a cooling fluid. Navier–Stokes equations with conjugate energy equation are discretized by the finite-volume method. CFD predictions of laminar and turbulent forced convection of CuO/water nanofluids by single-phase and two-phase models (mixture model) are compared. The parameters studied include the particle volume fraction (ϕ=0.204%, 0.256%, 0.294% and 0.4%), and the volumetric flow rate (V˙=10mL/min, 15mL/min and 20mL/min). Comparisons of the thermal resistance predicted by the single-phase and two-phase models with corresponding experimental results show that the two-phase model is more accurate than the single-phase model. In the laminar flow, the thermal resistance of nanofluids is smaller than that of the water, which decreases as the particle volume fraction and the volumetric flow rate increase. In addition, the pressure drop of both nanofluid-cooled MCHS and pure water-cooled MCHS is discussed. For the laminar flow case, the pressure drop increases slightly for nanofluid-cooled MCHS.

Trapezoidal Microchannel Heat Sink With Pressure-Driven and Electro-Osmotic Flows for Microelectronic Cooling

Thermal performances of the trapezoidal microchannel heat sink (MCHS) with pure pressure driven flow (PDF), pure electro-osmotic flow (EOF) and combined flow have been investigated and compared, using the multiphysics software COMSOL. The feasibility and accuracy of the simulation scheme for the microchannel are carefully validated with available experimental and numerical results for both PDF and EOF. The effects of the electric potential and driving pressure on the performance of the MCHS have been studied under different conditions. The flow rate, thermal resistance, and Nusselt number are investigated to determine the characteristic behavior of the trapezoidal MCHS of various sidewall angles, height-width ratios, and hydraulic diameters.