Thermal Performance and Pressure Drop of Galinstan-Based Microchannel Heat-Sink for High Heat-Flux Thermal Management

2015 ◽  
Author(s):  
Yoshikazu Hayashi ◽  
Navid Saneie ◽  
Yoon Jo Kim ◽  
Jong-Hoon Kim
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Specific Heat ◽  
Thermal Management ◽  
Heat Sink ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Pumping Power

We numerically investigated a novel galinstan-based microfluidic heat-sink. Galinstan is an eutectic alloys of gallium, indium, and tin. The thermal conductivity of galinstan is ∼27 times that of water, while the dynamic viscosity is only twice of water. Thus, heat transfer coefficient can be remarkably enhanced with a small penalty of pumping power. However, the specific heat of galinstan is significantly lower than that of water, which will inevitably undermine the cooling capability by increasing fluid outlet temperature (i.e., increase of caloric thermal management) and/or flow rate. As an alternative, therefore, galinstan/water heterogeneous mixture was proposed as a working fluid and the cooling performance was numerically explored with varying volume composition of galinstan. Effective medium theory for heterogeneous medium was used to evaluate the thermal conductivity of the mixture. The viscosity change with respect to the volume composition was also predicted considering both the viscosity of dispersed phase and interaction between the droplets. Classical models were used for the mixture density and specific heat calculations. Heat transfer and pressure drop characteristics of laminar flow through a silicon microchannel heat-sink was simulated using Fluent. The length and width of the channel array are 10 mm and 9.5 mm, respectively. The cross-sectional area of each channel is 300 μm × 300 μm and the spacing between channels is 100 μm. The heat dissipation was 50 W and the pumping power was fixed at 5 mW for the comparison between the varying galinstan/water compositions. The results showed that more than 30% of the thermal resistance enhancement was attainable using the novel working fluid. Due to the compromise between the convective thermal resistance (effect of thermal conductivity) and the caloric thermal resistance (effect of viscosity and specific heat), the lowest junction temperature was marked at the galinstan composition of ∼35% by volume.

Metallic Nanoemulsion for Microchannel Heat-Sink

2016 ◽  
Author(s):  
Yoshikazu Hayashi ◽  
Gordon Yip ◽  
Yoon Jo Kim ◽  
Jong-Hoon Kim
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Specific Heat ◽  
Heat Sink ◽  
Effective Medium Theory ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Viscosity Change ◽  
Transfer Capability ◽  
Heat Transfer Capability

Galinstan is a eutectic alloy of gallium, indium, and tin, of which thermal conductivity is ∼27 times higher than that of water, while the dynamic viscosity is only twice. Thus, heat transfer coefficient can be remarkably enhanced with a small penalty of pumping power. However, the direct use of galinstan can suffer from practical issues such as oxidation and low specific heat. Therefore, galinstan is mixed with a coolant as an additive to form a colloidal fluid; i.e., dispersion of nanoscale galinstan droplets in a coolant to enhance the thermal conductivity. It is expected that this “metallic nanoemulsion” can contribute to substantial improvement in heat transfer capability. Also, the common issues with colloidal fluids such as rapid sedimentation, erosion, and clogging, can be minimized by the “fluidity” of the liquid metal. It was shown that ultrasonic emulsification can yield few hundreds scale nanodroplets. However, the long exposure of galinstan to oxygen in water inevitably results in severe oxidation of the droplets. Theoretical analysis was also conducted to examine the feasibility of the metallic nanoemulsion as a microchannel heat-sink working fluid. Effective medium theory was used to evaluate the thermal conductivity of the mixture. The viscosity change was also predicted considering both the viscosity of dispersed phase and interaction between the droplets. Under one-dimensional laminar flow assumption, mass, momentum, and energy conservation equations were analytically solved. The effect of high thermal conductivity of galinstan was evident; the convection heat transfer capability was greatly enhanced, while the viscosity increase due to the nanoscale blending and the low specific heat of galinstan counteracts and reduce the flow rate and thus increase the caloric thermal resistance.

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.

Thermo-Fluidic Characteristics in a Cross-Linked Silicon Microchannel Heat Sink

2007 ◽  
Author(s):  
R. Muwanga ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Sections ◽  
Heat Sink ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Significant Difference ◽  
The Cross

This paper presents the flow and heat transfer characteristics in a cross-linked silicon microchannel heat sink. The heat sink is composed of 45 channels, 270 μm wide × 285 μm tall in a silicon substrate formed via deep reactive ion etching. A detailed discussion of the pressure drop data reduction is described, including characterization of the channel cross-sections and methods to account for inlet and exit loss coefficients. No significant difference is observed in the pressure drop measurements between the cross-linked and standard heat sinks flowing air and water. The use of un-encapsulated liquid crystal thermography was successfully utilized to obtain local heat transfer data with FC-72 as the working fluid. The heat transfer results show inflections in the thermal profile due to the cross-links.

Hot-Spot Thermal Management With Flow Modulation in a Microchannel Heat Sink

2005 ◽  
Author(s):  
Poh-Seng Lee ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Management ◽  
Heat Sink ◽  
Hot Spot ◽  
Microchannel Heat Sink ◽  
Transfer Enhancement ◽  
Local Enhancement ◽  
Flow Modulation ◽  
Flow And Heat Transfer

Recesses created in the lid of a microchannel heat sink can serve to modulate the flow, resulting in local and global heat transfer enhancement. Numerical analysis of laminar flow and heat transfer in such a modified microchannel heat sink has shown an augmentation of heat transfer without an added penalty of increased pressure drop. The presence of the recesses reduces the overall flow friction and thus pressure drop. The flow expansion into the recesses and the subsequent contraction into the downstream region causes significant local enhancement in heat transfer. Both the maximum and average wall temperatures are decreased as a result. The heat transfer is locally enhanced, by as much as 150% in the regions just downstream of the recesses due to the re-initialization of boundary layers as the flow re-enters the microchannels. The potential for hot-spot mitigation in microelectronics devices using this approach is discussed.

Microchannel Heat Sink for Thermal Management of Concentrated Photovoltaic Cells

2021 ◽  
Author(s):  
Dinumol Varghese ◽  
Ahmed Sefelnasr ◽  
Mohsen Sherif ◽  
Fadi Alnaimat ◽  
Bobby Mathew
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Management ◽  
Heat Sink ◽  
Stokes Equations ◽  
Photovoltaic Cells ◽  
Navier Stokes ◽  
Microchannel Heat Sink ◽  
Pumping Power ◽  
Energy Equations

Abstract This article conceptualizes a single-phase microchannel heat sink for thermal management of concentrated photovoltaic cells; details of the model-based parametric study that is carried out on the heat sink is also detailed in this article. The heat sink consists of multiple serpentine microchannels. The mathematical model consists of continuity equation, Navier-Stokes equations and energy equations. Fluent module of Ansys Workbench is used for solving the model. The performance of the device is quantified in terms two metrics such as thermal resistance and pumping power. Studies are done for Reynolds number ranging from 100 to 1250. It is observed that increase in Reynolds number decreases the thermal resistance while increasing the pumping power irrespective of the geometric parameters of the heat sink. Decrease in hydraulic diameter of the microchannel reduces the thermal resistance while increasing the pumping power. Increase in the length segment of the serpentine microchannel increases and decreases the thermal resistance and pumping power, respectively. With increase in the offset width of the serpentine microchannel the thermal resistance and pumping power decreases and increases, respectively.

THERMAL AND HYDRODYNAMIC PERFORMANCE OF A MICROCHANNEL HEAT SINK COOLED WITH CARBON NANOTUBES NANOFLUID

2016 ◽  
Vol 78 (10-2) ◽  
Author(s):  
Nik Ahmad Faiz Nik Mazlam ◽  
Normah Mohd-Ghazali ◽  
Thierry Mare ◽  
Patrice Estelle ◽  
Salma Halelfadl
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
Operating Temperature ◽  
Heat Removal ◽  
Hydrodynamic Performance ◽  
Spherical Particles ◽  
Microchannel Heat Sink ◽  
Pumping Power ◽  
Rectangular Microchannel ◽  
Aspect Ratios

The microchannel heat sink (MCHS) has been established as an effective heat removal system in electronic chip packaging. With increasing power demand, research has advanced beyond the conventional coolants of air and water towards nanofluids with their enhanced heat transfer capabilities. This research had been carried out on the optimization of the thermal and hydrodynamic performance of a rectangular microchannel heat sink (MCHS) cooled with carbon nanotube (CNT) nanofluid, a coolant that has recently been discovered with improved thermal conductivity. Unlike the common nanofluids with spherical particles, nanotubes generally come in cylindrical structure characterized with different aspect ratios. A volume concentration of 0.1% of the CNT nanofluid is used here; the nanotubes have an average diameter and length of 9.2 nm and 1.5 mm respectively. The nanofluid has a density of 1800 kg/m3 with carbon purity 90% by weight having lignin as the surfactant. The approach used for the optimization process is based on the thermal resistance model and it is analyzed by using the non-dominated sorting multi-objective genetic algorithm. Optimized outcomes include the channel aspect ratio and the channel wall ratio at the optimal values of thermal resistance and pumping power. The optimized results show that, at high operating temperature of 40°C the use of CNT nanofluid reduces the total thermal resistance by 3% compared to at 20°C and consequently improve the thermal performance of the fluid. In terms of the hydrodynamic performance, the pumping power is also being reduced significantly by 35% at 40°C compared to the lower operating temperature.  

Heat Transfer and Pressure Drop in a Pin Fin Heat Sink Using Nanofluids as Coolant

2015 ◽  
Vol 1105 ◽  
pp. 253-258 ◽  
Author(s):  
Weerapun Duangthongsuk ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Electric Heater ◽  
Uniform Heat Flux ◽  
Heat Transfer Area ◽  
Pin Fin ◽  
Aluminum Material

This research presents an experimental investigation on the heat transfer performance and pressure drop characteristics of a heat sink with miniature square pin fin structure using nanofluids as coolant. ZnO-water nanofluids with particle concentrations of 0.2, 0.4 and 0.6 vol.% are used as working fluid and then compared with the data for water-cooled heat sink. Heat sink made from aluminum material with dimension around 28 x 33 x 25 mm (width x length x thickness). The heat transfer area and hydraulic diameter of the each flow channel is designed at 1,565 mm2and 1.2 mm respectively. Uniform heat flux at the bottom of heat sink is achieved using an electric heater. The experimental data illustrate that the thermal performance of heat sink using nanofluids as coolant is average 14% higher than that of the water-cooled heat sink. For pressure drop, the data show that the pressure drop of nanofluids is a few percent larger than that of the water-cooled heat sink.

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.

Sign in / Sign up

Export Citation Format

Share Document