scholarly journals Water cooled micro-hole cellular structure as a heat dissipation media: An experimental and numerical study

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 683-692 ◽  
Author(s):  
Hussain Tariq ◽  
Ahmad Shoukat ◽  
Muhammad Anwar ◽  
Asif Israr ◽  
Hafiz Ali
Keyword(s):  
Flow Rate ◽  
Cellular Structure ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Volumetric Flow Rate ◽  
Experimental Results ◽  
Heat Sinks ◽  
Base Temperature ◽  
Micro Hole ◽  
Alumina Nanofluid

Thermal performance of micro-hole cellular structure using water as a cool?ing fluid was investigated through CFD and then numerical results were validated with the experimental results. The minimum base temperature for the micro-hole cellular structure was found to be 29.7?C and 32.3?C numerically and experimentally, respectively, with volumetric flow rate of 0.000034 m3/s (2 Lpm) at a heating power of 345 W. Numerical values of the base temperature are in close agreement with experimental results with an error of 8.75%. Previously, the base temperatures of heat sinks using alumina nanofluid with 1% of volumetric concentration and water with volumetric flow rate of 0.000017 m3/s (1 Lpm) have been reported to be 43.9?C and 40.5?C, respectively.

Experimental Investigation of a PCM-Based Topology Optimized Heat Sink for Passive Cooling of Electronics

2020 ◽  
Author(s):  
Jin Yao Ho ◽  
Kai Choong Leong
Keyword(s):  
Thermal Performance ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Base Temperature ◽  
Storage Unit ◽  
Cooling Of Electronics

Abstract A thermal energy storage unit filled with phase change material (PCM) can serve as a heat sink for the cooling of electronics with intermittent or periodic heat dissipation rates. The use of thermal conductive structures (TCS) is an effective method of improving the thermal performance of a PCM-based heat sink. In this paper, topology optimization is explored to develop a new class of TCS with a tree-like structure to enhance the thermal performance of a trapezoidal heat sink. The topology-optimized heat sink was then fabricated by Selective Laser Melting (SLM) using an aluminum alloy, AlSi10Mg, as the base powder. Experiments were performed to evaluate the thermal performance of the topology-optimized heat sink with the tree-like structure. In addition, a conventional longitudinal-fin heat sink of the same solid volume fraction (φ = 16.2%) and a heat sink without enhanced structure were also fabricated and experimentally investigated for comparison. Rubitherm RT-35HC paraffin wax was used as the PCM. Three different heat fluxes of 4.00 kW/m2, 5.08 kW/m2 and 7.24 kW/m2 were applied at the base of each specimen by a silicone rubber heater. The structure wall and the PCM temperatures were measured over time. Our results show that, for all heat rates tested, the topology-optimized heat sink was able to maintain a lower base temperature as compared to the fin-structure and the plain heat sinks. A thermal enhancement ratio (ε) is defined to evaluate the performance of the heat sinks with and without the use of PCM. From the experimental results, the highest ε value of 8.6 was achieved by the topology-optimized heat sink. These results indicate the better performance of the topology-optimized heat sink in dissipating heat as compared to the other specimens.

scholarly journals Numerical study for heat transfer enhancement using CuO water nanofluids through mini-channel heat sinks for microprocessor cooling

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2965-2976 ◽  
Author(s):  
Muhammad Anwar ◽  
Hussain Tariq ◽  
Ahmad Shoukat ◽  
Hafiz Ali ◽  
Hassan Ali
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Numerical Study ◽  
Heat Removal ◽  
Maximum Flow ◽  
Heat Sinks ◽  
Base Temperature ◽  
Transfer Enhancement ◽  
Percentage Difference ◽  
Fin Spacing

Water cooled heat sinks are becoming popular due to increased heat generation inside the microprocessor. Timely heat removal from microprocessor is the key factor for better performance and long life. Heat transfer enhancement is reached either by increasing the surface area density and/or by altering the base fluid properties. Nanoparticles emerge as a strong candidate to increase the thermal conductivity of base fluids. In this research, the thermal performance of mini-channel heat sinks for different fin spacing (0.2 mm, 0.5 mm, 1 mm, and 1.5 mm) was investigated numerically using CuO-water nanofluids with volumetric concentration of 1.5%. The numerical values computed were than compared with the literature and a close agreement is achieved. We recorded the minimum base temperature of chip to be 36.8?C for 0.2 mm fin spacing heat sink. A reduction of 9.1% in base temperature was noticed using CuO-water nanofluids for 0.2 mm fin spacing as compared to previously experimental estimated value using water [1]. The drop percentage difference in pressure between water and CuO-water nanofluids was 2.2-13.1% for various fin spacing heat sinks. The percentage difference in thermal resistance between water and CuO-water nanofluids was computed 12.1% at maximum flow rate. We also observed uniform temperature distribution for all heat sinks.

A Novel Micropump for Electronics Cooling

2004 ◽  
Author(s):  
Vishal Singhal ◽  
Suresh V. Garimella
Keyword(s):  
Numerical Model ◽  
Charge Transport ◽  
Flow Rate ◽  
Electronics Cooling ◽  
Experimental Results ◽  
Heat Sinks ◽  
Flow Rates ◽  
Microchannel Heat Sinks ◽  
Combined Action

A novel micropump design for electronics cooling applications capable of integration into microchannel heat sinks is presented. The pumping action is due to the combined action of Coulomb forces due to induction electrohydrodynamics (EHD) and a vibrating diaphragm with nozzle-diffuser elements for flow rectification. A comprehensive numerical model of the micropump accounting for transient charge transport and vibrating diaphragm deformation is developed. Each component of the model is validated by comparing to analytical, numerical or experimental results from the literature. It is shown that the flow rate achieved by the micropump with combined action of EHD and vibrating diaphragm can be higher than the sum of flow rates achieved from the action of the EHD and the vibrating diaphragm, independent of each other.

Micromixing Efficiency in High Gravity Reactor with Different Packing

2011 ◽  
Vol 233-235 ◽  
pp. 1184-1187
Author(s):  
Jun Ji ◽  
Hong Song ◽  
Jiao Liu
Keyword(s):  
Flow Rate ◽  
Glass Bead ◽  
Volumetric Flow Rate ◽  
Experimental Results ◽  
High Gravity ◽  
Flow Ratio ◽  
Test Reaction ◽  
Segregation Index ◽  
Ratio Size ◽  
Better Than

Micromixing efficiency in the high gravity(Higee) reactor with glass bead, rasching ring and pall ring was investigated respectively by using iodide-iodate test reaction as working system. The experimental results showed that segregation index of the Higee reactor increases while increasing volumetric flow ratio, size of pall ring and decreases with the increase of rotating rate, volumetric flow rate. The Micromixing efficiency of the Higee reactor with pall ring is better than glass bead and rasching ring.

Numerical Study the Performance of Microfluidic Fuel Cell with Porous Electrodes

2013 ◽  
Vol 291-294 ◽  
pp. 585-588 ◽  
Author(s):  
Ming Feng Gao ◽  
Yu Xin Zuo ◽  
Ying Yu ◽  
Chun Cheng Zuo
Keyword(s):  
Fuel Cell ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Volumetric Flow Rate ◽  
Porous Electrodes ◽  
Cell Performance ◽  
Physical Factors ◽  
Concept Design ◽  
Microfluidic Fuel Cell

Microfluidic fuel cell with flow-through porous electrodes is a new concept design which can significantly improve cell performance. In this paper, a three-dimensional numerical model which is based on mathematical formulations of laminar flow, species transport, and electrochemical reactions was developed to determine the effects of some important physical factors on cell performance. Moreover, this model also can be used to guide further optimization. The numerical simulation results obtained show that the cell performance is considered as functions of volumetric flow rate and porosity value. The peak power density increased almost linearly with the increase of flow rate when it less than 60µL min-1 .However, as the flow rate up to 60µL min-1, the cell performance becomes less sensitive to the increase of flow rate, and the corresponding maximum fuel utilization was achieved at the porosity value of 0.65.

Comparative Analysis Between Water-Cooled and Air-Cooled Heat Dissipation in a High-Power Light-Emitting Diode Chipset

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Yuanlong Chen ◽  
Tingbo Hou ◽  
Minqiang Pan
Keyword(s):  
Thermal Conductivity ◽  
Flow Rate ◽  
High Power ◽  
Heat Dissipation ◽  
Volumetric Flow Rate ◽  
Critical Value ◽  
Input Power ◽  
Substrate Thickness ◽  
Light Emitting ◽  
High Power Led

With a substantial increase in thermal power density, the operating temperature of high-power light-emitting diodes (LEDs) rises rapidly, exerting a notable effect on chipsets’ performance. A water-cooled microchannel radiator and an air-cooled radiator are proposed to solve this problem. The effects of key factors of both radiators on heat dissipation in a high-power LED chipsets, and general comparisons between each method, are analyzed via Fluent. The simulation results indicate that heat dissipation from the water-cooled microchannel radiator is readily affected by the microchannel’s flow rate and aspect ratio. A larger flow rate and larger aspect ratio favor improved heat dissipation in the water-cooled microchannel radiator. Heat dissipation in the air-cooled radiator is related to volumetric flow rate, rib number, rib height, rib thickness, and substrate thickness. A larger volumetric flow rate, rib number, and rib height favor heat dissipation in the air-cooled radiator. However, there is a critical thickness value: if the thickness is less than the critical value, heat dissipation is greatly affected by rib thickness and substrate thickness, if the thickness is larger than the critical value, the influence is insignificant. The high-power LED chipsets’ temperature is also related to the insulating substrate’ input power and thermal conductivity. A large input power leads to a substantial increase in temperature, and larger thermal conductivity of the insulating substrate minimizes temperature increase in the high-power LED chipsets. When comparing the two radiators, results show an air-cooled radiator should be used in low-power LED chipsets. When an air-cooled radiator cannot satisfy the chipset’s needs, a water-cooled microchannel radiator should be utilized.

scholarly journals REGRESSION MODEL OF THE CLASSIFICATION PROCESS AT JET GRINDING

2019 ◽  
Vol 6 (125) ◽  
pp. 113-120
Author(s):  
Lev Muzyka ◽  
Nataliya Pryadko
Keyword(s):  
Control System ◽  
Regression Model ◽  
Flow Rate ◽  
Mutual Influence ◽  
Bulk Material ◽  
Volumetric Flow Rate ◽  
Experimental Results ◽  
Gas Jet ◽  
Closed Cycle ◽  
Technological Parameters

The aim of the work is creating a regression model of the material classifying process in a jet grinding plant based on the experimental results. The data of various bulk material grinding in a laboratory mill and in industrial conditions were used. The main technological parameters affecting the performance of the classifier are determined. On gas-jet installations a number of dependences of changes in the volumetric flow rate of the material at the outlet of the classifier from the volumetric flow rate of the material at the inlet of the classifier and from the speed of the classifier rotor were experimentally got. The magnitude of the influence of each adopted factor and their mutual influence on the performance of the classifier with the determination coefficient R = 0.88 – 0.95 are obtained. The regression dependences make it possible to improve the control system for the classification process of jet grinding in a closed cycle.

Numerical Study on Droplet Formation in a Microchannel T-Junction Using the VOF Method

2010 ◽  
Author(s):  
Shobeir Aliasghar Zadeh ◽  
Rolf Radespiel
Keyword(s):  
Surface Tension ◽  
Flow Rate ◽  
Capillary Number ◽  
Numerical Study ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Vof Method ◽  
Experimental Results ◽  
Glycerol Solution ◽  
Hexahedral Elements

The liquid-liquid two-phase flow in a T-junction was numerically investigated applying the VOF method and is compared with experimental results. The geometry was generated and meshed using the software Gridgen, and the corresponding equations for the CFD analysis were solved by using the commercial software Fluent (Fluent 12). The generated mesh consists of block-structured grids with hexahedral elements. Water-Glycerol solution (to-be-dispersed phase) and silicone oil (continuous phase) at room conditions are considered as fluids for this work. The effect of various parameters such as flow rate of the phases, width of the channel, viscosity and surface tension on the droplet formation are investigated and compared with available experimental results [1]. The breakup mechanism of droplets in various capillary-number regimes are explained. The numerical results of the length of the generated droplets as a function of the capillary number (varying the flow rate of the continuous phase) are in good agreement with the experimental values, which were measured using the same geometrical and physical properties. Further studies indicate that at a constant flow rate of the continuous phase, the droplet length rises strongly if the flow rate of the disperse phase increases, whereas the relative effects of the viscosity of the continuous phase, and the surface tension between phases on the length of droplets are moderate.

Two-Phase Electronic Cooling Using Mini-Channel and Micro-Channel Heat Sinks: Part 2—Flow Rate and Pressure Drop Constraints

1994 ◽  
Vol 116 (4) ◽  
pp. 298-305 ◽  
Author(s):  
M. B. Bowers ◽  
I. Mudawar
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Phase Region ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Micro Channel ◽  
Two Phase ◽  
Channel Geometry

Increased rate of heat dissipation from electronic chips was explored by the application of flow boiling in mini-channel (D = 2.54 mm) and micro-channel (D = 510 μm) heat sinks with special emphasis on reducing pressure drop and coolant flow rate. A pressure drop model was developed that accounts for the single-phase inlet region, the single- and two-phase heated region, and the two-phase unheated outlet region. Inlet and outlet losses associated with the abrupt contraction and expansion, respectively, were also accounted for, and so were the effects of compressibility and flashing within the two-phase region. Overall, the major contributor to pressure drop was the acceleration caused by evaporation in the channels; however, compressibility effects proved significant for the micro-channel geometry. Based upon practical considerations such as pressure drop, erosion, choking, clogging, and manufacturing ease, the mini-channel geometry was determined to offer inherent advantages over the micro-channel geometry. The latter is preferred only in situations calling for dissipation of high heat fluxes where minimizing weight and liquid inventory is a must.

Near Critical Heat Flux From Small Substrates Under Controlled Spray Cooling

2009 ◽  
Author(s):  
Sergio Escobar-Vargas ◽  
Jorge E. Gonzalez ◽  
Orlando Ruiz ◽  
Cullen Bash ◽  
Ratnesh Sharma ◽  
...  
Keyword(s):  
Heat Flux ◽  
Mass Flow Rate ◽  
Critical Heat Flux ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Dissipation ◽  
High Heat ◽  
Heat Fluxes ◽  
Experimental Results ◽  
High Heat Flux

The increasing power density on electronic components has resulted in temperature problems related to the generation of hot spots and the need to remove high heat flux in small areas. This work is aimed at the cooling of small surfaces (1 mm × 1.2 mm) by using a monodisperse spray from thermal ink jet (TIJ) atomizers. Heat fluxes near the critical heat flux (CHF) are obtained for different conditions of cooling mass flow rate, droplet deposition, and number of active droplet jets. Experimental results at quasiequilibrium show the heat flux scales to the cooling mass flow rate. It is observed that two simultaneously activated jets result in slightly smaller heat flux compared to a single jet of droplets for the same mass flow rate. Droplet momentum and spreading or splashing, as determined by a combination of Weber number and Reynolds number effect via K = We1/2Re1/4, may impact the efficiency of the delivery of the cooling mass flow. Current experimental results at K = 24.5 and K = 52.2 for the copper surface temperatures ranging 110 – 120 °C indicate there is little influence of the splashing on the heat dissipation. System heat losses are measured experimentally and compared to a numerical and analytical solution to estimate the actual heat dissipated by the droplet change of phase.

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