Computational Modeling for a Microchannel Electronics Cooler

2007 ◽  
Author(s):  
Joseph Dix ◽  
Amir Jokar ◽  
Robert Martinsen
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Single Phase ◽  
Operating Conditions ◽  
Coolant Fluid ◽  
Working Fluid ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Through Flow ◽  
Phase Fluid

The objective of this study is to analyze the single-phase fluid flow and heat transfer through a microchannel electronics cooler with a hydraulic diameter of about 300 microns. For this purpose, commercial computational fluid dynamics software was used to first characterize the existing design that uses purified water as coolant fluid. The flow parameters of the cooler were then adjusted in order to optimize the design. Geometry modifications were used next to enhance heat transfer, and to reduce pressure drop and erosion from possible impurities in the working fluid. Different working fluids were also considered to investigate possible reductions in corrosion and further increases in heat transfer. Alternative combinations of boundary and operating conditions were explored during optimization. The results of this study showed the microchannel cooler had capacity in rejecting more thermal energy with less pressure drop through flow optimization and geometry modification.

scholarly journals Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Chirag R. Kharangate ◽  
Ki Wook Jung ◽  
Sangwoo Jung ◽  
Daeyoung Kong ◽  
Joseph Schaadt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Integrated Circuit ◽  
Single Phase ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pin Fin

Three-dimensional (3D) stacked integrated circuit (IC) chips offer significant performance improvement, but offer important challenges for thermal management including, for the case of microfluidic cooling, constraints on channel dimensions, and pressure drop. Here, we investigate heat transfer and pressure drop characteristics of a microfluidic cooling device with staggered pin-fin array arrangement with dimensions as follows: diameter D = 46.5 μm; spacing, S ∼ 100 μm; and height, H ∼ 110 μm. Deionized single-phase water with mass flow rates of m˙ = 15.1–64.1 g/min was used as the working fluid, corresponding to values of Re (based on pin fin diameter) from 23 to 135, where heat fluxes up to 141 W/cm2 are removed. The measurements yield local Nusselt numbers that vary little along the heated channel length and values for both the Nu and the friction factor do not agree well with most data for pin fin geometries in the literature. Two new correlations for the average Nusselt number (∼Re1.04) and Fanning friction factor (∼Re−0.52) are proposed that capture the heat transfer and pressure drop behavior for the geometric and operating conditions tested in this study with mean absolute error (MAE) of 4.9% and 1.7%, respectively. The work shows that a more comprehensive investigation is required on thermofluidic characterization of pin fin arrays with channel heights Hf < 150 μm and fin spacing S = 50–500 μm, respectively, with the Reynolds number, Re < 300.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

Effects of Taper Configurations on Heat Transfer and Pressure Drop in Single-Phase Flows in Microgaps

2020 ◽  
Author(s):  
Debora C. Moreira ◽  
Gherhardt Ribatski ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Single Phase ◽  
Bubble Nucleation ◽  
Low Flow ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Inlet Section ◽  
Flow Rates

Abstract This paper presents a comparison of heat transfer and pressure drop during single-phase flows inside diverging, converging, and uniform microgaps using distilled water as the working fluid. The microgaps were created on a plain heated copper surface with a polysulfone cover that was either uniform or tapered with an angle of 3.4°. The average gap height was 400 microns and the length and width dimensions were 10 mm × 10 mm, resulting in an average hydraulic diameter of approximately 800 microns for all configurations. Experiments were conducted at atmospheric pressure and the inlet temperature was set to 30 °C. Heat transfer and pressure drop data were acquired for flow rates varying from 57 to 485 ml/min and the surface temperature was monitored not to exceed 90 °C to avoid bubble nucleation, so the heat flux varied from 35 to 153 W/cm2 depending on the flow rate. The uniform configuration resulted in the lowest pressure drop, and the diverging one showed slightly higher pressure drop values than the converging configuration, possibly because the flow is most constrained at the inlet section, where the fluid is colder and presents higher viscosity. In addition, a minor dependence of pressure drop with heat flux was observed due to temperature dependent properties. The best heat transfer performance was obtained with the converging configuration, which was especially significant at low flow rates. This behavior could be explained by an increase in the heat transfer coefficient due to flow acceleration in converging gaps, which compensates the decrease in temperature difference between the fluid and the surface due to fluid heating along the gap. Overall, the comparison between the three configurations shows that converging microgaps have better performance than uniform or diverging ones for single-phase flows, and such effect is more pronounced at lower flow rates, when the fluid experiences higher temperature changes.

Laminar Flow Forced Convection Heat Transfer Behavior of Phase Change Material Fluid in Microchannels With Staggered Pins

2010 ◽  
Author(s):  
Satyanarayana Kondle ◽  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Gurunarayana Ravi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Phase Change ◽  
Single Phase ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
High Heat ◽  
High Heat Flux ◽  
Small Areas ◽  
Phase Fluid

Microchannels have been extensively studied for electronic cooling applications ever since they were found to be effective in removing high heat flux from small areas. Many configurations of microchannels have been studied and compared for their effectiveness in heat removal. However, there is little data available in the literature on the use of pins in microchannels. Staggered pins in microchannels have higher heat removal characteristics because of the continuous breaking and formation of the boundary layer, but they also exhibit higher pressure drop because pins act as flow obstructions. This paper presents numerical results of two characteristic staggered pins (square and circular) in microchannels. The heat transfer performance of a single phase fluid in microchannels with staggered pins, and the corresponding pressure drop characteristics are also presented. An effective specific heat capacity model was used to account for the phase change process of PCM fluid. Comparison of heat transfer characteristics of single phase fluid and PCM fluid are made for two pins geometries for three different Reynolds numbers. Circular pins were found to be more effective in terms of heat transfer by exhibiting higher Nusselt number. Circular pin microchannels were also found to have lower pressure drop compared to the square pin microchannels.

Thermal-Hydraulic Performance of SiC-Water and Al2O3-Water Nanofluids in the Minichannel

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Ji Zhang ◽  
Yanhua Diao ◽  
Yaohua Zhao ◽  
Yanni Zhang
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Volume Concentration ◽  
Working Fluid ◽  
Al2o3 Nanoparticles ◽  
Particle Sizes ◽  
Enhance Heat Transfer ◽  
Flow And Heat Transfer ◽  
Effective Particle Size ◽  
Effective Particle

The single-phase flow and heat transfer behaviors of SiC and Al2O3 nanoparticles dispersed in water were studied experimentally in a multiport minichannel flat tube (MMFT). The volume concentrations of the two nanofluids ranged from 0.001% to 1%. Their effective particle sizes, thermal conductivities, and viscosities were also measured. Results indicated that these nanofluids as a working fluid could enhance heat transfer but increase pressure drop and the Nusselt number by up to 85%. The two nanofluids exhibited a common optimal volume concentration of 0.01% for heat transfer. Effective particle size was also found to have a significant effect on heat transfer.

Effects of Surface Roughness on Single Phase Fluid Flow and Heat Transfer Characteristics in Microchannels

2009 ◽  
Author(s):  
Jinli Lu ◽  
Yingli Hao
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Velocity Distribution ◽  
Shape Factor ◽  
Single Phase ◽  
Peak Position ◽  
Centerline Velocity ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer

A two dimensional numerical simulation is conducted to investigate the flow and heat transfer characteristics of single phase liquid laminar flow through rough microchannels. The wall roughness is simulated in a series of cases with rectangular, triangular and trapezoidal elements, respectively. Shape factor and peak position have been used to analyze the influence of roughness elements on centerline velocity distribution, pressure drop and Nusselt number. It is found that the shape factor has a significant effect on the centerline velocity distribution, pressure drop and Nusselt number. It is also found that, for a given shape factor, the effect of peak position on pressure drop is strongly than centerline velocity distribution and heat transfer. In addition, for all considered roughness element shapes, the rectangular element displays a poor heat transfer and large pressure drop.

Numerical Simulation of Operating Performance of Heat Exchangers in a Residential Split Air-Conditioner

2011 ◽  
Vol 250-253 ◽  
pp. 3913-3918 ◽  
Author(s):  
Shun Yu Su ◽  
Tian Tian ◽  
Jian Chen
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Great Influence ◽  
Working Fluid ◽  
Air Conditioner ◽  
Two Phase ◽  
Air Conditioning System ◽  
Flow And Heat Transfer ◽  
Phase Fluid

The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.

Experimental Investigation of Flow and Heat Transfer Characteristics of Latent Functionally Thermal Fluid in Mini-Tube

2009 ◽  
Author(s):  
Jinli Lu ◽  
Yingli Hao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Single Phase ◽  
Deionized Water ◽  
Working Fluid ◽  
Experimental Measurements ◽  
Heat Transfer Characteristics ◽  
Latent Functionally Thermal Fluid ◽  
Flow And Heat Transfer ◽  
Phase Water

An experimental research using the latent functionally thermal fluid of n-hexadecane microcapsules in deionized water was conducted in order to investigate the flow and heat transfer characteristics of microencapsulated phase change material (MEPCM) slurry. Experimental measurements were done for a large region of Reynolds number in the mini-tube with a constant wall heat flux. Experimental measurements were also conducted using deionized water as the working fluid under the same conditions. Some important parameters such as pressure, temperatures of wall and fluid were obtained experimentally. The relationships between pressure drop and mass flow rate, dimensionless outlet temperature of working fluid and Reynolds number, mean convective heat transfer coefficient and Nusselt number and Reynolds number were obtained. Results show that the using of MEPCM particle increases the pressure drop and then close to that of single phase water with increasing mass flow rate. The outlet and wall temperatures decrease 50% comparing with single phase water under the same conditions. The Nusselt number of slurry containing small concentration MEPCM particle is about 2.0–2.3 times greater than that of single phase water in the minitube. The experimental data might be helpful in the design of thermal-energy transportation systems in small scale using MEPCM slurry.

Numerical Simulation and Experimental Validation of Flow and Heat Transfer in Flat-Tube Heat Exchangers

2007 ◽  
Author(s):  
Jiuyang Yu ◽  
Wenwu Xia ◽  
Xingkui Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Flat Tube ◽  
Flow Energy ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Measured Flow

A three dimensional numerical simulation study has been carried out to predict air flow and temperature distribution in flat-tube heat exchangers. Due to the symmetry in geometrical construction, a section of heat exchanger has been considered for CFD analysis by using PHOENICS software. The k-ε turbulence model has been used to solve the transport equations for turbulent flow energy and the dissipation rate. In order to check the validity of the computational modeling, the results were compared with the measured flow parameters such as pressure and velocity distribution. It is found that both the heat transfer coefficient and the pressure drop for the shell-side are in good arrangement with experimental results. Comparing with circular-tube heat exchangers, the simulation result shows that the pressure drop of flat-tube heat exchangers decreases 12%∼20%, and the coefficient of integral performance Nu/ζ0.29 has an increment, which is between 22%∼34%.

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