Microfeature Heat Exchanger Using Variable-Density Arrays for Near-Isothermal Cold-Plate Operation

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Noris Gallandat ◽  
Danielle Hesse ◽  
J. Rhett Mayor
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Sink ◽  
Convective Heat Transfer Coefficient ◽  
Water Flow Rate ◽  
Flow Path ◽  
Heat Sources ◽  
Cold Plate ◽  
Reduced Pressure ◽  
Discrete Heat Sources

The purpose of this paper is to demonstrate the possibility to selectively tune the convective heat transfer coefficient in different sections of a heat sink by varying the density of microfeatures in order to minimize temperature gradients between discrete heat sources positioned along the flow path. Lifetime of power electronics is strongly correlated to the thermal management of the junction. Therefore, it is of interest to have constant junction temperatures across all devices in the array. Implementation of microfeature enhancement on the convective side improves the heat transfer due to an increase in surface area. Specific shapes such as micro-hydrofoils offer a reduced pressure drop allowing for combined improvement of heat transfer and flow performance. This study presents experimental results from an array of three discrete heat sources (20 × 15 mm) generating 100 W/cm2 and positioned in line along the flow path with a spacing of 10 mm between each of the sources. The heat sink was machined out of aluminum 6061, and micro-hydrofoils with a characteristic length of 500 μm were embedded in the cold plate. The cooling medium used is water at a flow rate of 3.6–13.4 g/s corresponding to a Reynolds number of 420–1575. It is demonstrated that the baseplate temperature can be maintained below 90 °C, and the difference between the maximum temperatures of each heat source is less than 6.7 °C at a heat flux of 100 W/cm2 and a water flow rate of 4.8 g/s.

Micro-Feature Heat Exchanger Using Variable-Density Arrays for Near-Isothermal Cold Plate Operation

2015 ◽  
Author(s):  
Noris Gallandat ◽  
Danielle Hesse ◽  
J. Rhett Mayor
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Flow Rate ◽  
Heat Sink ◽  
Convective Heat Transfer Coefficient ◽  
Water Flow Rate ◽  
Variable Density ◽  
Flow Path ◽  
Cold Plate ◽  
Reduced Pressure

The purpose of this paper is to demonstrate the possibility to selectively tune the convective heat transfer coefficient in different sections of a heat sink by varying the density of micro-features in order to minimize temperature gradients between discrete heat sources positioned along the flow path. Lifetime of power electronics is strongly correlated to the thermal management of the junction. Therefore, it is of interest to have constant junction temperatures across all devices in the array. Implementation of micro-feature enhancement on the convective side improves heat transfer due to an increase in surface area. Specific shapes such as micro hydrofoils offer a reduced pressure drop allowing for combined improvement of heat transfer and flow performance. This study presents experimental results from an array of three discrete heat source (20 × 15 mm) generating 100 W/cm2 and positioned in line along the flow path with a spacing of 10 mm between each of the sources. The heat sink was machined out of aluminum 6061 and micro-hydrofoils with a characteristic length of 500 μm were embedded in the cold plate. The cooling medium used is water at a flow rate of 3.6–13.4 g/s corresponding to a Reynolds number of 420–1575. It is demonstrated that the baseplate temperature can be maintained below 90°C and the difference between the maximum temperatures of each heat source is less than 6.7 °C at a heat flux of 100 W/cm2 and a water flow rate of 4.8 g/s.

A Numerical Simulation of Conjugate Heat Transfer in an Electronic Package Formed by Embedded Discrete Heat Sources in Contact With a Porous Heat Sink

1997 ◽  
Vol 119 (1) ◽  
pp. 8-16 ◽  
Author(s):  
A. G. Fedorov ◽  
R. Viskanta
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
Model Parameters ◽  
Heat Sources ◽  
Similar System ◽  
Electronic Package ◽  
Conjugate System ◽  
Discrete Heat Sources

A physical/mathematical model has been developed to simulate the conjugate heat transfer in an actively cooled electronic package. The package consists of a highly conductive substrate with embedded discrete heat sources that are in intimate contact with a porous channel through which a gaseous coolant is circulated. The flow in the porous medium is analyzed using the extended Darcy model. The nonequilibrium, two-equation model which accounts for the near wall thermal dispersion effects was used for the heat transfer analysis. The concept of the general energy equation for the entire physical domain was employed as a method of solving numerically the conjugate system. The model has been validated by comparing the predictions with available experimental data for a similar system. A parametric study has been performed to examine the effects of some of the most important model parameters on the thermal performance of porous heat sink.

Thermal Performance Comparison for Five Liquid Heat Sink Designs

2011 ◽  
Author(s):  
Christopher Greene ◽  
Randall D. Manteufel ◽  
Amir Karimi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Heat Sink ◽  
Fluid Velocity ◽  
Water Flow Rate ◽  
High Flow ◽  
Heat Transfer Area ◽  
Flow Rates

Five high-flow liquid-cooled heat sink designs are compared for the cooling of a single chip CPU. Five distinctive design configurations are considered with regard to the introduction, passage, and extraction of cooling fluid. The typical water flow rate is about 3.8 liters per minute (lpm) with flow passages in the primary heat transfer area ranging from 2 to 0.1mm. The design configurations are summarized and compared, considering: the primary convective heat transfer area, flow passage streamlining, acceleration mechanisms, and nominal fluid velocity in the primary heat transfer area. Overall pressure drop and thermal resistance are compared for varying flow rates of water. At the nominal flow, the pressure drops ranged from 1 kPa to 20 kPa. In the restrictive designs, such as nozzles, flow acceleration accounts for the largest source of pressure drop. In some designs, a large fraction of the overall pressure drop is due to circuitous flow associated with the introduction and/or extraction of flow which contributes little to heat removal. At the nominal flow, the overall thermal resistance varied from 0.14 to 0.18 C/W. As flow rate increases the overall thermal resistance decreases. Results indicated that 80 to 85% of the total thermal resistance is due to conduction and about 15 to 20% attributed to convection at the nominal flow rate. There is minimal thermal benefit for flow rates beyond twice the nominal while this substantially increases fluid pumping requirements. This study highlights design features which yield above average heat transfer performance with minimal pressure drop for high-flow liquid-cooled heat sinks.

Cooling of a Multichip Electronic Module by Means of Confined Two-Dimensional Jets of Dielectric Liquid

1990 ◽  
Vol 112 (4) ◽  
pp. 891-898 ◽  
Author(s):  
D. C. Wadsworth ◽  
I. Mudawar
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Channel Height ◽  
Heat Sources ◽  
Two Dimensional ◽  
Chip Surface ◽  
Rectangular Slot ◽  
Fluid Properties ◽  
Cooling Module ◽  
Heater Length

Experiments were performed to investigate single-phase heat transfer from a smooth 12.7 × 12.7 mm2 simulated chip to a two-dimensional jet of dielectric Fluorinert FC-72 liquid issuing from a thin rectangular slot into a channel confined between the chip surface and nozzle plate. The effects of jet width, confinement channel height, and impingement velocity have been examined. Channel height had a negligible effect on the heat transfer performance of the jet for the conditions of the present study. A correlation for the convective heat transfer coefficient is presented as a function of jet width, heater length, flow velocity, and fluid properties. A self-contained multichip cooling module consisting of a 3 × 3 array of heat sources confirmed the uniformity and predictability of cooling for each of the nine chips, and proved the cooling module is well suited for packaging large arrays of high-power density chips.

Stacked Microchannel Heat Sinks for Liquid Cooling of Microelectronic Components

2000 ◽  
Author(s):  
X. Wei ◽  
Y. Joshi
Keyword(s):  
Flow Rate ◽  
Heat Sink ◽  
Water Flow Rate ◽  
Heat Removal ◽  
Single Layer ◽  
Heat Sinks ◽  
Computationally Efficient ◽  
Liquid Cooling ◽  
Number Of Layers ◽  
Microelectronic Components

Abstract A novel heat sink based on a multi-layer stack of liquid cooled microchannels is investigated. For a given pumping power and heat removal capability for the heat sink, the flow rate across a stack of microchannels is lower compared to a single layer of microchannels. Numerical simulations using a computationally efficient multigrid method [1] were carried out to investigate the detailed conjugate transport within the heat sink. The effects of the microchannel aspect ratio and total number of layers on thermal performance were studied for water as coolant. A heat sink of base area 10 mm by 10 mm with a height in the range 1.8 to 4.5 mm (2–5 layers) was considered with water flow rate in the range 0.83×10−6 m3/s (50 ml/min) to 6.67×10−6 m3/s (400 ml/min). The results of the computational simulations were also compared with a simplified thermal resistance network analysis.

Heat Transfer and Pressure Drop in a Converging Pedestal Array With Exit Area Variation

2018 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Reynolds Numbers ◽  
Flow Path ◽  
Internal Cooling ◽  
Channel Measurements ◽  
Trailing Edge ◽  
Cooling Air

The trailing edge of a vane is one of the most difficult areas to cool due to a narrowing flow path, high external heat transfer rates, and deteriorating external film cooling protection. Converging pedestal arrays are often used as a means to provide internal cooling in this region. The thermally induced stresses in the trailing edge region of these converging arrays have been known to cause failure in the pedestals of conventional solidity arrays. The present paper documents the heat transfer and pressure drop through two high solidity converging rounded diamond pedestal arrays. These arrays have a 45 percent pedestal solidity. One array which was tested has nine rows of pedestals with an exit area in the last row consistent with the convergence. The other array has eight rows with an expanded exit in the last row to enable a higher cooling air flow rate. The expanded exit of the eight row array allows a 30% increase in the coolant flow rate compared with the nine row array for the same pressure drop. Heat transfer levels correlate well based on local Reynolds numbers but fall slightly below non converging arrays. The pressure drop across the array naturally increases toward the trailing edge with the convergence of the flow passage. A portion of the cooling air pressure drop can be attributed to acceleration while a portion can be attributed to flow path losses. Detailed array static pressure measurements provide a means to develop a correlation for the prediction of pressure drop across the cooling channel. Measurements have been acquired over Reynolds numbers based on exit flow conditions and the characteristic pedestal length scale ranging from 5000 to over 70,000.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Chang-Yuan Liu ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Thermal Resistance ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Nusselt Number ◽  
Cold Plate ◽  
Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

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