Onboard Device Encapsulation With Two-Phase Cooling

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
S. J. Young ◽  
D. Janssen ◽  
E. A. Wenzel ◽  
B. M. Shadakofsky ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Integrated Circuit ◽  
Flow Boiling ◽  
Heat Removal ◽  
Coolant Flow ◽  
Coefficient Of Performance ◽  
Processing Unit ◽  
Two Phase ◽  
Central Processing

Onboard liquid cooling of electronic devices is demonstrated with liquid delivered externally to the point of heat removal through a conformal encapsulation. The encapsulation creates a flat microgap above the integrated circuit (IC) and delivers a uniform inlet coolant flow over the device. The coolant is Novec™ 7200, and the electronics are simulated with a resistance heater on a 1:1 scale. Thermal performance is demonstrated at power densities of ∼1 kW/cm3 in the microgap. Parameters investigated are pressure drop, average device temperature, heat transfer coefficient, and coefficient of performance (COP). Nusselt numbers for gap sizes of 0.25, 0.5, and 0.75 mm are reduced to a dimensionless correlation. With low coolant inlet subcooling, two-phase heat transfer is seen at all mass flows. Device temperatures reach 95 °C for power dissipation of 50–80 W (0.67–1.08 kW/cm3) depending on coolant flow for a gap of 0.5 mm. Coefficients of performance of ∼100 to 70,000 are determined via measured pressure drop and demonstrate a low pumping penalty at the device level within the range of power and coolant flow considered. The encapsulation with microgap flow boiling provides a means for use of higher power central processing unit and graphics processing unit devices and thereby enables higher computing performance, for example, in embedded airborne computers.

Multidevice Cooling With Flow Boiling in a Variable Microgap

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
S. J. Young ◽  
D. Janssen ◽  
E. A. Wenzel ◽  
B. M. Shadakofsky ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Memory Device ◽  
Coolant Flow ◽  
Coefficient Of Performance ◽  
Coolant Temperature ◽  
Memory Devices ◽  
Two Phase ◽  
Data Set ◽  
Average Device

Abstract Flow boiling in an onboard variable microgap is demonstrated as a viable cooling method for multidevice electronics. The microgap is created by a bonded conformal encapsulation that delivers uniform subcooled inlet coolant flow across a multidevice layout comprising a processor and two in-line, symmetrically placed memory devices. Each device is simulated with a ceramic resistance heater on a 1:1 scale, and the heights of the devices create the variable microgap under the roof line of the encapsulation. The gap height for the processor is 0.5 mm and 1 mm for the memory devices. Parameters investigated are pressure drop, average device temperature, processor power, and coefficient of performance (COP). For inlet coolant flow first over the memory devices, the average device temperature exceeds the 95 °C limit when processor power is ∼50 W or less. For inlet flow over the processor, memory device temperatures are approximately the same over all the levels of processor and memory chip power. For processor power <30 W and an inlet coolant temperature of 25 °C, single-phase heat transfer is the dominant cooling mechanism. When processor power is >40 W, two-phase heat transfer dominates, and processor power of 120 W is reached within the 95 °C threshold. Volumetric power density across the data set is 134 to 1209 W/cm3.

scholarly journals Effect of Metal Foam Insert Configurations on Flow Boiling Heat Transfer and Pressure Drop in a Rectangular Channel

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4617
Author(s):  
Sanghyun Nam ◽  
Dae Yeon Kim ◽  
Youngwoo Kim ◽  
Kyung Chun Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Test Section ◽  
Boiling Heat Transfer ◽  
Metal Foam ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Saturation Pressure ◽  
Two Phase

Heat transfer under flow boiling is better in a rectangular channel filled with open-cell metal foam than in an empty channel, but the high pressure drop is a drawback of the empty channel method. In this study, various types of metal foam insert configurations were tested to reduce the pressure drop while maintaining high heat transfer. Specifically, we measured the boiling heat transfer and pressure drop of a two-phase vertical upward flow of R245fa inside a channel. To measure the pressure and temperature differences of the metal foam, differential pressure transducers and T-type thermocouples were used at both ends of the test section. While the saturation pressure was kept constant at 5.9 bar, the steam quality at the inlet of the test section was changed from 0.05 to 0.99. The channel height, moreover, was 3 mm, and the mass flux ranged from 133 to 300 kg/m2s. The two-phase flow characteristics were observed through a high-speed visualization experiment. Heat transfer tended to increase with the mean vapor quality, and, as expected, the fully filled metal foam channel offered the highest thermal performance. The streamwise insert pattern model had the lowest heat transfer at a low mass flux. However, at a higher mass flux, the three different insert models presented almost the same heat transfer coefficients. We found that the streamwise pattern model had a very low pressure drop compared to that of the spanwise pattern models. The goodness factors of the flow area and the core volume of the streamwise patterned model were higher than those of the full-filled metal foam channel.

A Comparative Numerical Study on Two-Phase Boiling Fluid Flow and Heat Transfer in the Microchannel Heat Sink With Different Manifold Arrangements

2020 ◽  
Author(s):  
Yang Luo ◽  
Jingzhi Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Numerical Study ◽  
Flow Boiling ◽  
High Surface ◽  
Volume Ratio ◽  
High Heat Flux ◽  
Two Phase ◽  
Flow Maldistribution

Abstract The manifold microchannel (MMC) heat sink system has been widely used in high-heat-flux chip thermal management due to its high surface-to-volume ratio. Two-phase, three-dimensional numerical methods for subcooled flow boiling have been developed using a self-programming solver based on OpenFOAM. Four different types of manifold arrangements (Z-type, C-type, H-type and U-type) have been investigated at a fixed operational condition. The numerical results evaluate the effects of flow maldistribution caused by different manifold configurations. Before simulating the two-phase boiling flow in MIMC metamodels, single-phase liquid flow fields are performed at first to compare the flow maldistribution in microchannels. It can be concluded from the flow patterns that H-type and U-type manifolds provide a more even and a lower microchannel void fraction, which is conducive to improving the temperature uniformity and decreasing the effective thermal resistance. The simulation results also show that the wall temperature difference of H-type (0.471 K) is only about 10% of the Z-type (4.683 K). In addition, the U-type manifold configuration show the lowest average pressure drop at the inlet and outlet of the MIMC metamodel domain. However, H-type manifold also shows an impressive 59.9% decrease in pressure loss. Results indicate that both the H-type and the U-type manifolds for flow boiling in microchannels are recommended due to their better heat transfer performance and lower pressure drop when compared with Z-type and C-type.

Two-Phase Pressure Drop and Boiling Heat Transfer in a Single Horizontal Microchannel

2006 ◽  
Author(s):  
Cheol Huh ◽  
Moo Hwan Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Local Flow ◽  
Heat Transfer Coefficients ◽  
Phase Pressure

With a single microchannel and a series of microheaters made with MEMS technique, two-phase pressure drop and local flow boiling heat transfer were investigated using deionized water in a single horizontal rectangular microchannel. The test microchannel has a hydraulic diameter of 100 μm and length of 40 mm. A real time observation of the flow patterns with simultaneous measurement are made possible. Tests are performed for mass fluxes of 90, 169, and 267 kg/m2s and heat fluxes of from 100 to 600 kW/m2. The experimental local flow boiling heat transfer coefficients and two-phase frictional pressure gradient are evaluated and the effects of heat flux, mass flux, and vapor qualities on flow boiling are studied. Both the evaluated experimental data are compared with existing correlations. The experimental heat transfer coefficients are nearly independent on mass flux and the vapor quality. Most of all correlations do not provide reliable heat transfer coefficients predictions with vapor quality and prediction accuracy. As for two-phase pressure drop, the measured pressure drop increases with the mass flux and heat flux. Most of all existing correlations of two-phase frictional pressure gradient do not predict the experimental data except some limited conditions.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2004 ◽  
Vol 126 (3) ◽  
pp. 288-300 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406×2.032mm2 cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Features unique to two-phase micro-channel flow were identified and employed to validate key assumptions of an annular flow boiling model that was previously developed to predict pressure drop and heat transfer in two-phase micro-channel heat sinks. This earlier model was modified based on new findings from the adiabatic two-phase flow study. The modified model shows good agreement with experimental data for water-cooled heat sinks.

Numerical Investigation of Heat Transfer Enhancement in a Microchannel With Offset Micro Pin-Fins

2010 ◽  
Author(s):  
Haleh Shafeie ◽  
Omid Abouali ◽  
Khosrow Jafarpour
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Removal Rate ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
Navier Stokes ◽  
Liquid Region ◽  
Noticeable Effect ◽  
Pin Fins

This paper presents a numerical study of laminar forced convection in microchannels network heat sinks with fabricated offset pin-fins. A 3-dimensional mathematical model, for conjugate heat transfer in both solid and liquid is presented. For this aim the Navier-Stokes and energy equations for the liquid region and the energy equation for the solid region are solved simultaneously and the pressure drop together heat transfer characteristics of a single-phase microchannel heat sink were investigated. A typical microchannel was selected and it was shown that using offset pin-fins has a noticeable effect and heat removal rate can be increased using this technique. However the pressure drop is also highly increasing which leads to a low coefficient of performance for microchannel with this type of micro-structure.

Microchannel Size Effects on Two-Phase Local Heat Transfer and Pressure Drop in Silicon Microchannel Heat Sinks With a Dielectric Fluid

2007 ◽  
Author(s):  
Tannaz Harirchian ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
The Heat Transfer Coefficient

Two-phase heat transfer in microchannels can support very high heat fluxes for use in high-performance electronics-cooling applications. However, the effects of microchannel cross-sectional dimensions on the heat transfer coefficient and pressure drop have not been investigated extensively. In the present work, experiments are conducted to investigate the local flow boiling heat transfer in microchannel heat sinks. The effect of channel size on the heat transfer coefficient and pressure drop is studied for mass fluxes ranging from 250 to 1600 kg/m2s. The test sections consist of parallel microchannels with nominal widths of 100, 250, 400, 700, and 1000 μm, all with a depth of 400 μm, cut into 12.7 mm × 12.7 mm silicon substrates. Twenty-five microheaters embedded in the substrate allow local control of the imposed heat flux, while twenty-five temperature microsensors integrated into the back of the substrates enable local measurements of temperature. The dielectric fluid Fluorinert FC-77 is used as the working fluid. The results of this study serve to quantify the effectiveness of microchannel heat transport while simultaneously assessing the pressure drop trade-offs.

A semi-analytical model of heat transfer and pressure drop in annular flow regime for flow boiling in a horizontal microtube at uniform heat flux

2020 ◽  
Vol 44 (3) ◽  
pp. 362-384
Author(s):  
Amen Younes ◽  
Ibrahim Hassan ◽  
Lyes Kadem
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Regime ◽  
Analytical Model ◽  
Annular Flow ◽  
Present Model ◽  
Flow Boiling ◽  
Uniform Heat Flux ◽  
Two Phase

A semi-analytical model for predicting heat transfer and pressure drop in annular flow regime for saturated flow boiling in a horizontal microtube at a uniform heat flux has been developed based on a one-dimensional separated flow model. More than 600 two-phase heat transfer, 498 two-phase pressure drop, and 153 void fraction experimental data points for annular flow regime were collected from the literature to validate the present model. The collected data were recorded for various working fluids, R134a, R1234ze, R236fa, R410a, R113, and CO2, for round macro- and microsingle horizontal tubes with an inner diameter range of 0.244 mm ≤ Dh ≤ 3.1 mm, a heated length to diameter ratio of 90 ≤ Lh/Dh ≤ 2000, a saturation temperature range of –10 ≤ Tsat ≤ +50 °C, and liquid to vapor density ratios in the range 6.4 ≤ ρf/ρg ≤ 188. The model was tested for laminar and turbulent flow boiling conditions corresponding to an equivalent Reynolds number, 1900 ≤ Reeq ≤ 48 000, and confinement number, 0.27 ≤ Cconf ≤ 3.4. Under the annular flow regime, the present model predicted the collected data of the heat transfer, pressure drop, and void fraction with mean absolute errors (MAE) of 18.14%, 23.02%, and 3.22%, respectively.

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