Thermal oscillations during flow boiling of hydrocarbon refrigerants in a microchannels array heat sink

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

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A Study of Critical Heat Flux During Flow Boiling in Microchannel Heat Sinks

Journal of Heat Transfer ◽

10.1115/1.4004715 ◽

2011 ◽

Vol 134 (1) ◽

Cited By ~ 16

Author(s):

Tailian Chen ◽

Suresh V. Garimella

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Flow Rate ◽

Heat Input ◽

Heat Sink ◽

Flow Boiling ◽

Strong Dependence ◽

Heat Fluxes ◽

Abrupt Decrease ◽

Parallel Microchannels

The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the heat flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels.

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Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2008-62071 ◽

2008 ◽

Cited By ~ 1

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.

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Characteristics of Flow Boiling Oscillations in Silicon Microchannel Heat Sinks

Journal of Heat Transfer ◽

10.1115/1.2754946 ◽

2007 ◽

Vol 129 (10) ◽

pp. 1341-1351 ◽

Cited By ~ 29

Author(s):

R. Muwanga ◽

I. Hassan ◽

R. MacDonald

Keyword(s):

Heat Sink ◽

Flow Boiling ◽

Heat Fluxes ◽

Heat Sinks ◽

Working Fluid ◽

Inlet Temperature ◽

Outlet Temperature ◽

Standard Heat ◽

Flow Oscillations ◽

Footprint Area

Flow boiling oscillation characteristics in two silicon microchannel heat sink configurations are presented. One is a standard heat sink with 45 straight parallel channels, whereas the second is similar except with cross-linked paths at three locations. Data are presented over a flow range of 20–50ml∕min(91–228kg∕(m2s)) using distilled water as the working fluid. The heat sinks have a footprint area of 3.5cm2 and contain 269μm wide by 283μm deep reactive ion etching channels. Flow oscillations are found to be similar in characteristic trends between the two configurations, showing a decreasing frequency with increasing heat flux. The oscillation amplitudes are relatively large and identical in frequency for the inlet temperature, outlet temperature, inlet pressure, and pressure drop. Oscillation properties for the standard heat sink at two different inlet temperatures and various flow rates are correlated for different heat fluxes. This work additionally presents a first glimpse of the cross-linked heat sink performance under flow boiling instability conditions.

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Flow Boiling in a Parallel Strip Fin Heat Sink With Nonuniform Heat Flux Conditions

Journal of Heat Transfer ◽

10.1115/1.4048095 ◽

2020 ◽

Vol 142 (12) ◽

Author(s):

Kexian Ren ◽

Ze Miao ◽

Bo Yang ◽

Tongzhi Yang ◽

Weixing Yuan

Keyword(s):

Heat Flux ◽

Heat Sink ◽

Thermal Load ◽

High Speed ◽

Flow Boiling ◽

Uniform Heat Flux ◽

High Speed Camera ◽

Pressure Drops ◽

Boiling Process ◽

Parallel Strip

Abstract This study investigates the thermal performance of a parallel strip fin heat sink (PSFHS) under various heat flux conditions at a flowrate of 100 ml/min, including uniform heat flux and nonuniform heat flux. The heat sink consists of 150 fins with a width of 1 mm, a height of 5.5 mm, and a pitch of 1 mm and has a Z-type inlet/outlet arrangement. Nine separate heaters offer thermal load to the heat sink in order to provide a uniform or nonuniform heat flux. The flow boiling process is captured by a high-speed camera. The temperatures of the heaters have been measured under the uniform and nonuniform heat flux conditions. In addition, the pressure drops inside the heat sink are also obtained. A minichannel heat sink (MCHS) with the same channel dimensions and inlet/outlet configuration is tested too. A comparison between MCHS and PSFHS is discussed in detail, which helps to understand the flow boiling characteristic in PSFHS.

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

Volume 3: Computational Fluid Dynamics; Micro and Nano Fluid Dynamics ◽

10.1115/fedsm2020-20093 ◽

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.

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Performance of Concentrator Photovoltaic Systems Integrated With Double Layer Microchannel Heat Sink

ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2019-4259 ◽

2019 ◽

Author(s):

Ali Radwan ◽

Mohamed M. Awad ◽

Shinichi Ookawara ◽

Mahmoud Ahmed

Keyword(s):

Solar Cell ◽

Double Layer ◽

Heat Sink ◽

Flow Boiling ◽

Microchannel Heat Sink ◽

Temperature Uniformity ◽

Liquid Cooling ◽

Cell Temperature ◽

Wide Range ◽

Phase Liquid

Abstract In this study, a new design of double layer microchannel heat sink (DL-MCHS) has been monolithically fabricated using 3D metal printer and experimentally examined as a heat sink for concentrator photovoltaic (CPV) systems. Single phase liquid cooling using ethanol and flow boiling cooling using NOVEC-7000 coolant in the designed DL-MCHS are experimentally compared. The results proved that using the flow boiling cooling technique for the CPV systems attained a lower solar cell temperature with high temperature uniformity. In more details, flow boiling in counterflow (CF) operated DL-MCHS, attained a very low solar cell temperature close to the NOVEC-7000 boiling point with temperature uniformity of 0.2 °C over a wide range of coolant flow rate from 25–250 ml/hr.

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Numerical Investigation of Flow Boiling in a Manifold Microchannel Heat Sink With Conjugate Heat Transfer

ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2019-4042 ◽

2019 ◽

Author(s):

Zhichuan Sun ◽

Yang Luo ◽

Junye Li ◽

Wei Li ◽

Jingzhi Zhang ◽

...

Keyword(s):

Heat Transfer ◽

Numerical Investigation ◽

Heat Sink ◽

Conjugate Heat Transfer ◽

Flow Boiling ◽

High Heat Flux ◽

Microchannel Heat Sink ◽

Two Phase ◽

Boiling Process ◽

Manifold Microchannel

Abstract The manifold microchannel heat sink receives an increasing number of attention lately due to its high heat flux dissipation. Numerical investigation of boiling phenomena in manifold microchannel (MMC) heat sinks remains a challenge due to the complexity of fluid route and the limitation of numerical accuracy. In this study, a computational fluid dynamics (CFD) approach including subcooled two-phase flow boiling process and conjugate heat transfer effect is performed using a MMC unit cell model. Different from steady-state single phase prediction in MMC heat sink, this type of modeling allows for the transient simulation for two-phase interface evolution during the boiling process. A validation case is conducted to validate the heat transfer phenomenon among three phases. Besides, this model is used for the assessment of the manifold dimensions in terms of inlet and outlet widths at the mass flux of 1300 kg/m2·s. With different ratios of inlet-to-outlet area, the thermal resistances remain nearly stable.

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