scholarly journals Experimental setup for studying two-phase flows in micro-and minichannels at ultra-high heat fluxes: methodology and first experimental results

2021 ◽  
Vol 2119 (1) ◽  
pp. 012133
Author(s):  
D V Zaitsev ◽  
V V Belosludtsev
Keyword(s):  
Heat Flux ◽  
Test Section ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Losses ◽  
Heat Fluxes ◽  
Two Phase ◽  
Experiment Versus ◽  
Fast Development ◽  
Phase Change Phenomena

Abstract The study of phase-change phenomena under high and ultra-high heat fluxes is urgent because of fast development of electronics and microelectronics. We have developed a test section with power of 3.5 kW with a heater of 1x1 cm2 and adjustable geometry of the channel for achieving ultra-high heat fluxes in flow boiling and shear-driven liquid film experiments. The methodology of calculating heat losses in the test section is proposed and verified by flow boiling experiment versus another well studied test section. Observed trend of decrease of relative heat losses with increase in the heat flux makes it possible to assume that the heat flux as high as 2.5 kW/cm2 can be reached by this test section.

High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes

2015 ◽  
Author(s):  
Farzad Houshmand ◽  
Hyoungsoon Lee ◽  
Mehdi Asheghi ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Two Phase ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Inner Diameter ◽  
Phase Pressure

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.

Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes

2018 ◽  
Author(s):  
Jensen Hoke ◽  
Todd Bandhauer ◽  
Jack Kotovsky ◽  
Julie Hamilton ◽  
Paul Fontejon
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Flow Boiling ◽  
Laser Diodes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Average Maximum

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.

scholarly journals Numerical Simulation of Evaporating Two-Phase Flow in a High-Aspect-Ratio Microchannel with Bends

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Adam Girard ◽  
Seung M. You ◽  
Suresh V. Garimella
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Flow Boiling ◽  
Vertical Component ◽  
Hydrophobic Surface ◽  
Surface Tension Force ◽  
Heat Fluxes ◽  
Vertical Force ◽  
Two Phase ◽  
Hydrophobic Contact

Flow boiling was investigated on a hydrophobic surface by coating Teflon® onto a 1×1 cm2 copper surface, resulting in contact angle of 118°. The images depicted were taken using distilled water flowing at 299 kg/m2s with 3°C subcooling. In the first series, the number of active nucleation sites increased as heat flux increased. For lower values of heat flux (< 80 kW/m2), vapor bubbles remained almost stationary on the surface. The hydrophobic contact angle makes the horizontal component of surface tension force act radially outward, causing the bubble interface to grow. This leads to increased triple contact line and increased vertical component surface force. The buoyancy force due to the vapor bubble volume appears to be insufficient to overcome this vertical force for liftoff. This explains the stationary bubbles observed at the lower heat fluxes. The bubbles show an increase in size and number with heat flux. After this increasing trend, the bubble continues to grow larger when heat flux is higher than 80 kW/m2, eventually leading to the dryout at 117.5 kW/m2. The later bubble growth at high heat fluxes is caused primarily by the coalescences of neighboring bubbles. These larger bubbles are more affected by flow induced drag forces and move downstream. This can be seen in the lower sequential series at 100 kW/m2. The larger vapor masses slide across the surface, continue to absorb smaller bubbles as they move downstream, and are swept off the surface.

A Review of Two-Phase Forced Cooling in Three-Dimensional Stacked Electronics: Technology Integration

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Craig Green ◽  
Peter Kottke ◽  
Xuefei Han ◽  
Casey Woodrum ◽  
Thomas Sarvey ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Three Dimensional ◽  
High Heat ◽  
Heat Fluxes ◽  
Thermal Design ◽  
High Heat Flux ◽  
Two Phase ◽  
Forced Cooling ◽  
Fluidic Routing

Three-dimensional (3D) stacked electronics present significant advantages from an electrical design perspective, ranging from shorter interconnect lengths to enabling heterogeneous integration. However, multitier stacking exacerbates an already difficult thermal problem. Localized hotspots within individual tiers can provide an additional challenge when the high heat flux region is buried within the stack. Numerous investigations have been launched in the previous decade seeking to develop cooling solutions that can be integrated within the 3D stack, allowing the cooling to scale with the number of tiers in the system. Two-phase cooling is of particular interest, because the associated reduced flow rates may allow reduction in pumping power, and the saturated temperature condition of the coolant may offer enhanced device temperature uniformity. This paper presents a review of the advances in two-phase forced cooling in the past decade, with a focus on the challenges of integrating the technology in high heat flux 3D systems. A holistic approach is applied, considering not only the thermal performance of standalone cooling strategies but also coolant selection, fluidic routing, packaging, and system reliability. Finally, a cohesive approach to thermal design of an evaporative cooling based heat sink developed by the authors is presented, taking into account all of the integration considerations discussed previously. The thermal design seeks to achieve the dissipation of very large (in excess of 500 W/cm2) background heat fluxes over a large 1 cm × 1 cm chip area, as well as extreme (in excess of 2 kW/cm2) hotspot heat fluxes over small 200 μm × 200 μm areas, employing a hybrid design strategy that combines a micropin–fin heat sink for background cooling as well as localized, ultrathin microgaps for hotspot cooling.

Analysis of Two-Phase Pressure Drop Fluctuation Characteristics in a Single Mini-Channel

2016 ◽  
Vol 366 ◽  
pp. 151-156
Author(s):  
Bei Chen Zhang ◽  
Qing Lian Li ◽  
Yuan Wang ◽  
Jian Qiang Zhang
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Flow Boiling ◽  
Circular Cross Section ◽  
Low Frequency ◽  
Amplitude Fluctuation ◽  
Heat Fluxes ◽  
Two Phase ◽  
Phase Pressure

Two-phase pressure drop fluctuations during flow boiling in a single mini-channel were experimentally investigated. Degassed water was tested in circular cross section mini-channels with the hydraulic diameter of 1.0 mm at liquid mass fluxes range of 21.19-84.77 kg m-2 s-1 and heat fluxes of 0~155.75 kW m-2. Effects of heat flux and mass flux on pressure drop fluctuations were discussed based on the time and frequency domain analysis of the measured pressure drop. Two types of fluctuations were identified, which are the incipient boiling fluctuation (IBF) and the explosive boiling fluctuation (EBF) respectively. The IBF is a low frequency low amplitude fluctuation, which relates to the bubble dynamics when incipient boiling occurs. It is sensitive to the thermal and flow conditions. With the increase of heat flux and mass flux, the IBF is suppressed. The EBF is a low frequency high amplitude fluctuation, which occurs near the critical heat flux.

Single-Side Heated Monoblock, High Heat Flux Removal Using Water Subcooled Flow Boiling

2003 ◽  
Author(s):  
Ronald D. Boyd ◽  
Ali Ekhlassi ◽  
Penrose Cofie ◽  
Richard Martin ◽  
Hongtao Zhang
Keyword(s):  
Heat Flux ◽  
Wall Temperature ◽  
Test Section ◽  
Flow Boiling ◽  
Three Dimensional ◽  
High Heat ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Single Side

Plasma-facing components for fusion reactors and other high heat flux heat sinks are usually subjected to a peripherally non-uniform heat flux. The configuration under study is related to these applications and consists of a single-side heated monoblock cross-section test section with a circular coolant channel bored through the center. The monoblock test section has a heated length of 180.0 mm and has 10.0 mm and 30.0 mm inside diameter and outside square sides, respectively. It was subjected to a constant heat flux on one side only, and the remaining portion of the outside surfaces is not exposed to a heat flux. The inlet channel water temperature was held near at 26.0°C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59 Mg/m2s. The results consist of three-dimensional monoblock test section wall temperature distributions and a clear display of both critical heat flux and post-critical heat flux for this single-side heated configuration. These results are very encouraging in that they are among the first full set of truly three-dimensional monoblock test section wall temperature measurements for a one-side heated monoblock flow channel which contains the effects of conjugate heat transfer for turbulent, subcooled flow boiling. Comparisons are made between these results for the monoblock test section and those for a single-side heated circular test section.

High heat flux flow boiling in silicon multi-microchannels – Part III: Saturated critical heat flux of R236fa and two-phase pressure drops

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5426-5442 ◽  
Author(s):  
Bruno Agostini ◽  
Rémi Revellin ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Flux Flow ◽  
Pressure Drops ◽  
Phase Pressure

Experimental Characterization of Two-Phase Cooling of Power Electronics in Thermosiphon and Forced Convection Modes

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Fabio Battaglia ◽  
Farah Singer ◽  
David C. Deisenroth ◽  
Michael M. Ohadi
Keyword(s):  
Heat Flux ◽  
Thermal Resistance ◽  
Power Electronics ◽  
Forced Convection ◽  
Heat Removal ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Two Phase ◽  
Total Thermal Resistance

Abstract In this paper, we present the results of an experimental study involving low thermal resistance cooling of high heat flux power electronics in a forced convection mode, as well as in a thermosiphon (buoyancy-driven) mode. The force-fed manifold microchannel cooling concept was utilized to substantially improve the cooling performance. In our design, the heat sink was integrated with the simulated heat source, through a single solder layer and substrate, thus reducing the total thermal resistance. The system was characterized and tested experimentally in two different configurations: the passive (buoyancy-driven) loop and the forced convection loop. Parametric studies were conducted to examine the role of different controlling parameters. It was demonstrated that the thermosiphon loop can handle heat fluxes in excess of 200 W/cm2 with a cooling thermal resistance of 0.225 (K cm2)/W for the novel cooling concept and moderate fluctuations in temperature. In the forced convection mode, a more uniform temperature distribution was achieved, while the heat removal performance was also substantially enhanced, with a corresponding heat flux capacity of up to 500 W/cm2 and a thermal resistance of 0.125 (K cm2)/W. A detailed characterization leading to these significant results, a comparison between the performance between the two configurations, and a flow visualization in both configurations are discussed in this paper.

Preliminary Results of Pressure Drop Modeling During Flow Boiling in Open Microchannels With Uniform and Tapered Manifolds (OMM)

2013 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Full Potential ◽  
Transfer Coefficients ◽  
Open Microchannel

Flow boiling with microchannel can dissipate high heat fluxes at low surface temperature difference. A number of issues, such as instabilities, low critical heat flux (CHF) and low heat transfer coefficients, have prevented it from reaching its full potential. A new design incorporating open microchannels with uniform and tapered manifold (OMM) was shown to mitigate these issues successfully. Distilled, degassed water at 80 mL/min is used as the working fluid. Plain and open microchannel surfaces are used as the test sections. Heat transfer and pressure drop performance for uniform and tapered manifold with both the surfaces are discussed. A low pressure drop of 7.5 kPa is obtained with tapered manifold and microchannel chip at a heat flux of 263 W/cm2 without reaching CHF. The pressure drop data is further compared with the homogenous model and the initial results are presented.

Flow Boiling in Microgaps for Thermal Management of High Heat Flux Microsystems

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Xuefei Han ◽  
Andrei Fedorov ◽  
Yogendra Joshi
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Experimental Studies ◽  
High Heat ◽  
Bubble Nucleation ◽  
Inlet Temperature ◽  
High Heat Flux ◽  
Two Phase ◽  
Outlet Pressure

In the first part of this paper, a review of fundamental experimental studies on flow boiling in plain and surface enhanced microgaps is presented. In the second part, complimentary to the literature review, new results of subcooled flow boiling of water through a micropin-fin array heat sink with outlet pressure below atmospheric are presented. A 200 μm high microgap device design was tested, with a longitudinal pin pitch of 225 μm, a transverse pitch of 135 μm, and a diameter of 90 μm, respectively. Tested mass fluxes ranged from 1351 to 1784  kg/m2s, and effective heat flux ranged from 198 to 444 W/cm2 based on the footprint surface area. The inlet temperature varied from 6 to 12 °C, and outlet pressure ranged from 24 to 36 kPa. The two-phase heat transfer coefficient showed a decreasing trend with increasing heat flux. High-speed visualizations of flow patterns revealed a triangular wake after bubble nucleation. Flow oscillations were seen and discussed.

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