Two-Phase Flow in Microchannel Heat Sink with Nearly Uniform Heat Flux Boundary Condition

2006 ◽  
Author(s):  
Man Lee ◽  
Luthur Siu Lun Cheung ◽  
Yi-Kuen Lee ◽  
Yitshak Zohar
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Heat Sink ◽  
Two Phase Flow ◽  
Uniform Heat Flux ◽  
Phase Flow ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Flux Boundary Condition ◽  
Heat Flux Boundary Condition

Boundary Conditions and Integrated Sensors in Microchannel Convective Heat Transfer

2006 ◽  
Author(s):  
Man Lee ◽  
Luthur Siu Lin Cheung ◽  
Yi-Kuen Lee ◽  
Yitshak Zohar
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Boundary Conditions ◽  
Pressure Sensors ◽  
Uniform Heat Flux ◽  
Phase Flow ◽  
Convective Boiling ◽  
Flux Boundary Condition ◽  
Heat Flux Boundary Condition ◽  
Temperature And Pressure

A microchannel heat sink, integrated with pressure and temperature microsensors, is fabricated to study convective boiling under uniform heat flux boundary condition. Utilizing a wafer bond and etch back technology, the heat source, temperature and pressure sensors are separated from the fluid flow by a membrane only 1.5μm in thickness; thus, allowing good control of the thermal boundary conditions. Temperature and pressure distributions for various power levels and flow rates are measured while, simultaneously, the flow patterns are recorded. Single-phase flow results, compared with numerical simulations, confirm that the heat flux boundary condition is indeed nearly uniform. The sensor arrays, particularly for two-phase flow, provide the spatial and temporal dependence of both the temperature and pressures fields.

Effects of Non-Uniform Heating on Two-Phase Flow Through Microchannels

2013 ◽  
Author(s):  
Susan N. Ritchey ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Microchannel Heat Sink ◽  
Uniform Heating ◽  
Two Phase ◽  
Local Flow

As size, weight, and performance demands drive electronics packages to become increasingly thinner and more compact, volume restrictions prevent the use of large intermediate heat spreaders to mitigate heat generation non-uniformities. Instead, these non-uniform heat flux profiles are imposed directly on the ultimate heat sink, either due to chip-scale variations or the desire to cool multiple discrete devices. A better understanding of the impacts of non-uniform heating on two-phase flow characteristics and thermal performance limits for microchannel heat sinks is needed to address these thermal packaging trends. An experimental investigation is performed to explore flow boiling phenomena in a microchannel heat sink with point hotspots, as well as non-uniform streamwise and transverse heating conditions across the entire heat sink area. The investigation is conducted using a silicon microchannel heat sink with a 5 × 5 array of individually controllable heaters attached to a 12.7 mm × 12.7 mm square base. The channels are 240 μm wide, 370 μm deep, and separated by 110 μm wide fins. The working fluid is FC-77, flowing at a mass flux of approximately 890 kg/m2s. High-speed visualizations of the flow are recorded to observe the local flow regimes. It is found that even though the substrate thickness beneath the microchannels is very small (200 μm), significant lateral conduction occurs and must be accounted for in the calculation of the local heat flux imposed. For non-uniform heat input profiles, with peak heat fluxes along the central streamwise and transverse directions, it is found that the local flow regimes, heat transfer coefficients, and wall temperatures deviate significantly from a uniformly heated case. These trends are assessed as a function of an increase in the relative magnitude of the nonuniformity between the peak and background heat fluxes.

Computational Method for Characterization of a Microchannel Heat Sink Involving Two-Phase Flow

2005 ◽  
Author(s):  
Kanchan M. Kelkar ◽  
Suhas V. Patankar ◽  
Sukhvinder Kang
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Two Phase Flow ◽  
Phase Region ◽  
Heat Fluxes ◽  
Computational Method ◽  
Phase Flow ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Solid Region

Microchannel heat sinks are being increasingly considered for the cooling of electronic equipment because of their ability to absorb high heat fluxes directly from the heat-dissipating components in a compact manner with a low thermal resistance. In this study, a computational method is presented for the analysis of conjugate heat transfer and two-phase flow in a heat sink containing a single microchannel. It involves a two-domain solution of the three-dimensional conduction within the solid region and the one-dimensional two-phase momentum and energy transfer within a microchannel. The nonlinear coupling between the two domains that occurs through the heat exchange at the walls of the microchannels is handled using an iterative calculation. Analysis of the flow and heat transfer in the microchannel is based on the homogenous flow assumption that is deemed to be accurate for the flow of low surface tension coolants such as methanol, isobutane, and HFC’s. Representative single and two-phase correlations are used for the calculation of the friction factor and the heat transfer coefficient. The computational model is applied for the prediction of the performance of a microchannel heat sink over a range of mass flow rates. The results of the analysis show the important physical effects that govern the performance of the microchannel heat sink involving two-phase flow. These include the acceleration of the flow in the microchannel in the two-phase region that influences the pressure drop through it and the two-phase enhancement of heat transfer that determines the temperature field within the solid region.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

scholarly journals Two-phase flow pattern and heat transfer coefficients of R245fa/R134a under non-uniform heat flux

2019 ◽  
Vol 65 (17) ◽  
pp. 1741-1751
Author(s):  
Yani Lu ◽  
Li Zhao ◽  
Shuai Deng ◽  
Dongpeng Zhao ◽  
Xianhua Nie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Uniform Heat Flux ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Uniform Heat
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