scholarly journals Optimal design of subcooled triangular microchannel heat sink exchangers with variable heat loads for high performance cooling

2021 ◽  
Vol 2116 (1) ◽  
pp. 012052
Author(s):  
David Olugbenga Ariyo ◽  
Tunde Bello-Ochende
Keyword(s):  
Heat Sink ◽  
High Performance ◽  
Flow Boiling ◽  
High Heat ◽  
Geometric Optimization ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Microchannel Heat Sinks

Abstract Deionized water at a temperature of 25 °C was used as the cooling fluid and aluminium as the heat sink material in the geometric optimization and parameter modelling of subcooled flow boiling in horizontal equilateral triangular microchannel heat sinks. The thermal resistances of the microchannels were minimized subject to fixed volume constraints of the heat sinks and microchannels. A computational fluid dynamics (CFD) ANSYS code used for both the simulations and the optimizations was validated by the available experimental data in the literature and the agreement was good. Fixed heat fluxes between 100 and 500 W/cm2 and velocities between 0.1 and 7.0 m/s were used in the study. Despite the relatively high heat fluxes in this study, the base temperatures of the optimal microchannel heat sinks were within the acceptable operating range for modern electronics. The pumping power requirements for the optimal microchannels are low, indicating that they can be used in the cooling of electronic devices.

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.

Influence of channel diameter on subcooled flow boiling burnout at high heat fluxes

1993 ◽  
Vol 36 (13) ◽  
pp. 3407-3410 ◽  
Author(s):  
G.P Celata ◽  
M Cumo ◽  
A Mariani ◽  
H Nariai ◽  
F Inasaka
Keyword(s):  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Channel Diameter ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow

scholarly journals Surface Structure Enhanced Microchannel Flow Boiling

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Yangying Zhu ◽  
Dion S. Antao ◽  
Kuang-Han Chu ◽  
Siyu Chen ◽  
Terry J. Hendricks ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Capillary Flow ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Two Phase ◽  
Thin Film Evaporation ◽  
Surface Microstructures

We investigated the role of surface microstructures in two-phase microchannels on suppressing flow instabilities and enhancing heat transfer. We designed and fabricated microchannels with well-defined silicon micropillar arrays on the bottom heated microchannel wall to promote capillary flow for thin film evaporation while facilitating nucleation only from the sidewalls. Our experimental results show significantly reduced temperature and pressure drop fluctuation especially at high heat fluxes. A critical heat flux (CHF) of 969 W/cm2 was achieved with a structured surface, a 57% enhancement compared to a smooth surface. We explain the experimental trends for the CHF enhancement with a liquid wicking model. The results suggest that capillary flow can be maximized to enhance heat transfer via optimizing the microstructure geometry for the development of high performance two-phase microchannel heat sinks.

Experimental Investigation and Theoretical Model for Subcooled Flow Boiling Pressure Drop in Microchannel Heat Sinks

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Jaeseon Lee ◽  
Issam Mudawar
Keyword(s):  
Pressure Drop ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Heat Sinks ◽  
Bulk Liquid ◽  
Two Phase ◽  
Phase Layer ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Microchannel Heat Sinks

This study examines the pressure drop characteristics of subcooled two-phase microchannel heat sinks. A new model is proposed, which depicts the subcooled flow as consisting of a homogeneous two-phase flow layer near the heated walls of the microchannel and a second subcooled bulk liquid layer. This model is intended for conditions where subcooled flow boiling persists along the entire microchannel and the outlet fluid never reaches bulk saturation temperature. Mass, momentum, and energy control volume conservation equations are combined to predict flow characteristics for thermodynamic equilibrium qualities below zero. By incorporating a relation for apparent quality across the two-phase layer and a new criterion for bubble departure, this model enables the determination of axial variations in two-phase layer thickness and velocity as well as pressure drop. The model predictions are compared with HFE 7100 pressure drop data for four different microchannel sizes with hydraulic diameters of 176–416 μm, mass velocities of 670–5550 kg/m2 s, and inlet temperatures of 0°C and −30°C. The pressure drop database is predicted with a mean absolute error of 14.9%.

Experimental Investigation of Flow Boiling in a Single, Surface-Augmented Silicon Microchannel

2009 ◽  
Author(s):  
Naveenan Thiagarajan ◽  
Daniel T. Pate ◽  
Sushil H. Bhavnani ◽  
Rory J. Jones
Keyword(s):  
Pressure Drop ◽  
Single Channel ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Dielectric Fluid ◽  
Subcooled Boiling ◽  
Ongoing Research ◽  
Microchannel Heat Sinks

Advances in electronics such as chip level integration and die stacking have led to a bottleneck in further development since dissipation of the resulting high heat fluxes continues to be a challenge. Ongoing research in the field of flow boiling to meet the rising demands has resulted in the evolution of potential cooling technologies such as microchannel heat sinks. In an effort to understand the flow boiling in these micro-structures, experiments were previously conducted by the authors using 19 parallel, surface enhanced microchannels with a hydraulic diameter of 253μm. Flow instabilities which can be attributed to channel-to-channel interaction and the effect of compressible volumes at channel exit and inlet were observed under certain subcooled boiling conditions although these were mitigated in saturated conditions by the presence of re-entrant cavities. To completely eliminate the instabilities, it is important to identify the underlying mechanisms by isolating these causes. To achieve this, a study of flow boiling of dielectric fluid FC72 (C6F14) in a single microchannel test section of height 347 microns and width ranging from 100–400 microns was conducted. The base of the microchannel was augmented with reentrant cavities. The study was performed at mass fluxes ranging from 500–2000 kg/m2-s and inlet subcooling up to 20°C. The results include the parametric effects of inlet subcooling, mass flux, heat flux and number of cavities on the pressure drop. It was observed that the pressure drop oscillations in the subcooled boiling regime observed earlier in the multichannel configuration, were not observed in the subcooled regime in the single channel test device of width 100 microns. Further, adiabatic experiments were conducted to study the effect of channel size on the friction factor. These studies will help provide fundamental design input to enable the development of microchannel heat sinks.

An Experimental Study of Bubble Nucleation Frequency in Subcooled Flow Boiling

2010 ◽  
Author(s):  
Guodong Wang
Keyword(s):  
Flow Boiling ◽  
Rectangular Cross Section ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Dimensionless Frequency ◽  
Micro Channel ◽  
Subcooled Flow Boiling ◽  
Nucleation Frequency ◽  
Mass Fluxes ◽  
Subcooled Flow

In this paper, a simultaneous visualization and measurement study have been carried out to investigate bubble nucleation frequency of water in micro-channel at various heat fluxes and mass fluxes. A single micro-channel with an identical rectangular cross-section having a hydraulic of 137 μm and a heating length of 30 mm was used in this experiment. It is shown that the frequency of bubble nucleation increased drastically with the increase of heat flux and was also strongly dependent on the mass flux. A dimensionless frequency of bubble nucleation was correlated in terms of the Boiling number. The predictions of bubble nucleation frequency in the microchannel are found in good agreement with experimental data with a MAE of 10.4%.

A theoretical and experimental study on subcooled flow boiling at high heat flux

1994 ◽  
Vol 29 (5) ◽  
pp. 319-327 ◽  
Author(s):  
K. W. Lin ◽  
C. H. Lee ◽  
L. W. Hourng ◽  
J. C. Hsu
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow

Characteristics of Flow Boiling Oscillations in Silicon Microchannel Heat Sinks

2007 ◽  
Vol 129 (10) ◽  
pp. 1341-1351 ◽  
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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