Reducing instability and enhancing critical heat flux using integrated micropillars in two-phase microchannel heat sinks

2015 ◽  
Author(s):  
Y. Zhu ◽  
D.S. Antao ◽  
D.W. Bian ◽  
T.J. Zhang ◽  
E.N. Wang
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Heat Sinks ◽  
Two Phase ◽  
Microchannel Heat Sinks

Constrained Optimization of One-Dimensional Two-Phase Flow in Fractal-Like Branching Microchannel Heat Sinks

2011 ◽  
Author(s):  
Douglas B. Heymann ◽  
Deborah V. Pence
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Wall Temperature ◽  
Two Phase Flow ◽  
Heat Sinks ◽  
Phase Flow ◽  
Two Phase ◽  
One Dimensional ◽  
Temperature Constraint ◽  
Flow Through

The performance of two-phase flow through fractal-like heat sinks, subject to both geometrical and flow constraints was assessed. Constraints are crucial in order to satisfy physical requirements of a design. A one-dimensional model of two-phase flow through fractal-like branching microchannels was used to estimate pressure drop, wall temperature and critical heat flux. Water is employed as the working fluid. The exit pressure is varied between 6 kPa and 101.3 kPa (absolute) in order to achieve two-phase flow at temperatures lower than the maximum wall temperature constraint of 70°C. Preliminary results show that the benefit to cost ratio of two-phase flow is on the same order of magnitude as single-phase flow, both with a 70°C wall temperature constraint. Alternatively, a critical heat flux model is used to constrain the flow rate in order for the imposed heat flux to be 50% of the critical heat flux.

scholarly journals Determination of Pool Boiling Critical Heat Flux Enhancement in Nanofluids

2007 ◽  
Author(s):  
Bao H. Truong
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Porous Coating ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Sem Images ◽  
Heat Transfer Coefficients ◽  
Nucleate Boiling Heat Transfer

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed a CHF enhancement up to 68% and there seems to be a monotonic relationship between the nanoparticle concentration and the magnitude of enhancement. Alumina nanofluids had a CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. Scanning Electron Microscopy (SEM) images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater’s surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica.

Sign in / Sign up

Export Citation Format

Share Document