Copper Inverse Opal Surfaces for Enhanced Boiling Heat Transfer

2017 ◽  
Author(s):  
Hyoungsoon Lee ◽  
Tanmoy Maitra ◽  
James Palko ◽  
Chi Zhang ◽  
Michael Barako ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Bubble Formation ◽  
Copper Surface ◽  
Inverse Opal ◽  
Porous Structures ◽  
Optical Images ◽  
Nucleation Sites ◽  
Enhanced Boiling

Enhanced boiling is one of the popular cooling schemes in thermal management due to its superior heat transfer characteristics. This study demonstrates the ability of copper inverse opal (CIO) porous structures to enhance pool boiling performance using a thin CIO film with a thickness of ∼ 10 μm and pore diameter of 5 μm. The microfabricated CIO film increases microscale surface roughness that in turn leads to more active nucleation sites thus improved boiling performance parameters such as heat transfer coefficient and critical heat flux compared to those of smooth Si surfaces. The experimental results for CIO film show a maximum critical heat flux of 225 W/cm2 (at 16.2°C superheat) or about 3 times higher than that of smooth Si surface (80 W/cm2 at 21.6°C superheat). Optical images showing bubble formation on the microporous copper surface are captured to provide detailed information of bubble departure diameter and frequency.

Enhanced Heat Transfer Using Microporous Copper Inverse Opals

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Hyoungsoon Lee ◽  
Tanmoy Maitra ◽  
James Palko ◽  
Daeyoung Kong ◽  
Chi Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Pore Diameter ◽  
Bubble Formation ◽  
Copper Surface ◽  
Porous Structures ◽  
Inverse Opals ◽  
Optical Images ◽  
Nucleation Sites ◽  
Enhanced Boiling

Enhanced boiling is one of the popular cooling schemes in thermal management due to its superior heat transfer characteristics. This study demonstrates the ability of copper inverse opal (CIO) porous structures to enhance pool boiling performance using a thin CIO film with a thickness of ∼10 μm and pore diameter of 5 μm. The microfabricated CIO film increases microscale surface roughness that in turn leads to more active nucleation sites thus improved boiling performance parameters such as heat transfer coefficient (HTC) and critical heat flux (CHF) compared to those of smooth Si surfaces. The experimental results for CIO film show a maximum CHF of 225 W/cm2 (at 16.2 °C superheat) or about three times higher than that of smooth Si surface (80 W/cm2 at 21.6 °C superheat). Optical images showing bubble formation on the microporous copper surface are captured to provide detailed information of bubble departure diameter and frequency.

Critical Heat Flux of Graphene Coated Copper Surface at High Pressures

2015 ◽  
Author(s):  
Nanxi Li ◽  
Amy Rachel Betz
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Pressures ◽  
Pool Boiling ◽  
Copper Surface ◽  
Test Fluid ◽  
System Pressure ◽  
Wall Superheat ◽  
Copper Cylinder

Boiling is an efficient way to transfer heat due to the latent heat of vaporization. Many variables, such as surface properties, fluid properties, and system pressure, will affect the performance of pool boiling. Enhanced pool boiling has extensive applications in chemical, microelectronics, and power industries. Previous research has shown that micro- or nanostructured surfaces and coated surfaces will increase heat transfer coefficients up to one order of magnitude at atmospheric pressure. Graphene as a very good material with superb mechanical and electrical properties also has potential to enhance pool boiling performance. The purpose of this research is to investigate heat transfer enhancement on a graphene coated surface compared to a plane copper surface at atmospheric pressure and increased pressures with deionized water. The effect of the graphene coating on the critical heat flux is also investigated. To carry out the experiments, we designed and fabricated a special experimental facility that will withstand the high pressures (up to 20 bar) and high temperatures. Graphene is coated on a 1 cm2 copper surface using spray coating. The boiling vessel is pressurized with nitrogen and the system pressure is controlled by a back pressure regulator. The test fluid is preheated to saturation temperature by two 500 W cartridge heaters. Multiple 150 W cartridge heaters are inserted in a copper cylinder to provide wall superheat for bubbles to nucleate on the studied surface. When the system reaches steady state, a process controller controls these cartridge heaters to increase the heat flux gradually from 0 kW/m2 to the critical heat flux. The copper cylinder is insulated with PTFE to minimize heat loss from the side. The gap between the copper cylinder and the insulation surface is carefully sealed with high temperature epoxy to reduce undesired nucleation sites. The wall superheat corresponding to each heat flux is extrapolated using Fourier’s law from three thermocouple readings. The heat transfer coefficient can thus be calculated at each heat flux for the every test fluid at its corresponding pressure. A camera with 3.2 cm field of view at a working distance of 12 cm to 15 cm is used to visualize the bubble formation on the heated surface.

Pool Boiling on Multiple Surfaces in Proximity

2005 ◽  
Author(s):  
Nasser Ghariban ◽  
Ali Rostami
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Heated Surface ◽  
Bubble Formation ◽  
Pool Boiling ◽  
Lower Surface ◽  
Heat Transfer Process ◽  
Test Surface

Information on the boiling heat transfer on a surface when affected by the presence of other surfaces is scares. Pool boiling heat transfer process on multiple surfaces in proximity has been investigated in this work. In particular, the boiling curve and the critical heat flux on a surface located in the heated plume of another surface is studied experimentally. The surfaces are made of two identical wires with known diameter positioned horizontally in a predetermined short distance from each other. Tests were performed by heating the wires up to the critical heat flux in a pool of stationary FC-72 fluid. The boiling curves were experimentally developed for a surface when it is located in the plume of another heated surface. Initial results indicate that the critical heat flux on such a surface drops more than 30% compared to a single isolated wire. The change may be attributed to the plume effects on the bubble formation and bubble dynamics of upper surface as well as the effects on the degree of subcooling in the immediate neighborhood of the test surface. The research focused on the effects of spacing and the degree of subcooling on the boiling and the critical heat flux of the upper surface which is affected by the natural convection and boiling plume of the lower surface. The results of this project are expected to expand the existing knowledge of boiling heat transfer, particularly when it is affected by the presence of other surfaces in the proximity.

scholarly journals Predicting Critical Heat Flux With Multiphase CFD: 4 Years in the Making

2017 ◽  
Author(s):  
Emilio Baglietto ◽  
Etienne Demarly ◽  
Ravikishore Kommajosyula
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Heated Surface ◽  
Force Balance ◽  
Modeling Framework ◽  
Lift Off ◽  
Limiting Condition

Advancement in the experimental techniques have brought new insights into the microscale boiling phenomena, and provide the base for a new physical interpretation of flow boiling heat transfer. A new modeling framework in Computational Fluid Dynamics has been assembled at MIT, and aims at introducing all necessary mechanisms, and explicitly tracks: (1) the size and dynamics of the bubbles on the surface; (2) the amount of microlayer and dry area under each bubble; (3) the amount of surface area influenced by sliding bubbles; (4) the quenching of the boiling surface following a bubble departure and (5) the statistical bubble interaction on the surface. The preliminary assessment of the new framework is used to further extend the portability of the model through an improved formulation of the force balance models for bubble departure and lift-off. Starting from this improved representation at the wall, the work concentrates on the bubble dynamics and dry spot quantification on the heated surface, which governs the Critical Heat Flux (CHF) limit. A new proposition is brought forward, where Critical Heat Flux is a natural limiting condition for the heat flux partitioning on the boiling surface. The first principle based CHF is qualitatively demonstrated, and has the potential to deliver a radically new simulation technique to support the design of advanced heat transfer systems.

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