Enhanced Heat Transfer Using Microporous Copper Inverse Opals

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.

Download Full-text

Copper Inverse Opal Surfaces for Enhanced Boiling Heat Transfer

ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems ◽

10.1115/ipack2017-74090 ◽

2017 ◽

Cited By ~ 2

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.

Download Full-text

Integrated Eco-Thermal Management for Aerospace

Advanced Energy Systems ◽

10.1115/imece2005-82865 ◽

2005 ◽

Author(s):

Lev Reznikov

Keyword(s):

Heat Transfer ◽

Thermal Management ◽

High Performance ◽

Waste Heat ◽

Space Station ◽

Nucleate Boiling ◽

High Heat ◽

Novel Technologies ◽

Related Substances ◽

Nucleation Sites

Thermal Management System developed for aerospace carriers (missile, aircraft, space station), bounds processes of generation and dissipation, transfer and conversion of power, refrigeration, and of bio-metabolism related substances. Local ecosystem of the carrier combines technological and biological subsystems, interacting with internal and outer spaces. The conceptual IETM System performs recovery of waste thermal energy, generation of “free” refrigeration, and recovery of byproducts into safe coolants (ammonia - water). Thermal Management solutions include novel technologies of intensification of the heat transfer and of conversion of the waste resources into refrigeration for extension of cooling capabilities for high heat radars, lasers and microwave generators. The IETM includes Vacuum-Evaporative Refrigeration (VER) utilizing “free natural” vacuum and waste heat-activated refrigeration circuits. VER generates ~1000 Btu of “free” cold per pound of wastewater or ammonia. The introduced high performance microstructure of compound electrohydrodynamic (EHD) boundary microsystems intensifies nucleate boiling, preventing dryout. The coils of the microwires adjoin to the boiling surface and form precision microstructure of heat sink with microchannels between the coils and the surface. The microcavities form the active bubbling nucleation sites along the spiral zones of contacts of the microwires and basic surfaces. The fins-microelectrodes develop additional heat transfer surface and evenly distributed spiral zones of the nucleation sites. Like fibers of a fine wick, the electric forces in EHD capillary structures of the microelectrodes retain the liquid and push out generated vapor bubbles from the surface. Good manufacturability and performance of novel MEMS are based on well-developed materials and common winding technology “borrowed” from electrotechnical industry. Conversion of waste resources into refrigeration and EHD activation of boiling allow meeting strong limitations in weight, reliability and consumption of energy. These conceptual approaches provide diversities in refrigeration capabilities for IETM.

Download Full-text

Donald Q. Kern Lecture Award Paper: Odyssey of the Enhanced Boiling Surface

Journal of Heat Transfer ◽

10.1115/1.1834615 ◽

2004 ◽

Vol 126 (6) ◽

pp. 1051-1059 ◽

Cited By ~ 62

Author(s):

Ralph L. Webb

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Pore Diameter ◽

Surface Geometry ◽

Exchange System ◽

Heat Exchange System ◽

Fundamental Understanding ◽

Boiling Heat Transfer Coefficient ◽

Coated Surface ◽

Enhanced Boiling

This paper traces the evolution of enhanced boiling surfaces. Early work was highly empirical and done in industrial research. The 1968 Milton patent [“Heat Exchange System,” U.S. Patent 3,696,861] described the first porous coated surface, and the 1972 Webb patent [“Heat Transfer Surface Having a High Boiling Heat Transfer Coefficient,” U.S. Patent 3,521,708] described a “structured” tube surface geometry. The first fundamental understanding of the “pore-and-tunnel” geometry was published by Nakayama in 1980 [Nakayama, W., Daikoku, T., Kuwahara, H., and Nakajima, T. 1980, “Dynamic Model of Enhanced Boiling Heat Transfer on Porous Surfaces Part I: Experimental Investigation,” J. Heat Transfer, 102, pp. 445–450]. Webb and Chien’s flow visualization allowed observation of the evaporation in the subsurface tunnels [Chien, L.-H., and Webb, R. L., 1998, “Visualization of Pool Boiling on Enhanced Surfaces,” Exp. Fluid Thermal Sci., 16b, pp. 332–341]. They also performed an experimental parametric study that defines the effect of pore diameter and pitch on the boiling performance. The progression of work on analytical boiling models is also reviewed.

Download Full-text

Dynamic Model of Enhanced Boiling Heat Transfer on Porous Surfaces—Part I: Experimental Investigation

Journal of Heat Transfer ◽

10.1115/1.3244320 ◽

1980 ◽

Vol 102 (3) ◽

pp. 445-450 ◽

Cited By ~ 148

Author(s):

W. Nakayama ◽

T. Daikoku ◽

H. Kuwahara ◽

T. Nakajima

Keyword(s):

Heat Transfer ◽

Dynamic Model ◽

Boiling Heat Transfer ◽

Bubble Formation ◽

Nucleate Boiling ◽

Vital Role ◽

Structured Surfaces ◽

Wall Superheat ◽

Nucleate Boiling Heat Transfer ◽

Enhanced Boiling

Enhancement of nucleate boiling heat transfer has been studied with the structured surfaces composed of interconnected internal cavities in the form of tunnels and small pores connecting the pool liquid and the tunnels. The boiling curves of R-11, water and nitrogen show 80 to 90 percent reduction of wall superheat required to transfer the same heat flux as that on plain surfaces, when the pore diameter is set around 0.1 mm. The experimental data on bubble formation showed a significant contribution of latent heat transport to the enhancement. A visualization study made with a transparent structured model suggested that the liquid suction into the tunnel is triggered by the bubble growth at active pores and subsequent evaporation inside the tunnel plays a vital role in driving the bubble formation cycle. This observation led to a conception of the dynamic model expounded in Part II.

Download Full-text

Understanding Enhanced Boiling With Triton X Surfactants

Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology ◽

10.1115/ht2013-17497 ◽

2013 ◽

Cited By ~ 5

Author(s):

H. Jeremy Cho ◽

Vishnu Sresht ◽

Daniel Blankschtein ◽

Evelyn N. Wang

Keyword(s):

Heat Transfer ◽

Surface Tension ◽

Adsorption Model ◽

Nucleation Sites ◽

Boiling Enhancement ◽

Enhancing Heat Transfer ◽

Enhanced Boiling ◽

Solid Liquid Interface ◽

Triton X ◽

Solid Liquid

Heat transfer performance in pool boiling is largely dictated by bubble growth, departure, and number of nucleation sites. It is a well known phenomenon that adding surfactants can lower the liquid-vapor surface tension and increase the bubble departure frequency, thereby enhancing heat transfer. In addition to faster departure rates, surfactants are observed to dramatically increase the number of nucleation sites, which cannot be explained by simple surface tension arguments. Furthermore, it is not well understood which surfactant properties such as chemical composition and molecular structure affect boiling most significantly. From our experiments using Triton X-100 and Triton X-114 nonionic surfactants, we attribute boiling enhancement mainly to adsorption to the solid-liquid interface. Using the Mikic-Rohsenow model for boiling, a simple linear adsorption model, and the Cassie-Baxter description for contact angle, we developed a model that shows agreement with experimental results. This work offers some insights on how to predict boiling enhancement based on surfactant chemistry alone, which may aid in choosing optimal surfactants for boiling in the future.

Download Full-text