Biotemplated Superhydrophobic Surfaces for Enhanced Dropwise Condensation

2012 ◽  
Author(s):  
Emre Olceroglu ◽  
Stephen M. King ◽  
Md. Mahamudur Rahman ◽  
Matthew McCarthy
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Electronics Cooling ◽  
High Heat ◽  
The Self ◽  
High Heat Flux ◽  
Dropwise Condensation ◽  
Large Area ◽  
Hydrophobic Surfaces ◽  
Structured Surfaces

The increased heat transfer achieved through dropwise condensation, as compared to filmwise condensation, has the potential to substantially impact a variety of applications including high-heat flux thermal management systems, integrated electronics cooling, and various industrial and chemical processes. Here, we report stable dropwise condensation onto biotemplated nanostructured super-hydrophobic surfaces. We have demonstrated continuous droplet coalescence and ejection at diameters of less than 20 μm and compared directly with flat hydrophobic surfaces. The self-ejection mechanism characteristic of dropwise condensation has been shown using a simple bio-nano-fabrication technique based on the self-assembly and mineralization of the Tobacco mosaic virus (TMV). This process is extendable to commercially relevant nanomanufacturing of both microscale electronics devices as well as large-scale large-area industrial equipment. This manufacturing flexibility is unique as compared to many other micro/nano-structured surfaces fabricated to demonstrate similar increases in condensation heat transfer.

Effect of Orientation and Draining on Linear Spray Array Thermal Management

2007 ◽  
Author(s):  
Benjamin M. Regner ◽  
Timothy A. Shedd
Keyword(s):  
Heat Transfer ◽  
Fluid Management ◽  
High Heat ◽  
Practical Implementation ◽  
High Heat Flux ◽  
Large Area ◽  
Candidate Solution ◽  
The Impact ◽  
Volumetric Flux ◽  
Uniform Droplet

Spray cooling is a candidate solution for high heat flux cooling applications, and previous work has investigated the impact of parameters of conical sprays such as volumetric flux and Sauter mean diameter on heat transfer performance. However, there has been little work on the impact of drainage and spray orientation on spray performances. In addition, conical sprays are not very practical for large area coverage in compact packages, so this study, presents a novel arrangment that uses linear sprays impinging at an angle such that fluid management and uniform droplet coverage of large areas are both improved. Results for the heat transfer coefficient and CHF of a constrained, practical implementation of a spray array (as opposed to a laboratory-only geometry) are presented for FC-72, FC-40 and HFE-7000.

Mechanistic Considerations for Enhancing Flow Boiling Heat Transfer in Microchannels

2015 ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Nucleation Sites ◽  
Flow Boiling Heat Transfer ◽  
Underlying Mechanisms

Research efforts on flow boiling in microchannels were focused on stabilizing the flow during the early part of the last decade. After achieving that goal through inlet restrictors and distributed nucleation sites, the focus has now shifted on improving its performance for high heat flux dissipation. The recent worldwide efforts described in this paper are aimed at increasing the critical heat flux (CHF) while keeping the pressure drop low, with an implicit goal of dissipating 1 kW/cm2 for meeting the high-end target in electronics cooling application. The underlying mechanisms in these studies are identified and critically evaluated for their potential in meeting the high heat flux dissipation goals. Future need to simultaneously increase the CHF and the heat transfer coefficient (HTC) has been identified and hierarchical integration of nanoscale and microscale technologies is deemed necessary for developing integrated pathways toward meeting this objective.

Enhanced Pool Boiling Performance on Micro-, Nano-, and Hybrid-Structured Surfaces

2011 ◽  
Author(s):  
Qian Li ◽  
Wei Wang ◽  
Chris Oshman ◽  
Benoit Latour ◽  
Chen Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Management ◽  
Pool Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Structured Surfaces ◽  
Maximum Heat Transfer ◽  
Functional Components

Thermal management plays an important role in both high power electronics and energy conversion systems. A key issue in thermal management is the dissipation of the high heat flux generated by functional components. In this paper, various microstructures, nanostructures and hybrid micro/nano-structures were successfully fabricated on copper (Cu) surfaces, and the corresponding pool boiling heat transfer performance was systematically studied. It is found that the critical heat flux (CHF) of hybrid structured surfaces is about 15% higher than that of the surfaces with nanowires only and micro-pillars only. More importantly, the superheat at CHF for the hybrid structured surface is much smaller than that of the micro-pillared surface (about 35%), and a maximum heat transfer coefficient (HTC) of about 90,000W/m2K is obtained. Compared with the known best pool boiling performance on biporous media, a much larger HTC and much lower superheat at a heat flux of 250W/cm2 have been obtained on the novel hybrid-structured surfaces.

Experimental and Analytical Studies of Reciprocating-Mechanism Driven Heat Loops (RMDHLs)

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Analytical Studies ◽  
Evaporator Section

This paper conducts experimental and analytical studies of a novel heat-transfer device, reciprocating-mechanism driven heat loop (RMDHL) that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. A RMDHL normally includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300W∕cm2 in the evaporator section could be handled. A working criterion has also been derived, which could provide a guidance for the design of a RMDHL.

On Temporal Biphilicity: Definition, Relevance, and Technical Implementation in Boiling Heat Transfer

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Christophe Frankiewicz ◽  
Daniel Attinger
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Large Scale ◽  
High Efficiency ◽  
Pool Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Functional Surfaces ◽  
Phase Change Heat Transfer

Solid–fluid interfaces switching from a superhydrophilic to a superhydrophobic wetting state are desired for their ability to control and enhance phase-change heat transfer. Typically, these functional surfaces are fabricated from polymers and modify their chemistry or texture upon the application of a stimulus. For integration in relevant phase-change heat transfer applications, several challenges need to be overcome, of chemical stability, mechanical and thermal robustness, as well as large scale manufacturing. Here, we describe the design and fabrication of metallic surfaces that reversibly switch between hydrophilic and superhydrophobic states, in response to pressure and temperature stimuli. Characterization of the surfaces in pool boiling experiments verifies their thermal and mechanical robustness, and the fabrication method is scalable to large areas. During pool boiling experiments, it is experimentally demonstrated that the functional surfaces can be actively switched between a high-efficiency mode suitable at low heat flux, and a high-power mode suitable for high heat flux applications.

scholarly journals Spray Cooling On Enhanced Surfaces: a Review of the Progress and Mechanisms

2021 ◽  
Author(s):  
Rui-Na Xu ◽  
Gaoyuan Wang ◽  
Peixue Jiang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Gas Flow ◽  
Rapid Development ◽  
Spray Cooling ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Next Generation ◽  
Structured Surfaces

Abstract The rapid development of electronics, energy and propulsion systems has led us to the point where their performances are limited by cooling capacities. Heat fluxes of 10~100, even over 1,000 W/cm2 need to be dissipated with minimum coolant flow rate in next-generation power electronics. Spray cooling is a high heat flux, uniform and efficient cooling technique proven effective in various applications. However, its cooling capacity and efficiency need to be further improved to meet next-generation ultrahigh-power applications. Engineering of surface properties and structures can fundamentally affect the liquid-wall interactions, thus becoming the most promising way to enhance spray cooling. However, the unclear mechanisms of surface-enhanced spray cooling cause lack of guiding principles for surface design. Here, progress in spray cooling on surfaces with structures of different scales are reviewed and their performances evaluated and compared. Spray cooling can achieve critical heat flux (CHF) above 945 W/cm2 and heat transfer coefficient (HTC) up to 57 W/cm2K on structured surfaces for pressurized nozzle and CHF and HTC up to 1250 W/cm2 and 250 W/cm2K, respectively, on a smooth surface with the assistance of secondary gas flow. CHF enhancement of 110% was achieved on hybrid micro- and nanostructured surfaces. A clear map of enhancement mechanisms is proposed after analysis. Some future concerns are also proposed. This work helps the understanding and design of engineered surfaces in spray cooling and provides insights for interdisciplinary applications of heat transfer and advanced engineering materials.

Forced Convective Boiling in Microchannels for kW/cm2 Electronics Cooling

2003 ◽  
Author(s):  
Daniel J. Faulkner ◽  
Reza Shekarriz
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Electronics Cooling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Design Solution ◽  
High Heat Flux ◽  
Convective Boiling ◽  
High Heat Transfer

This paper reports some of the results of our tests for the development of a high heat flux cooling system for thermal management of high power electronics. Our objective is to develop a practical design solution for achieving 1000 W/cm2 cooling. To achieve such high heat transfer rates, we have pursued and combined design advantages of a microchannel heat exchanger, high heat fluxes associated with forced convective nucleate boiling, and the use of a nanoparticles laden fluid for enhancement of heat transfer. A laboratory test module was designed, built, and tested to verify its performance. The experimental system employed sub-cooled as well as saturated forced convection boiling heat transfer in a high aspect ratio parallel microchannel heat sink. The working fluids tested were water and a selection of ceramic-based nanoparticle suspensions (nanofluids). The system was observed to readily dissipate heat fluxes in excess of 275 W/cm2 of substrate, while maintaining the substrate at or below 125°C. For optimized fin geometry, the current conditions would result in greater than 500 W/cm2. While the use of nanofluids was intended for boiling enhancement to push the envelop beyond 1000 W/cm2, we discerned limited improvement in the overall heat transfer rate. Future studies are planned for further exploitation of nanoparticles for enhancement of convective nucleate boiling.

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