Pool Boiling of HFE 7200–C4H4F6O Mixture on Hybrid Micro-Nanostructured Surface

2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Aravind Sathyanarayana ◽  
Pramod Warrier ◽  
Yunhyeok Im ◽  
Yogendra Joshi ◽  
Amyn S. Teja
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Molecular Design ◽  
Pool Boiling ◽  
Dielectric Constants ◽  
Heat Transfer Fluid ◽  
Fluid Mixture ◽  
Immersion Cooling ◽  
Direct Immersion Cooling ◽  
Direct Immersion

Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints have led to the use of Novec fluids and fluroinerts as coolants. Although these fluids are chemically stable and have low dielectric constants, they are plagued by poor thermal properties like low thermal conductivity (about twice that of air) and low specific heat (same as that of air). These factors necessitate the development of new heat transfer fluids with improved heat transfer properties and applicability. C4H4F6O is a new heat transfer fluid which has been identified using computer-aided molecular design (CAMD) and knowledge-based approaches. A mixture of Novec fluid (HFE 7200) with C4H4F6O is evaluated in this study. Pool boiling experiments are performed at saturated condition on a 10 mm × 10 mm silicon test chip with CuO nanostructures on a microgrooved surface, to investigate the thermal performance of this new fluid mixture. The mixture increased the critical heat flux moderately by 8.4% over pure HFE 7200. Additional investigation is necessary before C4H4F6O can be considered for immersion cooling applications.

scholarly journals Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Eduardo Freitas ◽  
Pedro Pontes ◽  
Ricardo Cautela ◽  
Vaibhav Bahadur ◽  
João Miranda ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Pool Boiling ◽  
Temperature Drop ◽  
Surface Cooling ◽  
Average Temperature ◽  
Gold Silver

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

Experimental Investigation of a Thermosyphon With Microstructure on the Boiling Surface

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Y. Chai ◽  
W. Tian ◽  
J. Tian ◽  
L. W. Jin ◽  
X. Z. Meng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Pool Boiling ◽  
High Heat ◽  
Primary Concern ◽  
Heat Transfer Efficiency ◽  
Heater Wall ◽  
Micro Structures ◽  
Thermal Physical Properties ◽  
Graphite Foam

Abstract In recent years, a primary concern in the development of electronic technology is high heat dissipation of power devices. The advantages of unique thermal physical properties of graphite foam raise up the possibility of developing pool boiling system with better heat transfer efficiency. A compact thermosyphon was developed with graphite foam insertions to explore how different parameters affect boiling performance. Heater wall temperature, superheat, departure frequency of bubbles, and thermal resistance of the system were analyzed. The results indicated that the boiling performance is affected significantly by thermal conductivity and pore diameter of graphite foam. A proposed heat transfer empirical correlation reflecting the relations between graphite foam micro structures and pool boiling performance of Novec7100 was developed in this paper.

Design and Performance of Novel Low-Profile Heat Sinks Created Through Additive Manufacturing

2016 ◽  
Author(s):  
Pratik KC ◽  
Sangeet Shrestha ◽  
Adarsh Radadia ◽  
Leland Weiss ◽  
Arden Moore
Keyword(s):  
Additive Manufacturing ◽  
Heat Sink ◽  
Heat Sinks ◽  
Two Phase ◽  
Printed Circuit ◽  
Immersion Cooling ◽  
Low Profile ◽  
Direct Immersion Cooling ◽  
Power Densities ◽  
Direct Immersion

Traditional thermal management techniques such as air-cooled plate- and pin-fin heat sinks are today being pushed to their limits by the increasing power densities of computing hardware (power supplies, controllers, processors, and integrated circuits). In comparison, direct immersion cooling within an alternative cooling medium such as commercial dielectric fluids offers the ability to handle high power densities while also accommodating tighter printed circuit board spacing. Together, these attributes are critical to facilitating higher computing densities. However, this type of high density setup also requires that any heat sink present be low profile so as to not obstruct adjacent printed circuit boards. Such a stringent limit on heat sink height can make achieving cooling targets challenging with existing designs. In this work, the performance of several low profile (height less than 6 mm) heat sinks of varying design are evaluated within a carefully controlled direct immersion cooling environment. Commercial copper heat sinks fabricated through conventional manufacturing (CM) approaches serve as baselines for these performance tests. These same heat sink designs are also replicated via additive manufacturing (AM) utilizing a conductive, carbon-filled printable polylactic acid (PLA) composite material. The performance of these AM heat sinks are then compared to the CM heat sinks, with special emphasis on differences in thermal conductivity between the constituent materials. Finally, novel bio-inspired heat sink designs are developed which would be difficult or impossible to achieve using CM approaches. The most promising of these designs were then created using AM and their performance evaluated for comparison. The overall goal of this is to ascertain whether the design and fabrication flexibility offered by AM can facilitate low profile heat sink designs that can meet or exceed the performance of conventional heat sinks even with perceived deficiencies in material properties for AM parts. Experiments were carried out within Novec 7100 dielectric fluid for single-phase natural convection scenarios as well as two-phase subcooled boiling conditions at atmospheric pressure. A custom test rig was constructed consisting of mirror-polished stainless steel plates and polycarbonate viewing ports to allow visual access. A rotating sample stage allows for data to be obtained at varying heat sink orientation angles from 0° to 90°. For two-phase experiments, multi-angle video capture allows for analysis of the two-phase dynamics occurring at the heat sink samples to be visualized and temporally linked to the associated temperature and heat flux data.

Novel Immersion Cooling Technique for a 3D Chip Stack

2013 ◽  
Author(s):  
Ashish Sinha ◽  
Krishna Kota ◽  
Pablo Hidalgo ◽  
Yogendra Joshi ◽  
Ari Glezer
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Power Input ◽  
Synthetic Jet ◽  
Total Power ◽  
Dielectric Fluid ◽  
Immersion Cooling ◽  
Fluid Convection ◽  
Enhancing Heat Transfer ◽  
Jet Fan

An experimental investigation of a scheme for cooling electronics packaged in a 3D stack arrangement will be presented in this paper. The scheme utilizes immersion cooling of the stacked electronics in an enclosure filled with a dielectric fluid. Convection and conduction within the dielectric fluid drive heat from the 3D stack to the walls of the enclosure from where a ‘synthetic jet /fan air-cooled heat sink’ ultimately dissipates heat to the ambient. Four layers of thick film heaters embedded in FR-4 sheets, each attached to thin copper plates (innovatively stacked in a pyramidal arrangement for conducting heat laterally to the dielectric fluid and simultaneously promoting natural convection in the fluid), were used to simulate a 3D stack of electronics. For a comparative study, several runs were carried out, where the enclosure was filled with dielectric fluid (FC-770), FC-770 in combination with copper wool (with a goal of enhancing heat transfer in FC-770), and water. For a 40 W total power input to the stack, it was observed that the thermal resistance for heat dissipation to ambient from the four heaters varied from 1.67 K/W to 1.96 K/W with FC-770, 1.47 K/W to 1.87 K/W with FC-770 combined with copper wool, and 1.06 K/W to 1.50 K/W with water. The proposed cooling solution is passive and scalable, and is demonstrated to be practicable and effective in cooling 3D stacked electronics.

Analysis of Using Ferrofluid as an Interface Material in a Field Reversible Thermal Connector

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Ahmed S. Yousif ◽  
Gary L. Solbrekken
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Iron Nanoparticles ◽  
Heat Dissipation ◽  
The Other ◽  
Thermal Interface Material ◽  
Heat Transfer Fluid ◽  
University Of Missouri ◽  
Transfer Path ◽  
Current Design

The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore, it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be reworkable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the unexpanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands, it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material, the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.

Pool Boiling Heat Transfer Over Microchannel Surfaces With Ethanol at Atmospheric Pressure

2012 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Heat Dissipation ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Electronic Cooling ◽  
Fluid Medium ◽  
Important Research Topic ◽  
Quantity Of Heat ◽  
Enhanced Surface

The growing trend in miniaturization has brought forth boiling as an important research topic for augmentation of heat transfer in electronic cooling application. Pool boiling has the ability to dissipate a large quantity of heat while maintaining a small temperature difference. The heat dissipation capacity of pool boiling is further augmented through the use of enhanced microchannel surfaces. The objective of this work is to investigate the pool boiling performance of various microchannel structures using ethanol as the fluid medium. Ethanol has higher heat of vaporization compared to refrigerants and lower saturation temperature compared to water. Hence it has the potential to be used as an alternative cooling medium. This investigation will focus on experimentally studying the effect of enhanced surface structures on pool boiling of ethanol at atmospheric pressure.

Prediction of Nucleate Pool Boiling Heat Transfer Coefficients of Refrigerant-Oil Mixtures

1984 ◽  
Vol 106 (1) ◽  
pp. 184-190 ◽  
Author(s):  
M. K. Jensen ◽  
D. L. Jackman
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Fluid Mixture ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Oil Mixtures ◽  
Oil Concentration

This paper describes an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties. Boiling heat transfer data were taken in mixtures of up to 10 percent oil by weight in R-113. Thermophysical properties of the mixtures (density, viscosity, surface tension, specific heat, and contact angle) were measured. The decrease in heat transfer coefficient with increasing oil concentration is attributed to diffusion in an oil-enriched region surrounding the growing vapor bubbles. A correlation based on the postulated mechanism is presented which shows fair agreement with the experimental data from this study and with data obtained from the literature.

Corrections to “Selection and Evaluation of Organosilicon Coolants for Direct Immersion Cooling of Electronic Systems”

2013 ◽  
Vol 52 (24) ◽  
pp. 8354-8354
Author(s):  
Pramod Warrier ◽  
Aravind Sathyanarayana ◽  
Sara Bazdar ◽  
Yogendra Joshi ◽  
Amyn S. Teja
Keyword(s):  
Electronic Systems ◽  
Immersion Cooling ◽  
Direct Immersion Cooling ◽  
Direct Immersion
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