Enhanced Pool Boiling With HFE7000 Over Selectively Sintered Microchannels

2017 ◽  
Author(s):  
Travis S. Emery ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Pool Boiling ◽  
Electronics Cooling ◽  
Fold Increase ◽  
High Heat ◽  
Heat Fluxes ◽  
Dielectric Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer

As the need for efficient thermal management grows, pool boiling’s ability to dissipate high heat fluxes has gained significant interest. The objective of this work was to study the performance of pool boiling at atmospheric pressure using a dielectric fluid, HFE7000. Both plain and enhanced copper surfaces were tested, and these results were then compared to similar testing performed with water and FC-87. The enhanced surfaces utilized microchannels with porous coatings selectively located on different regions of the heat transfer surface. A maximum critical heat flux (CHF) of 41.7 W/cm2 was achieved here, which translated to a 29% CHF increase in comparison to a plain chip. A maximum heat transfer coefficient (HTC) of 104.0 kW/m2°C was also achieved, which translated to a 6-fold increase in HTC when compared to a plain copper chip. More notably, this HTC was achieved at a wall temperature of 38.4 °C. This HTC enhancement was greater than that of water and FC-87 when using the same enhanced surface. The effect of sintering location was found to have a similar effect on CHF with HFE7000 in comparison with water. The effect of microchannel size was shown to have similar effects on CHF when compared with FC-87 and water. From the results found here, it is concluded that the employment of selectively sintered open microchannels with HFE7000 has significant potential for enhanced heat dissipation in electronics cooling applications.

Guidelines for Designing Micropillar Structures for Enhanced Evaporative Heat Transfer

2021 ◽  
Author(s):  
Kidus Guye ◽  
De Dong ◽  
Yunseo Kim ◽  
Hyoungsoon Lee ◽  
Baris Dogruoz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Interfacial Area ◽  
High Heat ◽  
Heat Fluxes ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Evaporation Heat

Abstract Over the last several decades, cooling technologies have been developed to address the growing thermal challenges associated with high-powered electronics. However, within the next several years, the heat generated by these devices is predicted to exceed 1 kW/cm2, and traditional methods, such as air cooling, are limited in their capacities to dissipate such high heat fluxes. In contrast, two-phase cooling methods, such as microdroplet evaporation, are very promising due to the large latent heat of vaporization associated with the phase change process. Previous studies have shown non-axisymmetric droplets exhibit different evaporation characteristics than spherical droplets. For a droplet pinned atop a micropillar, the solid-liquid and liquid-vapor interfacial area, the volume, and thickness of the droplet are the major factors that govern the evaporation heat transport process. In this work, we develop a shape optimization tool using the particle swarm optimization algorithm to maximize evaporation from a droplet confined atop a micropillar. The tool is used to optimize the shape of a nonaxisymmetric droplet. Compared to droplets atop circular and regular equilateral triangular micropillar structures, we find that droplets confined on pseudo-triangular micropillar structures have 23.7% and 5.7% higher heat transfer coefficients, respectively. The results of this work will advance the design of microstructures that support droplets with maximum heat transfer performance.

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.

Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes

2018 ◽  
Author(s):  
Jensen Hoke ◽  
Todd Bandhauer ◽  
Jack Kotovsky ◽  
Julie Hamilton ◽  
Paul Fontejon
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Flow Boiling ◽  
Laser Diodes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Average Maximum

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.

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.

scholarly journals Enhancement of Nucleate Pool Boiling Heat Transfer with Sodium Oleate

2017 ◽  
Vol 29 (1) ◽  
pp. 44-48
Author(s):  
KM Tanvir Ahmmed ◽  
Sultana Razia Syeda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sodium Oleate ◽  
Surfactant Concentration ◽  
Chemical Engineering ◽  
Pool Boiling ◽  
Nucleate Pool Boiling ◽  
Maximum Heat ◽  
Maximum Heat Transfer

In this study saturated nucleate pool boiling of water with sodium oleate surfactant on a horizontal cylindrical heater surface has been investigated experimentally and compared with that of demineralized water. The concentration of sodium oleate in water was 100-300 ppm. The experimental results show that a small amount of surfactant enhances the heat transfer coefficient significantly. At low surfactant concentrations, heat transfer coefficient increases with increasing surfactant concentration in water. The maximum heat transfer enhancement is found to be at 250 ppm of sodium oleate solution. By adding more surfactant to water, heat transfer coefficient is found to be lowered. Surface tension of different concentration of sodium oleate solutions is measured. It is observed that the maximum heat transfer coefficient is obtained at a surfactant concentration that corresponds to the critical micelle concentration (cmc) of the sodium oleate solution.Journal of Chemical Engineering, Vol. 29, No. 1, 2017: 44-48

Experimental Study of a Single Microchannel Flow Under Non-Uniform Heat Flux

2017 ◽  
Author(s):  
Ahmed Eltaweel ◽  
Abdulla Baobeid ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Dissipation ◽  
Hot Spot ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Uniform Heat Flux ◽  
Maximum Heat ◽  
Uniform Heat ◽  
Microchannel Heat Sinks

Non-uniform heat fluxes are commonly observed in thermo-electronic devices that require distinct thermal management strategies for effective heat dissipation and robust performance. The limited research available on non-uniform heat fluxes focus mostly on microchannel heat sinks while the fundamental component, i.e. a single microchannel, has received restricted attention. In this work, an experimental setup for the analysis of variable axial heat flux is used to study the heat transfer in a single microchannel with fully developed flow under the effect of different heat flux profiles. Initially a hot spot at different locations, with a uniform background heat flux, is studied at different Reynolds numbers while varying the maximum heat fluxes in order to compute the heat transfer in relation to its dependent variables. Measurements of temperature, pressure, and flow rates at a different locations and magnitudes of hot spot heat fluxes are presented, followed by a detailed analysis of heat transfer characteristics of a single microchannel under non-uniform heating. Results showed that upstream hotspots have lower tube temperatures compared to downstream ones with equal amounts of heat fluxes. This finding can be of importance in enhancing microchannel heat sinks effectiveness in reducing maximum wall temperatures for the same amount of heat released, by redistributing spatially fluxes in a descending profile.

scholarly journals Wettability and nanostructure effect on oscillating heat pipes

2015 ◽  
Author(s):  
◽  
Feng Zhao Zhang
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Maximum Heat Transfer ◽  
Heat Transfer Limit ◽  
Efficient Heat Transfer ◽  
Oscillating Motion ◽  
Transfer Device

As electronics technologies rapidly develop with a demand for more power and miniaturization, effective thermal management of these systems becomes much more important. The oscillating heat pipe (OHP) is a promising highly efficient heat transfer device that is great for high heat flux applications common in the electronics industry. In the current investigation, the wettability effect on the heat transfer performance of OHPs has been conducted. 1). The overall performance of configuration of hydrophilic evaporator/ hydrophobic condenser and hydrophobic evaporator/ hydrophilic condenser was worse than the nontreated OHP, however; the oscillations were much damper when comparing the amplitudes. 2). High oscillating motion occurs in the OHP with the hydrophilic surface while low oscillating motion occurs in the untreated OHP. 3). A mathematical model shows that contact angle increases the oscillating motion decreases. 4). A theoretical model predicting operating limit is developed. Results show that radius and charging ratio has a large effect on the maximum heat transfer limit. Working fluids changes the operating limit.

Numerical Investigation on Pool Boiling Over a Vertical Tube Coupled With In-Tube Condensation

2019 ◽  
Author(s):  
Shuai Ren ◽  
Wenzhong Zhou
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Boiling Heat Transfer ◽  
Power Plants ◽  
Pool Boiling ◽  
Heat Removal ◽  
Vertical Tube ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract Pool boiling and in-tube condensation phenomena have been investigated intensively during the past decades, due to the superior heat transfer capacity of the phase change process. In passive heat removal heat exchangers of nuclear power plants, the two phase-change phenomena usually occur simultaneously on both sides of the tube wall to achieve the maximum heat transfer efficiency. However, the studies on the effects of in-tube condensation on external pool boiling heat transfer are very limited, especially in numerical computation aspect. In the present study, the saturated pooling boiling over a vertical tube under the influences of in-tube steam condensation is investigated numerically. The Volume of Fluid (VOF) interface tracking method is employed based on the 2D axisymmetric Euler-Euler multiphase frame. The phase change model combining with a mathematical smoothing algorithm and a temporal relaxation procedure has been implemented into CFD platform by user defined functions (UDFs). The two-phase flow pattern and bubble behavior have been analyzed. The effects of inlet steam mass flow rate on boiling heat transfer are discussed.

Pool Boiling Heat Transfer With Binary Mixture on Open Microchannel Surface

2013 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Binary Mixture ◽  
Heat Dissipation ◽  
Surface Effect ◽  
Pure Water ◽  
Pool Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Two Phase ◽  
Maximum Heat ◽  
Fluid Medium

Two-phase cooling is considered an attractive option for electronics cooling due to its ability to dissipate large quantities of heat. In recent years, pool boiling has shown tremendous ability in high heat dissipation applications. Researchers have used various fluid medium for pool boiling including water, alcohol, refrigerants, nanofluids and binary mixture. In the current work, binary mixture of water with ethanol was chosen as the working fluid. Plain copper chip was used as the boiling surface. Effect of various concentrations of binary mixture was investigated. A maximum heat flux of 1720 kW/m2 at a wall superheat of 28°C was recorded for 15% ethanol in water. It showed a 1.5 fold increase in CHF over pure water.

Sign in / Sign up

Export Citation Format

Share Document