Pool Boiling of FC-87 Over Microchannel Surfaces at Atmospheric Pressure

2012 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Atmospheric Pressure ◽  
Pool Boiling ◽  
Electronics Cooling ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Maximum Heat ◽  
Wall Superheat ◽  
Maximum Heat Flux ◽  
Two Phase Cooling ◽  
Surface Area Increase

Advances in technology and trends towards higher processing speeds have generated a greater need for thermal management. Two-phase cooling (boiling) has the ability to dissipate large amounts of heat and is attractive because of lower mass flow requirement and uniform substrate temperature. Further improvements can be obtained through passive surface enhancements. The objective of this work is to investigate the effect of microchannel surfaces on pool boiling performance at atmospheric pressure with FC-87. Being a dielectric fluid with a low normal boiling point, FC-87 has desirable characteristics for an electronics cooling fluid. A maximum heat flux of 550 kW/m2 at a wall superheat of 37°C was obtained with the microchannel surface. Surface area increase is noted as the primary reason for the enhanced performance for FC-87 on microchannel surfaces.

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.

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.

Subcooled Boiling in the Ultrasonic Field (on Cause of MEB Generation)

2009 ◽  
Author(s):  
Fumio Inagaki ◽  
Koichi Suzuki ◽  
Chungpyo Hong
Keyword(s):  
Heat Flux ◽  
Aqueous Solutions ◽  
Ultrasonic Vibration ◽  
Pool Boiling ◽  
Atmospheric Condition ◽  
Heating Surface ◽  
Ultrasonic Field ◽  
Subcooled Boiling ◽  
Maximum Heat ◽  
Maximum Heat Flux

Subcooled quasi-pool boiling for water, ethanol aqueous solutions of 10wt% and 50wt% and ethanol in ultrasonic field is performed for the upward flat heating surface of copper block with 10mm in diameter under the atmospheric condition. Tested liquid subcooling is 15K, 20K and 25K for water and aqueous solutions of ethanol and 20K, 30K and 40K for 100wt% ethanol. At 20K of liquid subcooling for water and ethanol aqueous solutions, no microbubble emission boiling (MEB) has been observed in quasi-pool boiling. Even if MEB occurred, the heat flux does not increase and it turns easily to film boiling. In ultrasonic field, MEB occurs remarkably and the heat flux increases higher than the ordinary critical heat flux as observed in highly subcooled boiling. The experimental results show that the ultrasonic vibration introduces the instability of interface of liquid and vapor and accelerate MEB at 20K of liquid subcooling for water and aqueous solutions of ethanol. At 15K of liquid subcooling for water and aqueous solutions, no effect of ultrasonic vibration is observed. At 25K of liquid subcooling, the ultrasonic vibration extends MEB region to higher superheat of heating surface for aqueous solutions of ethanol. The maximum heat flux in MEB decreases with increasing of ethanol concentration and becomes CHF for 100wt% ethanol. No effect of ultrasonic vibration on boiling is observed for the 100wt% ethanol in the present experiments.

Pool Boiling Using Thin Enhanced Structures Under Top-Confined Conditions

2006 ◽  
Vol 128 (12) ◽  
pp. 1302-1311 ◽  
Author(s):  
Camil-Daniel Ghiu ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Pool Boiling ◽  
Single Layer ◽  
Temperature Limit ◽  
Heat Fluxes ◽  
The Other ◽  
Vapor Flow ◽  
Maximum Heat ◽  
Maximum Heat Flux

An experimental study of pool boiling using enhanced structures under top-confined conditions was conducted with a dielectric fluorocarbon liquid (PF 5060). The single layer enhanced structures studied were fabricated in copper and quartz, had an overall size of 10×10mm2, and were 1mm thick. The parameters investigated in this study were the heat flux (0.8-34W∕cm2) and the top space S(0-13mm). High-speed visualizations were performed to elucidate the liquid/vapor flow in the space above the structure. The enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. On the other hand, the maximum heat flux for a prescribed 85°C surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime.

scholarly journals Влияние наножидкостей на теплопередающую способность миниатюрных термосифонов для охлаждения электроники

2019 ◽  
Vol 45 (6) ◽  
pp. 54
Author(s):  
Б.И. Бондаренко ◽  
В.Н. Морару ◽  
В.Ю. Кравец ◽  
Г. Бехмард
Keyword(s):  
Thermal Resistance ◽  
Closed Loop ◽  
Electronics Cooling ◽  
Sharp Decrease ◽  
Vapor Film ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Boiling Process ◽  
Heat Transfer Capacity

AbstractStable nanofluids based on DG-100 grade carbon black and carbon nanotubes have been prepared, and their influence on the maximum heat-transfer capacity and thermal resistance of closed-loop two-phase thermosyphons (TPTs) intended for electronics cooling have been studied. A more than twofold increase in the critical heat flux of these TPTs as compared to those filled with water has been obtained along with a sharp decrease in their thermal resistance. It is suggested that this effect is not only due to the high thermal conductivity of the proposed nanofluids, but is also related to the formation of a specific porous structure hindering the appearance of a vapor film and enhancing the boiling process.

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.

A high-performance solid-state electrocaloric cooling system

Science ◽  
2020 ◽  
Vol 370 (6512) ◽  
pp. 129-133 ◽  
Author(s):  
Yunda Wang ◽  
Ziyang Zhang ◽  
Tomoyasu Usui ◽  
Michael Benedict ◽  
Sakyo Hirose ◽  
...  
Keyword(s):  
Heat Flux ◽  
Solid State ◽  
High Performance ◽  
Cooling System ◽  
Electronics Cooling ◽  
Multilayer Ceramic Capacitors ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
System Temperature ◽  
Performance System

Electrocaloric (EC) cooling is an emerging technology that has broad potential to disrupt conventional air conditioning and refrigeration as well as electronics cooling applications. EC coolers can be highly efficient, solid state, and compact; have few moving parts; and contain no environmentally harmful or combustible refrigerants. We report a scalable, high-performance system architecture, demonstrated in a device that uses PbSc0.5Ta0.5O3 EC multilayer ceramic capacitors fabricated in a manufacturing-compatible process. We obtained a system temperature span of 5.2°C and a maximum heat flux of 135 milliwatts per square centimeter. This measured heat flux is more than four times higher than other EC cooling demonstrations, and the temperature lift is among the highest for EC systems that use ceramic multilayer capacitors.

scholarly journals An Experimental Investigation Of Pool Boiling At Atmospheric Pressure

1970 ◽  
Vol 6 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Md Saimon Islam ◽  
Khadija Taslima Haque ◽  
Suman Chandra Saha
Keyword(s):  
Heat Flux ◽  
Experimental Investigation ◽  
Heat Input ◽  
Atmospheric Pressure ◽  
Pool Boiling ◽  
Voltage Regulator ◽  
Heat Sources ◽  
Time Intervals ◽  
Wall Superheat ◽  
Time Required

This paper deals with an experimental investigation of pool boiling of water and methanol at atmospheric pressure from small horizontal heat sources. The heat sources are inserted into the copper tube submerged in a laterally-confined, finite pool of liquid. The saturated pool boiling heat transfer characteristics and the critical heat flux (CHF) condition were determined in the experiments. In the experiment, an attempt has been made to estimate the heat flux for pool boiling of Water and Methanol at atmospheric pressure. An indoor experiment was conducted to measure (i) the heat flux of water and methanol, (ii) the temperature of the working fluids, (iii) the wall superheat temperatures, (iv) the temperatures at the bottom and side of the pot, (v) time required to be superheated at definite time intervals for a given heat input. The heat input has been varied by changing the voltage with the help of a voltage regulator. A regression analysis has been performed by using the experimental data in the correlation of Rohsenow for pool boiling. Keywords: Pool Boiling; Heat Flux; Wall Superheat; Correlation. DOI: http://dx.doi.org/10.3329/diujst.v6i1.9337 DIUJST 2011; 6(1): 80-86

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