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.

Comparison of Ethylene-Glycol Coolants With/Without Additives for Subcooled Boiling Conditions

2012 ◽  
Author(s):  
Ryan Ehid ◽  
Edward V. McAssey ◽  
Lee Reichard ◽  
Jurgen De Kimpe ◽  
Serge Lievens
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Ethylene Glycol ◽  
Corrosion Protection ◽  
Thermal Performance ◽  
Experimental Results ◽  
Subcooled Boiling ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Aqueous Ethylene Glycol

This paper presents experimental data comparing the thermal performance of aqueous ethylene-glycol mixtures with and without additives. These additives are used to provide corrosion protection, but their presence can also improve the coolant thermal performance. The experimental results show that the coolant with additives yields wall temperatures approximately 50°C lower than the non-additive coolant at the maximum heat flux condition.

scholarly journals Boiling of FC-72 on Surfaces with Open Copper Microchannel

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7283
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pool Boiling ◽  
Fold Increase ◽  
Heat Transfer Process ◽  
Cross Sectional ◽  
Maximum Heat ◽  
Maximum Heat Flux

The paper presents the results of experimental research on pool boiling heat transfer of dielectric liquid FC-72. Measurements were made at atmospheric pressure on open surfaces with microchannels. Heat transfer surfaces, in the form of parallel milled microchannels, were made of copper. The rectangular cross-sectional microchannels were 0.2 to 0.5 mm deep and 0.2 to 0.4 mm wide. The surfaces, compared to a smooth flat surface, provided a five-fold increase in the heat transfer coefficient and a two-fold increase in the critical heat flux. The article analyses the influence of the width and height of the microchannel on the heat transfer process. The maximum heat flux was 271.7 kW/m2, and the highest heat transfer coefficient obtained was 25 kW/m2K. Furthermore, the experimental results were compared with selected correlations for the nucleate pool boiling.

High Heat Flux Dissipation Using Symmetric Dual-Taper Manifold in Pool Boiling

2019 ◽  
Author(s):  
Aranya Chauhan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pool Boiling ◽  
Heat Removal ◽  
Heating Surface ◽  
High Heat ◽  
Copper Surface ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Continuous Increase

Abstract The trend of miniaturization in electronics presents a great challenge in the thermal management of devices. The continuous increase in the number of transistors in the processor leads to high heat flux generation, limiting the performance of the device. Boiling heat transfer offers a great heat removal competency while maintaining the low chip temperatures. The critical heat flux (CHF) dictates the maximum heat removal ability, and heat transfer coefficient (HTC) defines the efficiency of the boiling process. This pool boiling study is focused on using a manifold containing a symmetric dual taper over the heating surface. The heat transfer performance of this configuration is evaluated for different taper angles in the manifold. The macro-convection assisted by vapor columns during boiling enhance the CHF and HTC limit significantly. A CHF of 287 W/cm2 with an HTC of 116 kW/cm2°C was achieved with a plain copper surface, representing greater than a 2-fold increases in each over a plain surface.

Pool Boiling Studies on Nano-Structured Surfaces

2007 ◽  
Author(s):  
S. R. Sriraman ◽  
D. Banerjee
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Test Fluid ◽  
Wafer Surface ◽  
Test Surface ◽  
Maximum Heat ◽  
Structured Surfaces ◽  
Nano Structures ◽  
Maximum Heat Flux ◽  
Rectangular Pattern

The effect of nano-structures on pool boiling heat transfer is explored in this study. The silicon nano-structures are fabricated on 4″ double-side polished silicon wafers using Step and Flash Imprint Lithography (SFIL) process. An array of “nano-fins” consisting of 200 nm diameter pillars of 100 nm height, lateral pitch of 1 μm and transverse pitch of 0.9 μm are created in a rectangular pattern on the wafer surface. The test surface is used for pool boiling experiments using PF-5060 as the test fluid (Manufacturer - 3M Co., boiling point - 56 °C). Experiments are performed under saturation and liquid sub-cooling conditions. The heat flux measurements on the nanostructures are compared with that of bare surfaces. The test rig is of constant heat flux type. Results are reported at the maximum heat flux point. The nano-structured test surface showed a 41% increase in heat flux compared to the bare test surface under the saturation test condition. The 10-degree sub-cooling and 20-degree sub-cooling test conditions showed a 19% and 27% enhancement at the maximum heat flux point respectively.

Boiling Heat Transfer Characteristics of Rotary Hollow Cylinders with In-Line and Staggered Multiple Arrays of Water Jets

2021 ◽  
Author(s):  
Mohammad Jahedi ◽  
Bahram Moshfegh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stagnation Point ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Maximum Heat ◽  
Water Jets ◽  
Maximum Heat Flux ◽  
Inner Surface ◽  
Hollow Cylinders

Abstract Transient heat transfer studies of quenching rotary hollow cylinders with in-line and staggered multiple arrays of jets have been carried out experimentally. The study involves three hollow cylinders (Do/d = 12 to 24) with rotation speed 10 to 50 rpm, quenched by subcooled water jets (ΔTsub=50-80 K) with jet flow rate 2.7 to 10.9 L/min. The increase in area-averaged and maximum heat flux over quenching surface (Af) has been observed in the studied multiple arrays with constant Qtotal compared to previous studies. Investigation of radial temperature distribution at stagnation point of jet reveals that the footprint of configuration of 4-row array is highlighted in radial distances near the outer surface and vanishes further down toward the inner surface. The influence of the main quenching parameters on local average surface heat flux at stagnation point is addressed in all the boiling regimes where the result indicates jet flow rate provides strongest effect in all the boiling regimes. Effectiveness of magnitude of maximum heat flux in the boiling curve for the studied parameters is reported. The result of spatial and temporal heat flux by radial conduction in the solid presents projection depth of cyclic variation of surface heat flux in the radial axis as it disappears near inner surface of hollow cylinder. In addition, correlations are proposed for area-averaged Nusselt number as well as average and maximum local heat flux at stagnation point of jet for the in-line and staggered multiple arrays.

Thermal Aspects of Using Uranium Mononitride Fuel in a SuperCritical Water-Cooled Reactor at Maximum Heat Flux Conditions

2010 ◽  
Author(s):  
Ashley Milner ◽  
Caleb Pascoe ◽  
Hemal Patel ◽  
Wargha Peiman ◽  
Graham Richards ◽  
...  
Keyword(s):  
Heat Flux ◽  
Supercritical Water ◽  
Thermal Efficiency ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Maximum Heat ◽  
Light Water ◽  
Maximum Heat Flux ◽  
Centerline Temperature ◽  
Uranium Mononitride

Generation IV nuclear reactor technology is increasing in popularity worldwide. One of the six Generation-IV-reactor types are SuperCritical Water-cooled Reactors (SCWRs). The main objective of SCWRs is to increase substantially thermal efficiency of Nuclear Power Plants (NPPs) and thus, to reduce electricity costs. This reactor type is developed from concepts of both Light Water Reactors (LWRs) and supercritical fossil-fired steam generators. The SCWR is similar to a LWR, but operates at a higher pressure and temperature. The coolant used in a SCWR is light water, which has supercritical pressures and temperatures during operation. Typical light water operating parameters for SCWRs are a pressure of 25 MPa, an inlet temperature of 280–350°C, and an outlet temperature up to 625°C. Currently, NPPs have thermal efficiency about of 30–35%, whereas SCW NPPs will operate with thermal efficiencies of 45–50%. Furthermore, since SCWRs have significantly higher water parameters than current water-cooled reactors, they are able to support co-generation of hydrogen. Studies conducted on fuel-channel options for SCWRs have shown that using uranium dioxide (UO2) as a fuel at supercritical-water conditions might be questionable. The industry accepted limit for the fuel centerline temperature is 1850°C and using UO2 would exceed this limit at certain conditions. Because of this problem, there have been other fuel options considered with a higher thermal conductivity. A generic 43-element bundle for an SCWR, using uranium mononitride (UN) as the fuel, is discussed in this paper. The material for the sheath is Inconel-600, because it has a high resistance to corrosion and can adhere to the maximum sheath-temperature design limit of 850°C. For the purpose of this paper, the bundle will be analyzed at its maximum heat flux. This will verify if the fuel centerline temperature does not exceed 1850°C and that the sheath temperature remains below the limit of 850°C.

EMC3-EIRENE simulations of neon impurity seeding effects on heat flux distribution on CFETR

2022 ◽  
Author(s):  
Shuyu Dai ◽  
Defeng Kong ◽  
Vincent Chan ◽  
Liang Wang ◽  
Yuhe Feng ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
Flux Distribution ◽  
Three Dimensional ◽  
Input Power ◽  
Heat Flux Distribution ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Heat Loads ◽  
Injection Location

Abstract The numerical modelling of the heat flux distribution with neon impurity seeding on CFETR has been performed by the three-dimensional (3D) edge transport code EMC3-EIRENE. The maximum heat flux on divertor targets is about 18 MW m-2 without impurity seeding under the input power of 200 MW entering into the scrape-off layer. In order to mitigate the heat loads below 10 MW m-2, neon impurity seeded at different poloidal positions has been investigated to understand the properties of impurity concentration and heat load distributions for a single toroidal injection location. The majority of the studied neon injections gives rise to a toroidally asymmetric profile of heat load deposition on the in- or out-board divertor targets. The heat loads cannot be reduced below 10 MW m-2 along the whole torus for a single toroidal injection location. In order to achieve the heat load mitigation (<10 MW m-2) along the entire torus, modelling of sole and simultaneous multi-toroidal neon injections near the in- and out-board strike points has been stimulated, which indicates that the simultaneous multi-toroidal neon injections show a better heat flux mitigation on both in- and out-board divertor targets. The maximum heat flux can be reduced below 7 MWm-2 on divertor targets for the studied scenarios of the simultaneous multi-toroidal neon injections.

Maximum heat flux in relation to quenching of a high temperature surface with liquid jet impingement

2006 ◽  
Vol 49 (17-18) ◽  
pp. 2877-2888 ◽  
Author(s):  
Aloke Kumar Mozumder ◽  
Masanori Monde ◽  
Peter Lloyd Woodfield ◽  
Md. Ashraful Islam
Keyword(s):  
Heat Flux ◽  
High Temperature ◽  
Jet Impingement ◽  
Liquid Jet ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Temperature Surface
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