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

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.

Download Full-text

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

18th International Conference on Nuclear Engineering: Volume 2 ◽

10.1115/icone18-29998 ◽

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.

Download Full-text

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

Nuclear Fusion ◽

10.1088/1741-4326/ac47b5 ◽

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.

Download Full-text

Ablation of a Solid Material by High Temperature Liquid Jet Impingement: An Application to Corium Jet Impingement on a Sfr Core-Catcher

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4051448 ◽

2021 ◽

Author(s):

Alexandre Lecoanet ◽

Michel Gradeck ◽

Xiaoyang Gaus-Liu ◽

Thomas Cron ◽

Beatrix Fluhrer ◽

...

Keyword(s):

High Temperature ◽

Deep Understanding ◽

Jet Impingement ◽

Severe Accident ◽

Mitigation Measures ◽

Liquid Jet ◽

Cavity Formation ◽

The Core ◽

Core Catcher ◽

Temperature Liquid

Abstract This paper deals with ablation of a solid by a high temperature liquid jet. This phenomenon is a key issue to maintain the vessel integrity during the course of a nuclear reactor severe accident with melting of the core. Depending on the course of such an accident, high temperature corium jets might impinge and ablate the vessel material leading to its potential failure. Since Fukushima Daiichi accident, new mitigation measures are under study. As a designed safety feature of a future European SFR, bearing the purpose of quickly draining of the corium out of the core and protecting the reactor vessel against the attack of molten melt, the in-core corium is relocated via discharge tubes to an in-vessel core-catcher has been planned. The core-catcher design to withstand corium jet impingement demands the knowledge of very complex phenomena such as the dynamics of cavity formation and associated heat transfers. Even studied in the past, no complete data are available concerning the variation of jet parameters and solid structure materials. For a deep understanding of this phenomenon, new tests have been performed using both simulant and prototypical jet and core catcher materials. Part of these tests have been done at University of Lorraine using hot liquid water impinging on transparent ice block allowing for the visualizations of the cavity formation. Other tests have been performed in Karlsruhe Institute of Technology using liquid steel impinging on steel block.

Download Full-text

Calibration of the Sandia One-Dimensional Direct and Inverse Thermal (SODDIT) Code for Estimating Heat Flux to a Large Pipe Calorimeter in a Jet Fuel Fire

Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer ◽

10.1115/ht2009-88521 ◽

2009 ◽

Author(s):

Tim Bullard ◽

Miles Greiner

Keyword(s):

Heat Flux ◽

Fire Test ◽

Spent Nuclear Fuel ◽

Jet Fuel ◽

Maximum Heat ◽

One Dimensional ◽

Uncertainty Range ◽

Safety Standards ◽

Maximum Heat Flux ◽

Fire Environment

Industry and safety standards demand the knowledge of the thermal behavior of systems subjected to fire, particularly for the transportation of radioactive materials for spent nuclear fuel disposal and reprocessing. Experimentally benchmarked fire test data from Container Analysis Fire Environment (CAFE) are used to calibrate the Sandia One Dimensional Direct and Inverse Thermal (SODDIT) code by optimizing number of future times (NFT) at 11 and identifying a linear correlation and uncertainty range between the SODDIT input and output. The calibration is then used to predict the heat flux to a large pipe calorimeter in a jet fuel fire, for which the result is an 11 second window average of the actual heat flux. The maximum heat flux occurred at the beginning of the fire and was found to be 195 ± 37.3 kW/m2 at a 95% confidence level.

Download Full-text

Effect of Fluid Loading on the Performance of Wicked Heat Pipes

Volume 3 ◽

10.1115/ht-fed2004-56403 ◽

2004 ◽

Author(s):

R. Kempers ◽

A. Robinson ◽

C. Ching ◽

D. Ewing

Keyword(s):

Heat Flux ◽

Heat Pipe ◽

Heat Transport ◽

Heat Pipes ◽

Working Fluid ◽

Fluid Loading ◽

Maximum Heat ◽

Horizontal Orientation ◽

Maximum Heat Flux ◽

Dry Out

A study was performed to experimentally characterize the effect of fluid loading on the heat transport performance of wicked heat pipes. In particular, experiments were performed to characterize the performance of heat pipes with insufficient fluid to saturate the wick and excess fluid for a variety of orientations. It was found that excess working fluid in the heat pipe increased the thermal resistance of the heat pipe, but increased maximum heat flux through the pipe in a horizontal orientation. The thermal performance of the heat pipe was reduced when the amount of working fluid was less than required to saturate the wick, but the maximum heat flux through the heat pipe was significantly reduced at all orientations. It was also found in this case the performance of this heat pipe deteriorated once dry-out occurred.

Download Full-text

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

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82106 ◽

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.

Download Full-text