Study on enhancement of heat transfer in the reactor vessel auxiliary cooling system of a fast breeder reactor.

In the HTGR (High Temperature Gas Cooled Reactor), the Reactor Cavity Cooling System (RCCS) is equipped to remove the heat transferred from the reactor vessel to the structure of the containment. The function of the RCCS is to dissipate the heat from the reactor cavity during normal operation including shutdown. The system also removes the decay heat during the loss of forced convection (LOFC) accident. A new concept of the water pool type RCCS was proposed at Seoul National University. The system mainly consists of two parts, water pool located between the containment and reactor vessel and five trains of air cooling system installed in the water pool. In normal operations, the heat loss from the reactor vessel is transferred into the water pool via cavity and it is removed by the forced convection of air flowing through the cooling pipes. During the LOFC accident, the after heat is passively removed by the water tank without the forced convection of air and the RCCS water pool is designed to provide sufficient passive cooling capacity of the after heat removal for three days. In the present study, experiments and numerical calculations using CFX5.7 for the water pool and cooling pipe were performed to investigate the heat transfer characteristics and evaluate the heat transfer coefficient model of the MARS-GCR (Multi-dimensional Analysis of Reactor Safety for Gas Cooled Reactor Analysis) which was developed for the safety analysis of the gas cooled reactor. From the results of the experiments and CFX calculations, heat transfer coefficients inside the cooling pipe were calculated and those were used for the assessment for the heat transfer coefficient model of the MARS-GCR.

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Performance Assessment of the Heat Exchanger with and without a Coating of Hybrid Nanoparticles the User Cooling System in Solar Heating Systems

International Journal of Heat and Technology ◽

10.18280/ijht.390507 ◽

2021 ◽

Vol 39 (5) ◽

pp. 1460-1468

Author(s):

Khalid Faisal Sultan ◽

Mohammed Hassan Jabal ◽

Ameer Abed Jaddoa

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Cooling System ◽

Hybrid Nanoparticles ◽

Coating Process ◽

Enhancement Of Heat Transfer ◽

Lotus Effect ◽

Nano Structure ◽

Nano Coating ◽

The Stability

The aim of this article was to examine the effect of hybrid nano – coating that could potentially impact the enhancement of heat transfer coefficient of distilled water, Reynolds number, and temperature through a swirl heat exchanger, as well as the indicator of the effect Zeta voltage in the coating process. In this experimental work, type of coating used was Aluminum (Al) + Aluminum oxide Al2O3. Outcomes of study showed that the coating of heat exchanger is much better than without coating in improving the thermal properties for liquids passing through heat exchanger as well as increasing the heat exchange through the surface of the exchanger. Results in the article indicated that the use of hybrid nano – structure coating is for inducing the feature of super – hydrophobicity for the surface that touches the fluid included within the heating transferring. Such feature can make an increase in the heating transferring factor and a decreasing in power losing produced via friction. This article indicated that the Zeta voltage analysis is to show the stability of the hybrid nanofluids used in the coating process. The enhanced technology depends upon the concept that exists in nature under the name “Lotus effect” to get super-hydrophobic surfaces. The rate of improvement in heat transfer using hybrid nanoparticles is 33% compared to that without coating condition.

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Enhancement of heat transfer using turbulent wall jet

Proceedings of the Institution of Mechanical Engineers Part E Journal of Process Mechanical Engineering ◽

10.1177/0954408919891391 ◽

2019 ◽

Vol 234 (1) ◽

pp. 123-136

Author(s):

Tej Pratap Singh ◽

Amitesh Kumar ◽

Ashok Kumar Satapathy

Keyword(s):

Heat Transfer ◽

Goodness Of Fit ◽

Stokes Equations ◽

Cooling System ◽

Plane Wall ◽

The Self ◽

Wall Jet ◽

Enhancement Of Heat Transfer ◽

Self Similar ◽

Turbulent Wall

Enhancement of heat transfer is very important in many engineering applications. The present study explores one of such possibilities by increasing the surface area of a plane wall. The effect of wavy wall on thermal and flow characteristics of a turbulent wall jet is studied in detail. The amplitude of the wavy surface is varied between 0.1 and 0.7 with an interval of 0.1. The Reynolds number is set to 15,000. The Reynolds averaged Navier Stokes equations are solved using the finite volume approach. The semi-implicit pressure linked equation algorithm is used to couple the pressure and velocity. A new scale, other than the traditional outer scaling, is defined for carrying out the self-similar behavior of the flow. Unlike the plane wall case, the self-similar characteristic is obtained at the respective crests and the troughs. However, it is also noticed that the two characteristics differ significantly with each other. Even, these characteristics are found to differ with each other for different amplitudes. The minimum pressure near the nozzle decreases as the amplitude increases and it is noted to be equal to −0.541 for the highest amplitude, i.e. A = 0.7. It is observed that the strength of convection near the exit of the jet is very high, and it decreases in the downstream direction. This increase in convection augments heat transfer by almost 10% as compared to the plane wall case. Based on the results, a quartic curve is fit for the average Nusselt number with a 99.75% goodness of fit. It is expected that the present study opens a new line in designing a proper cooling system.

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Effects of Aging on the Thermal Conductivity of the AP1000® Containment Vessel Inorganic Zinc Coating

Volume 1: Plant Operations, Maintenance, Engineering, Modifications, Life Cycle and Balance of Plant; Nuclear Fuel and Materials; Plant Systems, Structures and Components; Codes, Standards, Licensing and Regulatory Issues ◽

10.1115/icone22-31157 ◽

2014 ◽

Cited By ~ 1

Author(s):

Thomas A. Kindred ◽

Richard F. Wright

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Cooling System ◽

Mechanistic Model ◽

Zinc Coating ◽

High Energy ◽

Reactor Vessel ◽

Transfer Coefficients ◽

Water Storage Tank ◽

Containment Vessel

During a loss-of-coolant accident (LOCA) event the AP1000® passive safety features actuate to provide emergency core cooling (ECC) to the reactor core using passive features that do not rely on electrical power being available. The core makeup tanks (CMTs), and accumulators (ACCs) actuate to quench the fuel rods and refill the reactor vessel. After the CMTs and ACCs empty, the in-containment refueling water storage tank (IRWST) utilizing gravity injects a large volume of sub-cooled fluid into the reactor vessel. This floods the vessel and the lower region of containment (containment sump) initiating gravity induced long-term recirculation cooling. The discharge of high energy fluid during the blowdown, re-flood, and re-fill phases is assumed to condense on the colder structures inside the containment including the containment vessel shell. Heat is transferred through the shell to the film of water from the Passive Containment Cooling System (PCS) applied to the outside of the containment vessel shell. This results in evaporative heat transfer on the outside of the containment vessel. Due to the large heat transfer coefficients on the inside and outside of the shell the heat conduction through the shell is very important to the heat rejection capability of the PCS, and plays a large part in ensuring the containment vessel pressure is not exceeded during design basis events. The AP1000® containment vessel is forged from a high strength carbon steel alloy that is coated with an inorganic zinc coating which protects the containment vessel from corrosion during its design life. The coating acts as a sacrificial anodic layer which corrodes in lieu of corrosion of the substrate beneath it. The corrosion of the coating can potentially lead to degradation in thermal conductivity of the coating due to metallic oxides typically having a lower thermal conductivity than that of the non-oxidized state. A reduction in thermal conductivity of the protective coating will impact the overall heat transfer through the containment vessel during PCS operation. The purpose of this work is to develop a mechanistic model demonstrated against empirical validation for assessing the effects of oxidation on the thermal conductivity of the protective inorganic zinc coating (IOZ) on the AP1000® containment vessel.

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Study on the Turbulent Mixed Convection Phenomena Inside the Air-Cooled RCCS Riser

Volume 6B: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-82071 ◽

2018 ◽

Author(s):

Dong-Ho Shin ◽

Sin-Yeob Kim ◽

Chan Soo Kim ◽

Goon-Cherl Park ◽

Hyoung Kyu Cho

Keyword(s):

Heat Transfer ◽

Mixed Convection ◽

Cooling System ◽

Reactor Core ◽

Reactor Vessel ◽

Transfer Coefficients ◽

Concrete Wall ◽

Experimental Conditions ◽

Decay Heat ◽

Reactor Types

High Temperature Gas cooled Reactor (HTGR) that is one of GEN-IV reactor types enhances its safety adopting a passive cooling system, Reactor Cavity Cooling System (RCCS). When the active cooling system for the reactor core in a HTGR doesn’t work, the decay heat from the reactor core is transferred to the reactor vessel and the concrete wall of the reactor cavity, which are cooled by the RCCS. The RCCS consists of the vertical rectangular ducts, called risers, surrounding reactor vessel at a certain distance and chimneys that are connected to risers. Risers receiving the decay heat from the reactor vessel, the air inside the riser is heated and flows up to the chimney which accelerates exhalation of the air to the external atmosphere. The RCCS performance depends on the heat transfer rate inside the riser ducts, but the turbulent mixed convection that may occur in the riser ducts can complicate the verification. In this study, an experimental facility had been constructed to investigate heat transfer phenomena inside a riser duct and experiments with various heat flux and flow rate conditions were carried out. The experimental results showed that the turbulent mixed convection occurred for certain experimental conditions in the riser duct, which leads to heat transfer deterioration. Therefore, a correlation was suggested to predict how much the heat transfer could decrease compared to the forced convection. Large eddy simulation was carried out for CFD analysis. The heat transfer coefficients from LES showed consistent results with the correlation. The unique velocity profile and secondary flow was observed when the heat transfer was deteriorated. This study will contribute to the evaluation of the RCCS performance.

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