scholarly journals ASSESSMENT OF HEAT TRANSFER IN FUEL CHANNEL OF INDIAN PHWR UNDER POSTULATED LARGE BREAK LOSS OF COOLANT ACCIDENT: EXPERIMENTAL AND NUMERICAL STUDY

2021 ◽  
Vol 247 ◽  
pp. 11003
Author(s):  
Ketan Ajay ◽  
Ravi Kumar ◽  
Akhilesh Gupta
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Numerical Study ◽  
Safety Concern ◽  
Thermal Characteristics ◽  
Fission Products ◽  
Hydrogen Gas ◽  
Gas Generation ◽  
Radial Temperature ◽  
Fuel Bundle

The behaviour of the channel under postulated large break LOCA scenario had been a prime safety concern. The radiative heat transfer is predominant in a channel when the convective cooling environment is marred. The estimation of temperature distribution in the fuel pins at elevated temperature is essential from the point of view of hydrogen gas generation and release of fission products. In this paper, the thermal characteristics of a channel for Indian PHWR under critical break failure is studied using experimental and numerical techniques. The experiment is carried out on an Indian PHWR having a fuel bundle of 37-fuel elements. The temperature profiles for different parts of the simulated channel comprising of fuel pins, PT and CT are obtained under steady condition. The numerical analysis is also performed using ANSYS Fluent 19.0. From the study, it is found that there is a significant radial temperature gradient in the fuel bundle from the center ring to the outer ring. Also, no significant circumferential temperature gradient is observed in the fuel bundle, PT and CT.

scholarly journals Numerical Investigation of a two-inlet PVT air collector

2019 ◽  
Vol 136 ◽  
pp. 05014
Author(s):  
Zhangyang Kang ◽  
Zhaoyang Lu ◽  
Xin Deng ◽  
Qiongqiong Yao
Keyword(s):  
Heat Transfer ◽  
Single Channel ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Thermal Characteristics ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Heat

A numerical study of heat and mass transfer characteristics of a two-inlet PV/T air collector is performed. The influence of thermal characteristics and efficiency is investigated as the area ratios of inlet and outlet of the single channel with two inlets are changed. The design of the two-inlet PV/T air collector can avoid the poor heat transfer conditions of the single inlet PV/T air collector and improve the total photo-thermal efficiency. When the inlet/outlet cross-sectional area ratio is reduced, the inlet air from the second inlet enhances the convection heat transfer in the second duct and the temperature distribution is more uniform. As the cross-sectional area of the second inlet increase, the maximum heat exchange amount of the two-inlet PV/T air collector occurs between the inlet and outlet cross-sectional area ratio L=0.645 and L=0.562.

scholarly journals Water Jacket Systems for Temperature Control of Petri Dish Cell Culture Chambers

2019 ◽  
Vol 9 (4) ◽  
pp. 621 ◽  
Author(s):  
Samira Uharek ◽  
Sara Baratchi ◽  
Jiu Zhu ◽  
Majed Alshehri ◽  
Arnan Mitchell ◽  
...  
Keyword(s):  
Cell Culture ◽  
Temperature Gradient ◽  
Transition Period ◽  
Thermal Characteristics ◽  
Petri Dish ◽  
Sample Volume ◽  
Radial Temperature ◽  
Transient Conditions ◽  
Water Jacket ◽  
Stable Conditions

Water jacket systems are routinely used to control the temperature of Petri dish cell culture chambers. Despite their widespread use, the thermal characteristics of such systems have not been fully investigated. In this study, we conducted a comprehensive set of theoretical, numerical and experimental analyses to investigate the thermal characteristics of Petri dish chambers under stable and transient conditions. In particular, we investigated the temperature gradient along the radial axis of the Petri dish under stable conditions, and the transition period under transient conditions. Our studies indicate a radial temperature gradient of 3.3 °C along with a transition period of 27.5 min when increasing the sample temperature from 37 to 45 °C for a standard 35 mm diameter Petri dish. We characterized the temperature gradient and transition period under various operational, geometric, and environmental conditions. Under stable conditions, reducing the diameter of the Petri dish and incorporating a heater underneath the Petri dish can effectively reduce the temperature gradient across the sample. In comparison, under transient conditions, reducing the diameter of the Petri dish, reducing sample volume, and using glass Petri dish chambers can reduce the transition period.

Increase in ovality of uranium tubes due to creep under external pressure

1968 ◽  
Vol 3 (3) ◽  
pp. 226-231
Author(s):  
W S Blackburn ◽  
J Percy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Creep Rate ◽  
Temperature Gradient ◽  
Outer Surface ◽  
External Pressure ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Principal Axes ◽  
Inner Surface

The increase in ellipticity of a concentric slightly elliptical tube is theoretically investigated for the case of external pressure and radial temperature gradient when the creep rate is proportional to the stress and the constant of proportionality varies slightly between the principal axes. The presence of a radial temperature gradient accelerates the increase in ovality due to initial ovality on the outer surface and that due to circumferential variation of strength (except after very small collapses) and decreases that due to initial inner ovality. Further allowance for circumferential variation in temperature, due to an insulated inner surface and to a uniform heat-transfer coefficient to a gas at constant temperature around the outer surface, reduces the increase in all cases.

Thermal effect on large-aspect-ratio Couette–Taylor system: numerical simulations

2015 ◽  
Vol 771 ◽  
pp. 57-78 ◽  
Author(s):  
Changwoo Kang ◽  
Kyung-Soo Yang ◽  
Innocent Mutabazi
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Aspect Ratio ◽  
Numerical Simulations ◽  
Convective Cell ◽  
Base Flow ◽  
Large Aspect Ratio ◽  
Radial Temperature ◽  
Instability Modes ◽  
Momentum And Heat Transfer

We have performed numerical simulations of the flow in a large-aspect-ratio Couette–Taylor system with rotating inner cylinder and with a radial temperature gradient. The aspect ratio was chosen in such a way that the base state is in the conduction regime. Away from the endplates, the base flow is a superposition of an azimuthal flow induced by rotation and an axial flow (large convective cell) induced by the temperature gradient. For a fixed rotation rate of the inner cylinder in the subcritical laminar regime, the increase of the temperature difference imposed on the annulus destabilizes the convective cell to give rise to co-rotating vortices as primary instability modes and to counter-rotating vortices as secondary instability modes. The space–time properties of these vortices have been computed, together with the momentum and heat transfer coefficients. The temperature gradient enhances the momentum and heat transfer in the flow independently of its sign.

scholarly journals Numerical Study on Influence of Cross Flow on Rewetting of AHWR Fuel Bundle

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Mithilesh Kumar ◽  
D. Mukhopadhyay ◽  
A. K. Ghosh ◽  
Ravi Kumar
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Cross Flow ◽  
Fluid Temperature ◽  
Initial Surface ◽  
Fuel Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Fuel Bundle ◽  
Fuel Pin

Numerical study on AHWR fuel bundle has been carried out to assess influence of circumferential and cross flow rewetting on the conduction heat transfer. The AHWR fuel bundle quenching under accident condition is designed primarily with radial jets at several axial locations. A 3D (r,θ,z) transient conduction fuel pin model has been developed to carry out the study with a finite difference method (FDM) technique with alternating direction implicit (ADI) scheme. The single pin has been considered to study effect of circumferential conduction and multipins have been considered to study the influence of cross flow. Both analyses are carried out with the same fluid temperature and heat transfer coefficients as boundary conditions. It has been found from the analyses that, for radial jet, the circumferential conduction is significant and due to influence of overall cross flow the reductions in fuel temperature in the same quench plane in different rings are different with same initial surface temperature. Influence of cross flow on rewetting is found to be very significant. Outer fuel pins rewetting time is higher than inner.

On the Calculation of Flow and Heat Transfer Characteristics for CANDU-Type 19-Rod Fuel Bundles

1987 ◽  
Vol 109 (3) ◽  
pp. 590-598 ◽  
Author(s):  
Yuh-Shan Yueh ◽  
Ching-Chang Chieng
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Turbulent Viscosity ◽  
Transfer Coefficients ◽  
Fully Developed Flow ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Fuel Bundle ◽  
Basic Equations ◽  
Calculated Velocity

A numerical study is reported of flow and heat transfer in a CANDU-type 19 rod fuel bundle. The flow domain of interest includes combinations of triangular, square, and peripheral subchannels. The basic equations of momentum and energy are solved with the standard k–ε model of turbulence. Isotropic turbulent viscosity is assumed and no secondary flow is considered for this steady-state, fully developed flow. Detailed velocity and temperature distributions with wall shear stress and Nusselt number distributions are obtained for turbulent flow of Re = 4.35 × 104, 105, 2 × 105, and for laminar flow of Re ∼ 2400. Friction factor and heat transfer coefficients of various subchannels inside the full bundle are compared with those of infinite rod arrays of triangular or square arrangements. The calculated velocity contours of peripheral subchannel agreed reasonably with measured data.

Onset of Benard-Marangoni Instability on a Flat Meniscus in a Microchannel

2012 ◽  
Author(s):  
Zhenhai Pan ◽  
Hao Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Gradient ◽  
Liquid Layer ◽  
Marangoni Number ◽  
Numerical Study ◽  
Marangoni Flow ◽  
Thin Liquid Layer ◽  
Marangoni Instability

Attention Marangoni instability in a microchannel is of interest in various heat transfer and microfluidic applications. In this work, a numerical study is conducted on a flat meniscus in a square adiabatic microchannel. The evaporative heat flux is uniform, and thus the initial meniscus temperature is uniform. However, the simulations showed that a temperature gradient perpendicular to the meniscus can also lead to an instability that starts a strong Marangoni flow, which should be a type of the Benard-Marangoni instability that was originally observed on a thin liquid layer. A new expression of the Marangoni number (Ma) is derived for the Benard-Marangoni instability in a microchannel. The threshold Ma values are obtained, providing guidance for microfluidic design.

Numerical Study of Friction Factor and Heat Transfer Characteristics for Single-Phase Turbulent Flow in Tubes with Helical Micro-Fins

2012 ◽  
Vol 59 (4) ◽  
pp. 469-485 ◽  
Author(s):  
Piotr Jasiński
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Friction Factor ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Thermal Characteristics ◽  
Pressure Drops ◽  
Experimental Stand ◽  
Helical Angle

The paper presents a numerical study on the heat transfer and pressure drop, related to flow in pipes with helical micro-fins. For all tested geometries, one applied a constant wall heat flux and fully developed 3D turbulent flow conditions. The influence of the angle of micro fins (referred to the tube axis) on thermal-flow characteristics were tested. The value of this angle was varied - with a step of 10 degrees - from 0 to 90 degrees (representing grooves parallel and perpendicular to the axis, respectively). Before numerical investigation, the pipe with helical angle of 30 degree was tested on an experimental stand. The results obtained from experiment and numerical simulations were compared and presented on the charts. As an effect of the numerical simulations, the friction factor f and Nusselt number characteristics was determined for the range of Re=104 ÷ 1.6 × 106. The analysis of the results showed high, irregular influence of the helical angle on thermal characteristics and pressure drops. Additionally, the ratios: f / fplain, Nu/Nuplain and efficiency indexes (Nu/Nuplain)/( f / fplain) as a function of the Reynolds number for every helical angle were shown on the charts.

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