Comparison Between Experimental Data and Numerical Modeling for the Natural Circulation Phenomenon
The study of natural circulation phenomenon has been object of crescent interest in scientific community in recent years. The new generation of compact nuclear reactors uses natural circulation of the fluid as a residual heat removal cooling system in case of accident or shutdown. The objective of this paper is to present a comparison between experimental data and numerical simulation results for the natural circulation phenomenon in single and two-phase flow regime. Experimental data were obtained from a circuit built with glass tubes, through which thermal hydraulic phenomenon visualization was possible. The circuit is composed of an electric heater as the heat source, a heat exchanger as the heat sink and an expansion tank to accommodate fluid density changes. Instrumentation data acquisition is performed through thermocouples and pressure meters, and controlled by a computer interface developed using LABVIEW. Numerical modeling and simulations were done with the thermal hydraulic code RELAP5, which is widely used for this purpose. The cyclic reverse flow observed in the circuit was well represented by the numerical model. The comparison demonstrated that the numerical simulations are very close to the experimental data.
Closed-loop experimental investigation of single-phase natural circulation flow phenomena based on temperature and heating power variations
Abstract Experimental investigation of single-phase, low pressure natural circulation flow phenomena has been carried out. The study aims to critically analyze the thermal hydraulic parameters (temperature and heating power) variations as it affects transfer of heat in a closed-loop rectangular natura l circulation facility having a single heated channel at predetermined inlet sub cooled temperature varied from 40 to 80 °C. Heating power varies between 7 kW−13 kW to portray several conditions of the reactor power in response to temperature changes while sustaining single-phase flow circulation through the hydraulic loop. Real-time signals of thermal hydraulic responses are observed via a graphical interface for data acquisition when stable flow or self-sustained flow oscillations are achieved. Results obtained were analyzed at several sections of the hydraulic circuit which are basically pressure drops and flow rate due to temperature differences and heating power increments. These results and observations made through them thus contribute to the database which is important for characterizing natural circulation phenomena and acquisition of dominants parameters for the scaling analysis of future designs.
Do Arab public opinion support policies of regional powers in MENA? View from Tunisia
ABSTRACT The Arab Uprisings and subsequent events continue to transform policies of regional and major powers toward the Middle East and North Africa. These powers have shown different approaches toward the Uprisings, ranging from support for the status quo to endorsing regime changes. Their policies have also exerted a significant impact on the course of events. Despite this growing importance and implications of policies of regional powers on the Uprisings and the Syrian conflict, we still do not know much about how the public assesses these policies and to what extent domestic cleavages shape these assessments. Using a nationally representative original survey conducted in 2014 in Tunisia, this study examines the perceptions of the policies of France, Turkey, and Saudi Arabia towards the Uprisings and the Syrian conflict. It finds that French and Turkish policies about the Uprisings have garnered substantial support among citizens, whereas most citizens negatively assess the Saudi policies. On the other hand, the majority of Tunisians negatively assess all these countries’ policies toward the Syrian conflict. Another major finding suggests that political identity reflecting secular/religious cleavages shapes how citizens view the policies of these three countries toward both issues, but its effect is higher in assessing the Uprisings.