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Investigations on the role of mixed convection and wall friction factor in single-phase natural circulation loop dynamics

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Title Investigations on the role of mixed convection and wall friction factor in single-phase natural circulation loop dynamics
 
Creator KUMAR, N
DOSHI, JB
VIJAYAN, PK
 
Subject HEATED FLUID LOOP
STABILITY CHARACTERISTICS
OSCILLATORY INSTABILITY
RECTANGULAR LOOP
STEADY-STATE
THERMOSIPHON
BEHAVIOR
FLOW
PREDICTION
TRANSIENT
Natural circulation
Hysteresis
Instability
Natural convection
Mixed convection
 
Description The objective of the present paper is to present a 1-D model for simulating the startup from rest of water cooled single-phase natural circulation loops having horizontal heaters. The starting point of analysis is the inability of the 1-D codes to account for natural convection in the heater. Present 1-D models are unable to account for axial diffusion in the fluid caused by natural convection. Start-up from rest and many other characteristics cannot be simulated using classical 1-D models because of the inherent tendency of the predicted dynamics to be attracted by zero flow condition. The paper presents an elegant approach for taking into account both natural and forced convection. The enhancement of fluid motion and thermal mixing by natural convection is an important consideration in the design of nuclear reactors. Hence, the model developed is of direct relevance to nuclear reactor thermal hydraulics. The model developed for natural convection has been validated against the CFD simulations. The model developed has been incorporated in a classical 1-D model developed by the authors previously. The application of model to a rectangular single-phase natural circulation loop show that the model can predict the loop behavior from start-up with fidelity. The model reproduces most of the characteristics like unidirectional oscillation, bidirectional oscillations and chaotic switching reasonably well. Finally, model has been used to investigate the phenomenon of hysteresis observed in experimental loop. The paper also brings out the role of constitutive laws for wall friction in predicting the loop dynamics. (C) 2011 Elsevier Ltd. All rights reserved.
 
Publisher PERGAMON-ELSEVIER SCIENCE LTD
 
Date 2012-06-26T06:11:07Z
2012-06-26T06:11:07Z
2011
 
Type Article
 
Identifier ANNALS OF NUCLEAR ENERGY,38(10)2247-2270
0306-4549
http://dx.doi.org/10.1016/j.anucene.2011.06.004
http://dspace.library.iitb.ac.in/jspui/handle/100/14013
 
Language English