scholarly journals On the occurrence of superimposed density wave oscillations on pressure drop oscillations and the influence of a compressible volume

AIP Advances ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 075022 ◽  
Author(s):  
Il Woong Park ◽  
Maria Fernandino ◽  
Carlos A. Dorao
Keyword(s):  
Pressure Drop ◽  
Density Wave ◽  
Density Wave Oscillations

Transient 3D Stability Analysis of SCWR Rod Bundle Subchannels by a CFD Code

2008 ◽  
Author(s):  
M. Sharabi ◽  
W. Ambrosini ◽  
S. He ◽  
Pei-Xue Jiang ◽  
Chen-Ru Zhao
Keyword(s):  
Stability Analysis ◽  
Pressure Drop ◽  
Conceptual Design ◽  
Constant Pressure ◽  
Density Wave ◽  
Heating Rates ◽  
Rod Bundles ◽  
Rod Bundle ◽  
Density Wave Oscillations ◽  
Relap5 Code

The paper describes the application of CFD in simulating density wave oscillations in triangular and square pitch rod bundles. The FLUENT code is used for this purpose, addressing typical conditions proposed for SCWR conceptual design. The RELAP5 code and an in-house 1D linear stability code are also adopted to compare the results for instability thresholds obtained by different techniques. Transient analyses are performed both by the CFD code and RELAP5, with increasing heating rates and constant pressure drop across the channel, up to the occurrence of unstable behaviour. The obtained results confirm that the density wave mechanism is similar in rod bundle and in axisymmetric configurations.

Periodically-forced density wave oscillations in boiling flow at low forcing frequencies: Nonlinear dynamics and control issues

2016 ◽  
Vol 140 ◽  
pp. 123-133 ◽  
Author(s):  
Swapan Paruya ◽  
Nababithi Goswami ◽  
Subramaniam Pushpavanam ◽  
Dipin S. Pillai ◽  
Oinam Bidyarani
Keyword(s):  
Nonlinear Dynamics ◽  
Density Wave ◽  
Dynamics And Control ◽  
Boiling Flow ◽  
And Control ◽  
Density Wave Oscillations ◽  
Nonlinear Dynamics And Control

Control of density wave oscillations in boiling channel

2014 ◽  
Vol 110 ◽  
pp. 119-133 ◽  
Author(s):  
Nababithi Goswami ◽  
Swapan Paruya
Keyword(s):  
Density Wave ◽  
Density Wave Oscillations

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

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