Analysis of natural convection in IPWR type SMR test facility
In advanced and conventional reactors natural circulation plays an important role in cooling of core. This dissertation is based on modeling of a test facility using RELAP5/MOD 4.0. Test facility (TF) comprises of heating core, riser, helical coil heat exchanger, and shell and tube heat exchanger and down comer these components are joined with associate piping and fittings. In the TF, heating core is cooled by natural circulation. In this thesis, analysis of natural circulation depends on geometry and operational parameters. The primary objective of this thesis is to investigate the effects of riser height, riser diameter, Source and sink distance, power and secondary side mass flow rate on primary loop mass flow rate, which is established due to natural convection. Natural circulation loop of TF modeled with the aid of RELAP5/MOD 4.0 thermal hydraulic system code. Riser length=78 inch, Pressure= 1Bar, Pitch to diameter = 1.4, SS Flow rate = 0.45kg/s, ΔH = −5 inch, Riser Diameter = 6 inch and power 37.0kw. Primary loop mass flow rate is 0.17kg/s (612kg/hr), analytical solution mass flow rate is 0.18kg/s, average error is 12.8% in computational solution. This error reduces as power increases with constant intervals. The RELAP5/MOD 4.0 results give good agreement with analytical solution.
Analysis of natural circulation stability in a low pressure thermohydraulic test loop
This paper discusses an instability study of a natural circulation (NC) loop performed with the aid of Relap5 thermal-hydraulic system code. This loop has been designed and constructed for the analysis of relevant thermohydraulic parameters of a nuclear reactor. In this study, the main parameters for the stability of NC are identified and characterized through the execution of proper code runs. The obtained stability boundary (SB) in the dimensionless “Zuber- Sub-cooling” plane is compared with the SB reported in referenced literature. The agreement of predicted NC stability boundaries with the results of independent studies demonstrates both the capability of the mentioned code in assessing NC loop stability and the quality of the performed calculations.
Prediction of stability of one-dimensional natural circulation with a low diffusion numerical scheme
Abstract This paper presents the results obtained in the analysis of stability of flow in single-phase natural circulation loops by a computer program incorporating two different numerical schemes for the discretisation of the energy balance equation. In particular, in addition to an usual first order upwind scheme, a low diffusion numerical method, devised as an application of a classical second order explicit upwind scheme, has been introduced by simply using an appropriate definition of the “donor cell rule”. Both transient behaviour and linear stability are addressed, the latter obtained by a numerical perturbation technique providing full consistency with the transient algorithm. The behaviour of heat structures is also accounted for both in the non-linear transient program and in its linearised counterpart. After a detailed description of the adopted models, examples of their application are provided in the paper, addressing single-phase natural circulation loop behaviour. The results obtained by the low diffusion scheme are compared with those provided by the first order numerical scheme and with available information from a previous work on experimental loop behaviour, showing a remarkable improvement in the reliability of stability predictions.