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.
Experimental observations on the general trends of the steady state and stability behaviour of single-phase natural circulation loops
The steady state flow in uniform or non-uniform diameter single-phase natural circulation loops (NCLs) can be expressed as Re ss = C[Gr m /N G ] r where the constants C and r depend on the nature of the flow (i.e. laminar or turbulent). Testing these correlations with experimental data showed reasonable agreement. The above equation suggests that simulation of the steady state flow in single-phase NCLs can be achieved by simulating the non-dimensional parameter (Gr m /N G ). The stability behaviour of a non-uniform diameter loop is found to depend on a large number of geometric parameters in addition to the modified Stanton number (St m ) and the ratio (Gr m ) b/(3 - b) / (N G ) 3/(3 - b) . The transient and stability behaviour of a uniform diameter loop can be simulated by simulating the product (Gr m ) b/(3 - b) × (D/L t ) 3/(3 - b) and St m if the length scales are preserved.