Experimental observations on the general trends of the steady state and stability behaviour of single-phase natural circulation loops

Abstract

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.