A STUDY OF MULTIPLE STEADY-STATE SOLUTION IN PARALLEL CHANNEL NATURAL CIRCULATION LOOP WITH FLASHING
This study presents a steady-state analysis of double-channel flashing driven natural circulation loop (FDNCL) using homogeneous equilibrium model (HEM). In flashing driven parallel channel NCL, the presence of two-phase creates a complicated interplay between pressure drops in the loop, which may be responsible for multiple steady-state solutions. Parallel channel natural circulation loop (NCL) is investigated for uniformly heated channels. The model also addressed the Ledinegg instability in the two-phase FDNCL.
The proposed model is based on HEM to estimate the pressure drop in two-phase regions of the loop. Three components of pressure drop such as frictional, acceleration and gravitational are considered for each section. An iterative root finding method is used to find the resulting circulation rate, which starts from an initial guess of loop mass flow rate.
The computationally obtained stability map confirms the existence of a static instability region under the condition of flashing in the riser. The results suggest that the flashing in the riser cannot be neglected below 20 bar loop pressure. A comparison of the flow characteristics with flashing and without flashing in the adiabatic section of the risers brings out some interesting differences.