Experimental and Analytical Investigation of a Natural Circulation System with Parallel Loops

TLDR

The study investigates natural circulation loops through theoretical modeling and experiments. The authors use a one‑dimensional model of continuity, momentum, and energy equations and conduct experiments with an electrically heated section and two parallel loops with heat exchangers to examine core flow resistance, power distribution, and plenum design effects. The analysis yields steady‑state and transient flow and temperature expressions, and experiments show flow oscillations, instabilities, and reversals, with analytical predictions matching measurements within about 30 %.

Abstract

A theoretical and experimental study of a natural circulation loop is presented. The analysis is based on a one-dimensional model in which the continuity, momentum, and energy equations are given and solved. Expressions for the steady-state and transient flow rates and temperature distributions are derived. The apparatus consisted of an electrically-heated section and two parallel loops with heat exchangers. Steady-state and transient experiments were conducted to study the effects of core flow resistance, power distribution and upper plenum design. Flow oscillations were observed under certain conditions, which were accompanied by instabilities and flow reversals. Reasonable agreement (±30 percent) is obtained between the analytical and experimental results.