Oscillatory behavior of a two‐phase natural‐circulation loop

Abstract

A program of study of the transient operation of natural-circulation loops has been underway at the University of Minnesota (1) and this paper is concerned with the oscillatory behavior of a twophase natural-circulation loop. These studies are of interest for the emergency cooling of nuclear reactors and in the design of boiling-water reactors. The lib erature survey pertaining to the transient operation of a natural-circulation loop is given by Alstad, Isbin, Amundson, and Silvers ( l ) , and a survey of two-phase flow literature is given by Isbin, Moen, and Mosher (2). Normally the surge tank, El, was not used for two-phase natural-circulation runs. For those runs in which the pressure a t one point in the loop was held constant, the gate valve between the surge tank E, and the loop was opened; for the constant-volume run, the gate valve waa closed. A heater and pump were installed to maintain the cooling-watcr supply a t 5 gal./min. and a t 130°F. EXPERIMENTAL LOOP THEORETICAL ANALYSIS General EquationsThe continuity equation, the equation of motion, and the energy equation for a viscous fluid flowing in a region of general geometry were formulated for a phase having continuous properties. A similar set of equations was derived for flow across a surface of discontinuity. The combination of these two sets of equations gave the equations for the two-phase flow. If these equations are applied to flow through a pipe of uniform cross section in which the steam and water phases are assumed to be in equilibrium (that is, p

Experimental and numerical investigations on flashing-induced instabilities in a single channel

“…Flashing-induced flow oscillations were first pointed out by the pioneering work of [31], who reported about flashing-induced instabilities in a natural circulation steam/water loop in the 1950s. Since then, several experimental studies have addressed stability of natural circulation two-phase flow systems at low pressure [2,6,10,16,17,24,33,18,27] emphasizing that well-defined start-up procedures are needed to cross the instability region during the transition from single-phase to two-phase flow operation.…”

A Review of Two-Phase Flow Instabilities

“…In one of the earlier studies, Wissler, Isbin and Amundsen [7] investigated the oscillatory behavior of a natural circulation loop. They solved the homogeneous model equations by an analog computer.…”

Throughflow effects on the transient and stability characteristics of a thermosyphon

“…Most of the available information about the nuclear energy applications is concerned, however, with two-phase flow instabilities, cf. Wissler et al [6], and transients and stability in liquid metal loops for LMFBRS, cf. Gillette et al [7], Garrison et al [8].…”