2-PHASE FLOW INSTABILITY EXPERIMENT IN A NATURAL CIRCULATION LOOP USING THE TAGUCHI METHOD

The thermal-hydraulic instability of a two-phase natural circulation l oop, which is a complex multivariable system with high nonlinearity, w as investigated experimentally based on the Taguchi method. Excellent results were obtained and a broad picture of the trends produced by th e various parameters that affect instability is presented. This study concluded that, within the experimental range, the inlet temperature, heating power and the presence of the unheated bypass channel are the three most dominant factors affecting the loop instability. The Taguch i method is found to be very efficient and there is a great deal of sa ving in the experimental work. The 20 runs of experiment based on the Taguchi method suggests that the stability of the present two-phase na tural circulation loop (TPNCL) would be improved under the following c onditions: decreased inlet temperature, decreased thermal load, discon nected unheated bypass channel, installing the compressible volume wit h a higher water level in the downstream two-phase flow region, discon nected upstream compressible volume, increased single-phase flow restr ictions, and decreased two-phase flow restrictions. Although the same trends bear the standard method of stabilizing a boiling channel, the restriction factors in the present experimental investigation are foun d to be ineffective in dampening the thermal-hydraulic instability. (C ) 1998 Elsevier Science Inc. All rights reserved.