Determining parameters where pressure drop oscillations occur in a boilingchannel using singularity theory and the D-partition method

Sustained oscillations have been experimentally observed when a surge tank is introduced up stream of a boiling channel. This dynamic state arises fro m an instability of the steady state of the system. These low-frequency osc illations are called pressure drop oscillations to distinguish them from th e high-frequency density wave oscillations of boiling channels under consta nt pressure drop. The conditions under which these oscillations arise are t hat the steady-state operating point should be in the negative slope region of the boiling channel pressure drop characteristic and in the positive-sl ope region of the system pressure drop characteristic. The steady state sho uld also be unique in the system pressure drop characteristic i.e. there sh ould be no coexisting steady states. Under these conditions when this state is dynamically unstable the system shows sustained oscillations having a l ow-frequency. In this paper we discuss how the parameter values where these conditions ar e satisfied can be determined analytically and elegantly using results from the D-partition method and the singularity theory. The former allows us to determine regions in parameter space where an operating point is stable wh ile the latter allows us to obtain different regions in parameter space whe re the bifurcation diagrams are qualitatively different. The superposition of results of these theories is used to determine parameter values where pr essure drop oscillations occur. The predictions are verified with numerical simulations of the original nonlinear model for a horizontal-channel. (C) 2000 Elsevier Science Ltd. All rights reserved.