Joachim Blum, Wolfgang Marquardt, R. Hohl, H. Auracher:
Theory and experimental validation of boiling systems stability
In: M. Lehner, F. Mayinger (Eds.): Engineering Foundation Conference 'Convective Flow and Pool Boiling II', Irsee, Germany, May 18-23, 1997, 253-260
The negative slope of the boiling curve in the transition region prevents systematic measurements without some stabilization scheme such as feedback control of the boiling surface temperature. In this study we outline a procedure for stability analysis based on a mathematical model of the controlled test heater and the assumption of uniform boiling on the heated surface. We then exemplarily validate this rigorous approach by comparing the theoretical results with experimental findings. The pool boiling experiments are carried out with an electrically heated copper block using FC-72 as a test fluid. Stable and unstable operating regions were found by deliberate variation of the controller gain. As predicted by the theory, no steady-state measurements are possible for high feedback gains along the entire boiling curve, while in the transition boiling region no steady-state measurements are obtained for low gains as well. The excellent quantitative agreement of the theoretical and experimental results validates the proposed approach.
Stability analysis, distributed parameter systems, heat transfer, boiling experiments, control