Author(s)

L Cammarata, G Desrayaud, A Fichera & A Pagano

Abstract

This paper presents some theoretical and experimental new results concerning the modeling and control of rectangular natural circulation loops. Despite the structural simplicity of these systems, which are used to cool a heat source by means of natural circulation of a fluid without mechanical pumping, they can exhibit unstable dynamics. The first part of this study is devoted to describing and experimentally validating a non-linear mathematical model, which has been derived by truncating the Fourier series expansion of the fluid temperature and of the function describing the system geometry and the heating conditions at the boundaries. In the second part the model has been used to design a set of controllers to stabilize the fluid motion in order to guarantee efficient heat removal. In particular, the proportional control strategy has been considered for a set of nominal heating powers, using both the fluid velocity and a temperature difference as the feedback variable. The results of simulations corresponding to each designed controller have been compared with the experimental trends, showing in all cases good agreement. In particular, the controllers have been proved to be capable of stabilising the system to the desired equilibrium point.

Keywords