On the efficiency of active control of thermal convection in a thermosyphon with time-delayed controller
The paper deals with the problem of automatic control of the motion of an inhomogeneously heat-ed liquid in long vertical channels connected at the ends. Such a rectangular loop (a non-simply connected thermosyphon) makes it easy to maintain the mechanical equilibrium of a liquid with a vertical temperature gradient. The fluid flow is controlled by small discrete channel orientation changes with respect to the static component of the inertial field, for example, gravity. Such chang-es are made by the computer according to the law of proportional negative feedback. The effect of a time delay, which naturally arises in the controller's commands, is considered. To study the effect in detail, an artificial time delay has been also added. A mathematical model of the phenomenon is developed. Dynamic modes of the work of a controlled convective loop are numerically studied. It was found that the excessive feedback gain can cause non-stationary convection modes in the sys-tem. Methods for weakening the delay effect are discussed.