Analog Methods for the Simulation, Control, and Identification of a Process

The inherent instability of boiling processes in one of the boiling modes generates difficulties for many investigators. It was proposed to control the temperature of the heater in an elementary pool boiling heat transfer process, consisting of a metallic element (the heater) immersed in a boiling liquid and electrically energized so that boiling occurs at the interface between heater and liquid. Three boiling modes are in evidence, one of which is unstable under the usual operating conditions. It was expected that by controlling temperature, stable operation in all boiling modes could be obtained. An analog simulation of the boiling process was constructed, together with a simulation of a feedback system for controlling the simulated heater temperature, and it was found that the simulated temperature could be controlled. A feedback system was then designed and constructed for controlling the temperature of the actual heater. Analog components in the Donner Model 3400 analog computer were used to the maximum extent considered possible in this system. The process was in this way very successfully controlled. When the controlled system became available, experiments were performed to identify the static and dynamic characteristics of the process. New measurement methods were deviced using analog circuitry to obtain accurate measurements in the presence of noise generated by the process.