7 - QUASI-CONTINUOUS AND CONTINUOUS TEMPERATURE CONTROL

Abstract

This chapter discusses quasi-continuous and continuous temperature control. Improvements in the control of temperature in thermal processes are affected by the introduction of intermediate values of manipulated variable. Techniques are used to analyze quasi-continuous control that is not applicable to multiposition controllers, which incorporate one or two values of manipulated variables. Quasi-continuous control is often used for the manufacturing operations. The chapter also describes an expensive temperature-control system. This expense is only justified when the manufacturing operation requires a high degree of precision in the temperature control. Good engineering practice is to use the system appropriate to the economic and performance requirements of the process. The majority of applications can be controlled by two- or three-position systems, with only occasional recourse to quasi-continuous control. The phase-plane techniques apply to a process controlled by a quasi-continuous temperature-control system, and the controlled variable behavior is governed by both the process properties and the temperature controller. To gain an understanding of the behavior of the control system, the three-dimensional display already described is equally applicable to quasi-continuous and continuous systems, whether linear or nonlinear.