Design and performance of conventional and fuzzy controls for a hight temperature short time pasteurization system

Abstract

Fuzzy control was applied in a high-temperature short time (HTST) pasteurization system and experimentally evaluated and compared with proportional-integralderivative (PID)/feedback and PID/feedback/feedforward controllers. The product, a juice model solution, was pasteurized for 91C/40 s in a three-stage plate heat exchange (regeneration, heating and cooling sections). Hot water and propylene glycol were responsible to heat and cool the product, respectively. A control system was designed to assure the pasteurization temperature manipulating the hot fluid flow rate. Controllers were evaluated by means of dynamic behavior of the pasteurization temperature and performance criteria after the imposed step changes of the product inlet temperature. Configured controllers kept the process temperature within HTST requirements, having a variation of 0,5C, and the similar values of performance criteria indicate an efficiency for all three tested controllers.