A Pulse Width Modulation Control System for Regulating Refrigerant Flow Into an Evaporator

ABSTRACT: In this paper, a pulse width modulation control system for regulating the refrigerant flow into an evaporator is presented. The mathematical model of the evaporator, which may be viewed as a first-order plus delay, is introduced. This leads to a conclusion that PI (PID) is adequate. To realize minimum stable signal (MSS) control and guarantee the system's safety, some rules based on knowledge and experience about refrigeration have been extracted. The advantages of the system are independent of refrigerant, independent of changes of condenser pressure, adaptation to MSS and adjustable superheat set.