Research On The Flow Control System Of Constant Temperature And Humidity System

In order to optimize the operation control of refrigeration system, base on constant temperature and humidity cold store, this dissertation has studied the control system of refrigeration aimed at higher control precision of temperature and higher resistibility against disturbing.The control system of cold store based on PLC has been established with advanced control strategy. To be specific, the main work contains several aspects as follows:The application of frequency conversion and electronic expansion valve (EEV) make it possible to adjust compressor speed quantitatively.PID, fuzzy controller and self-adapting fuzzy controller are used in our control system. Some comparison experimentation between them have been made and the results indicate that fuzzy controller performed rather better.Equipped and adjusted the electronic expansion valve and the drive circuitry. The dynamic characteristics of evaporator-EEV system are studied using test methods. The experiments on the stability of superheat are carried out, which investigate the superheat control. A new start-up control strategy named tracing control is promoted in this paper.Considering the disturbing of internal fans, we have finished Feed-forward control based on feedback control system, which improves the capacity of Anti-interference and reduces the temperature fluctuation of the cold store.