Optimization of temperature control during cooling in a multizone refrigeration system

This paper describes the performance of a refrigeration system when applied to a multizone industrial application driven by a common compressor. The limitations of current on/off type control using solenoid valves for such applications are outlined and methods of achieving more accurate temperature control are considered. As a result, electronic pressure regulating valves were selected and introduced to replace on/off type solenoids in a multizone refrigeration system consisting of three compartments, and their performance is compared against that obtained using solenoid valves for a series of temperature pull-down (cooling) tests. This paper describes the system hardware, the control algorithms used for controlling the electronic pressure regulating valves, and presents test Results from both the electronic pressure regulating valves and solenoid activated control systems for three different test conditions. Overall, the electronic pressure regulating valves produced improved performance, indicating the following average results over the three zones: (1) 40% faster temperature pull-down to the setpoint, (2) 80% better setpoint temperature control, and (3) reduced temperature control problems arising from sudden changes in control valves in the status of neighboring zones.