Authors : Naissir Hidalgo Perez, Evert De Los Rios Trujillo and Guillermo Valencia Ochoa
Abstract: This study presents a cascade control system implementation to regulate the outlet temperature in a evaporator of a vapor compression refrigeration systems which is integrated by an evaporator, a compressor, the expansion valve and the condenser. The equipment is partially instrumented with 4 temperature sensors and 4 pressure sensors, connected to the NI USB 6210 and NI USB 6008 data acquisition that allows manipulate the fans speed in the condenser and evaporator heat exchanger. The transfer functions of heat exchangers was approximated to a first order plus dead time in order to study the evaporator outlet temperature and the faster dynamic in the condenser outlet temperature for inner loop which allowed to design and tune the PID controllers through the Ziegler-Nichols method for the primary controller and the Austin tuning laws for the secondary controller. Finally, the performance controllers was evaluated using the integral of absolute value of error indicator, resulting the P-PI cascade controller under changes of set point whit comparative advantages rather than PI controller.
Naissir Hidalgo Perez, Evert De Los Rios Trujillo and Guillermo Valencia Ochoa, 2018. Cascade Control Loop Implementation in a Vapor Compression Refrigeration System Using LabVIEW®. Journal of Engineering and Applied Sciences, 13: 5820-5825.