22 May 2002
Performance of a water-to-water multi-type heat pump system was investigated by experiment. This system consists of two indoor units and one outdoor unit. Controlled variables are the evaporator outlet pressure of refrigerant and the outlet temperature of secondary fluid at each indoor unit. In this study, capacity control is aimed at controlling the outlet temperature of secondary fluid at each indoor unit using predictive control logic, and test results are compared with those obtained by PID control logic. To find parameters of predictive control, DARMA(Deterministic Auto Regression Moving Average) model was used to describe the system, and on-line parameter estimation method was used to update the parameters. Experiments were carried out when the set temperature was changed and when the load was changed. When the set temperature was changed, both predictive control and PID control gave similar outputs. When one indoor unit was shut off, predictive approach resulted in a better performance.