Susumu Nakayama

Modelling of Refrigeration Cycle Dynamics for Air Conditioner.

A method for modelling refrigeration cycle dynamics for a test air conditioner is investigated. The main actuators in regulating the test refrigeration cycle performance are an inverter-driven compressor and motor-driven control valves. Refrigeration cycle dynamics are investigated experimentally by making step changes in the compressor capacity and the valve openings. The refrigeration cycle is modelled as a multivariable linear system around balancing points. A method for identifying the experimental responses is developed and the refrigeration dynamics are described by compounds of the first-order delay, second-order delay and time lag characteristics. The modelled dynamics are combined with PID controllers to simulate control conditions. The good agreement between simulation results and experimental data validates this modelling method.