Transient modeling of an air-cooled chiller with economized compressor. Part I: Model development and validation

Air-cooled chillers are widely used and the control design is important for the chiller performance and reliability under the varying operating conditions. A mathematical model is developed for a chiller with an economized screw compressor and to assist the controller design. The model covers both the economized mode and non-economized mode. The two modes can be automatically switched depending on the operating conditions. Comparisons made between simulations and experiments indicate that the model can reasonably simulate the transients of the chiller. Based on the validated model, a follow-up paper will describe its application to the controller design.