Testing and validation of simulation tools of HVAC mechanical equipment including their control strategies. Part III: validation of an air-cooled chiller model

This paper presents a semi-empirical steady-state model of an air-cooled water chiller. The first part of the paper shows how the model is built by associating a scroll compressor and two heat exchanger sub-models. The second part of the paper presents the parameters identification process based on published manufacturer data (for the compressor and the whole chiller models). The only encountered difficulty is the characterization of the fan control model, since information is lacking to identify its parameters.  The third part of the paper presents results of an experimental investigation carried out on the same chiller integrated into an existing cooling plant. A detailed analysis of the experimental data allowed a better understanding of the chiller’s operation and a better identification of the model’s parameters (such as the models of the fan control and of the compressor staging control). Moreover, a simple but realistic model of the condenser hot gas by-pass was introduced. As a result, deviations between predictions by the model and the experimental data were considerably reduced. The model is finally found to predict the total cooling energy and the total electrical consumption over a long-term simulation period with a very good accuracy.