Predicting Improved Chiller Performance Through Thermodynamic Modeling

Abstract

This paper presents two case studies in which thermodynamic modeling was used to predict improved chiller performance. The model predicted the performance (COP and total energy consumption) of water-cooled centrifugal chillers as a function of condenser inlet temperature, evaporator outlet temperature, and evaporator load. The model was validated using experimental data from a chiller used at a high school in South Texas and chillers located at the physical plant of a university campus in Arkansas. The validation results showed that the average actual vs. predicted COP and total electricity consumption differed by no more than 2 percent. Simulations were run to discover improvements in chiller performance and ways to save energy. Both case studies showed reasonable values for power and energy savings for reduced condenser inlet water temperature. Predictions showed energy savings of 1.6 percent per °C (1.8 °F) and 2.4 percent per °C (1.8 °F) for the 144 kW (192-ton) and 10,550 kW (3000-ton) chillers, respectively. Similarly, it was found that the reduction in power consumption would range between 0.015 -0.02 kW/ton per °C (1.8 °F) for the 10,550 kW (3000-ton) chiller. This papers outlines the model development based on fundamental thermodynamics, experimental setups, validation, case studies, conclusions and recommendations.