Simplified Model for the Operation of Chilled Water Cooling Coils Under Nonnominal Conditions

This study presents a cooling coil model for calculating energy consumption in air-conditioned buildings that has a minimal number of inputs. The model accurately determines the cooling energy rate and dehumidification energy rate under nonnominal conditions, and takes into account operation under variable air and water flows. In this manner, the model enhances the simplified ASHRAE Toolkit model without requiring more input data. The main assumptions are justified considering the common existing configurations of cooling coils in the air-conditioning industry. The parameters of the model are identified from only one nominal rating point. The model has been validated on a VAV facility with an average deviation of 5% for total energy rate. Errors are mainly due to the assumption that the coil is either completely wet or dry even if the surface is partially wet.