This paper presents a one-zone steady-state system model of an oil-injected screw chiller. The model can be used as a design and optimization too] for system performance of multiple-chiller plant in process industries. All major components of the system are modelled in a modular format including the oil-injected screw compressor, shell and tube condenser, flooded evaporator and a high side-float value. The model results are validated with the experimental data from a multiple-chiller plant at a process industry. The validated results show that the part-load ratio and the glycol-water temperature at the evaporator inlet significantly affect the system performance as compared to the temperature of cooling water entering the condenser. Copyright (C) 2004 John Wiley Sons, Ltd.