STEADY-STATE MODEL OF CENTRIFUGAL LIQUID CHILLERS

A new steady-state model of vapour-compression type centrifugal liquid chillers is presented. The model has a number of advanced features an d is capable of simulating both hermetic and open-drive centrifugal co mpressors. The model accounts for the real process phenomena such as s uperheating and subcooling in the heat exchangers as well as a capacit y control formulation of the inlet guide vanes. The model algorithm is developed with the aim of requiring only those inputs that are readil y known to the design engineer, e.g. the general parameters of the chi ller, the chilled water flow temperature out of the evaporator and the return water temperature to the condenser inlet. The outputs include the condenser capacity, the refrigeration capacity (at the evaporator) , the coefficient of performance, and also the mass flow rates and the rmodynamic states of the refrigerant throughout the cycle. The model i s validated with the experimental data on part load to full load perfo rmance of three different chillers operating at the University of Auck land and the agreement is found to be within +/- 10%. The model also d emonstrates that the COP of the chillers increases with increasing coo ling capacity. (C) 1998 Elsevier Science Ltd and IIR. All rights reser ved.