An Insight into the Application of the NTU-? Approach for Modelling Vapour-Compression Liquid Chillers

This paper presents a steady-state model that is useful for predicting the performance of centrifugal liquid chillers over a wide range of operating conditions. The model employs an elemental NTU-E methodology to model both the shell-and-tube condenser and the flooded evaporator. The approach allows the change in heat transfer coefficients throughout the heat exchangers to be accounted for, thereby improving the accuracy of the simulation model. The model requires only those inputs that are readily available to the user (ie. condenser inlet water temperature and evaporator water outlet temperature). The outputs of the model include system performance variables such as the compressor electrical work input and the coefficient of performance (COP). The model is validated with data from a 450 kW open-drive centrifugal chiller where the agreement is found to be within ±10%.