Empirical model for evaluating power consumption of centrifugal chillers

A novel steady-state empirical power consumption model using water pressure difference, instead of water flow rate or cooling capacity, as one of the input variables is proposed for centrifugal chillers of a cooling plant with multiple parallel chillers. It is possible to evaluate the energy consumption and performance of a chiller without measuring the chilled water flow rate, which is difficult to measure directly and accurately in many on-field operating chiller plants. The on-field measurement and analysis indicates that the accuracy of the proposed model is slightly superior to that of the four empirical models quoted from literature-Yik model, Braun model, Comstock model and Chang model. When the internal data is considered, the coefficient of variation of root-mean-square error (CV) of the novel model for the chillers 1-3# are respectively 2.51%, 3.48% and 2.67% with the vast majority of relative errors being ±8%, ±10% and ±10%, respectively. When external data are adopted, the proposed model is obviously superior to the other four models with CV values for chillers 1-3# respectively being 4.94%, 7.79% and 5.98% and the vast majority of relative errors being ±8%, ±12% and ±10%, respectively. This result is acceptable for engineering applications, such as fault detection and diagnostics (FDD), building energy audit, energy conservation management and operation management of chiller plants.