4689 – Thermodynamic Modeling and Experimental Validation of Screw Liquid Chillers PDF

This study presents an empirically based model, involving the first and second laws of thermodynamics and the NTU-e method of heat exchanger, to predict the coefficient of performance (COP) of screw liquid chillers under various operating conditions, especially for capacity control by return chilled water sensing. A series of experiments were performed to verify this model. The input operating parameters of the model are readily measured data from the water side of liquid chillers; they include the chilled water inlet temperature, the cooling water inlet temperature, and the cooling capacity. By incorporating the experimental data and the theoretical predictions, an empirical correlation form can be obtained to predict the performance of a screw liquid chiller. The result indicates that comparison between the predicted value and the measured data yields an R^2 (explained fraction of variance) of around 98.87%, an RMSE (absolute root-mean-square error) of about 0.0524, and an R-RMSE (relative root-mean-square-error) of about 1.43%. The results of this work should be applied for the purposes of performance prediction, evaluation of energy-efficiency improvements, fault detection, and other diagnoses of screw liquid chillers.

Units: Dual