An Experimentally Validated Model of a Cross-Flow Sub-Wet Bulb Evaporative Chiller

Abstract

Abstract A simplified model to predict the performance of a novel sub-wet bulb evaporative chiller (SWEC) for producing chilled water is presented. The SWEC design uses a daisy-chained arrangement of cross-flow heat exchangers (HXs) with evaporative media located in between the heat exchangers to chill water below the outdoor wet bulb temperature (WB) in either a one-pass or two-pass arrangement. Sub-models, based on the effectiveness-number of transfer units (ɛ-NTU) method, for the heat exchanger and evaporative media are coupled together to form the SWEC model. The model is validated using field data from a SWEC that is designed with a single water pass. The model results are observed to match the SWEC experimental data within a mean average error (MAE) of 0.74% in supply chilled water temperature and 5.6% in chiller capacity over a range of outdoor air dry bulb and wet bulb temperatures, inlet water temperatures, and water flowrates. The validated model is then used in a parametric study of geometrical and thermofluidic variables. The model is also used to predict the performance of the SWEC in a typical hot and dry weather over a summer week.