Probabilistic analysis of mist cooler effectiveness for air-cooled chiller systems

摘要

This study investigates electricity saving potentials of mist coolers for air-cooled chiller systems in commercial buildings in a subtropical climate. Extensive operating data were collected from an experimental chiller with mist cooling of condenser air. The chiller had a nominal capacity of 282 kW and was retrofitted with dual condenser fan controls: constant speed with fixed condensing pressure and variable speed with floating condensing temperature. The variation of the cooling effectiveness of the cooler was identified to depend mainly on the wet bulb temperature, followed by the relative humidity and the multiplication of dry bulb temperature and relative humidity under fixed condensing pressure control. While under floating condensing temperature control, the significant independent variables for modelling cooling effectiveness were the wet bulb temperature, followed by the relative humidity and the condensing temperature. Simulation was conducted to find the hourly chiller system load distributions of a reference office building and a hotel in a subtropical climate. The probabilistic distribution of cooling effectiveness was examined with the hourly system load distributions under two system configurations with 6 chillers and 8 chillers. Using mist coolers improved the coefficient of performance of chillers by 0.70-9.35%, resulting in an annual electricity saving of 2.50-2.94% under the diverse patterns of weather and system load distributions. Mist coolers complemented the advanced condenser fan control and improved system configurations with 8 chillers. Higher electricity savings were achieved by prolonging the operation of chillers near full capacity. (C) 2017 Elsevier B.V. All rights reserved.