A system-level study has been conducted of a cooling system consisting of a chiller, a cooling tower and a Brayton-cycle-based-system to precool the air entering the cooling tower. The novelty of this system is the air precooling system that is expected to enhance the cooling load of the chiller. The simulations consist of thermodynamic relations for compression, expansion and phase change processes, and heat and mass transfer balances in the heat exchange components. Simulation results are compared against measured data collected in a laboratory set up consisting of a blower, a water-cooled heat exchanger and an expander, and the simulation results agree well with the measured data validating the various elements of the model. Simulations are performed for a warm summer day with 35 degrees C inlet air and 47% relative humidity. Three different configurations are considered: (a) a closed loop water flow system (Case A) where the water flow between the cooling tower, chiller, and the air-water heat exchangers form a closed loop system (b) open loop water flow system (Case B) where the water flow through the air to water heat exchangers is provided by municipal water and the cooling tower and chiller operate in closed loop (c) same as the (b) configuration but with an air to air heat exchanger placed downstream of the blower to precool the air entering the air-water heat exchanger.

Results are presented utilizing a few empirical models for the cooling tower that assume a certain performance across the cooling tower. These results demonstrate that Cases B and C provide improvements in the chiller load and COP of the system compared to case A, but no substantial differences between Case B and Case C is observed.