Optimum setpoint of condensing temperature for air-cooled chillers

Under headpressure control, air-cooled chillers appear inefficient because the condensing temperature is kept high; it is essential to explore how to optimize the condensing temperature to improve their efficiency. With the simulation program TRNSYS, a chiller model is developed and experimentally verified to ascertain all parameters within chiller components. An algorithm, which can be used to determine the number of staged condenser fans by a setpoint of condensing temperature, is first introduced. The model with this algorithm serves to illustrate the extent of decrease in the condensing temperature, which has rarely been studied. When the setpoint of condensing temperature varies linearly with outdoor temperature, maximum chiller efficiency is obtained. The condensing temperature also becomes controllable, resulting in less fluctuation in chiller efficiency in different operating conditions.