Experimental Optimization of Cooling Tower Fan Control Based on Field Data

Energy costs continue to play an important role in the decision- making process for building design and operation. Since the chiller, cooling tower fans, and associated pumps consume the largest fraction of energy in a heating, ventilating, and air-conditioning HVAC system, the control of these components is of major importance in determining building energy use. A significant control parameter for the chilled water system is the minimum entering condenser water set point temperature at which the cooling tower fans are cycled on and off, several studies have attempted to determine the optimum value for this minimum set point temperature, but direct measurements are not available to validate these studies. The purpose of this study was to experimentally determine the optimum minimum entering condenser water set point temperature from field data based on minimum energy consumption and to validate a chilled water system analytical model previously developed in earlier work. The total chiller system electrical consumption chiller and cooling tower fan energy was measured for four entering condensor water set point temperatures 70, 75, 80, and 85 deg F. The field results were compared to results obtained using an analytical model previously developed in a thesis entitled Optimized Design of a Commercial Building ChillerCooling Tower System, written by Joyce.