Energy Savings Potential of Variable Condenser Water Flow Systems

Most chilled water systems are designed and operated with constant condenser water flow rates. Recently, there is a trend to apply VSDs to all the components to achieve higher operation performance when specially tailored operating strategies are incorporated. This paper studied the energy savings potential of varying condenser water flow rates by simulating an example condenser water loop. The simulation results show that, if the pump water flow and fan airflow are throttled by valves or dampers, the system could consume more energy when reducing the condenser water flow. If the pump and cooling tower are equipped with VSDs, the optimal condenser water flow is highly dependent on the design conditions and the sensitivity of chiller performance to the condenser water flow. The local climate has a minor effect on the optimal condenser water flow rate. At around the optimal CW flow rate, the system annual total energy usage is not sensitive to the CW flow rate. Compared to operation with a constant optimal CW flow, the savings of applying variable optimal CW flows are negligible. This method can be applied to actual systems to find the optimal condenser water operating strategies.