Patent ID: 8132420

Claim:
A method of controlling a chiller system, the method comprising: operating the chiller system at a first capacity by circulating a refrigerant at a refrigerant flow rate through an evaporator system, wherein the refrigerant flow rate is adjustable; chilling an aqueous liquid by pumping the aqueous liquid at a variable liquid flow rate through the evaporator system such that the aqueous liquid enters the evaporator system at an inlet temperature and leaves the evaporator system at an outlet temperature, wherein the inlet temperature and the outlet temperature may vary; without actually measuring the variable liquid flow rate, calculating a first capacity value representative of an estimate of the first capacity; establishing a target outlet temperature of the aqueous liquid leaving the evaporator system; measuring the outlet temperature of the aqueous liquid; and adjusting the refrigerant flow rate based on the first capacity value and a temperature difference between the outlet temperature and the target outlet temperature.