Patent ID: 7637315

Claim:
A constant temperature liquid circulating device having a conduit for delivering circulating liquid temperature-controlled at a constant temperature due to a heat exchanger by a pump and a circulating flow channel for allowing the circulating liquid to circulate therein, the circulating flow channel formed by respectively connecting a discharge port and a return port of the conduit to both ends of a piping that defines a flow channel of the circulating liquid in the external device whose temperature is controlled by the circulating liquid, the liquid circulating device comprising: a flow amount sensor provided in the conduit; temperature sensors for detecting a discharge temperature (T 1 ) of the circulating liquid from the conduit and a return temperature (T 2 ) of the circulating liquid returned to the conduit; and a controller configured to control the flow amount and the temperature of the circulating liquid according to a heat load of the external device obtained on the basis of the outputs from the sensors the controller configured to calculate a heat load of the external device from a difference between discharge and return temperatures (T 1 , T 2 ) of circulating liquid detected by the temperature sensor and a flow amount of circulating liquid detected by the flow amount sensor, to perform only temperature control of circulating water at the heat exchanger while keeping the flow amount of circulating water constant when the heat load is smaller than a preset value, and to perform control to increase the flow amount or the pressure of the circulating water flowing through the piping of the external device besides the temperature control of circulating water by the heat exchanger when the heat load of the external device becomes greater than the preset value, thereby reducing the temperature difference and maintaining the discharge temperature (T 1 ) or return temperature (T 2 ) at the preset temperature.