Cooling system and cooling method

A cooling system configured to cool a fluid used in a device mounted on a vehicle, by exchanging heat with cooler cooling water in a cooler, the cooling system comprising:

• a cooling water passage connected to the cooler and having an undercover cooling water passage provided to an undercover forming a bottom surface of the vehicle and where the cooler cooling water is cooled by exchanging heat between the cooler cooling water and air below the undercover;
• a cooler radiator provided in the cooling water passage and configured to cool the cooler cooling water by exchanging heat between the cooler cooling water and air flowing into an engine bay from a grille that is an opening portion formed at a front end of the vehicle;
• a flow rate adjuster including a pump or valve, configured to adjust a flow rate of the cooler cooling water supplied to the undercover cooling water passage;
• and
• a controller configured to control the flow rate adjuster, the controller acquiring at least one of a pressure and a temperature of the fluid, and controlling the flow rate adjuster to increase the flow rate of the cooler cooling water supplied to the undercover cooling water passage based on an increase in one of the pressure and the temperature of the fluid.