A method of cooling or heating a plurality of computer processor heat sources, such as processors in a data center or the like, is disclosed with individual sources having a control valve associated therewith. Individual heat sources are in communication with a supply of a coolant fluid and individual control valves have an inlet for receiving coolant fluid from its respective computer processor heat source reflective of the heat source temperature. The control valve has a chamber with an inlet that receives coolant, and an outlet. A valve member within the chamber is movable in response to changes in temperature of the coolant fluid within the chamber between a closed position and an open position. The valve member is of a material that changes shape in response to changes in temperature. The coolant is carbon dioxide (CO2) that is in its supercritical state as it passes through the heat sources.