Referring now to FIG. 1, a computer system control valve, which may also be known as a Passive Temperature Gate (PTG), of the present disclosure is indicated in its entirety at 1. In accord with this disclosure, control valve 1 may serve as a control valve for the “on demand” supplying of an influent (e.g., an operating fluid, such as a coolant fluid or a heating fluid) to a respective heat source 3 if the system is a cooling system or a respective heat sink 3 if the system is a heating system. However, the term “heat source” is used in this disclosure to mean either a heat source that is being cooled or a heat sink that is being heated. As shown in FIG. 2, the heat source may, for example, be a microprocessor or a processor or other heat producing electronic element 3 in a computer system, and more particularly to a plurality of processors in a data center or the like. Each of the processors 3 may be in heat exchange relation with a respective heat exchanger (not shown, but well known to those skilled in the art), which may, for example, be a finned heat sink or a radiator with flow passages therein for the circulation of the operating fluid through the heat exchanger to cool the heat exchanger and thus to cool the processor. Of course, such a radiator may have an inlet and an outlet for the flow of the operating fluid therethrough.