Along with pressure, flow and level, temperature of different process fluids is also an important parameter to be monitored and maintained within a desired range. Temperature control valves are used widely for this purpose.
Depending on the heating and cooling requirement, temperature is measured and it send signal to controller. Controller compares the reading and gives inputs to throttle (open or close) the control valve. Typical process scheme of temperatures is shown below
Generally temperature control valve are found in utility side of heat exchanger, process side bypass line of heat exchanger, etc.