Thermal Control Valves
Thermal control valves provide a means to control the temperature of coolant at a particular point in a system to a defined value. The valves produced by PDT are passive, thermostatic-type valves which do not require electrical power or a control circuit to operate. The valves use a high-output linear actuator to move a sliding spool or poppet element. Movement of the valve element serves to selectively open or close fluid passages in the valve to achieve the desired temperature control.
The design of the thermal control valve allows it to be used in both diverting and mixing applications which provides great flexibility for the system designer. Typical installation schematics for both configurations are shown below. PDT can incorporate additional features such as temperature sensors, supplemental fluid ports and relief valves to consolidate system plumbing and reduce the cost of the system. Contact our application engineers to discuss how a PDT thermal control valve can bring benefit to your liquid system.
Two different actuators types are utilized, depending upon the usage and system considerations for the valve. The most popular choice for airborne and ground vehicle applications is the sealed paraffin actuator. This unit is available with elastomeric seals that can be selected for compatibility with most typical coolants or oils. For critical applications, such as long-duration spacecraft, PDT can supply a thermal control valve utilizing an all-welded design with no elastomeric seals. In this unit, a flexible metal bellows filled with a high-expansion liquid replaces the paraffin actuator.
PDT can supply thermal control valves which are suitable for use with a variety of typical coolants or oils. The performance of the valve is specified by the nominal control temperature and the control band. Standard paraffin actuators are available with nominal control temperatures from 35°F to 210°F (2°C to 98°C). The control band for these actuators is ± 8°F (± 5°C).
Tight tolerances between the sliding spool and housing allow this unit to provide flow control without the use of elastomeric seals on the sliding element. PDT has produced thermal valves with nominal control temperatures from 32°F to 77°F (0°C to 25°C). The control band for these actuators is ± 18°F (± 10°C).