Performance evaluation of a Nickel-Titanium shape memory alloy-based thermostat valve

Efficient thermal management in automotive engines is essential for maintaining optimal operating conditions, improving fuel efficiency, and reducing emissions. Conventional wax-based thermostat valves commonly used in engine cooling systems exhibit delayed actuation and relatively large thermal hysteresis, which can limit the precision of temperature regulation during engine warm-up and operation. In this study, the design, fabrication, and experimental evaluation of a Shape Memory Alloy (SMA)-based thermostat valve are presented as an alternative to conventional wax-based systems. A Nickel–Titanium (NiTi) SMA spring actuator was selected due to its repeatable thermo-mechanical phase transformation behavior, compact form factor, and suitability within automotive engine operating temperature ranges. The SMA-based valve mechanism was analytically designed, functionally heat-treated to ensure stable actuation behavior, and integrated into a laboratory-scale experimental test rig. The performance of the proposed valve was experimentally evaluated and compared with a commercially available wax-based thermostat valve under identical operating conditions over a two-minute test duration. The experimental results indicate that the SMA-based thermostat valve reached full actuation within 35 s, whereas the wax-based valve required approximately 60 s, corresponding to a 41.67% reduction in actuation time. In addition, the SMA-based valve exhibited a 57.14% reduction in thermal hysteresis, contributing to improved temperature regulation. An overall performance efficiency improvement of approximately 48.61% was observed when compared with the conventional wax-based system. These results indicate that SMA-based actuators provide faster thermal response and reduced hysteresis under the tested conditions. The outcomes of this study confirms that SMA-based thermostat valves represent an alternative approach for automotive cooling applications and provide a basis for further investigation of long-term durability and system-level integration in advanced thermal management systems.