SMA actuator for gas combi boiler diverting valve

Abstract

This article deals with a three way diverting valve for heating boilers using a shape memory alloy material to move its actuator. This project was realized by the Research & Development Department of MTS (Merloni Termosanitari) together with the Energy Department of the University of Ancona; this device is protected by a European patent. As is well known, the three way diverting valve inside a heating boiler has the function to shift hot water flow coming from the primary heat exchanger either towards the sanitary circuit or the domestic heating system, depending on the demand. The idea of a shape memory alloy to realize the actuator movement of the three way valve represents a good alternative to traditional actuator moving systems using a electric motor. A shape memory alloy is characterised by the ability to recover a pre-macroscopic deformation during a phase change caused by heating; moreover the deformation recovery brings to a increase to the mechanical properties of a shape memory alloy. In this article, we will present in detail the valve functionality, the equations we used for the dimensioning, and the description of the most important tests on the device to verify its efficacy and reliabililty.