Fabrication of SMA based hot water actuated heat engine

Abstract

Shape Memory Alloys (SMA's) were invented many years ago, though using of SMA in applications related to engineering is only prominent from last few years. Reason behind using SMA is its ability to change its crystalline structure by applying a temperature gradient. Its simultaneous memory effect and elastic behavior makes it suitable for applications involving actuation and control. In this process of finding application of this interesting material, a device for conversion of waste heat into work could be of utmost importance. In this work SMA is employed for conversion of waste heat energy into mechanical work. A typical power plant works on Rankin’s cycle with condenser temperature of around 70°C thus we need to maintain temperature at condenser by circulating water which gets heated to around 55 to 60 °C. This 60 °C water is waste energy which can be utilized for getting some work output. SMA with its property of hot water actuation is utilized for conversion of heat energy into mechanical work. In later part of work exhaust gases from automobile is used for actuation, and thus serving purpose of waste heat recovery. SMA (NiTi) springs are used for conversion of heat energy into mechanical work. The design of setup is simple and inexpensive involving very less expenditure. The prototype is tested multiple times and it is serving the purpose of conversion of energy and acting like a Heat Engine. The design consists of Nitinol springs connected radially to a steel rim with a hub (serving purpose of bearing) in middle. When this setup is inserted in hot water of around 60°C the steel rim starts rotating thus serving purpose of converting waste heat into mechanical work.