US Patent 7921640 Exhaust gas waste heat recovery

An exhaust heat recovery heat exchanger assembly for use along a main exhaust flow path of an exhaust system for an engine, and a method of operation, is disclosed. The exhaust heat recovery heat exchanger includes a sealed vacuum chamber, including a hydride pellet mounted in the chamber, and electrical leads extending from the hydride pellet. An exhaust chamber along the main exhaust flow path is located along an inner wall of the vacuum chamber. A housing surrounds the vacuum chamber and defines a heat receiving medium chamber. A heat receiving medium flows through the heat receiving medium chamber and absorbs heat from the exhaust flowing through the exhaust chamber when an electric current is applied to the hydride pellet.