Patent ID: 6955213

Claim:
An exhaust gas heat exchanger of the shell and tube type, said heat exchanger comprising a shell having a hollow interior between opposite ends, an exhaust gas manifold secured to one end of the shell, and thermally conductive tube means extending through the interior of the shell from said one end of the shell, the exhaust gas manifold comprising first and second exhaust gas chambers which are mutually adjacent, each of said exhaust gas chambers comprising a respective exhaust gas inlet and an exhaust gas outlet, wherein the exhaust gas inlet of the first exhaust chamber and the exhaust gas outlet of the second exhaust chamber are disposed at an angle greater than 0° and less than 180°, said tube means providing an exhaust gas flow path between the exhaust gas outlet of said first exhaust gas chamber and the exhaust gas inlet of said second exhaust gas chamber, said heat exchanger being characterised by valve means providing a gas flow path directly between said first and second exhaust gas chambers and substantially closing the exhaust gas outlet of the first exhaust chamber when said valve means is fully open, said valve means substantially closing a direct gas flow path between said first and second exhaust gas chambers when said valve means is closed, whereby when a source of flowing exhaust gas is coupled to the exhaust gas inlet of said first exhaust gas chamber and said valve means is closed, exhaust gas is constrained to flow from the exhaust gas inlet of said first exhaust gas chamber to the adjacent exhaust gas outlet of said second exhaust gas chamber by way of said thermally conductive tube means to exchange heat with fluid in the interior of the shell and surrounding said tube means, whereas when said valve means is open, exhaust gas is allowed to flow from the exhaust gas inlet of said first exhaust gas chamber directly to the adjacent exhaust gas outlet of said second exhaust gas chamber and so bypass said tube means.