Cooling device for exhaust of e.g. direct injection diesel engine has two paths each of same axial length with different heat exchange properties and valve directing flow from one path to other path

摘要

A cooling device for installing in a vehicle exhaust system has two paths each having conduit(s) with an external surface contacted by cooling air. Each path has the same axial length but different heat exchange characteristics. A valve switches the gas flow from one path to the other depending upon a thermal parameter of the exhaust system. Preferred Features: The first path may have tube(s) with a simple metallic surface and the second path has relatively smaller diameter tube(s) insulated by an air jacket between internal and external surfaces. A temperature sensor operates the valve located at the downstream end of the first path. The device is located upstream of a NOx filter