Abstract: There is provided a gas heat exchanger 101 comprising a coolant conduit 102 having a coolant inlet 103 and a coolant outlet 104, a gas cooling conduit 201, and a gas bypass conduit 203. At least a portion of the gas cooling conduit 201 is disposed between at least a portion of the coolant conduit 102 and a portion of the bypass conduit 203. During a first mode of operation, the gas cooling conduit 201 is configured to carry gas. During a second mode of operation, the bypass conduit 203 is configured to carry gas and the gas cooling conduit 201 is configured to reduce a heat exchange between the coolant conduit 102 and the bypass conduit 203.

Abstract: An exhaust gas re-circulation system provides for intake of exhaust gases from a first end 206 into one of a plurality of corrugated inner tubes 204 housed within an outer tube 200. Corrugations in said inner tube 204 provide for an increased surface area for heat exchange with a surrounding coolant medium and for decreased velocity of flow of exhaust gas increasing the density of charge of exhaust gas returned to a combustion chamber of an associated internal combustion engine by an inlet manifold where said exhaust gas re-circulation system connects to said inlet manifold at a second end 207. Said outer tube provides for inlet 203 and outlet 202 of coolant medium. Said outer tube further comprises corrugated portions to withstand vibration/expansion. Said inner and outer tubes are manufactured from thin wall metal tubes.