Abstract: The heat exchanger comprises at least one heat-transfer wall which forms a separation between a hot primary fluid and a secondary fluid to be heated. Each heat-transfer wall is either a vertical cylinder having a cross-section in the form of a circle with a wavy profile in the case of a tubular heat exchanger or a vertical rectangular plate having wavy corrugations in the case of a plate-type exchanger, a series of assembled plates being intended to form leak-tight compartments for receiving primary fluid and secondary fluid in alternate succession. The secondary fluid is introduced into the upper end of the heat-transfer wall in the vicinity of the wave crests of the wall face which is directed towards the fluid.

Abstract: An air valve, in the snorkel leading to the air cleaner in the induction system of an internal combustion engine, is actuated by a vacuum operated servo controlled by the depression in the snorkel to maintain a constant depression at the air cleaner. An exhaust gas recirculation control valve, operated by the air valve control servo, opens proportional to air valve opening to control exhaust gas flow into the induction system proportional to exhaust back pressure and air valve opening thereby providing exhaust gas recirculation flow proportional to engine load.