PURPOSE: To improve the durability of heat exchangers and their heat collection efficiency by inserting a rotary type heat exchanger between the exhaust pipe of an engine and a duct for air ventilation arranged adjoining to it and providing the other heat exchanger at the downstream duct of the said heat exchanger.

CONSTITUTION: A duct 26 for air ventilation is arranged adjoining to the exhaust pipe 23 of an engine and a rotary type exchaust gas heat exchanger 24 driven by a motor 25 is inserted between both 23 and 26. For example, this heat exchanger 24 is comprised by using a platinum catalyst as an alumina carrier and is also comprised as a catalytic converter for exhaust gas treatment. In addition, the other heat exchanger (evaporator) 5' is provided at the downstream side of the heat exchanger 24 in the said duct 26 and an air blower device 27 is provided at the upperstream side. As a result, engine exhaust heat is sucked by the heat exchanger 24 and is transmitted to the heat exchanger 5' through air and then is collected with good efficiency. At the same time, the durability of the heat exchanger 5' is improved and exchaust gas is purified.