A heat exchanger unit is disclosed, the heat exchanger unit including a first tube element unit, a second tube element unit, and an engine machine apparatus having an expansion step unit and a compression step unit. Each of the tube element units is adapted to condition a fluid flowing therethrough. Desirably, the fluid is compressed in the compression step unit and expanded in the expansion step unit in such a manner that technical operation is transferred from the expansion step unit to the compression step unit so that an inner recovery of energy is made possible.