HEAT EXCHANGER, AND INTERNAL COMBUSTION ENGINE BLOW-BY GAS PROCESSING DEVICE

This heat exchanger is provided with an inner tube , a first flow passage formed inside the inner tube , an outer tube disposed coaxially with the inner tube on the radially outer side thereof, a second flow passage formed between the inner tube and the outer tube , annular separating walls P to P which divide the second flow passage into a plurality of spaces S to S in the axial direction of the outer tube , and space outlets E formed in one location in the circumferential direction of each separating wall P to P, wherein the spaces S to S are configured to cause a second fluid to swirl about second axes Y perpendicular to a first axis X positioned at the center of the outer tube