Abstract: A heat exchanger is disclosed for transferring energy between a first flowing fluid and a second flowing fluid. The heat exchanger comprises a first, second and third tube having an input end and an output end. A primary and a secondary angled couplers join the output end of the first tube to the input end of the second tube and the output end of the second tube to the input end of the third tube respectively. A continuous conduit conveys the second flowing fluid between a conduit input and a conduit output. The continuous conduit has a cross sectional area less than the cross sectional area of the first tube and the third tube for enabling the continuous conduit to be inserted within the first tube and the third tube. The continuous conduit enters a first aperture to extend inside the first tube for enabling heat exchange between the first flowing fluid and the second flowing fluid. The continuous conduit exits from a second aperture of the primary angled coupler to extend outside the second tube.