A heat exchanger assembly including a first and second heat exchangers disposed in sandwiched relationship with one another. The tubes and air fins of the first and second heat exchangers are aligned with one another in a transverse air flow direction. A plurality of middle connecting portions are integral with and extend in the transverse air flow direction between the aligned first and second air fins of the two heat exchangers. Each of the middle connecting portions has a slot for impeding heat conduction between the first and second air fins, and each of the slots in the middle connecting portions is disposed closer to the first tubes than to the second tubes to maximize the effective length of the second air fin.