Abstract: Improved condensate drainage is achieved while compact size is retained in a condenser/evaporator for use in a heat pump system in a construction having first and second, curved, generally congruent tubular headers (10), (14) with one of the headers (10) being an upper header and the other of the headers (14) being a lower header. A first row of elongated tube slots (18) is located in the upper header (10) while a second row of elongated tube slots (20) is located in the lower header (14). Each tube slot (18) in the first row has a corresponding tube slot (20) in the second row and corresponding tube slots (18), (20) in the rows are aligned with one another. Elongated, straight, flattened tubes (22) extend between the headers (10), (14), in parallel with each other and a first port (32) is provided for refrigerant in one of the headers (10) and a second port (36) is provided for refrigerant in the other of the headers (14).