An evaporative heat exchanger (10) is provided for the transfer of heat to a first fluid (30) from a second fluid (28) and a third fluid (22) to vaporize the first fluid (30). The heat exchanger (10) includes a core (40), a first flow path (60) in the core for the first fluid (30), a second flow path (66) in the core (40) for the second fluid (28), and a third flow path (68) in the core (40) for the third fluid (22). The core (40) includes a first section (42), a second section (44), and a third section (46), with the second section (44) connecting the first and third sections (42, 46). The first flow path (60) extends through all of the sections (42, 44, 46), the second flow path (66) extends through the first section (42), and the third flow path (68) extends through the third section (46).