A heat exchanger system includes a first fluid layer defining a first flowpath for a gas, a second fluid layer defining a second flowpath for a liquid, a first vapor cycle layer located between the first fluid layer and the second fluid layer for enabling heat transfer between the first and second fluid layers, a first boundary wall defining a shared boundary between the first fluid layer and the first vapor cycle layer, and a second boundary wall defining a shared boundary between the second fluid layer and the first vapor cycle layer. The first vapor cycle layer includes a working medium configured to transfer heat through an evaporation and condensation cycle, and the working medium of the first vapor cycle layer is sealed between the first and second boundary walls.