Abstract: An essentially tubeless heat exchange structure and an attendant controlled evaporative or condensing process is disclosed. A finned heat exchanger body has multiple spaced through passages constructed by locally deforming the fin metal. Each through passage includes multiple terraced liquid traps and coaxial orifices for counter-flowing gas. A liquid supply device and gas pressure relief device is provided for each through passage. The physical construction of the finned heat exchanger body can vary widely depending upon application.