An apparatus and methods are provided for finless heat exchanger cores. A heat exchanger core includes an inlet header and an outlet header. The heat exchanger core also includes one or more curved channel frames disposed at least partially between the inlet header and the outlet header. The one or more curved channel frames have a first end and a second end, and one or more fluid passageways that direct flow of a first fluid in a first direction therethrough from the first end to the second end. In some embodiments, at least one of the one or more curved channel frames includes a rounded leading edge and a tapered trailing edge.