The goal of this study was to develop heat transfer designs or techniques that will allow construction of condensers for automobile Rankine-cycle engines that have frontal area, volume, and fan horsepower requirements which are not appreciably greater than those of present automobile radiators. The first phase of the study included a parametric study of air-side heat transfer surfaces using available heat transfer data. Plain, ring dimpled, and finned tubes as well as plain, strip, offset, louvered, wavy, and perforated plate-fin surfaces were evaluated. A perforated plate-fin gave the best analytical results when the fin thickness was changed from 0.012 in. to 0.004 in. A small test core utilizing the new perforated fin design was fabricated and tested. The performance of this core did not achieve the calculated performance. Ten more test cores were fabricated and tested with a range of perforation sizes and spacings. (Author)