A method of assembling a radiant cooler is provided. The method includes providing a vessel shell that includes a gas flow passage defined therein that extends generally axially through the vessel shell, coupling a plurality of cooling tubes and a plurality of downcomers together to form a tube cage wherein at least one of the plurality of cooling tubes is positioned circumferentially between a pair of circumferentially-adjacent spaced-apart downcomers, and orienting the tube cage within the vessel shell such that the tube cage is in flow communication with the flow passage.