Helical Coil Heat Exchangers. These heat exchangers, including a sister type called a spiral heat exchanger, refer to a helical tube configuration that are coiled to form the two channels in a counter-flow arrangement. Each channel has one long curved path. These compact units present a small footprint, have less pressure drop, less pumping energy, higher thermal efficiency, and lower energy costs. Due to their flow characteristics, they are virtually self cleaning. They are often used in such applications as pasteurization, digester heating, heat recovery, pre-heating, and effluent cooling.