Double-spiral-type equipment is proposed as a new compact heat exchanger. Initially, the behavior of heat transfer coefficients is quantitatively determined through experiments of the heat exchange between hot and cold water flows in the exchanger. Subsequently, the heat-recipient water is changed with phase change material (PCM)-water slurry to ascertain the effects of PCM-melting on heat transfer enhancement through direct measurements of heat transfer rates. By appropriately evaluating the physical properties of the slurries with PCM-melting, we finally propose a heat transfer correlation which is applicable to both the water and slurry flows.