In this study, the actual heat transfer coefficient of a phase-change material (PCM) was measured experimentally with the purpose of improving the heat storage rate of an automotive coolant waste heat storage system using the latent heat of the PCM. The heat transfer rate and time required to store heat was theoretically analyzed in the system where engine coolant was heated by a fin-tube heat exchanger filled with solid PCM. The amount of heat storage necessary for sufficient heating of vehicle coolant was calculated, and the appropriate amount of PCM was determined accordingly. Based on this data, a heat exchanger capable of storing heat under the lowest possible influence of natural convection and conduction thermal resistance of the PCM was designed, and its estimated heat storage rate was calculated. We identified the most effective methods to improve the heat storage rate and efficiency of the PCM-filled heat exchanger. (C) 2013 Elsevier Ltd. All rights reserved.