Design, development and performance evaluation of latent heat storage foot warmers

In this paper, three PCM based foot warmers of cylindrical and rectangular in shape were designed, developed and fabricated to store solar energy during sunshine hours. The stored energy was utilised to warm the feet in the late evening to replace electric heaters. By trial experiment, it was found out that the surface temperature of the storage units of the foot warmer should be between 37°C–41°C for heating the feet. Therefore, commercial grade lauric acid (Melting Point 42.2°C, Latent Heat of Fusion 181 × 103 J/kg) was used as a latent heat storage material. Experiments were conducted during a winter season to study the latent heat storage units and the thermal performance of the rectangular shaped foot warmer was found better than the cylindrical shaped with the same storage capacity. The experimental thermal performance studies of these latent heat storage systems showed that such type of foot warmer can be used for heating purpose of the feet and legs in composite and cold and sunny climates.