A Thermal Accumulator Based on Phase-Change Materials

The concept of a water thermal accumulator based on phase-change materials (PCMs) has been proposed and analyzed. In such a system, energy accumulation (release) occurs due to a phase transition in PCMs, and water is used as a working fluid. The thermal accumulator consists of identical modules, the number of which determined by the quantity of accumulated energy. Each module represents a double concentric tube, in which the inner cavity is filled with flowing water and the outer cavity is filled with PCMs. The PCM used is paraffin wax, which has a specific melting enthalpy of 216 J/g. To increase the PCM heat conductivity coefficient, an additive of thermally reduced graphene oxide is used. The passage of hot water through the inner tube results in the melting of paraffin wax, which accumulates the thermal energy corresponding to the melting enthalpy. This energy is recovered when cold water is passed through the system containing the melted paraffin wax and heated as a result of paraffin wax solidification. Some estimates of thermal accumulator regimes and the results of calculating the unsteady longitudinal and transversal temperature distributions at different time moments are given.