Study on growth characteristics of TBAB clathrate hydrate using directional solidification method

Tetra-n-butyl ammonium bromide (TBAB) is a quaternary ammonium salt whose hydrate has been identified as a promising phase-change material, exhibiting a suitable phase-change temperature for air-conditioning applications. In thermal energy storage systems utilizing TBAB hydrate, the hydrate formation process plays a crucial role in system design. However, the growth rate of TBAB hydrate is known to be significantly slower than that of ice, making it important to reveal the growth characteristics of the hydrate crystals. In this study, the growth behavior of TBAB hydrate crystals was investigated using a directional solidification method. The crystal morphology during solidification was examined, and the temperature at the solid-liquid interface was measured. The results revealed that the crystal morphology was influenced by both the migration speed and the solute concentration. Furthermore, it was found that the interface temperature was lower than the phase-equilibrium temperature of the hydrate and decreased with increasing migration speed.