シュリーレン法によるTBAB包接水和物の結晶成長と濃度場の同時計測

抄録

To improve the coefficient of performance (COP) in air-conditioning systems, the liquid-solid phase change temperature of the cold energy storage material should be approximately 10°C. Tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate possesses the qualities of an efficient cold storage material. TBAB aqueous solutions form a clathrate hydrate at temperatures between 5 and 12°C, depending on the concentration. The temperature region is well suited to air conditioning systems. A 20 wt% TBAB solution has a latent heat of fusion of approximately 220 kJ/kg, and its clathrate hydrate suspension is a slurry with sufficient fluidity. The objective of this study is to examine the dynamic characteristics of the formation of TBAB clathrate hydrate. The schlieren system was used for simultaneous measurement of crystal growth and concentration field in TBAB aqueous solution. Results showed that the concentration diffusion layer of the leading edge of TBAB clathrate hydrate crystal moved with the crystal growth. Based on the measured spread rate and thickness of the diffusion layer, the diffusion coefficient of the TBAB molecule in the vicinity of solid-fluid interface was estimated.