Study on the enhancement of TBAB on compressed CO₂ Hydrate cool storage systems

This study employed tetrabutylammonium bromide （TBAB） as a thermodynamic additive to enhance the cool storage performance of carbon dioxide hydrate. Compared with the pure water system, the addition of TBAB significantly elevated the phase transition temperature of CO₂hydrates and reduced the charging pressure required for hydrate formation. The formation characteristics and cool storage properties of the hydrate were investigated under different charging pressures （2.4–3.0 MPa） and TBAB concentrations （5–20 wt%）. The experimental results indicated that the phase transition temperature of CO₂hydrates increased with the rise in charging pressure and TBAB concentration, and the higher the charging pressure, the better the cold storage performance. As the TBAB concentration increased, the cool storage performance first improved and then declined. The optimal cool storage performance was achieved at a TBAB concentration of 15 wt% and a charging pressure of 3.0 MPa, with the maximum total cool storage capacity （6256.25 kJ）, fastest average cool storage rate （2.49 kW）, and highest COP （2.5）. The study demonstrated that TBAB significantly enhanced the performance of compression-type CO₂hydrate cool storage systems.