Kinetic and rheological studies of CO2 semi-clathrate hydrates
for cold storage air-conditioning systems
Cold storage air-conditioning, as an advocated energy-saving technology,
offers a mean to alleviate the peak load on electricity grids
and utilize power in the off peak period.
CO2 hydrate slurry is well suited for use as secondary
refrigerant for cold storage applications, since it can be generated
by CO2 injection in a cold aqueous solution (non-mechanical)
and has a large thermal storage capacity due to the large dissociation
enthalpy of CO2 hydrate (501~507 kJ kg-1).
However, in many cases CO2 clathrate hydrates cannot achieve
equilibrium within an adapted pressure range and temperature range
for cold storage systems. The main aim of this project is to lower
the equilibrium pressure of CO2 hydrates by forming CO2
semi-clathrate hydrates using aqueous solutions of additives,
such as TBAB, TBPB and TBAF. The testing system is indicated
in Fig. 1, which consists of a hydrate reactor cell, gas supply,
a cooling/heating source and data gathering facility.
CO2 hydrate equilibrium testing system.
Solar air-conditioning system with a CO2 hydrate cold storage.
Specifically, the equilibrium conditions CO2
semi-clathrate hydrates and the induction time at different
concentrations of additive solution are obtained during
the formation process. The influencing factors on formation
and dissociation behaviour of CO2 hydrates are investigated.
The rheological properties of the formed CO2 hydrates
are tested by an external circulating system.
Furthermore, the application of an optimized CO2 hydrate
cold storage will be developed in air-conditioning system
by means of simulation, as is illustrated in Fig. 2.