The characteristics of system cycle and cool storage of CO2 Hydrate with an initial charge pressure of 3.5–4.0 MPa were investigated in the direct-contact type cool storage test bench. Based on the experimental data

the p-h diagram of the cycle and cool storage rate under different initial charge pressure were drawn. The experimental results indicate that the system cycle corresponds to a sub-critical cycle when the initial charge pressure is 3.5 MPa or 3.6 MPa. Additionally

the system cycle corresponds to a trans-critical cycle when the initial charge pressures are 3.7

3.8

3.9

and 4.0 MPa

and the time in the trans-critical cycle corresponds to 8

10

9

and 8 min

respectively

while the proportion of time that the system cycles through the trans-critical region corresponds to 38%

58%

60%

and 73% respectively. When the initial charge pressure is increased

the cool storage time is decreased

the decrease of cool storage rate is accelerated

and the cool storage performance is improved.