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The application of hydrate-based technology is restricted by challenges such as high phase equilibrium pressure, long induction time, and slow formation rate, which could be overcome by different promoters. Compared to traditional accelerators such as tetrabutylammonium bromide (TBAB), 1,1,1,2-tetrafluoroethane (R134a) is an effective gas promoter in lower phase equilibrium conditions and easy to separate. The paper proposed a method to trigger and synergize CO2hydrate rapid nucleation and formation by controlling the trace (3 wt %) of R134a. The effect of different CO2partial pressures on the induction time, gas consumption, and growth pattern of the CO2hydrate was investigated. The effect of different R134a and CO2injection intervals (τ) on the triggering and synergizing of rapid CO2hydrate nucleation was also studied. The results indicated that the induction time of the CO2hydrate was reduced to approximately 97.4% of the original duration with the addition of the R134a gas promoter. At a CO2partial pressure of 2.8 MPa, the gas consumption of the CO2hydrate reached 0.34 mol, which increased by 47.8% compared to 2.4 MPa. Notably, the induction time of the CO2hydrate was reduced to 4.5 min when the injection interval (τ) was 30 min. Through an injection interval, R134a acts as a “kick-start” to trigger and synergize the rapid nucleation and formation of CO2hydrate. This study showed that the injection interval facilitated the first form of the R134a hydrate clusters, providing more nucleation sites and the CO2molecules’ enclathration into the R134a hydrate cluster to form R134a-CO2hydrate, which further triggers and synergizes the rapid nucleation and formation of CO2hydrate. Finally, the mechanism of triggering and synergizing rapid nucleation and formation of CO2by R134a was explained with visual observations and theoretical model diagrams.

Hydrate cold storage technology offers a promising solution for effectively storing high energy density. Therefore, the aim of this study is to explore the cycling and gas circulation-enhanced formation characteristics of TBAB hydrate at different concentrations. Notably, it was observed that when the concentration of TBAB hydrate surpassed 25 wt%, the hydrate exhibited a consistent high formation efficiency without displaying any discernible decay characteristics. Upon reaching a TBAB concentration of 35 wt%, a notable concentration stratification phenomenon became evident following the complete dissociation of hydrates. Remarkably, the introduction of gas circulation to enhance hydrate formation yielded a bulk phase uniform nucleation mode for TBAB hydrate formation. This led to a remarkable 72 % reduction in the induction time. Even under conditions of 45 wt% concentration, the subcooling was as low as 4.35 °C. These research findings hold significant implications for the advancement of efficient hydrate cycling formation technology and its potential industrial applications.

With its high latent heat of phase change and suitable phase change temperature, hydrates are emerging cooling medium cold storage. A 4000 L experimental system was firstly developed to investigate the mechanism of nucleation and growth, accumulation regularity, and time-varying heat transfer characteristics during the formation and decomposition processes of TBAB hydrates. A novel hydrate bulk phase uniform nucleation and growth characteristics has been discovered. Experiments demonstrated that TBAB hydrate undergoes immediate uniform nucleation, without induction time, once phase equilibrium conditions are reached. Stable formation of TBAB hydrate at approximately 9–10 °C is achievable with subcooling of only 2–3 °C. Moreover, it was clarified that the delamination caused by diffusive deposition of TBAB molecules disappears when the concentration of TBAB reaches 37 wt%. Simultaneously, even after 100 cycles, the stability of hydrate formation is preserved, displaying no signs of decay, while achieving a conversion rate surpassing 90 %. Otherwise, through the analysis of heat transfer characteristics, it was proved that during the hydrate growth process, the heat transfer coefficient decreases by 56 %, and the growth rate decreases by 73 % due to the attachment of hydrates to the heat exchange tubes. This first study provides crucial theoretical for the application of hydrate-based cold storage technology.

Spectrum auction is one of the most effective ways to achieve dynamic spectrum allocation in cognitive radio networks, and it provides one effective way to manage the spectrum demands of IoT devices with limited resources. Most spectrum auctions focus on protecting bidder privacy and achieving excellent social efficiency, but few tackles the verification of auction results that are controlled by the auctioneer. In this paper, we propose a cloud-based framework for verifiable privacy-preserving spectrum auctions. Our framework adopts a modified AFGH re-encryption algorithm that achieves both bid privacy protection and auction results verification at the same time. The cloud server helps to compute auction results based on homomorphic encryption, and an auctioneer decrypts the encrypted data from the server to obtain auction results. Meanwhile, the property of re-encryption makes it possible for any bidder to verify the auction results without compromising other bidders’ privacy.