Frosting usually has a negative impact on device, when ultrasound is used for frost retardation/defrosting, can realize no downtime defrosting, cooling and heating without interruption during defrosting time. But due to its mechanism is not clear, technical difficulties to pragmatize, failed to get popularization and application. This paper reviews the research progress of ultrasound in the field of frost retardation and defrosting from two aspects of its mechanism and pragmatization. Firstly, the ultrasound characteristics is introduced, including commonly used ultrasound wave types and their propagation, ultrasound effects on frost retardation and defrosting, distribution of equivalent force on the cold surface; then, the growth of frost is inhibited by delaying the generation of liquid droplets, delaying the freezing of droplets, crushing the frozen droplets and suppressing the frost branch growing; based on the frost crystal fracture breaking, defrosting effecting factors and defrosting enhancement methods, ultrasonic defrosting mechanism is summarized; and, from the equipment frost retardation/defrosting effects and its energy consumption comparison, practical difficulties and problems, the ultrasound frost retardation/defrosting practical applications is sorted; Finally, a outlook of the ultrasound used for frost retardation/defrosting in the future is given to provide reference.

Lithium silicate serves as a novel CO₂ absorbent with moderate absorptionregeneration temperature range (500∼700°C) and excellent cycling stability. In this study, Li₂CO₃ was selected as the precursor for the preparation of lithium silicate. Additionally, a eutectic co-doping method with potassium elements was employed to enhance its reactivity. Using extrusion-spheronization, we successfully produced absorbent particles with high mechanical strength and cycling stability. The effects of absorption-regeneration temperature, CO₂ concentration and particle diameter on the performance of absorbent particles have been studied in detail. Furthermore, mixed with NiO oxygen carriers, sorption-enhanced chemical looping reforming (SE-CLR) experiments were conducted at the range of 500∼650°C for hydrogen production and in situ CO₂ capture factors such as reaction temperatures and oxygen carrier to absorbent mass ratios were then investigated The results showcase that at the optimal reaction temperature of 600◦C, the SE-CLR process effectively lowered the reaction temperature by 25°C, achieving a 13% increase in methane conversion rate and hydrogen purity and CO₂ capture rate above 90% were attained 

This paper proposed a solar-assisted ammonia-water absorption refrigeration system using ocean thermal energy. This paper first introduced the module and working principle of this refrigeration system, and subsequently established and verified its numerical model. Based on this model, the thermo-economic performance of solar-assisted ammonia-water absorption refrigeration system using ocean thermal energy is analyzed and compared with that without solar assistance. The effects of generation temperature and primary rectified temperature on the coefficient of performance (COP) and the exergy efficiency of this refrigeration system are examined and analyzed. The results indicate that the utilization of solar-assisted ocean thermal energy to drive the ammoniawater absorption refrigeration system can obtain 11.6 times more refrigeration capability than that without solar assistance. In addition, the solar assistance can also improve the thermal perfection of refrigeration cycle with 43.3%. The optimal thermal performance of this refrigeration system can be achieved by selecting a combination of generation temperature and primary rectified temperature.

Developing natural gas hydrates is essential for the development of oceanic energy resources. However, the current research on hydrate pressure reduction exploitation has not yet established a systematic and comprehensive theoretical framework. Consequently, there is a lack of key theoretical models to validate large-scale commercial exploitation. This study clarifies the pressure reduction exploitation characteristics of natural gas hydrates through experimental research. By combining the actual distribution of hydrate occurrence in porous media, a hypothesis is proposed that the number of hydrate decomposition particles determines the decomposition rate. Based on this, a model for the skewed normal decomposition gas volume of hydrates is established. Subsequently, a complete non-equilibrium thermodynamic calculation method for hydrate pressure reduction exploitation is proposed, achieving high-precision predictions of dynamic responses including temperature, pressure, and reaction parameters throughout the entire process of hydrate pressure reduction decomposition. The research results effectively address the current shortcomings in hydrate theory and have significant guiding implications for optimizing natural gas hydrate exploitation strategies.

In the field of solar thermal power generation, the control model of the traditional linear Fresnel collector subsystem does not take into account the complexity of the working environment, which leads to poor adaptability and low control accuracy of the collector control subsystem. In order to improve the power generation efficiency of a linear Fresnel thermal power system, a multi-model of the collector system is established based on the complexity of the environment in the western part of China by considering multiple factors and according to the time-varying characteristics of its parameters. Taking the vacuum collector tube, which is commonly used in the current linear Fresnel collector subsystem, as the research object, using COMSOL Multiphysics software, the threedimensional steady state model is established and the multi-physics field is constructed by considering the inlet temperature, the normal direct irradiance, the molten salt flow rate and the wind speed, etc.; the performance of which is analyzed and the data are extracted to carry out the FCM clustering, and the parameter identification by using the forgetting-factor recursive least-squares method is carried out, so as to get the multivariate prediction model for the heat-collector subsystem. The model has been validated and analyzed by the data of the collector field which has been put into use, and the reliability of the model has been confirmed. Certain ideas are provided to improve the performance of the collector subsystem.