Chemical looping can achieve high product selectivity using lattice oxygen in oxygen carriers for partial oxidation of methane. Oxygen carrier La_1−xSr_xFe_0.8Al_0.2O₃ was prepared by sol-gel method for chemical looping dry reforming of methane. The reaction performance of the oxygen carrier doped with different proportions of Sr was tested by thermogravimetric and fixed bed reactor. The experimental results showed that the oxygen capacity of x=0.4 oxygen carrier in La_1−xSr_xFe_0.8Al_0.2O₃ is as high as 1.88 mmol·g⁻¹, with excellent reaction performance and less carbon deposition. The stability of the oxygen carrier La_0.6Sr_0.4Fe_0.8Al_0.2O₃ was further tested for 20 redox cycles. The oxygen carrier maintained excellent redox performance, achieving 61.2% methane conversion, 97.1% CO selectivity, and 1.81 H₂/CO. The material characterization results displayed that the morphology and crystal structure of the oxygen carrier were stable. The results show that La_0.6Sr_0.4Fe_0.8Al_0.2O₃ is an excellent oxygen carrier suitable for chemical looping dry reforming of methane.

Heat pump heating technology can effectively reduce the energy consumption and environmental pollution caused by coal-fired heating. However, the low-temperature adaptability of commonly used heat pump heating systems is poor, making it difficult to meet the heating demand in cold regions. Considering that Stirling heat pump technology has a wide range of available temperature zones, an electrically-driven free-piston Stirling air source heat pump is developed in this paper to investigate its heating performance under different climatic conditions. The experimental results show that the overall coefficient of performance of the Stirling heat pump reaches 2.31, 1.97 and 1.78 for normal, cold and very cold regions, respectively. In addition, the relative Carnot efficiency of the Stirling heat pump gradually increases with rising heat-pumping temperature difference. Its advantage is more obvious at large heat-pumping temperature difference.

A thermo-economic model was used to analyze the thermodynamic and economic characteristics of a geothermal ORC system. The evaporation and condensation temperatures of typical hydrofluoroolefins (HFOs) working fluids including R1224yd(Z), R1233zd(E) and R1336mzz(Z) were optimized to obtain the maximum net power. The thermo-economic characteristics were analyzed and compared with the traditional working fluids R601, R601a and R245fa. The results show that the evaporation and condensation parameters of R1224yd(Z) and R245fa are close under the optimal conditions. When the geothermal water inlet temperature is lower than 130°C, the net output power of R1336mzz(Z) is the maximum among the selected fluids, which is 1.47%∼1.89% more than that of R1233zd(E); but the heat exchanger area increases by more than 17%. When the geothermal water inlet temperature is higher than 130°C, the net output power of R245fa is the maximum, and the power generation cost is reduced by 15.5%∼16.8% compared with R1336mzz(Z).

In this paper, a flow calorimeter was developed for the measurement of isobaric specific heat capacity (c_p) at low temperature. The calorimeter was composed of four parts: thermostatic bath, flow system, calorimeter and data acquisition system. The calorimeter can measure the c_p in the temperature range of 115 ∼ 340 K, and the pressure can reach 8 MPa. The uncertainty of temperature, pressure and heat capacity were 11 mK, 0.02 MPa and 0.9%, respectively. The c_p data of propane, isobutane, ethane and ethane + propane binary mixtures at low temperature were measured. The measured data showed a good agreement with the calculated values of high-precision Helmholtz equation of state. The average absolute relative deviations of propane, isobutane, ethane and ethane + propane was 0.26%, 0.32%, 0.31% and 0.38%, respectively, which verified the reliability of the device.

The exploitation of natural gas hydrate is a major strategic demand of the country, and further improvements in 
production and efficiency are needed before its commercial development. How to realize its efficient exploitation depends on the thermodynamic mechanism of the hydrates. Traditional hydrate thermodynamics studies are limited to phase equilibrium characteristics and lack the consideration of non-equilibrium thermodynamics in the hydrate decomposition process. At the same time, the hydrate decomposition process may be accompanied by icing and melting. The thermodynamic characteristics of hydrate exploitation under complex heat and mass transfer conditions need to be clarified. In this study, a 2 L natural gas hydrate depressurization decomposition experimental system was used to simulate the hydrate reservoirs with different distributions and perform long depressurization (to 1.0 MPa) at a constant exhaust rate of 0.55 L·min−1(normal conditions). The results show that there is a non-equilibrium thermodynamic relationship (T[°]=8533.8/{38.98−ln(1000p[MPa])}−275.25) between the temperature and pressure in the hydrate-bearing area during the depressurization process, which is only controlled by the hydrate decomposition and is not affected by the reservoir temperature gradient. According to the Gibbs phase law, the thermodynamic freedom of phase transition process is 1. As a result, the natural gas hydrate decomposition belongs to the phase transition process, and the quantitative relationship between temperature and pressure is consistent with the thermodynamic theory. When the hydrates depressurize to about 2.1∼2.3 MPa, instantaneous icing occurs in the reservoir, leading to a sudden increase in temperature and accelerating the hydrate decomposition. Due to the constant exhaust rate, the accumulated gas increases the pressure up to 2.36 MPa. It is found that the temperature and pressure of hydrate-bearing reservoir still satisfy the non-equilibrium thermodynamic phase diagram of hydrates before and after icing. This study illustrates the thermodynamic mechanism of phase transition in the presence of heat and mass transfer in the natural gas hydrate decomposition process, which can provide a more practical theoretical basis for the process of exploitation site monitoring.