[en] In this paper we reveal a systematic study of a series of samples with various Sm₂BaO₄ additions to compare the effect of the initial composition on the superconductivity. It is found that with the addition of 40 mol% Sm₂BaO₄ (Sm210) a significant improvement of superconductivity (T_c∼89 K, J_c(77 K, 1 T)∼10⁴ A cm^-2) can be achieved with melted-textured growth under ambient conditions. Both the Sm₂BaCuO₅ (Sm211) particle size and the Sm/Ba ratio in the SmBa₂Cu₃O₇ (Sm123) matrix are reduced. We discuss in detail the microstructural evolution, the Sm/Ba substitution ratio and the superconducting properties. (author)

[en] Highlights: • A look-up table was built for wall temperatures of supercritical pressure water. • The best heat transfer correlation was selected to supplement wall temperatures. • Four-dimensional linear interpolation was adopted to calculate wall temperatures. • 81.33% of the predicted wall temperatures fall into the ±1% error band. Wall temperature of heat transfer tubes is one of the most important parameters indicating the operation safety of various heat transfer facilities, and as a result, estimation of the wall temperature becomes one of the main tasks in the design of heat transfer facilities. The wall temperature look-up table (Tw-LUT) can be established directly from experimental data and can be then used to estimate the wall temperature of the heat transfer tubes, avoiding the approximation or extrapolation of fluid properties that inevitably exists in the heat transfer correlations. In view of the problems existing in applications with wall temperature estimations of the heat transfer tube, such as limited data points and the limited application scopes of parameters, a look-up table is built in this paper for wall temperatures of vertically-upward round tubes of 10 mm tube diameter with heat transfer to supercritical water (SCW), under conditions with pressure in the range from 22.5 to 31 MPa, the mass velocity in the range from 200 to 3000 kg·m⁻²·s⁻¹, the heat flux in the range from 200 to 1800 kW·m⁻², and the bulk fluid enthalpy in the range from 1000 to 3000 kJ·kg⁻¹. In order to cover the gaps between the experimental data points, and to improve the prediction accuracy of the Tw-LUT, the best heat transfer correlation is selected for each local area of interest in the LUT based on its prediction accuracy in the corresponding local area, and then the best heat transfer correlation is adopted to supplement wall temperature results to fill up the Tw-LUT. The comparison between the wall temperatures by the Tw-LUT and the experimental wall temperatures is carried out to verify the accuracy of the Tw-LUT, and it is shown that the mean absolute deviation of the results is 0.87%, and 87.81% of the results fall into the $\pm$3% error band, indicating that the Tw-LUT has a good accuracy for wall temperature prediction and the establishment method is reliable and can be used to build other look-up tables. The Tw-LUT can be applied not only to normal heat transfer conditions but also to deteriorated heat transfer conditions and enhanced heat transfer conditions with a satisfactory accuracy.

[en] Highlights: • The Allam cycle with liquefied natural gas cold energy utilization is analyzed. • Exergoeconomic analysis and multi-objective optimization are conducted. • The electrical efficiency of the optimized system is up to 65.7%. • The optimal total product unit cost of 16.654 $/GJ is obtained. • The introduction of bypass stream compression heat improves the system performance. The Allam cycle is a promising oxy-fuel combustion power cycle with high electrical efficiency and near-zero carbon dioxide emissions. In this paper, the thermodynamic and exergoeconomic analyses are performed for a novel combined power and cooling oxy-fuel power cycle, which combines the Allam cycle with liquefied natural gas regasification process. Parametric study is conducted to investigate the effects of key cycle variables on the electrical and exergy efficiencies and total product unit cost of the proposed cycle. Multi-objective optimization is carried out to maximize the exergy efficiency and minimize the total product unit cost. The results show that Condenser 2 has the highest exergy destruction of 22.81 MW, followed by the combustor (22.72 MW). The combustor, Condenser 2 and gas turbine are the three most important components from exergoeconomic aspects. The introduction of adiabatic compression heat of the bypass stream has a positive impact on the system performance, especially when the outlet temperature of the combustor is low. The optimization results indicate that the exergy efficiency and the total product unit cost cannot reach the optimal values at the same time. The highest exergy efficiency of 50.31% and the lowest total product unit cost of 16.654 $/GJ are obtained respectively with different sets of cycle variables. In addition, the electrical efficiency of the optimized proposed cycle is up to around 65.7%, about 11 percentage points higher than that of the Allam cycle.