Analysis of Platen Superheater Tube Degradation in Thermal Power Plants via Destructive/Non-Destructive Characteristic Evaluation

Coal-fired power plants operating under Korea’s standard supercritical pressure operate in a high-temperature environment, with steam temperatures reaching 540 °C. A standard coal-fired power plant has a 30-year design life, and lifespan diagnosis is performed on facilities that have operated for more than 100,000 h or 20 years. Visual inspection, thickness measurements, and hardness measurements in the field are used to assess the degree of material degradation at the time of diagnosis. In this study, aging degradation was assessed using an electromagnetic acoustic transducer to measure the change in transverse ultrasonic propagation speed, and the results were compared to microstructural analysis and tensile test results. Based on the experimental results, it was found that the boiler tube exposed to a high-temperature environment during long-term boiler operation was degraded and damaged, the ultrasonic wave velocity was reduced, and the microstructural grains were coarsened. It was also confirmed through tensile testing that the tensile and yield strengths increased with degradation. Our findings prove that the degree of change in mechanical properties as a function of the material’s degradation state is proportional to the change in ultrasonic wave velocity.

Active cooling system for downhole electronics in high temperature environments

Downhole high temperature environment is an important factor affecting the performance of downhole instrument electronic system.At present, various active cooling technologies and passive cooling technologies have been proposed to reduce the temperature of downhole electric circuit system.However, passive cooling technologies can only provide limited cooling capacity for drilling tools under high temperature environment, and the duration of cooling is short, which can not meet the long-time drilling task.This paper presents an Active cooling system(ACS)for downhole electronics and the effects of different temperatures on the performance of electronic components are analyzed.The ACS mainly includes a micro supercharger, condenser tube, evaporation pipe, capillary tube and refrigerant.The theoretical analysis of heat transfer and refrigerant capacity in high temperature environment is carried out.The thermal characteristics of the ACS is evaluated experimentally.The results show that the temperature of electronic components can be reduced to below 163°C in the 200°C downhole environment and components.The geomagnetic field data measured by electronic components at room temperature, 200 °C and with ACS are compared.The results show that ACS can keep electronic components working normally.

Heat Stress Affects Seed Set and Grain Quality of Vietnamese Rice Cultivars during Heading and Grain Filling Period

Environmental stress trigger a variety of rice plant response, ranging from alters seed set, grain yield and grain quality during flowering and grain filling stage. Efforts are required to improve our understanding of the impact of heat stress on rice production, which are essential strategies in rice cultivation. This article investigated the seed set, yield components and grain yield of Vietnamese rice cultivars (Indica germplasm) under high temperature environment during the flowering and grain filling stage. Six rice cultivars, including popular cultivars and new cultivars of Cuu Long Delta Rice Research Institute, and one popular extraneous cultivar with differences in maturing time, were grown in pots at high temperature (HT) and natural temperature condition as control (CT). All rice cultivars were subjected to the high temperature starting from the heading stage to the harvest maturity, applied by greenhouse effect. The greenhouse has about 25 cm window opening on 3 sides for air ventilation. The seed set rate of the heat-sensitive rice genotypes decreased significantly under HT, leading to a significant reduction in grain yield. The lowest seed set was recorded in “OM4900” (44.3%) and “OM18” (39.9%) under high temperature environment. The lower yield in all rice cultivars at an elevated temperature resulted in a dramatic decrease of filled grains and contributed to a loss of 1000-grain weight. ‘“OM892” is a potential rice cultivar for heat tolerant breeding program due to the seed set percentage was above 80% in both HT and CT conditions. High temperature during the grain filling stage resulted in a decreased amylose and increased chalkiness for all OM cultivars.

Effect of Temperature on the Microwave-Absorbing Properties of an Al2O3–MoSi2 Coating Mixed with Copper

To obtain a high temperature-resistant microwave absorbing coating, an Al2O3–MoSi2/Cu composite coating was prepared by atmospheric plasma spraying. Compared with a normal temperature environment, there are a few reports on Cu as an absorbent for high temperature microwave absorbing coatings. Therefore, in this regard, wave absorbing property can be improved by using a Cu absorbent. The microstructure of a Al2O3–MoSi2/Cu coating was observed, and the dielectric properties of the composite coating in the high-temperature environment of the X-band were tested. The experimental results show that with the increase in temperature, Cu transforms Cu2O in the high-temperature environment and improves the coating’s wave absorption performance with MoSi2. In addition, a 1.4 mm-thick coating showed best microwave absorbing performance at 700 °C. The reflection loss was −19.09 dB, and the effective microwave absorbing bandwidth was 2.83 GHz (Reflection Loss < −10 dB). It was found that the Al2O3–MoSi2/Cu composite coating has good wave-absorbing performance in a 700 °C high-temperature environment.