When pressure vessels operate in high-temperature environments, the non-uniformity of the internal temperature field easily leads to the generation of thermal stress. Thermal stress, as one of the important factors affecting the structural safety of pressure vessels, directly relates to the strength, stability, and service life of the vessel. In-depth analysis of the formation mechanism of thermal stress and identification of key factors affecting its distribution are of great significance for optimizing structural design and improving equipment safety. In relevant engineering practices, FRHE has accumulated rich experience in thermal stress analysis and structural optimization of pressure vessels, providing reliable technical references for the industry.

The generation of thermal stress mainly originates from temperature gradients. When the temperature of the medium inside the pressure vessel rises rapidly, the inner wall of the vessel expands faster than the outer wall due to heat. The greater the temperature difference between the inside and outside, the more significant the thermal stress. If the temperature change is concentrated in certain areas, such as nozzles, near welds, or geometric transitions, local stress peaks are more likely to occur. Furthermore, the periodic fluctuations of the high-temperature medium can also induce thermal fatigue, subjecting the material to repeated tension and compression, thus creating a potential risk of cracking.

The factors affecting the distribution of thermal stress mainly include material properties, structural design, medium temperature changes, and operating conditions. First, different materials exhibit significant differences in their coefficients of thermal expansion and thermal conductivity. For high-temperature pressure vessels, if the material has low thermal conductivity, the temperature transfer rate slows down, further amplifying the temperature difference between the inner and outer walls, thus increasing the level of thermal stress. Second, discontinuities in structural design (such as abrupt thickness changes, end cap transitions, and nozzle connections) can cause stress concentration, resulting in pronounced local peaks in thermal stress distribution. Furthermore, drastic fluctuations in medium temperature during operation, such as rapid heating or sudden cooling, also increase the amplitude of thermal stress changes, exposing the vessel to a higher risk of thermal fatigue.

To effectively reduce the impact of thermal stress, engineering designs typically employ methods such as gradually varying thickness structures, optimized transition curves, and improved material heat resistance. Simultaneously, by rationally setting the heating rate and operating temperature fluctuation range, transient thermal stress can be significantly reduced. In addition, finite element analysis can be used to simulate the temperature and stress fields, allowing for the early identification of hazardous areas and providing a reliable basis for structural optimization and operational strategy development.

The thermal stress distribution of pressure vessels is influenced by multiple factors, and its analysis and control are crucial for ensuring equipment safety. Through scientific design and reasonable operating condition control, the thermal stability and service life of pressure vessels can be effectively improved.