In the design process of pressure vessels, thermal stress analysis is a crucial step in ensuring the safe and reliable operation of the equipment. Because pressure vessels are often used in high-temperature or large-temperature-difference environments, materials expand or contract upon heating. If the temperature distribution is uneven, thermal stress will be generated within the structure, affecting the vessel's strength, sealing performance, and service life. Therefore, scientific thermal stress analysis is of great significance for optimizing structural design and preventing failures.

The first step in thermal stress analysis is to determine the temperature field distribution of the vessel. This is typically achieved through the finite element method (FEM) or analytical methods to simulate temperature changes under different operating conditions. The analysis must consider various heat transfer mechanisms, including conduction, convection, and radiation, as well as the material's thermal conductivity and boundary conditions. An accurate temperature field distribution is fundamental for calculating thermal stress.

After obtaining the temperature field, the stress distribution caused by temperature can be calculated using a structural mechanics model. Common thermal stress analyses include steady-state analysis and transient analysis. Steady-state analysis studies the stress distribution of a vessel at a constant temperature; while transient analysis focuses on stress changes during dynamic processes such as start-up, shutdown, or rapid heating. This type of analysis is particularly crucial for assessing the thermal fatigue of the vessel.

Furthermore, the structural characteristics of different parts significantly affect thermal stress. For example, the connection area between the shell and the head, flange interfaces, and weld seams are often stress concentration points. In the design, increasing transition fillets, selecting materials with low coefficients of thermal expansion, or optimizing wall thickness distribution can effectively reduce peak thermal stress.

In modern pressure vessel design, 3D modeling and simulation using computer-aided engineering (CAE) software has become the mainstream method for thermal stress analysis. This method not only improves calculation accuracy but also identifies potential risks in the early stages of design, thus providing data support for structural optimization.

Thermal stress analysis is an indispensable technical step in pressure vessel design. FRHE, through scientific temperature field simulation, rational structural design, and advanced simulation methods, can effectively improve the safety and reliability of pressure vessels under high-temperature conditions.