Silicon carbide heat exchangers are susceptible to thermal stress under extreme conditions due to their material properties, necessitating multi-dimensional innovation in their structural design to enhance thermal shock resistance. The core approach involves mitigating differences in thermal expansion, optimizing heat transfer paths, and enhancing structural stability, while simultaneously combining material modification and intelligent monitoring technologies to achieve systemic optimization from local to overall performance.
The difference in thermal expansion coefficients between silicon carbide and metal is a key factor leading to thermal stress concentration. Traditional fixed connections are prone to cracking due to deformation mismatch during rapid temperature changes; therefore, a gradient transition structure is required. For example, a silicon carbide-metal composite layer can be formed at the tube-sheet connection using chemical vapor deposition (CVD), gradually transitioning the thermal expansion coefficient from the higher value of the metal to the lower value of silicon carbide, reducing interfacial stress. Simultaneously, flexible compensation elements such as expansion joints or bellows are introduced to absorb thermal stress through elastic deformation during temperature changes, avoiding the breakage risk associated with rigid connections.
The flow channel design directly affects heat transfer efficiency and temperature distribution uniformity. Three-dimensional spiral flow channels extend the fluid path and enhance turbulence, resulting in more uniform heat transfer and reducing localized overheating. For example, replacing traditional straight pipes with a spiral winding structure utilizes centrifugal force to create secondary circulation, reducing boundary layer thickness and significantly decreasing fouling deposition rates, while avoiding localized thermal shock caused by uneven flow velocity. Furthermore, biomimetic bifurcated flow channel design further optimizes fluid distribution, achieving uniform heat dissipation through a tree-like branching structure and reducing areas of concentrated thermal stress.
Modular design decomposes the overall structure into independent units, improving the equipment's adaptability to thermal stress. Each module can expand and contract independently, avoiding the impact of deformation of a single component on the whole. For example, a free-segment tube bundle design allows the tube bundle to expand and contract freely in the axial direction, absorbing thermal expansion stress and preventing tube sheet cracking. Flexible sealing connections between modules ensure fluid isolation while allowing for minor displacement to adapt to temperature cycling changes. This design has proven effective in multi-condition switching scenarios in chemical industrial parks, significantly reducing maintenance time.
Material modification is a fundamental means of improving thermal shock resistance. Silicon carbide heat exchanger nanocoating technology can form a self-healing layer on the silicon carbide surface. When microcracks appear, the coating generates dense oxides through oxidation to fill the cracks, preventing stress propagation. For example, graphene-modified coatings can significantly improve the surface contact angle, reduce scale adhesion, and enhance material toughness. Furthermore, the development of silicon carbide-graphene composite materials utilizes the high thermal conductivity of graphene and the high strength of silicon carbide to achieve a dual improvement in thermal conductivity and flexural strength, adapting to conditions with higher temperature gradients.
Intelligent monitoring technology provides real-time assurance for thermal shock resistance. Integrating IoT sensors and digital twin systems, key parameters such as pipe wall temperature gradients and fluid flow rates can be monitored in real time, constructing virtual models to predict thermal stress distribution. When abnormal thermal shock is detected, the system automatically adjusts fluid distribution or activates cooling devices to prevent stress accumulation. For example, in catalytic cracking units of oil refineries, this technology improves overall equipment efficiency, significantly reduces failure rates, and achieves a shift from passive maintenance to proactive prevention.
The precision of the manufacturing process directly affects structural reliability. Utilizing diamond wheel grinding and laser cutting technologies, micron-level machining of silicon carbide components can be achieved, reducing stress concentration caused by surface defects. For example, mirror finishing significantly reduces surface roughness and strictly controls flatness, improving structural stability. Simultaneously, 3D printing technology can manufacture complex flow channel structures, avoiding seams in traditional machining and reducing thermal stress origin points.
In the future, silicon carbide heat exchangers will evolve towards a material-structure-intelligence integrated approach. Research and development of silicon carbide-based composite materials resistant to higher temperatures, combined with topology optimization algorithms to generate optimal tube bundle arrangements, will further improve heat transfer efficiency and thermal shock resistance. An adaptive control system integrating AI algorithms can dynamically adjust fluid distribution according to operating conditions, achieving dual optimization of energy efficiency and reliability. With the growing demand from emerging fields such as hydrogen energy and supercritical CO₂ power generation, the structural design of silicon carbide heat exchangers will continue to break through, providing more efficient solutions for industrial heat exchange.
