Numerical thermal modelling of rotary airlock valves for industrial powder-handling applications

Rotary airlocks are essential components in various industrial systems, enabling controlled material transfer while maintaining pressure differentials between connected environments. Their ability to prevent air leakage during consistent material flow is vital in pneumatic conveying systems used across industries such as food processing, chemical manufacturing, cement production, and pharmaceuticals. In applications involving fine powders, abrasive materials, or high temperatures, rotary airlocks encounter several challenges, including air leakage, thermal expansion, jamming, and accelerated wear. These issues can compromise operational efficiency, reliability, and equipment longevity. In high-temperature settings—such as cement kilns and chemical reactors—thermal effects become particularly significant, affecting clearances between the rotor and casing, weakening seals, and increasing the risk of failure. Recent research emphasizes the importance of understanding thermal behavior and heat transfer in rotary systems to mitigate efficiency losses and operational disruptions. Against this backdrop, the present study addresses two key questions: (i) how rotor-to-housing clearance evolves with time under high-temperature (300 °C) powder handling conditions, and (ii) how mild steel and SS316 rotors differ in their transient thermal response and expansion behaviour. An analytical heat-transfer model coupled with transient numerical simulations is developed to quantify temperature evolution and thermal expansion in rotary airlocks. The simulations predict peak blade temperatures of approximately 170–175 °C for mild steel and 210–216 °C for SS316 under hot sand operation. Results indicate that mild steel exhibits faster thermal response but lower maximum radial expansion (≈ 0.553 mm), whereas SS316 shows slower heating but higher thermal growth (≈ 0.705 mm), leading to distinct clearance-reduction and sealing-risk characteristics. These quantitative insights aim to provide a basis for material selection and clearance design in high-temperature rotary airlock applications, thereby improving the performance and reliability of rotary airlocks in demanding industrial environments.