Porous Media-Based Full-Scale Modeling of Thermal Behavior in Rotary Gas-Gas Heat Exchangers

The rotary gas-gas heat exchanger (GGH) is a vital component in waste heat recovery systems, particularly for Selective Catalytic Reduction (SCR) processes employed in cement kiln operations. This study investigates the thermal performance of a rotary GGH in medium- and low-temperature denitrification systems, using a simplified porous medium model based on its actual internal structure. A porous medium representation is developed from the structural characteristics of the most efficient heat transfer element, and a local thermal non-equilibrium (LTNE) model is employed to capture the distinct thermal behaviors of the solid matrix and gas phase. To account for the rotational dynamics of the system, the multiple reference frame (MRF) approach is adopted. Numerical simulation results exhibit an average error of less than 5%, demonstrating the model’s reliability and predictive accuracy. The temperature distributions of both the metallic heat exchange surfaces and the flue gas are systematically analyzed. Results indicate that the solid and gas phases exhibit significant non-equilibrium thermal behavior. Notably, the circumferential temperature fluctuations of both the heat exchange surfaces and flue gas vary markedly with changes in rotational speed. At low rotational speeds, the temperature non-uniformity coefficient reaches 4.296, while at high speeds it decreases to 0.4813—indicating that lower speeds lead to more pronounced temperature fluctuations. The simulated temperature field patterns are consistent with experimental observations, validating the effectiveness of the modeling approach.