A Quasi-Dimensional Model of Heat Transfer between Multi-Concentric Monolith Structures

Metallic monolith structures are often used in compact reactor applications due to their superior heat transfer properties and lower pressure drop when compared to ceramic monoliths. Endothermic reactions like steam reforming depend heavily on externally supplied heat, making highly conductive supports especially useful. Simulations are invaluable for designing effective reactors with complex catalyst support structures but are conventionally resource-intensive. Additionally, few dedicated heat transfer experiments between monoliths exist in prior literature. To expand general knowledge of heat transfer between metal monolith structures, this work investigated heat exchange in concentric monoliths brazed to a common mantle. A computationally inexpensive quasi-dimensional model was developed and used to predict the heat exchange effectiveness and intrinsic heat transfer rate. The model used a discretized control volume approach and simplified geometries to reduce computational intensity. The model was calibrated against experimental data collected using a steady-state flow bench. After calibration, a parametric study was performed where monolith construction and flow conditions were varied. A parametric analysis showed that for identical catalyst space velocities and volumes, heat exchange effectiveness can be increased by 43.2% and heat transfer rates by 44.8% simply through increasing the surface area to volume ratio of the monolith. The described approach serves as an alternative framework for modeling catalytic heat exchangers without heavy computation and for quickly matching monolith geometries to their intended use and operating range.