The effect of wetting characteristics, thermophysical properties, and roughness on spray-wall heat transfer in selective catalytic reduction systems

Abstract

The effects of wettability, thermophysical properties, and roughness on spray-wall heat transfer in automotive selective catalytic reduction (SCR) systems are investigated experimentally. Using static contact angle measurements the wetting characteristics of ferritic and austenitic steel, iron, tungsten, silver, nickel, aluminum oxide, and technical ceramics (Shapal-M, Sialon) are analyzed. Details of the transient spray-wall interaction on the heated material samples (initial wall temperatures 120 ∘C–400 ∘C) are captured with a high-speed camera. The heat transfer from the wall to the impinging spray is calculated from transient temperature fields by using infrared thermography measurements of the plate’s rear side. Our results reveal that the thermal preconditioning of the plate has a significant influence on its wettability, which induces a hysteresis in the spray-wall heat transfer boiling curve. Higher contact angles and higher thermal effusivity have considerable influence on the Leidenfrost temperature. On the contrary, changes in roughness Rz show only a minor effect.