Numerical Analyses of AdBlue® Thawing Performance According to EU Norms

Abstract

<div class="section abstract"><div class="htmlview paragraph">Controlling NOx emission demand is getting more severe with Euro 7 legislation. In turn, this brings more focus on SCR (Selective Catalytic Reduction) technology, which uses a eutectic mixture of Urea (32.5%)– Water (67.5%) solution, more popularly known as Diesel Exhaust Fluid (DEF/ AdBlue®). Under extreme winter conditions, AdBlue® freezes as the ambient reaches below the freezing point (-11°C). Due to Legislation requirements (EU), estimating the time required to thaw a desired volume of frozen AdBlue® using forced heating is a matter of interest, leading to the concept of overall Melting/Thawing performance. So far, testing has been the primary method for arriving at a suitable melting mechanism and for designing electrical coils or hot coolant lines, which is expensive. This paper proposes a novel digital method using the 3D CFD tool STAR CCM+ to study the melting behavior of AdBlue®. The method is characterized by capturing phase change using the popular multiphase (VOF) approach and different modes of heat transfer involved in the process. The numerical analyses aided in understanding the influence of ambient (external airflow) conditions around the tank. Estimated AdBlue® temperature distribution inside the tank at various locations was benchmarked with two different test scenarios, viz., Climatic chamber test with external airflow around the tank &amp; without any external airflow. The benchmarked simulation method showed good agreement with the test data. The effect of a completely insulated tank is also explored by modeling the AdBlue® tank under adiabatic condition. Additionally, one of the possible ways to reduce the computation time to estimate the melting performances is also explored. The computation domain was restricted to the region of interest around the sensors and benchmarked with test data. Using this digital method, clear design directions can be arrived at during the initial development stage, eliminating the need for multiple proto builds and validation.</div></div>