Numerical analyses of Ad-Blue thawing performance according to EU Norms

Controlling NOx emission demands is getting more serious with Euro 7 legislation. This in turn brings more focus on SCR (Selective Catalytic Reduction) technologies which uses a eutectic mixture of Urea (67.5%) - Water (32.5%) solution more popularly known as Diesel Exhaust Fluid (DEF/Ad-Blue). Under extreme winter conditions, Ad-Blue freezes as ambient reaches well below the freezing point (-11 deg.C). Due to Legislation requirement (EU), it is a matter of interest to estimate the time required by Ad-Blue to melt the desired volume inside the tank thereby defining overall Melting/Thawing performance. So far, testing has been the primary method for arriving at right melting mechanism and for designing electrical coils or hot coolant lines which is expensive. This paper proposes a novel digital method using 3D CFD tool STAR CCM+ to study the melting behavior of Ad-Blue. 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 Ad-Blue temperature distribution inside the tank at various locations was benchmarked with two different test scenarios viz., vehicle moving with airflow around the tank & climatic chamber test without any external airflow. Benchmarked simulation method showed good agreement with test data. Followed by the effect of completely insulated tank explored by modeling 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 during initial development stage can be arrived which eliminates the need for multiple proto build and validation.