Numerical analysis of the optimum heating pipe to melt frozen urea-water-solution of a diesel urea-SCR system

摘要

A numerical analysis was conducted in order to find the best shape for a heating pipe to prepare a sufficient amount of urea-water solution, in order to ensure normal de-NOx operation of a diesel vehicle with a urea-SCR system within the shortest amount of time from a cold start. The accuracy of the numerical analysis was verified by comparing its results with those of an experiment melting a tank of frozen urea. The STAR-CCM commercial software package was used for the numerical analysis. In addition, the effect that the insulation material of the outer urea tank had on the freezing time was also calculated. The selected melting system circulated the engine coolant into a pipe, and the comparison of the numerical analysis with the experimental measurements indicated a 6% error with respect to the melting with standard conditions. The insulation material blocked 25% of the heat transfer from outside of the tank, when compared to a tank without insulation. The melting rate was calculated based on the circulation of the engine coolant in the pipes for up to 1000 s after melting, and the heating pipe was configured to have a lower part of the tank containing 1410 mL which is the highest level possible. As the circulation flow rate increased, the melting rate increased, and more than 1400 mL of urea-water solution was obtained after 1000 s when the heating water flow rate was of 200 L/h. (C) 2015 Elsevier Ltd. All rights reserved.