PSI - Issue 42

Ricardo Pires et al. / Procedia Structural Integrity 42 (2022) 639–646 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

642

4

Additionally, the use of a 445M2 ferritic stainless steel was considered in the analyses. This new marine-grade stainless steel is a sensible alternative to the austenitic stainless steel AISI 316 (Austral Wright Metals). In fact, the ferritic steels possess higher conductivity and lower thermal expansion coefficient, which allows them to reach higher heat dissipation and thermal fatigue resistance. In a study developed by Soares et al. (2019), results supporting this conclusion are presented. The main physical and mechanical properties of the two steels considered in the analyses are presented in Table 1. Similarly, the use of a high-strength duplex stainless steel, Infante et al. (2003), has been considered; nevertheless, spinodal decomposition occurs in duplex stainless steels at temperatures of 250 – 500 °C, which causes embrittlement and has a significant effect on mechanical properties such as hardness, impact toughness and corrosion to a greater or lesser extent (Outokumpu Research & Development). This would limit the operating range of the final product. Table 1. Physical and mechanical properties of the two stainless steels considered for the manufacture of the EGR cooler.

3. Results and discussion Firstly, it is relevant to mention that, in addition to NO x emissions, other products like hydrocarbons and particles are formed during the combustion process. These products deposit on the internal fins throughout the EGR; this phenomenon is called fouling and creates an insulating layer that reduces the thermal efficiency by up to 30% and ultimately compromises the component's performance, Abd-Elhady et al. (2011). However, this phenomenon will not be considered in the analyses presented hereafter. Hence, in Fig. 4a, the temperature distribution obtained in the EGR made of AISI 304L, with a fin’s length of 120 mm, is shown. Moreover, the fins' length influence in the heat transfer process is shown in Fig. 4b. a b

Fig. 4 (a) Section view of the EGR with the temperature distribution obtained for a fin’s length of 120 mm. (b) Gas and coolant temperature variation as a function of the length of the inner fin.