Evaluation of the Efficiency and Strength Analysis of Profiled Heating Surfaces with Controlled Flow Separation in Marine Waste Heat Recovery Boilers

Abstract The utilisation of exhaust gas heat from diesel engines is one of the most effective ways to improve the performance of marine power plants. Achieving the same boiler performance, given the reduction in the exhaust gas temperature resulting from increased engine thermal efficiency, has led to an increase in boiler dimensions and has complicated their installation within the exhaust gas ducts of power plants. To reduce these parameters, the efficiency of using elliptical heating surfaces with a controlled flow separation mechanism in the form of a triangular notch has been considered for the intensification of heat transfer processes. It was found that for a main engine power of about 10,000 kW, the steam production rate of the waste heat recovery boiler can reach up to 3,000 kg/h, which is sufficient to fully meet the steam demand under cruising conditions or to significantly reduce the load on the auxiliary boiler. A strength analysis of the elliptical surfaces was carried out to determine the required wall thickness. The wall thickness must ensure that the surface retains its shape under an internal pressure of no less than 0.7 MPa. The analysis was performed using the finite element method. Verification was conducted by comparing the results with available experimental data. The results showed that, depending on the internal pressure, the pipe wall thickness should be within the range of 1 to 2 mm. According to the strength requirements, the pipe material must comply with AISI A 283-C, A516-55, or A182 Grade F12.