Thermo-fluid characteristics of an IRS system with louvered cylindrical diathermic funnels considering surface radiation: A three-dimensional numerical exercise

Abstract

The thermo-fluid characteristics of an IRS (infrared suppression) system with louvered cylindrical diathermic funnels considering surface radiation are investigated in the present analysis. An IRS device's flow and heat transfer features are challenging as the cold atmospheric air is entrained into the system through the inter-funnel openings and mixed with hot exhaust gas from the turbine in cargo/naval ships. The numerical simulations of the full Navier–Stokes equation with the energy equation and radiative transfer equation (when required) are carried out for the three-dimensional IRS model with louvered cylindrical funnels. This study elucidated the influence of louver position, louver pattern, Reynolds number (6.1 × 105 to 3.18 × 106), funnel overlapping (zero, negative, and positive), nozzle overlapping, and nozzle shape (circular, square, triangular, and lobed) on mass intake and system exit temperature in detail. Zero overlapping cases or/and lobed shape of the nozzle are better than other considered cases. For the funnel walls, three different boundary conditions, namely adiabatic wall, diathermic wall, and diathermic wall with surface radiation, are also considered for the present analysis. The diathermic wall with surface radiation conditions was found to improve the performance appreciably.