Free convection cooling of a real-scale IRS device with a louvered cylindrical funnel: A three dimensional numerical study

Abstract

The present investigation is carried out on the free convection cooling of an IRS device with a louvered cylindrical funnel used in naval and marine ships for infrared suppression. The conjugate heat transfer with surface radiation is considered in this study. The fluid flow and heat transfer characteristics are obtained, and results are compared with a funnel without louvers. The lumped system analysis is used for calculation of cooling time. The governing equations (three-dimensional Navier-Stokes equation, energy equation, radiative transfer equation, and turbulence equation (k − ϵ equation)) are solved to obtain the buoyancy-induced flow and temperature distribution. The input parameters like Rayleigh number (1.2 × 1010 ≤ Ra ≤ 2.4 × 1012), surface temperature (400 K - 700 K), surface emissivity (0 to 1), and geometrical parameters like number of holes in each row (6 to 14), number of rows of louvers (2 to 8), and shapes of holes are also varied. The Nusselt number and mass suction ratio increase with the number of rows of holes and the number of holes in each row. The Nusselt number is highest for the funnel with circular holes, whereas the lowest is for triangular holes. Moreover, results show that the surface radiation contribution is significant even at low emissivity.