Numerical investigation of buoyancy-induced thermo-fluid characteristics of different types of infrared suppression (IRS) devices

The present work reports numerical investigation of natural convection heat transfer characteristics for three different types of infrared suppression (IRS) devices (i.e., conical, cylindrical, and hybrid) by varying Rayleigh number and diameter ratio in the range of 1010-1012, and 1.025-1.5, respectively. The effect of relevant parameters on average Nusselt number and induced air-flow rate through the IRS device has been elucidated graphically. Numerically computed results indicate that the average Nusselt number from IRS device is higher for cylindrical IRS devices for all Rayleigh number when DR>1.05. The average Nu initially increases with diameter ratio, attains the maximum (1.1 <= DR <= 1.15), and decreases with a further increase in diameter ratio. The Nu is significantly influenced by the diameter ratio of cylindrical and hybrid IRS devices than the conical IRS devices. It has been found that the dimensionless induced mass-flow rate at a particular diameter ratio decrease with the Rayleigh number and is found to be more for conical IRS device. In addition, correlation for the average Nusselt number as function of relevant input parameters has been proposed. The cooling time estimation based on lumped parameter analysis shows a faster cooling rate for cylindrical IRS devices followed by hybrid and conical IRS devices.