Natural Convection in Open Square Enclosure with Different Heat Source Sizes

In this study, a real-time experimental investigation is performed by a nonintrusive technique using a Mach-Zehnder interferometer. Experiments are performed in a partially open square enclosure with an internal heat source located at the center of bottom wall. The enclosure contains two openings at the bottom and top of the left and right vertical walls, respectively. The openings occupy 25% of the wall's height. The experimental interferograms give temperature distribution in the investigating domain. The effect of heat source size and Rayleigh number on natural convection is evaluated experimentally, and the results are compared with numerical results obtained using ANSYS Fluent 2020. A dense fringe pattern is observed at larger heat source size and Rayleigh number. An air velocity transducer is used to measure inlet velocity and observe that high velocity air enters the cavity from bottom region of opening. Heat transfer and volume flow rate in the enclosure increase with increase in heat source size and Rayleigh number. Within the range of Rayleigh number 107 to 108, an increase in the heat source size by four times leads to an average increment in Nusselt number by about 33%, whereas the increment in volume flow rate is about 1%.