No abstract

The present study analyzes conjugate heat transfer in a differentially heated square cavity. The left wall of the cavity is cooled, and the right wall is heated while the horizontal walls are adiabatic. Normalized continuity, momentum and energy transport equations were solved with the aid of COMSOL Multiphysics 5.4 software. The effects of Rayleigh number in the range of 102 ⩽ RA ⩽ 106 and Prandtl number in the range of 0.71 ⩽ PR ⩽ 100 on streamlines, isotherms, and the overall heat transfer in the cavity are reported. The results show that for all the Rayleigh numbers considered, the local Nusselt number and the average Nusselt number increase with increasing value of Rayleigh number. Furthermore, for 0.71 ⩽ PR ⩽ 100, the study reveals that Prandtl number has a minimal effect on the overall rate of heat transfer.

Cellar workplaces are considered as confined environment with challenging indoor air quality having higher than normal pollutants particularly that of soil gas origin. Radon, a major soil gas, infiltrates and accumulates within indoor spaces and becomes harmful in the absence of ventilation. Radon level in bank basements (cellars) in Ilorin, Lagos and Akure have been sampled and analysed in this study. In Nigeria, most workers in basements are unaware of radon, and there is limited documented research on its health hazards. The survey parameters of radon concentrations were floor types, geographical locations and the influence of atmospheric conditions. Corentium monitor, a continuous, digital radon monitor, temperature meters and Prologue wireless weather station were used for the experiments. Annual average indoor radon concentration for the survey period was 23 Bq/m 3 . The calculated mean annual effective doses in basements and different floors were below the recommended ICTR level of 3 mSv/y.

A numerical study of mixed convective heat transfer in a lid‐driven square enclosure containing a hot elliptic cylinder is conducted. The impacts of the Grashof number , Reynolds number , cylinder tilt angle , and aspect ratio have been examined for a fluid of of 0.71. The horizontal enclosure walls are insulated, while its vertical walls are restricted to a nonvarying temperature Tc, whereas a sinusoidal temperature of is imposed on the wall of the elliptical cylinder. The governing equations are solved using COMSOL Multiphysics 5.6 software. The fluid dynamic and the heat transport profiles between the enclosure and the elliptical cylinder walls are represented by the stream function, isothermal contours, and average Nusselt number. Results established that for all the considered aspect ratios, the thermal heating range of is predominantly a conduction mechanism. The critical position of the ellipse where the inclination effect becomes insignificant is determined by the Grashof number and aspect ratio when the Re = 100. The strength of vortices and cell numbers are significantly influenced by the aspect ratio, particularly when the . When , the average heat transfer from the cylinder remains the same regardless of the cylinder's orientation. The impact of cylinder orientation on heat transfer from the cylinder wall is minimal for . For AR values of , increasing the inclination angle does not result in improved heat transfer. The influence of the increasing inclination angle on the right wall diminishes as the angle increases, except when the Grashof number is greater than 105, where the rate of heat transfer is enhanced for inclination angles beyond 45°.