A complete heatline analysis on mixed convection within a square cavity: Effects of thermal boundary conditions via thermal aspect ratio

► Analysis on heatlines is carried out for various thermal aspect ratios. ► Mixed convection for fuids within square cavities are considered. ► Detailed analysis on flow, temperature and heatline characteristics has been done. ► Natural and forced convection dominant transport have been discussed for various dimensionless numbers. ► Heat transfer rates are found to exhibit non-monotonic variation with thermal aspect ratios for specific cases.