The present investigation was carried out to understand the sub-cooled nucleate boiling heat transfer over a flat stainless steel (SS-304) surface in water at atmospheric pressure. The bubbles generated during pool boiling were observed using a high-resolution camera (1.4 HD -Chronos high-speed camera @ 1326 fps) situated at the front sight glass of the boiling chamber. For smooth surfaces having small cavity sizes, the bubble departure size is mainly determined by a balance between the dynamic inertial forces and the buoyancy. The vapor bubbles had grown in size and coalesced with each other to form larger bubbles. The bubbles merged at a heat flux of 172 W/m² because surface tension force dominated over inertia due to vapor generation. Hence the larger departure bubble size on the smooth surface resulted in a higher degree of superheat. To simulate the physics, the Volume of fluid (VOF) method coupled with an energy equation was deployed using a commercial computer code (ANSYS-Fluent). The bubble growth, departure diameter, and bubble travel velocity from experimental and numerical results were compared. The numerical results were found to be in good agreement with experimental results.