Examples of natural convection are?

Natural convection, also known as free convection, is a mechanism or mode of transport of mass and heat in which the movement of a fluid is generated only by density differences in the fluid due to temperature gradients, and not by any external source (for example, a pump, fan, suction device, etc.).
With natural convection, the liquid surrounding the heat source receives heat and the thermal expansion becomes less dense and rises. Thermal expansion of the liquid is critical.