Question

why does transfer of heat in fluids take place by convection???​

Answer 1

Transfer of heat in fluids take place by convection because the hotter part of the fluid is not as dense as the cooler part.

Answer 2

When fluid absorb heat where the contact is made, it gets less dense and floats up to be replaced by cooler fluid, which can then absorb more heat. So, in a fluid, all three methods of heat removal happen at the same time. In a solid, convection doesn’t happen because the material that absorbs the heat , although it gets less dense ( just like in the fluid), can not move.