Conduction takes place in fluids (liquids or gases). As fluid is heated, the molecules increase in motion, and the flute begins to expand molecules to move further apart. This gives a decrease in density which causes the hotter fluid to rise and cool the fluid to fall, setting up a circulation within the fluid. The heat energy is gradually increased throughout the fluid.

This method of heat transfer is seen in the use of space heating and heat distribution in a furnace. Convection can take place by the natural currents set up by the application of heat or increased heat transfer biomechanical means forced convection as when a fan for pump is used.