Heat Transfer is the scientific knowledge that builds upon the principles of thermodynamics and fluid dynamics to describe how heat moves from one body to another. For heat to transfer, a temperature difference or gradient is needed. Heat will move from a higher temperature to a lower one (hot to cold). This concept is important to Engineering Literacy, as it is the knowledge that informs how engineering professionals understand, design, create, and analyze material selections, machinery efficiency, reaction kinetics, heat exchangers, and cooling towers.