Heat transfer, simply put is the transfer of heat from one component to another. It involves temperature and the flow of heat. Temperature is the thermal energy that is available and heat flow is the movement of the thermal energy. Heat transfer falls under the realm of thermal engineering which is the study of heating and cooling processes.
Thermal engineering includes:
These disciplines are used by mechanical and chemical engineers to solve problems in many fields, including solar heating, boiler designs and computer chip cooling.
Thermodynamics
Thermodynamics is a part of natural science and involves heat and its relation to energy. It also involves the work that is performed by one system and the energy that work creates and transfers to another system. Thermodynamics is applied to a variety of areas, including chemical, aerospace, and mechanical engineering and cell biology.
Thermodynamics was first used in steam engines. In 1824, a French physicist and military engineer, Nicolas Leonard Sadi Carnot, believed that heat engines could help the French win the Napoleonic Wars. However, it was a Scottish physicist, Lord Kelvin, who in 1854 came up with the first formal definition of thermodynamics:
“Thermodynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency.”
Interest in heat engines progressed to interest in energy transferred in chemical processes.
Fluid Mechanics
Fluid mechanics is the study of fluids such as liquids, gases and plasmas, and the forces that affect them. As a branch of physics, it is separated by the study of three different types of fluids or fluid statics:
- Fluids at rest
- Fluid kinematics or fluids in motion
- Fluid dynamics (the effect of forces on fluid motion)
Kinematics uses geometry to describe fluid in motion. For instance, kinematics uses point trajectory and geometric objects. Kinematics is used in astrophysics in describing the motion of the solar system and in robotics in describing a joined part.
Fluid dynamics or fluid flow is used considerably in aerodynamics, which is the study of air and gases in motion. In solving a fluid dynamic problem, scientists measure such things as speed or velocity, pressure and temperature of the fluid as functions of space and time.
Mass Transfer
Mass transfer is the movement of one system to another location. For example, in the human body, the purification of blood in the kidneys and liver would be considered a mass transfer. Evaporation of water and distillation are also examples of mass transfer.
Heat Transfer
Heat transfer is involved in many forms of energy. These include:
- Conduction or diffusion
- Convection
- Radiation
- Advection
Conduction or diffusion is seen when energy is transferred between objects in contact with each other.
Convection occurs when heat is transferred by the movements of fluids from one place to another.
Radiation results from the movements of atoms and molecules. The emissions cause electromagnetic radiation. This can then be harnessed to create solar power.
Advection is the transport of a fluid by its motion. An example would be heat causing humidity in the atmosphere.
