Petrie Ltd

What are Conventional Heating Techniques?
Conventional heating techniques are a wide classification of heating methodologies that rely on traditional heat transfer mechanisms in order to heat an object. Heat is the process of energy transfer from one body to another because of the difference in temperature of the bodies; in accordance with the Second Law of Thermodynamics this energy transfer is structurally from the hotter to the colder body in order to equalise the temperature. This energy transfer can be achieved via one of three mechanisms:

1. Conduction – the transfer of thermal energy from adjacent bodies resulting from the presence of a temperature gradient. The classification of bodies can range from individual molecules right up to large physical objects and can comprise all forms of matter including solids, liquids, gases and plasmas. Conduction is a heat transfer mechanism that requires the presence of matter, but not the bulk motion of matter.
2. Convection – the transfer of thermal energy resulting from the movement of molecules in liquids and gases. Convective heat transfer takes place through a process of diffusion - random motion the particles within the material, and advection – transfer of heat through motion of current within the material. There are two forms of heat convection; firstly there is forced convection where heat is carried passively through the material in the absence of an external head process, and secondly, there is natural convection where heating causes fluid motion which acts to transport heat via the bulk motion of the fluid. Typically both forced and natural convection exist together in what is known as mixed convection.
3. Radiation – is the transfer of heat energy in the form of electromagnetic radiation emitted from the surface of a material based on the materials temperature. Thermal radiation is created when heat from the movement of charged particles with atoms of the material is converted to electromagnetic radiation. Radiative heating is classified as a form of electro-heat where portions of the electromagnetic spectrum are utilised as the primary energy source to heat a material; however it is important in conventional heating because it is a factor in heat transfer of traditional conventional heaters and acts to supplement the conductive or convective heating processes.

Conventional heating processes may utilise one or more of these mechanisms as the means of heating an object.

Types of Conventional Heating Techniques
The types of conventional heating techniques are varied. Any source that can support a conductive, convective or radiative heating process can be classed as a conventional heater. From the perspective of industrial heating applications there are two main techniques that are used in commercial heating systems:

1. Hot-air
2. Steam

Utilisation of these techniques is dependant on the applications, and is carefully selected to extract the functional benefits these techniques offer over other heating methodologies, including non-conventional heating such as electro-heat techniques.

Advantages of Conventional Heating
The advantages of conventional heating for industrial processes are:

• Diversity – the range of conventional heating techniques is large and varied. This makes conventional heating highly versatile to a wide range of applications across many industries.

• Established technology – the underpinning science behind conventional heating has been understood for many years. Technology built using conventional heating techniques benefits from this extensive knowledge base. Established knowledge also has commercial implications as the need to research and develop from primitive principles is reduced.

• Complimentary to electro-heat techniques – conventional heating techniques are complementary to electro-heat techniques allowing applications to extract the benefits from each technique. In RF and microwave heating applications, hot-air and steam are widely used to supplement volumetric heating by driving thermal energy into a product and maintaining product moisture profiles, whist obtaining rapid heating times and desirable product textures and appearances.

Back to top of page