Heating Processes

Any process which involves the application of direct or indirect heating, for its execution, can be termed as a heating process. The process of heat transfer can take place by conduction, convection, radiation, or a combination of these processes. Basically, the process of heat transfer takes place from a body or volume at higher temperature to a body at lower temperature to equalize the net thermal energy, and thus to achieve thermal equilibrium.

Heating processes have wide applications, which include, Chemical Industry, Automobile Industry, HVAC (Heating, Ventilation, and Air-Conditioning)/ Climate Control, Heat Treatment, Electronics Industry, Food Industry, Core Manufacturing Industry etc.

Modes of Heat Transfer

Heat Conduction:

On application of heat at a specific point on a solid body, the kernel or the molecules comprising the solid start vibrations. These vibrating molecules transfer their vibrational potential energy to the surrounding molecules, which then also start vibrating. The process continues and the whole body gets heat up after a certain interval of time. The vibrating molecules continue their dynamics due to continuous application of heat. Heat conduction takes place by direct contact between solids, and the rate of heat transfer is directly proportional to the temperature difference between the two bodies or surfaces in contact.

Heat Convection:

Heat convection in heating system is the process of heat and mass transfer in liquids, which takes place by the processes of advection and diffusion.

This may be of two types:

• Free or Natural Heat Convection:
In this type, mass transfer between two masses of liquids, takes place due to density differences caused by thermal/temperature gradients. In natural convection, a fluid volume receives heat, becomes less dense and rises. The surrounding, cooler fluid then moves to replace it. This cooler fluid is then heated in a cycle, and the process continues, which forms a convection current. The driving force for natural convection is buoyancy, which is caused due to the difference in fluid densities.

The tendency of any system towards natural convection depends on Grashof number (Gr), which is the ratio of buoyancy force and viscous force

• Forced Heat Convection:
In forced convection, heat and mass transfer processes are achieved by the application of external pressure, using pump, blower, fan etc. It is frequently employed, while designing heat exchangers, pipes etc.

The behavior of a particular system towards forced convection relies on Peclet number (Pe), which is the ratio of coefficients of advection and diffusion

Heat Radiation:

Heat radiation involves, the transfer of heat between any media, through electromagnetic waves. This mode of heat transfer does not require any media, and heat transfer can take place between any kind of bodies, including solids, liquids, and gases. Heat radiation takes place continuously and at all temperatures. The frequency of radiations emitted by a body, increases with the temperature of the body, which can be analyzed by Wien's Displacement Law.

NSW India is a pioneer manufacturer and exporter of Heating Systems.