Understanding the Peltier Effect
Learn about thermoelectric coolers and how they operate according to the peltier effect inside an enclosure.
The peltier effect, or thermoelectric effect, is the name given to the occurrence of heat when an electric current passes across a junction between two conductors.
The primary function of the thermoelectric unit or peltier unit is to transfer this heat using electricity without fluorocarbons or other contaminants. They are small static heat pumps which operate according to the principles of the peltier effect, discovered by the French physicist Jean-Charles Peltier more than a century ago. The basic principles of thermodynamics can be applied to these devices just as is done with traditional heat pumps or other heat transfer devices.
How Does It Affect Enclosures?
In practice, the heat transfer phenomenon described is obtained by assembling the thermoelectric modules within a complete thermoelectric unit, by using each module singularly or in mini-assemblies of multiples of the same module. When installed within an enclosure, the use of air or liquid heat sinks allowing the heat transferred through the module(s) to be absorbed on one side and dissipated on the other. The complete units are designed for easy mounting and offer several advantages to a compressor system.
The “motor” of the thermoelectric system is represented by the thermoelectric module more commonly known as the “Peltier module”. This module consists of a certain number of thermocouples, all identical and made of semi-conducting material, with the two components of the couple having different electrical characteristics. These thermocouples are electrically connected in series, and thermally connected in parallel, so as to create different junctions. They are then put into a “sandwich”, between two very thin ceramic plates which serve both as mechanical support and electrical insulation. The system starts up when tension is given to both ends of the circuit. As soon as current flows through, one side of the element cools (gives off energy to the opposite side) and the other side heats up (absorbs energy from the cold side).
Many years of research aimed at the improvement of the efficiency of the thermoelectric modules, which represent the main component of the unit, and the continuous reduction in their cost are making the application of this technology more and more convenient both in the consumer and industrial fields.
How Much Heat Can BeTransferred?
The cost/performance ratio usually remains competitive for cooling capacities up to a maximum of 200W. This is currently a limitation of this technology; however Continuous research efforts might increase this value and so make this cooling system suitable also when greater cooling power is required.
The thermoelectric unit does not feature any moving mechanical parts (except fans, if used) and is therefore extremely reliable, enjoying an almost unlimited life span and does not require maintenance. Its “static” construction makes the thermoelectric unit immune to vibrations thus allowing its use in any position, for this reason it is particularly suitable for applications where mounting is required on moving systems.
The thermoelectric unit does not contain any polluting substances such as CFC or other gases which may harm the ambient, making them the more environmentally friendly option over conventional compressor systems. They also have a more compact and simple structure than a compressor system and can be easily customised and mounted. Furthermore, they can cool hermetically sealed units and are extremely quiet.
What Is the Most Important Part of Thermoelectric Coolers?
The motor of the TEC system is known as the peltier module. Peltier elements can be connected in series to construct the cooling capability of the TEC. Generally the TEC has an array of cubes or pellets made of couples of semi conductors marked with different electrical charges, each of which is in contact with the radiators on the hot and cold side of the peltier element. Peltier modules combine low energy requirements with the ability to provide both cooling and heating from the same element. These couples are laid between two ceramic plates, like a sandwich, that act as a mechanical support while also working as an electrical insulator. On applying a DC current to the module or TEC, the system starts to work, cooling one side of the module and warming the opposite one. The heat sink that heats up in the system can get very hot while the system is working, in this case it is necessary to incorporate a fan to dissipate the heat. Usually through the use of a compact frame axial fan. Normal Peltier modules are roughly a few cm’s thick and have a few mm on a side. To obtain greater cooling abilities, the individual elements are connected in stacks or they can be connected in some combination of series or parallel electrical connections.
Where Are TEC’s Used?
Thermoelectric coolers are used in a wide range of demanding industries including laboratory, telecom, industrial and medical. The uses for these can be as important as temperature control for missiles and military equipment. Their capacity ranges from heat removal from milli-watts to several thousand watts. TEC’s are particularly effective in small applications where even the smallest vapour compressor system would provide much more cooling than necessary. In these situations, the TEC provides a smaller, lighter and more reliable solution in comparison to the small compressor system.
For more information on our range of thermoelectric coolers or peltier modules to facilitate enclosure cooling, contact our team at sales@axair-fans.co.uk. Or view a wide range of thermal management components available to buy online, including filter fans, heaters, thermostats and adaptors.