In the past two weeks we have looked at heat pipes and heat sinks, two common electronic thermal management components. To continue the series this week we focus on a slightly less common device known as the Peltier Cooling Plate, or Thermoelectric Cooler. One of the many cooling designs used in the electronics and circuit board design fields. The Peltier Plate is different from the heat pipe, but partially similar to the heat sink in that it utilizes steady-state technology, or in other words there are no moving parts. The Peltier effect, named for Jean Peltier, explains that all electric current is accompanied by heat current as well, and when that current passes between a thermocouple (two dissimilar conductors) there was a heating or cooling effect depending on the direction of the current which could then be harnessed for heat transfer. Peltier Plates have certain benefits over other devices, such as no vibration or maintenance due to its steady state form, it has no refrigerants that contain environmentally harmful CFCs, enables reduced operation of cooling fans, can be manufactured very small and they can provide cooling below the ambient temperature of the device.
Basic Workings of a Peltier Cooling Plate
When two conductors are placed in electric contact, electrons flow out of the capacitor with looser binds and into the capacitor with tighter bounds. This is explained by examining the Fermi levels between the two conductors. The Fermi level represents that demarcation in energy within the conduction band of a metal and between the occupied and unoccupied electron energy levels. When two conductors with unequal Fermi levels touch, electrons will travel between them until they have the same value. Current passing across the junction results in what becomes the temperature gradient. If the temperature of the hotter junction is kept low, through a heat sink or similar, the temperature of the cold plate can be cooled by tens of degrees.
Cooling plates have versatile uses.
While this style of cooling device is used in the computer and electronics industries, one of the main uses for this type of cooling system is in satellites and spacecraft to counteract the effect of direct sunlight on one side of the craft by dissipating it to the cool side. It is also utilized in fiber optic design where a wavelength of a component is dependent on temperature. Peltier devices have many more applications due to the fact that they can also be used for comparable heating as well as cooling depending on the amount of power supplied such as heat plates.
Engineering Improvements in the Future
Just like any other products, Peltier Cooling Plates must adapt as the technology it is used in becomes more advanced. Licensed mechanical engineers with the ability to utilize computation fluid dynamics (CFD) software can run analysis on CAD models to create more effective designs for electronics cooling. Because of their ability to control temperature so well with little wear and tear. While a Peltier Cooling Plate with a heat sink or waterblock can cool a chip far below its ambient temperature, one downside to this type of cooling is that the hot side of the plate generates more heat and needs to be cooled via liquid or air. This means that while the do a good job of transferring heat away, the hot side will usually require a fan for cooling. As engineers look for new materials and methods of electronics cooling, the thermoelectric or Peltier plate designs will have their part in the basis for the newer technology.