Thermoelectric cooler (TEC) is a semiconductor device which is characterized by unique heat pump performance with high efficiency, compactness and durability. The unique ability of TECs to heat and cool, permits them to lower temperature of an object below ambient as well as to stabilize temperature of objects in widely varying ambient conditions.
Here we mention some application tips that can help in optimal use of TECs.
In most cases TEC specifications advise by manufacturers show module performance for vacuum conditions. It means that ambient does not affect TEC operation.
In many practical applications TEC operates in gas filled ambient. In the case the TEC gives performance less then specified.
Ambient gas supply additional heat load to TEC, even is nothing else load heat to TEC - gas convection and thermal conductance transfer heat from ambient (from base wall etc) to TEC cold side.
This heat load must be taken into account at designing stage of cooling system.
It is possible to reduce this «passive» heat load by:
Special gases are expensive but better performance is much more important for many applications.
Particularly it is a solution for multi-stage TEC applications where deep cooling is required and gas thermal lead can reduce TEC performance considerable.
Thermoconductive properties of some widely used gases for thermoelectric cooling systems are given in the table.
|Gas||Thermocondictivity W/mK||Typical reduction of maximal cooling capacity (to vacuum conditions) δT, K|
Deeper cooling (multistage TECs) - more effect of gas
The example shows four-stage TEC performance (power consumption) depending on gas ambient.
The TEC cool down a photodetector:
Worth case - dry air, best - inert heavy gases like as xenon, krypton.