The cooling capacity of a thermoelectric system depends on many conditions such as the ambient temperature, the characteristics of the heat load, the optimal current of the module, and the heat dissipation system. When the ambient temperature is 75°C, the THot required to lower the temperature of the hot side to 35°C can be theoretically obtained (this is the temperature drop by the thermoelectric element itself, and in the system itself, such as the hot side temperature rising above the ambient temperature) loss was ignored)
However, this theoretical maximum is not possible in a real system. In general applications, the temperature difference when a single-layer thermoelectric module is used is about half of the above theoretical value. If cooling to a lower temperature is required, a system with multiple multi-layer modules or single-layer modules is required, or another technology must be applied to the thermoelectric module.
For example, you can cool the hot side with a compressor to achieve a lower hot side temperature. However, if the module is operated under extremely low temperature conditions, the efficiency of the thermoelectric module decreases. In the case of a multi-stage thermoelectric module, although it can produce a larger temperature difference, it has less heat absorption and is much more expensive than a module.
2. How much heating is possible with a thermoelectric element?
The heating capacity is entirely determined by the melting temperature of the solder used to manufacture the thermoelectric module. The standard thermoelectric module has the ability to heat about 100℃, but we have developed a thermoelectric module that can be used in the temperature range up to 200℃.
It is very important for the user to keep the temperature of the hot side below a certain ratio. This is because if the solder melts and flows back toward the semiconductor device, the efficiency of the thermoelectric device decreases or its lifespan ends.
3. Are thermoelectric systems only used to heat or cool air?
no. Thermoelectric systems are often designed for use in both liquids and gases. For solids it attaches directly to the thermoelectric module, but for liquids it is usually made of aluminum or copper and is designed to circulate a heat exchanger attached to the Peltier module.
This characteristic value does not represent the maximum current that the module can withstand. This is completely different from what most people think. Imax is the amount of direct current that can produce the maximum temperature difference in the thermoelectric module. If the module is operated below Imax, the desired temperature cannot be obtained. When a current over Imax flows, Joule heat generated inside the thermoelectric element increases the temperature of the module and consequently reduces the temperature difference.
Imax is measured simultaneously with Vmax. That is, Imax is the current that flows when Vmax is applied to the module. Unlike Vmax, Imax is not particularly temperature dependent and tends to have a constant constant regardless of the ambient temperature in which the device is used.
Contrary to popular belief, Vmax is not the limiting voltage a module can withstand. In fact, Vmax is the DC voltage that causes the maximum temperature difference across both sides of the module. If the input voltage is less than Vmax, the maximum temperature difference of the module cannot be reached because less current flows. If the input voltage is greater than Vmax, the power consumption of the thermoelectric module increases, increasing the temperature of the system itself and reducing the temperature difference.
Keep in mind that Vmax is temperature dependent. The higher the temperature, the higher the voltage applied to the thermoelectric module.
6. What is Q max?
Qmax is one of the most confusing properties in the thermoelectric field, as its practical meaning is not clear. The definition of this property is practical. As the thermal load increases in a given thermoelectric system, ΔT consequently decreases. For example, for any given metal structure, you will get a lower ΔT at 40W than at 30W. When the temperature difference decreases to 0 in the random load characteristic, the load in this case is called Qmax and is expressed in watts.
Please note that this characteristic Qmax does not represent the maximum amount of heat handled by the module. If the heat load exceeds Qmax, endothermic heat cannot be achieved, and only the most appropriate value of Qmax in the characteristic table due to the heat load is usually used as the endpoint of 'load lines' in the running graph.
8. How accurately can you control the temperature using thermoelectric technology?
With an appropriately controlled and well-designed steady-state controller (usually when using a PID controller), it is possible to control the temperature within the range of 0.1°C from the set temperature (of course, in this case, large If there is no interference!)
As an indirect measure of temperature stability, stability can be obtained within a range of several hundred degrees (and possibly even a thousand degrees). Of course, when discussing stability possibilities, it is important to stress the thermal load that will create a temperature gradient. And part of the load is displayed as fluctuating from the set temperature regardless of the accuracy of the number displayed on the digital display. Also, an equivalent response cannot be expected under the full load. Designers have to be very careful with long-term nuances such as set temperature shifts and calibration losses.
Yes it is. However, it is not enough to simply stack two different thermoelectric modules on top of each other. The second module must extract heat from its own resistance along with the heat from the thermal load as well as the radiated heat from the first module. Since this is a very cost-sensitive issue, the first module is typically designed to be smaller than the second module. One thing to note when stacking modules is that the heat absorption capacity (W) of the entire stair module is limited by the smallest module. That is, ΔT increases, but the endothermic energy decreases.
It is very important to measure the temperature of the external ceramic substrate of the thermoelectric element as precisely as possible while the module is operating. It is recommended to select a temperature sensor that is not sealed on the outside and is very thin. This allows the thermocouple to be attached very close to the center of the module. Of course, with the exception of the exposed end of the thermocouple, the rest of the connection along the groove in the wire must be electrically insulated. Also, the thermocouple must be attached snugly into the groove using thermally conductive adhesive, and the attachment surface must be wiped clean to remove unnecessary adhesive or debris.
Some people put a very thin thermocouple inside the module to get the desired temperature, but that's not a good idea. First, it is difficult to properly attach the thermocouple to the inside of the module. And these mechanical manipulations can seriously impair the performance of the module. Also, without internal insulation, the thermocouple will have a thermal gradient between the ceramic substrate and the air temperature inside the thermoelectric element. Thermal gradients inside the thermoelectric module reduce the accuracy of reading the temperature.