How to choose Semiconductor refrigeration sheet? An application case teaches you!
Welcome to TEC Science Lesson! In this issue, we will teach you how to find the semiconductor refrigeration sheet that meets your needs in many models through a specific application case. If you have questions about this article or want to learn more about TEC, please leave a comment in the comments section
1.TEC core parameters and selection recommendations
First of all, we need to consider the following key parameters when conducting TEC selection. These parameters have been mentioned in previous lessons, so let's review them today:
01 Qcmax (Maximum cooling capacity)
Definition: The maximum cooling capacity of TEC at a maximum temperature difference ΔTmax of 0.
Selection suggestion: We should calculate according to the actual refrigeration demand in the application scenario, and then increase a certain margin.
02 ΔTmax (Maximum temperature difference)
Definition: The temperature difference between the exothermic and endothermic surfaces of TEC when the semiconductor cooler is connected to the maximum current value Imax.
Selection suggestion: The actual selection of ΔTmax should be slightly higher than the temperature difference required by the application. However, it should be noted that the greater the temperature difference, the lower the COP, Qc and other parameters tend to be.
03 Imax (Maximum operating current)
Definition: The current required to achieve the maximum cooling capacity Qcmax.
Selection suggestion: We should choose the TEC that can match the power output according to the power supply system capability to avoid exceeding the current limit.
04 Umax (Maximum operating voltage)
Definition: The voltage required to achieve the cooling capacity Qcmax.
Selection suggestion: Ensure that the power supply voltage range covers the maximum voltage of the TEC to avoid failure to drive the TEC to design performance. When the recommended maximum voltage is exceeded, the product efficiency will decrease significantly.
05 COP (Coefficient of Performance)
Definition: TEC energy efficiency index, COP = Qc/Pin, the higher the value, the more energy saving.
Selection suggestion: On the premise of meeting the performance requirements, it is recommended to choose a TEC with high COP, which is helpful to reduce energy consumption.
2.The specific steps of TEC selection are as follows
01 Define application requirements
Refrigeration requirements (Qc) : For example, you want to cool the target object to 5 ° C in 1 minute.
Operating temperature difference (ΔT) : For example, the ambient temperature is 35℃, the cold end needs to be maintained at 15℃, because the temperature of the hot surface of the cold sheet will rise when the cold sheet is working, the temperature difference between the cold sheet and the hot surface will increase, so ΔT≥25℃.
Power supply: For example, it can actually provide 12V constant voltage power supply, the maximum power is 40W.
Confirm whether there are other heat sources outside.
02 Calculate related parameters
According to the parameters of the target object, it is calculated to determine the required cooling capacity, whether there are other heat loads, and the contact mode between TEC and the target object.
03 Select the TEC model according to your requirements
Go to the official website (www.advanced-te.com), select and compare according to the requirements, and preferentially select the model that meets the current, voltage and heat requirements. The voltage and current are typically 70%-80% of Imax/Vmax. For example, if the TEC-12706 Vmax is 15.4V at 31 ° C, the recommended power supply voltage is about 12V. If multiple TEC models meet the parameter requirements of actual applications, you can compare the curves of each model to make the optimal selection.
04 Evaluation of thermal solutions
The performance of the TEC is closely related to the heat dissipation efficiency of the hot end. During the selection, ensure that the heat dissipation solution can meet the heat dissipation requirements of the hot end of the TEC (for example, select an appropriate heat sink and fan). The heat dissipation capacity of the heat dissipation solution must be greater than or equal to the heat dissipation of the cooling plate.
3. Practice time: TEC selection for a brand hair removal instrument
01 Clear application requirements:
A brand hair removal device needs to cool a 30*30*8mm artificial sapphire from room temperature 25 ° C to 10 ° C in half a minute, in order to reduce the discomfort of users in the process of use. The customer can provide a 5V constant voltage power supply, the maximum power does not exceed 10W, and the TEC installation space does not exceed 30*30mm.
02 Calculate relevant parameters:
Sapphire required cooling capacity Qc calculation formula:
Qc= (c*m*∆T) /t
c is the specific heat of sapphire, about 0.7788J/(g*℃) at room temperature (25℃); The mass m is 11.52g; Temperature difference ∆T takes 20℃; The working time t is 30s. Qc=(0.7788*11.52*20)/30=5.98W, without considering the thermal resistance, select Qc ≥5.98W, length and width are less than 30*30mm TEC.
03 Select TEC model according to your requirements:
If there are multiple TEC models that can meet the above requirements, then the optimal selection needs to be made by comparing the curves of different models. The following are the four performance curves of the TEC-07103:
First check the V-I curve: at the temperature difference of 20 ° C, the current corresponding to the 5V voltage is about 1.7A, which does not exceed the upper limit of the power supply current.
Then check the QC-I curve according to the current: the Qc is about 7.3W under the temperature difference of 20℃, meeting the cooling capacity demand.
Then look at the COP-I curve: in this case, the COP value is about 0.9.
Finally, check the QH-I curve: Qh corresponding to 1.7A current is about 16W. The calorific value Qh=U*I+Qc=5V*1.7A+7.3W=15.8W can also be obtained through the calculation formula.
04 Evaluate cooling solutions:
After the selection is completed, in order to ensure the heat dissipation efficiency, we need to choose a heat sink with excellent thermal conductivity and control circuit: that is, the heat dissipation capacity of the fan and fin must be greater than the heat output of the cold sheet 15.8W, otherwise it will lead to heat accumulation on the hot surface when the cold sheet is working, resulting in reduced refrigeration effect or even damage to the refrigeration sheet.
🔵Pay attention to avoid common mistakes when selecting:1. Excessive pursuit of ΔTmax: high temperature difference is often accompanied by low COP, resulting in decreased efficiency. 2. Ignore heat dissipation problems: insufficient heat dissipation at the hot end will significantly reduce TEC performance and even cause faults. 3. Only pay attention to parameters, do not consider brand and quality: inferior refrigeration pieces may have problems of short life and unstable performance.
The above is the TEC selection tutorial organized by us. In short, how to correctly select semiconductor refrigeration pieces is a process of balancing performance, energy efficiency and cost. Mastering the application skills of Qmax, ΔTmax, Imax, Umax these core parameters can effectively help you find the right model. In addition, don't forget to evaluate the heat dissipation scheme after the selection is completed, otherwise the overall performance and stability of the system will be affected
