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Thermoelectric Technology
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An Introduction To Thermoelectric cooling module 

 

    Thermoelectric technology is an active thermal management technique based on the Peltier  effect. It was discovered by J.C.A Peltier in 1834, this phenomenon involves the heating or cooling of the junction of two thermoelectric materials(bismuth and telluride) by passing current through the junction. During operation, direct current flows through the TEC module causing heat to be transfered from one side to the other. Creating a cold and hot side. If the direction of the current is reversed, the cold and hot sides are changed. Its cooling power also can be adjusted by changing its operating current. A typical single stage cooler (Figure. 1) consists of two ceramic plates with p and n-type semiconductor material (bismuth ,telluride) between the ceramic plates. The elements of semiconductor material are connected electrically in series and thermally in parallel.

 

http://www.huimao.com/upload/1.jpg

http://www.huimao.com/upload/2.jpg

   Thermoelectric cooling module,Peltier device,TEC modules can be considered as a type of solid-state thermal energy pump, and due to its actual weight, size and the rate of reaction, it is very suitable to be used as part of the inbuilt cooling systems (due to limitation of space). With advantages such as quiet operation, shatter proof, shock resistance, longer useful life and easy maintenance, modern thermoelectric cooling module,peltier device,TEC modules have a wide range application in the fields of military equipments, aviation, aerospace, medical treatment, epidemic prevention, experimental apparatus, consumer products (water cooler, car cooler, hotel refrigerator, wine cooler, personal mini cooler, cool & heat sleep pad, etc).

 

 

Today, because of its low weight, small size or capacity and low cost, thermoelectric cooling is widely used in medical, pharmaceutical equiment, aviation, aerospace, military, spectrocopy systems, and commercial products(such as hot& cold water dispenser, portable refrigerators, carcooler and so on)

 

Parameters

I

Operating Current to the TEC module (in Amps)

Imax 

Operating Current that make the maximum temperature difference Tmax (in Amps)

Qc 

Amount of heat that can be absorbed at the cold side face of the TEC (in Watts)

Qmax 

Maximum amount of heat that can be absorbed at the cold side. This occurrs at I = Imax and when Delta T = 0. (in Watts)

Thot 

Temperature of the hot side face when the TEC module operatiing (in °C)

Tcold 

Temperature of the cold side face when the TEC module operating (in °C)

T 

Difference in temperature between the hot side (Th) and the cold side (Tc). Delta T = Th-Tc (in °C)

Tmax 

Maximum difference in temperature a TEC module can achieve between the hot side (Th) and the cold side (Tc). This occurrs (Maximum cooling capacity) at I = Imax and Qc = 0. (in °C)

Umax

Voltage supply at I = Imax (in Volts)

ε

TEC module cooling efficiency ( %)

α

Seebeck coefficient of thermoelectric material (V/°C)

σ

Electrical coefficient of thermoelectric material (1/cm·ohm)

κ

Thermo conductivity of thermoelectric material (W/CM·°C)

N

Number of thermoelectric element

Iεmax

Current attached when the hot side and old side temperature of TEC module is a specified value and it required getting the Maximum efficiency (in Amps)

 

Introduction of application Formulae to TEC module

 

Qc = 2N[α(Tc+ 273)-L I²/2σS-κs/Lx(Th - Tc ) ]

T= [ Iα(Tc+ 273)-L I/²2σS] / (κS/L + I α]

U = 2 N [ I L /σS +α(Th - Tc )]

ε = Qc /U I

Qh = Qc + I U

Tmax = Th + 273 + κ/σα² x [ 1-√2σα²/κx (Th+ 273) + 1]

Imax =κS/ Lαx [√2σα²/κx (Th+ 273) + 1-1]

Iεmax = ασS (Th - Tc ) / L (√1+0.5σα²(546+ Th - Tc) / κ-1)

To install a module using thermal pads, perform the following operations:

1. Check the quality of the surface on which a module is to be mounted. The surfaces of heat sinks must be clean and free from foreign particles and fat stains; its non flatness and roughness must not exceed0.02 mm.

2. Clean your workplace and remove foreign objects. Prepare thermal pads of required dimensions matching those of the module surfaces.

3. Remove protective film from the thermal pad. Without touching the working surface of the pad, place it on the module surface. Make sure the entire module surface is covered by the pad. Evenly press the pad to the module.

4. Repeat operation 3 for the other side of the module.

5. Install the module on the proposed contact area.

(Note: When using pads with protective film on both sides, remove the film from the pad outer side.)

6. Use the required number of screws to ensure a hold-down pressure of 13 to15 kg/cm2 to keep the module to the heat conducting surfaces. Such pressure affords the minimum contact thermal resistance. Controlled pressure is insured by the use of torque wrench. Allow the assembled structure to stand for 1 hour. After this time expires check the hold-down pressure with torquing screws and adjust it to the requirements, if necessary.



Size

Clamping Force

Diameter of screw/quantity of screw/ Torque per screw

30X30mm

120Kgs/260Pounds

4mm/2/0.072Kgxm

40X40mm

230Kgs/500Pounds

4mm/2/0.128Kgxm

50X50mm

350Kgs/760Pounds

5mm/2/0.250Kgxm

62X62mm

430Kgs/920Pounds

5mm/2/0.300Kgxm