ThermalLM

 

Analysis (Modeling of Thermoelectric Cooler):

Flow and Thermal Analysis was conducted in Ansys Icepak. Ansys Icepak is based on FVM (finite volume method).The Finite Volume Method is one of the most versatile discretization techniques used in CFD.

Steps:

• Model the Heat Sink , Fan, TEC, Interface resistances. ( There is a direct Macro for TEC in Ansys Icepak)
• Put at least 3 elements in between gaps between fins, and at least two elements in fin thickness
• Lower the momentum under relaxation factor from 0.7 to about 0.5 – 0.3, if divergence occur in residuals
• Make sure to insert correct fan curve , in order to get correct pressure profile
• Run TEC to solve the problem

 

Thermometric module pellet material properties need to be specified correctly.

Say for Bistuth Telluride (Bi₂Te₃) :

Temperature-dependent basic material parameters for the typical bismuth-telluride materials:

Seebeck coefficient (V/K):

S = S₀ + S₁T + S₂T² + S₃T³

S₀ = 2.2224E-5

S₁ = 9.306E-7

S₂ = -9.905E-10

S₃ = 0

 

Resistivity (ohm- cm):

ρ = ρ ₀ + ρ ₁T + ρ ₂T² + ρ ₃T³

ρ₀ = 5.112E-5

ρ₁ = 1.634E-6

ρ₂ = 6.279E-9

ρ₃ = 0

 

Thermal Conductivity (watt/cm- K):

k = k ₀ + k ₁T + k ₂T² + k ₃T³

k₀ = 6.2605E-2

k₁ = -2.777E-4

k₂ = 4.131E-7

k₃ = 0

All temperatures are in Kelvin and are average temperatures between the hot and cold sides. Useful values for the above coefficients at an average between 298 K and 278 K are:

S_m = 2.0 x 10-4 V/K

ρ = 1.0 x 10-3 ohm-cm

k_m = 1.5 x 10-2 watts/cm-K

 

 

 

TEC Cold side temperature ( The temperature gradient visible on TEC cold side in image below is due to the side channel wall attached to TEC edges in the model under analysis)

 

 

Heat Sink base temperature

 

 

Temperature across channel ( Y-Z Plane)

 

 

Temperature across channel ( X-Z Plane)

 

 

Pressure across channel

 

 

Particle traces representing velocity

 

 

 

Experimental Test:

A rectangular channel with thermoelectric cooler (TEC) was attached to a plate fin heat sink. Forced convection over the heat sink was provided with DC fan. Four Thermocouples were attached to cold side of TEC, hot side of TEC, channel inlet and outlet.

Components used to build the channel

Assembled Channel

Complete Assembled Closed Channel

Ambient Conditions : 28°C, 70% RH, natural convection

Thermal Load on cold side of TEC : Ambient Air Conditions ( minor load)

 

Steady State Result:

T_c = Cold Side Temperature of TEC (^°C) = 1^°C

T_h = Hot Side Temperature of TEC (^°C) =  33^°C

T_i = Inlet air temperature (^°C) = 28^°C

T_o = Outlet air temperature (^°C) = 31^°C

Total Power Input (TEC + Fan) = (3.39 + .5) W = 3.89 W