E. Select an Appropriate TEC
The performance graphs used in this brochure have been normalized to provide a universal curve for use with any single- or two-stage TEC for which the "maximum" values are known. By using ratios of actual to "maximum" performance values, performance may be estimated over a wide range of operating conditions.
- Determine the ratio of DT/DTmax.
Example Your Case
Record DT from step 2 35°C _______ °C
Record DTmax from step 3 64°C _______ °C
Calculate DT/Tmax 35°C/64°C = 0.55 _______
- On the performance graph (Figure 2) draw a horizontal line on the graph corresponding to the calculated value of DT/DTmax (0.55 in this example).
- Obtain the optimum value of Q/Qmax at the intersection of the horizontal line just drawn and the diagonal Optimum Q/Qmax line. Interpolation between curves may be necessary.
Example Your Case
Optimum Q/Qmax = 0.25
- Obtain the maximum value of Q/Qmax at the intersection of the horizontal line (drawn in Step 4b) and the right vertical axis.
Maximum Q/Qmax = 0.45
- Divide the total heat load (from Step 1) by the Q/Qmax ratios above to calculate the optimum and maximum Qmax.
Optimum Q/max = 9.0W / 0.25 = 36W ¸ = W
Maximum Q/Qmax = 9.0W / 0.45 = 20W ¸ = W
f. Select a TEC from Marlow's Standard Thermoelectric Coolers product list with a Qmax greater than the maximum Qmax (20 watts in this example), but less than the optimum Qmax (36 watts in this example).
Keep in mind that within this range, a TEC with a Qmax close to the optimum Qmax will provide maximum efficiency, and a Qmax close to the maximum Qmax will yield smaller and possibly less expensive TECs. Reading down the Qmax column results in the selection of the following TECs:
Example TEC Values Your Case TEC Values
Range Location Model# Qmax Imax Vmax Model# Qmax Imax Vmax
Near Optimum RC6-6 30 5.6 8.2 ______ _____ ____ _____
Nearer Maximum RC6-4 20 3.7 8.2 ______ _____ ____ _____
For this example, let us assume maximum efficiency is desired. Thus, the 5.6 amp, 8.2 volt cooler is selected, because between these two potential TECs, its Qmax (30 watts) is closest to the optimum Qmax (36 watts).