Quote:
Originally Posted by traveller
Thanks Rowland,
So just to summarise, there is no advantage in having a large conductive surface to the cold side of the TEC, as it would only decrease the efficiency of the module.
Therefore, a copper strip size of a camera base plate (similar to your drawing below) would be sufficient and more effective than a large copper sheet covering the lower half of camera body (which was what I planned).
I will also need a lower current than the one rated on the TEC and a slightly larger fan over the hot surface to increase the efficiency.
Thanks,
Bo
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Hi Bo
I guess whatever additional metal you add inside the box must be cooled. A plate to the bottom of the camera is merely a way of covering the area as evenly as possible, but the size of the TEC will determine this as well, because all the surface of the TEC should be in contact with whatever medium you use.
The hot side heatsink/fan combo is more complex as it must dissipate the energy produced by the TEC and the energy required to drive the TEC. Theoretically, if your TEC is rated at 60w the heatsink should be capable of dissipating 120w (rule of thumb, ignoring inefficiences). This will get you the magic ambient/fan exhaust <10C deltaT - best efficiency.
If the hs/fan is only capable of 80w (for example) running the TEC at 60w will add energy that cannot be dissipated - heating the system. In this case, running the TEC below rated produces best efficiency. Instead of 12v you might run the TEC at 9 - 10v - in any case, the result is less cooling. End of day, hs/fan/TEC ratings should be complimentary. If not play, around with the TEC voltage to get the <10C ambient/fan exhaust deltaT, if this produces adequate cooling.
It gets more complex because cooling energy requirements are not linear, particularly over the last 5C deltaT. I have spent considerable time plotting various cooling combo's to arrive at a sensible compromise in performance, weight and size. My system is cooling the sensor, not the whole camera - although conduction is unavoidable and the camera gets cold.
Make sure your camera electronics are kept free of condensation using the cold plate design. In some ways this is more complex than building a dry air freezer box. The cold plate gets very very cold and you dont want condensation in the bottom PCB near the camera base plate - or anywhere else for that matter.