Main Question or Discussion Point
hI'm hoping someone here is well versed at using thermoelectric cooling modules. I'm not able achieve anywhere near the cooling capacity shown in the datasheets and I'm pretty sure I've covered all possible things that could be going wrong. All I'm trying to do is maintain chilled water recirculating into an insulated line bundle at about 38 deg F about 20' long. Ambient air temp is 75 deg F. I'm using off the shelf components that are normally used in PCs which includes a small water pump with reservoir, liquid heat exchanger and multiple TECs secured to the heat exchanger using thermal grease on the cooling side and a 1/8 thick copper heat spreader and heavy aluminum heat sink on the hot side using forced air fan. I've calculated the heat load at around 100 btu or about 30 watts per hour when it's reached it's target temp. The modules I'm using are rated at DT 70C with a Qmax of 60 watts. I've run them at a few current levels that would be considered reasonably efficient 8 watts up to what should be over 30 watts each. There are six of them. For whatever reason I'm not able to drop the temp below 50 deg. Even when I've cut out most of the heat load. I've used online calculators for TECs to determine what it should take and what I have should be way overkill. Even if I remove the heat load I can't seem to get the temps down. I assume it may have something to with the construction of the heat exchanger. Does anyone have experience with this?