I’m reconfiguring my printing closet (~6’x6’) for a new printer and thought about enclosing the printer in a moderate sized cabinet (~2’x3’x6’ - one “shelf” of the closet) for thermal control. Since there will be inevitable opening and closing, as well as just normal infiltration of the ambient air (usu ~65F between 40-75% RH) it would seem like a good application for a Peltier dehumidifier to keep the RH in the chamber low and reduce my need to re-dry filament which has been on the machine during (inevitable) multi-day or -week downtime between projects.
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Peltier units are solid state heat pumps with awful efficiency. Where power consumption is not an issue, It is significantly cheaper to simply get a normal resistive heating dehumidifier, as the additional heating efficiency of a Peltier operating at 0.6 COP is not worth the upfront investment.
Small heating box dehumidifiers are a bit of a misnomer too. All they do is heat the air so it’s relative humidity is lower since hot air can hold more water. The amount of water does not change. However for most environments this works OK. Only units with full refrigerant pumps inside that can cool the air to its dew point, condense the water out, then warm it back up are true dehumidifiers.
Peltier operating at 0.6 COP is not worth the upfront investment.
Small correction: Did you mean 0.06 COP? 60% efficiency (0.6 COP) at room temperature is impossible. 6% would be about right. Some of the Pelletier coolers are operating at just 1-2%.
You’re thinking of carnot efficiency power cycles where you are removing energy from a fluid, maybe? I meant exactly what I said with their COP.
Refrigeration/heat pump cycle COP’s can be all over the place. Often they are much higher than 1.0. Where a refrigeration cycle’s COP is calculated as Q(cold) / Work(electrical), many heat pumps can move more watts than they take to run. TEC’s are no exception.
TEC’s in particular are especially sensitive to the total temperature differential between hot and cold plates when it comes to COP. They hate making temperature differentials much higher than 30-40 kelvin. Most efficient when the temperature delta is like 10K or less. COP 0.6 is about typical for a TEC running across the fairly large temperature differential that you would need to get air down to dew point and condense water, at a high current required to make the TEC’s cost effective. Example graph of COP vs temperature differential
I think it should be theoretically possible to make a Peltier based machine that will extract moisture the same as a refrigerant pump machine. Ask any overclocker who’s tried to use a Peltier directly on a CPU or motherboard; it’s perfectly possible to get the cold side of a Peltier below the dew (or frost!) point when it has little or no thermal load on it.
Now as to whether or not any commercial product exists that actually works that way is another story. I see a ton of them e.g. on Amazon, but I have not tried any out or taken one apart or anything. But with a suitably shaped heat sink you could get condensation to form on the cold side and then drip or shake or blow it off or whatever into a catch bucket, just like your basement dehumidifier does.
oh, anything is technically possible. It’s totally possible to get a peltier to drive a sufficient temperature delta to condense water at a low dew point. The issue is the exponentially worsening efficiency curve as delta-T increases that would make it’s power requirements - and waste heat generation - quickly become untenable for what you’re accomplishing.
Right thought. Wrong answer:
Build an air-tight box and use orange gel.
Which is great if I were storing it and only opening the box for a new roll. I expect to open the enclosure multiple times a day when I’m working with it and the moisture would quickly require recharging. Also, since the box will be accessible for two printers sharing the volume (I might be able to isolate them, but it makes the working space more difficult) and there will be two doors it will be impossible to create it at the budget level I’m considering. Management of moisture, in this case, is a more achievable engineering solution than perfect moisture isolation.
