Peltier Filament Dryer (WIP)

Current Status

This project is very much a work in progress. Nothing is quite ready for printing yet but I've solved all the big issues I could think of. I'm at a stage where feedback (especially from people who actually understand airflow and thermodynamics and stuff) would be extremely valuable. Don't hesitate to reach out to me if any of this sounds interesting!

History

It all started with the delusion that I could easily turn an old cooling box into the most power efficient filament dryer ever - and it would be cheaper than an ordinary dryer! Truly, the naivety of my past self never ceases to amaze me. So, I bought a Giostyle cooling box so ugly the internet refuses to acknowledge its very existence, enthusiastically freed the poor components from their hideous prison and started aimlessly spinning around the Fusion viewport. A few months later, here we are with a concept that may or may not work and a project that may or may not be easy to adapt to other cooling boxes or just raw off the shelf components.

Theory

A Brief Explanation of Peltier Elements

Why the fridge would you put a cooling element in a filament dryer? Well, I'm no physicist, but I know that every cooling element is also a heating element. In fact, a Peltier element heats way more than it cools. This is because it essentially moves heat from the cold side to the hot side and generates a bunch of extra heat doing so. So, when you plug your cooling box into your car, not only will each watt it draws heat the interior of your car by a watt, each watt removed from your drinks will be added as well, making the hot summer day all the more enjoyable.

The Main Idea

Imagine putting a Peltier element with the hot side inside the filament dryer and the cold side on the outside. In theory the heating would be more than 100% efficient, that is, each watt of electrical energy would heat the inside air by more than one watt. Now, filament dryers need to let out some air in order to actually dry anything. By placing the exhaust such that the air needs to flow through the cold side heatsink, we should be able to steal (at least some of) the exhaust heat back into the system while getting rid of the humid air.

Here's an ugly illustration of the airflow and the main electronics:

The purple airflow is ambient air pulled in through a hole behind the inlet/outlet door. The more you open this door, the more of the ambient air will be replaced by the humid air from the inside (red), while more of the ambient air flows into to the heater. All the ambient air first flows across the power adapter in order to steal some of its heat.

Electronics

Here's my current idea of how the electronics will work, although I haven't coded anything yet.

• ESP32 with Humidity/Temperature Sensor - Turns Peltier on and off, controls inlet/outlet door, maybe fans as well, all to achieve desired temp/humidity.

• Peltier - Heating.

• SG90 - Servo to open/close inlet/outlet door.

• Main Fan - Circulates air through the dryer.

• Front Fans - Pull air (ambient and exhaust) through the cold heatsink.

• W1209 (Optional) - A thermostat running independently of the ESP, providing a quick temperature display on the box itself and a failsafe against overheating. (To be honest, the main reason it's there is that I bought it early on, thinking it could run the show all on its own. Maybe a simple display connected to the ESP would be preferable?)

• Power Adapter - 12V, 5A, heating the intake air a bit.

• Buck Converter - For the ESP.

Printing and Assembly

Don't.

FAQ (Fictitiously Asked Questions)

• How many spools does it fit?  - Default parameters are for two typical 1kg spools (or smaller).

• What's the max temp? - I'm hoping for at least 70°C but I think it'll be able to get way hotter.

• Can I use my old cooling box for this? - As long as you can make the heatsinks fit.

• Which dimensions can I change in Fusion? - All the fun ones! (Theoretically.)

• Release date? - Your guess is pretty much as good as mine.

• Which filament(s) do I need to print this? - I'm thinking mainly ABS and a little TPU, maybe PETG for some parts.

• Will it cool my workshop? - Not really. All the heat will eventually find its way out because thermodynamics sucks.

License

I will switch to a way nicer one later on but I wanna keep it restrictive in early development.

Special Thanks

pontpont