I noticed that food gets dry in the refrigerator, so I would like to use this effect to dry some objects otherwise difficult to dry (more specifically: nylon filament for 3D printers, which would requires many hours of heating in an oven).
How can I calculate the humidity inside the refrigerator?
My refrigerator can be set down to -18°C (255 K) so I think the air very close to the cooling pipes reaches, during active operation of the compressor, maybe -20°C (253 K). My assumption is that, at that temperature, air is completely saturated and every excess gets converted into frost/ice.
Since I set the temperature to -12°C (261 K), and looking at the psychrometric chart at http://www.uigi.com/UIGI_SI.PDF, my idea is to move horizontally to the right starting from -20°C, 100% rel. humidity. It looks like air at the end is about 50% rel. humid air -12°C.
Is that reasonable? I would say that at 50% humidity the food should not get that much dry, since it's about the humidity of the external atmosphere (maybe it's 60% outside), so maybe my assumption about -20°C of the cooling element and air 100% saturated around it, or the way I calculated the rel. humidity, is wrong.