hope someone finds this interesting :-)
What I'm trying to accomplish is:
Having a heating wire getting in contact with an airstream in a ventilation system as much as possible (200mm metal duct). The goal is to 1) heat the air 2) Dry the air 3) Sterilize as much as possible before the air comes in contact with a HEPA filtration system further downline in the ventilation system.
I've built a heating element that does the job somewhat, used it for ½ a year now with success.
The heating element is turned on 10 mins. a time (automatically shuts off) 2x daily, with use of 120v AC that can be regulated up to 240v or down to 0. Right now the design is a simply twisted wire-coil (gauge 28) placed in a ZigZag manner in the 200mm duct using non-cunducting/heat resistant mica sheet with holes to hold the wire. Please see the picture.
Is there any way you could imagine a design that could get more contact between the wire and the air? I have 30 feet of fresh wire and plenty of mica sheet. The air hitting the wires is prefiltered by 2x HEPA vacuum filters, but they do not meet EN2118 filter standards, and we need very clean air. I cannot tell you how hot the wire needs to be, other than it has to be glowing(burning micro particles as it comes in contact with them) with a giving airspeed that also is variating a lot. I monitor the heat to max. hit 70Degree C, measured inside the duct, just 5 cm and 5 cm to the back from the heating wires.
For safety, I have a 120 degree C temp. fuse, nothing that can burn near the installation, mesh wire in front and after the element, I can monitor the temperature inside and further downline in the system. A main emergency power cutt off and a fire extinguisher and fire alarm installed (detects smoke). Automatically shuts off after 10mins runs. Any other safety suggestions are welcome!
Please answer as simple as possible to eliminate misunderstandings, this project came to live due to pretty servire health issues, all help is very appreciated.