Help me design a Vacuum Drying system

[kunalv]

Hello all,

I've been entrusted a project of developing a Vacuum Drying System for my company. This system will be used for instant drying of automotive parts after washing. Needless to say the parts will be wet and at an elevated temperature (approx 50 degree C). The requirement is to dry the parts in less than 30 seconds.

How do I go about this? What will be the type of vacuum pump required? And what are the other parts of a Vacuum Drying system?

The parts loaded in the machine shall be sealed in a chamber (size approx 300mm x 300mm x 300mm) with a Pneumatic cylinder applying force from the top.

For reference - https://grabcad.com/library/vacuum-drying-machine-1

Any help will be appreciated. Thanks

Thread moved to DIY

 

[russ_watters]

This has the feel of an undergraduate senior/internship design project. Otherwise it is an awfully odd/specific/expensive(!) thing to be coming to an internet forum for help on! Can you give us more background on you, the project and its constraints? Just about everything you gave us must have a "why" behind it.

I'm an HVAC and I guess you could say process engineer in the pharma industry. Companies come to me for help designing and implementing ...parts... washers. But out of the gate they always have an existing system, relationships with vendors, ideas about what they need and why, etc. It's a rigorous, professional process, and it must be to justify spending hundreds of thousands or millions of dollars and ensure you are spending it effectively.

 

[berkeman]

This system will be used for instant drying of automotive parts after washing. Needless to say the parts will be wet and at an elevated temperature (approx 50 degree C). The requirement is to dry the parts in less than 30 seconds.

@russ_watters is much better qualified than I am to help you with this project, but to me it seems a poor fit to use vacuum drying for the application you have outlined.

If you want to dry parts very quickly, I would think that a high velocity hot/dry air knife approach would work much better. There's a reason that air knifes are used at car wash businesses as the last step in the car wash process... (well, plus a vacuum would kill the car occupants, but ignoring that inconvenient aspect...)

 

[russ_watters]

@russ_watters is much better qualified than I am to help you with this project, but to me it seems a poor fit to use vacuum drying for the application you have outlined.

If you want to dry parts very quickly, I would think that a high velocity hot/dry air knife approach would work much better.

I've carved out a little niche for this in my company, but mostly by luck of assignment. Drying is fairly simple and any generic mechanical engineer should be able to figure this stuff out and help design a machine. It's just the needs could be highly specific...

Drying in air is just convection and evaporation. To dry something faster, just use more, hotter air, like you said - it was my first thought as well. I don't associate a vacuum chamber with "fast". But if what you are drying is light, fragile, heat sensitive, porous, hydroscopic, wet with something besides water, etc., there might be a reason hotter and more air won't work. I can't think of a reason that would apply to "car parts", but it's probably in one of those "why"s, I asked for.

 

[anorlunda]

Drying in air is just convection and evaporation.

Isn't there a 3rd factor; water drops falling off by gravity or by high velocity air, without evaporation? Or is that part of convection?

 

[russ_watters]

Isn't there a 3rd factor; water drops falling off by gravity or by high velocity air, without evaporation? Or is that part of convection?

I'd say you're right that that's an additional process/factor. I don't want to start a quibble about definitions; mechanically removing liquid water isn't strictly "drying", but certainly part of what can be done to remove water from an object!

 

[trurle]

Hello all,

I've been entrusted a project of developing a Vacuum Drying System for my company. This system will be used for instant drying of automotive parts after washing. Needless to say the parts will be wet and at an elevated temperature (approx 50 degree C). The requirement is to dry the parts in less than 30 seconds.

How do I go about this? What will be the type of vacuum pump required? And what are the other parts of a Vacuum Drying system?

The parts loaded in the machine shall be sealed in a chamber (size approx 300mm x 300mm x 300mm) with a Pneumatic cylinder applying force from the top.

For reference - https://grabcad.com/library/vacuum-drying-machine-1

Any help will be appreciated. Thanks

Thread moved to DIY

Basically, for fastest possible drying without making over-engineering, you need pump inlet pressure about half of water vapour pressure at 50C. It mean ~6kPa pump. The main problem is actually heater, not the pump - the vaporization of 0.1mm layer of water absorb ~220 kJ of heat from each square meter, and to deliver it in 30 second you likely need infrared heater about 7 kW/m2. Also, you need to ensure water vapour flow of at least ~4000 liters/minute per every square meter of part to keep 6kPa pressure during drying (plus if you take into account time to bring pressure to 6 kPa). I think this cover the pump specs.

 

[jrmichler]

Search Minton vacuum dryer for information on using vacuum to dry paper in paper mills. Vacuum drying of paper was done in the 1920's, but various practical realities made the process not economical. One link: https://www.tandfonline.com/doi/abs/10.1080/07373938508916270.

Finding better ways to dry paper is huge in the paper industry. The paper mill where I once worked evaporated over 200,000 gallons of water per day as part of the papermaking process.