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from the washin'-dishes-and-baby-clothes dept.
Washing Dishes with Superheated Steam More Effective, Earth-Friendly:
Conventional dishwashers often do not kill all the harmful microorganisms left on plates, bowls, and cutlery. They also require long cycle times that use large quantities of electricity, and the soap pumped in and out is released into water sources, polluting the environment.
Superheated steam dishwashers could provide a more effective, environmentally friendly solution. In Physics of Fluids, by AIP Publishing, researchers from the Technical University of Dortmund and the Technical University of Munich simulated such a dishwasher, finding that it killed 99% of bacteria on a plate in just 25 seconds.
[...] "Steam comes out of the nozzle at a very high velocity. We can see shocks, and the turbulent flow that is created has eddies and vortices," said author Natalie Germann, of the Technical University of Dortmund. "We also include heat transfer, which shows how the heat changes in the simulation box and the condensation on the solid surfaces."
[...] The superheated steam dishwasher would initially cost more but would pay off in the long run with savings on water, electricity, and detergent. It would be ideal for use in restaurants, hotels, and hospitals, which must meet high hygienic standards.
"We confirmed that the dishwasher application using superheated steam is promising," said Germann. "This is the first work combining fluid dynamics and heat transfer with phase change and bacterial inactivation. It thus lays the foundation for future computational research and further technical work."
Journal Reference:
L. Abu-Farah and N. Germann. Simulations of thermal phase changes and bacterial inactivation in a superheated steam dishwasher [open], Phys Fluids, 2022. DOI: 10.1063/5.0090418
(Score: 2) by Entropy on Wednesday September 07 2022, @03:45PM (10 children)
"Super" heated steam/water actually takes a ton of energy to create because as far as materials goes water has a very high specific heat. It's true one may use less soap, but less energy is pretty doubtful. Also with all the talk of global warming how is converting more energy into more heat a good thing?
(Score: 2) by FatPhil on Wednesday September 07 2022, @03:56PM (7 children)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by JoeMerchant on Wednesday September 07 2022, @07:50PM (6 children)
I think superheated steam may melt your perspex.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 3, Interesting) by FatPhil on Wednesday September 07 2022, @09:32PM (5 children)
The thought-experiment is unconvincing. Where's Mythbusters?
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Interesting) by JoeMerchant on Wednesday September 07 2022, @09:45PM (4 children)
You bring up a cool point: pressure. So, yeah, make your generic perspex into 4" lexan (as used in bulletproof applications" and then raise the dishwasher pressure to 10atm while we're at it, raising the boiling point of water to ~175C... no plastic dishes please, but... anything that lives through a steam bath at that temperature should be cultured and studied... just need to hold the dishes in the heat soak long enough for all their bio-contaminatable surfaces to come up to temp, reminds me vaguely of flash pasteurization.
Hell, just barely boiling water at 10atm pressure would do the heat transfer faster than gaseous phase steam, even if the steam were much hotter, and "jet spray" action of the water should mechanically clean the dishes better than steam. Just need a pressure-rated vessel to contain the process in, and as mentioned elsewhere a heat-recovery process so all that lovely energy isn't wasted down the drain.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 5, Funny) by deimtee on Thursday September 08 2022, @05:48AM (3 children)
That gives me a great idea for cleaning the dishes. Soak at boiling point at 10 atmospheres pressure, then just drop one side off the steam chamber. Explosive decompression should blow any food scraps right off the dishes.
No problem is insoluble, but at Ksp = 2.943×10−25 Mercury Sulphide comes close.
(Score: 3, Interesting) by JoeMerchant on Thursday September 08 2022, @10:27AM
Only slightly more seriously: commercial kitchen, two dish chambers, dirty dishes loaded and sealed with air at STP. Recently cleaned chamber 90% filled with water at 175C 150psig. Just open a valve between the chambers and you get spray action on the dirty dishes as the chambers equalize pressure, and the areas not under scalding water are hit with superheated steam as the 175C water flash boils with the pressure drop to ~75 psig. Finish the pumping / filtering / heating process to bring the newly filled chamber up to pressure, and any water remaining on the washed dishes should flash off due to the heat of the dishes themselves. Move the washed dishes aside to cool, and repeat.
Soap / surfactant input requirements should be minimal, and mostly recycled. As pointed out earlier, solar power makes cheap hot water, so just have enough dishes to save the washing until 10am to 2pm, and move to a cloudless area for best efficiency.
10 atm may be overkill, further study is warranted.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by acid andy on Tuesday September 13 2022, @01:25AM (1 child)
This is why i love SoylentNews. Thank you!
Master of the science of the art of the science of art.
(Score: 2) by deimtee on Tuesday September 13 2022, @10:35AM
If you try it out, let me know how well it works.
No problem is insoluble, but at Ksp = 2.943×10−25 Mercury Sulphide comes close.
(Score: 3, Interesting) by JoeMerchant on Wednesday September 07 2022, @07:50PM (1 child)
If the process is big enough, you can insulate the washing chamber and run heat exchangers to pre-heat incoming water with waste steam/water on the way out. It's not 100% recovery, but it's significant.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 1) by anubi on Thursday September 08 2022, @11:59AM
Heat exchangers often provide quite significant energy savings. I often rue my not plumbing my bathroom shower to recover the heat from the drain water by a pipe-in-pipe exchanger to preheat my incoming "cold" water line.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]