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Help Me With This!

02/21/2017 11:53 PM

I wished to fabricate a compact desalination kit using induction based distillation unit at around 2 litre capacity. Can anyone suggest any quick method for either condensing or evaporating 1litre of water ?

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#1

Re: Help me with this!

02/22/2017 12:10 AM
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#2
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Re: Help me with this!

02/22/2017 12:15 AM

Thank you for ur answer. But is there a quicker method for condensation? Here the hi-tech device that you mentioned takes nearly an hour for desalinating 890ml of water

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#3
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Re: Help me with this!

02/22/2017 12:27 AM

Yes but it is hand operated...no juice required...If you're boiling the water, it will condense as fast as you can boil it off...but energy is required....You want more water faster get a bigger pot and bigger fire and a bigger still....What is the application for this device?

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#7
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Re: Help me with this!

02/22/2017 9:14 AM

depends how much available energy you want to put into it.

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#8
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Re: Help me with this!

02/22/2017 9:19 AM

Two units operating in parallel would produce the same quantity of water in half the time...

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#5
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Re: Help me with this!

02/22/2017 7:53 AM

Please don't drink distilled water. It doesn't do the body any good and it tastes bloody awful. Always re-harden after desalinating.

Aim for [Ca++] >= 60mg/l.

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#4

Re: Help me with this!

02/22/2017 3:25 AM

Your question, Can anyone suggest any quick method for either condensing or evaporating 1litre of water?

Condensation is about ΔT, the RH of the ambient air, and condensation surface geometry. Since you can't change the internal geometry of an existing product, we will not consider surface geometry as a variable; work is already underway to contribute to calculations of surface of the internal surface area or the condensation surface.

That means that we need to know what the condensation surface area is, please.

Evaporation works pretty much the opposite. In an evaporation scheme, the higher rates are by the greater the difference in the temperature and RH of the ambient air and the temperature and RH of what you are evaporating, and the surface area of the condensation surface.

If the surface areas of the condensation surface and the evaporation surface are the same, great! (we can use the same number, heh.)

You should be able to take it from here now.

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#6

Re: Help me with this!

02/22/2017 7:55 AM

Are you looking to design a kit for personal use? My first thought was of all the refugees around the Mediterranean. Small -- and inexpensive -- desalination devices would be a boon to this population.

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#16
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Re: Help me with this!

02/23/2017 9:58 AM

That is a crazy thought to have. The refugees get bottled water for free, by the trolley load. They have no need of a desalination system.

Even in Africa they have no need as they all know where to obtain water at the wells and any piped water to cities, they just set up a few taps along the pipe line and help themselves. And oddly, I have never seen any indigenous person die from a lack of water. They actually know where to find water in the bush. It is only westerners who have no idea.

A table spoon of bleach in 25litrs of water, leave to stand for 1 hour, and you can drink water and not get ill.

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#17
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Re: Help me with this!

02/23/2017 10:33 AM

And oddly, I have never seen any indigenous person die from a lack of water.

A number of issues here

  1. It isn't because of a lack of water, but a lack of supply of potable water.
  2. getting your drinking water while living in the bush is one thing, but concentrate the population in an area, and the resources like potable water are not there.

It is only westerners who have no idea.

Are you saying the westerners should not meddle? because that is also becoming a growing consensus among westerners.

As far as adding bleach,... your over simplifying it by just disinfecting water, not purifying it. There needs to be more prepping and this is for temporary emergency usage.

Cloudy water should be filtered before boiling. Filter cloudy water using coffee filters, paper towels, cheesecloth or a cotton plug in a funnel. Bring the water to a rolling boil for at least one full minute. Add two drops of household bleach per gallon to maintain water quality while in storage.

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#9

Re: Help Me With This!

02/22/2017 12:21 PM

Most desalination techniques heat the water in bulk when, really, evaporation takes place only at the surface. So just heat the surface. That's what these guys are doing, and they're getting excellent results:

Abstract

Passive solar vapor generation represents a promising and environmentally benign method of water purification/desalination. However, conventional solar steam generation techniques usually rely on costly and cumbersome optical concentration systems and have relatively low efficiency due to bulk heating of the entire liquid volume. Here, an efficient strategy using extremely low-cost materials, i.e., carbon black (powder), hydrophilic porous paper, and expanded polystyrene foam is reported. Due to the excellent thermal insulation between the surface liquid and the bulk volume of the water and the suppressed radiative and convective losses from the absorber surface to the adjacent heated vapor, a record thermal efficiency of ≈88% is obtained under 1 sun without concentration, corresponding to the evaporation rate of 1.28 kg (m2 h)−1. When scaled up to a 100 cm2 array in a portable solar water still system and placed in an outdoor environment, the freshwater generation rate is 2.4 times of that of a leading commercial product. By simultaneously addressing both the need for high-efficiency operation as well as production cost limitations, this system can provide an approach for individuals to purify water for personal needs, which is particularly suitable for undeveloped regions with limited/no access to electricity.

Full paper here:

http://onlinelibrary.wiley.com/doi/10.1002/gch2.201600003/full

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#10
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Re: Help Me With This!

02/22/2017 1:01 PM

evaporation takes place only at the surface.

When I designed a 'debrining' system to increase the surface area, I ran it through a cyclone under vacuum to and bring the flash point down to around 115º F.

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#11

Re: Help Me With This!

02/22/2017 1:23 PM

You can run the distillation tubing through cold water to facilitate rapid cooling and condensation in a more compact package...and use a relatively small amount of water in a larger 5 gallon vessel, just be careful not to burn the pot...However for induction heating a magnetic pot is necessary....

...or buy it ready to go....this is a SS pot....

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#12

Re: Help Me With This!

02/22/2017 9:47 PM

Thank you All. I wished to do it as my college project.

I thought of making it portable as well as economical. Can anyone explain me what kind of battery to use for such an induction heater..?

And also, let me know if there is any better method for the same. I would be happy if there is any method that would desalinate 1l of water in less than 20 or 30minutes

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#13
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Re: Help Me With This!

02/23/2017 12:30 AM

That's the fun thing about a college project.

You get to do all of the research and development on your own,,,

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#15
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Re: Help Me With This!

02/23/2017 8:13 AM

And the best thing is, if your do a mistake, do it in college.

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#14
In reply to #12

Re: Help Me With This!

02/23/2017 4:36 AM

Just use sunshine, a large shallow tray and utilise surface evaporation. Simple, no other resoutses required, economical, and transportable.

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#20
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Re: Help Me With This!

02/23/2017 12:48 PM

Very good IDEA for a college project. Here is an IDEA for a "battery operated desalination gizmo" for you.

Take a number of THERMOELECTRIC modules, . . . mount these together with heat sinks on both sides, . . . apply DC power from battery, . . . one side will become HOT - while the other side will become COLD.

Dip the hot heatsink in the salt water, . . . this will cause the water to boil-evaporate, . . . the steam travelling to the cold heatsink will condense.

This arrangement is VERY ENERGY EFFICIENT as it uses the same energy to heat as well as cool the required elements.

What you need to do is design a clever arrangement to separate the salt water from the distilled water and for the steam to travel and condense on the cold heatsink.

You will have to figure out how much power (how many thermoelectric modules) you will need to distill one liter in 30 minutes.

Have a look at . . . http://cdn.lairdtech.com/home/brandworld/files/ETS-BRO-Thermoelectric%20Modules.pdf

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#21
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Re: Help Me With This!

02/24/2017 4:08 AM

Thank you.And the cost estimation for your idea would be?

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#22
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Re: Help Me With This!

02/24/2017 9:59 AM

High time for YOU to do something useful on this project, . . . go and figure it out. You will not get a passing mark just by skimming information from the internet.

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#18

Re: Help Me With This!

02/23/2017 10:41 AM

It sounds like what you want to do is add a counterflow regenerative heat exchanger to preheat the feed water.

Simply stated, one side of the heat exchanger draws the feedwater and preheats it to nearly boiling temperature at a chamber of some sort. The steam enters the other side of the heat exchanger near the feedwater discharge, flows back parallel to the feedwater flow, but in the opposite direction and condenses back to water. If the exchanger is moderately efficient, the discharge water will leave at nearly the temperature of the feed water entering the heat exchanger.

Your demand for energy to maintain the boiling temperature in the reservoir will be to make up for heat loss to the surrounding environment.

There is a variety of heat exchanger referred to as microchannel that is fairly effective in getting high heat transfer in minimum space. You would need to make provision for breakdown of the unit for periodic cleaning if you actually get boiling in the heat exchanger.

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#19
In reply to #18

Re: Help Me With This!

02/23/2017 10:46 AM

Depending on the situation, having a regenerative heat exchanger in the process starts getting costly... and with lower flows you'd need a plate heat exchanger to do it more efficiently. Unless you can justify doing so.

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#23

Re: Help Me With This!

02/24/2017 8:31 PM

All I wished to do is to shrink the size of the kit to a 2l capacity. But the use of thermoelectric modules or regenerators might not be suitable for that although they seem to be efficient. and this is my mini project only. So I am not willing to spend much. But still I am putting my effort to the core.

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