Heating Water Through Friction

lol
very nice suggestions!
However... I'm not really willing to wreck my bicycle just yet :p

So everyone wants us to do vanes, I guess we'll stick a few in there with the non-newtonian liquid. Hmm, I'll sketch out a diagram just to illustrate what we want right now...

The efficiency of vanes is generally limited by the smoother of the two opposing surfaces.

Please don't get carried away with the concept of a non-Newtonian fluid. If fluid mechanics and the relationship between momentum transfer and heat transfer is of interest it can be studied during an undergraduate course in Chemical Engineering at a higher education institution, probably in the second year of study.

For the time being, just think about simple energy balances:

Energy in = energy out + energy accumulated (which manifests itself as a rise in temperature). "Energy is Conserved".

To raise the temperature of the system, take steps to maximise the difference between the energy going into the system and the energy leaving it as radiated, convected and conducted heat. There are simple, practical ways to do this. What about some home loft insulation from the local home improvement store, perhaps?

Is there any scope for modifying an old washing machine ? OK, that's probably OTT and slightly tongue in cheek. Can you provide a ball-park figure on how big the thing is going to be. Skateboard bearings sound good. It may be pointing out the obvious, but bearings and drive can be mounted on the can sides/rim.Have you got a local scrap-yard you can hunt around ? It might provide inspiration for components, and you can possibly get odds and ends for free. I'd be wary of insulation materials unless you know what they are, even glass fibre can be nasty stuff.

I wonder if anyone has investigated the rise in washing machine water temp. purely by agitation? Without the effect of external heating & chemical reaction from washing powder etc. Would be interesting on the spin cycle, you could be onto something there, wind powered of course.

RE: my own question / comment about you washing machine idea.

If you agitate the water too much would the cooling effect outweigh the heating effect? There must be a 'point of no return'; cooling rather than heating, especially in an unsealed system.

Let's see:

Leaks: I'd suggest keeping the bearings away from the liquid. For instance, the shaft could be mounted on two bearings, spaced apart on an overhanging support (a la food mixer), the several cans would be below, and have holes only in their tops, which could be crudely sealed and still leak little or nothing if the liquid level is kept below the tops.

Insulation: Treat fiberglass (the pink stuff) with care. I'm not convinced that the fiber fragments that make you itch after handling it might not have effects similar to asbestos fibers, which are carcinogenic if inhaled). Expanded polystyrene is excellent insulation and far too prevalent in landfills. If you took old packaging materials (blocks, "peanuts", etc.) and crumbled it up and enclosed it in cloth bags...

Calories: These come in big calories (Calories or kilocalories) and small calories (calories) The big ones are the amount of heat required to increase the temp of one kilo of water one degree. So if you start with a liter of water and raise its temp from 20C to 77C you will be (as you say) using 57 kilocalories. That's about half a candy bar's worth. Equivalent to 66 watt-hours, it is also about the energy a human could expend in about half an hour. A small (1 meter blades) windmill can produce on the order of 1000 watts, so could do this work in about 4 minutes.

A 5 gallon paint bucket would be a great outer can. These can easily be found used.

Prototype by Friday???!! You are clearly not suited for corporate life, in which you would simply have a meeting on Friday to determine when the best time to meet might be to discuss the feasibility of undertaking this project. Actually staffing the project, and subsequently accomplishing anything, would have to come much later in the process.

Please bring Powerpoints to the first meeting.

Ha, you think I would forget the powerpoints??

Hehe youre right about friday, duncan and I are kicking ourselves over being so naive about the deadline.

thanks for all your suggestions, this is some good stuff.

We're now looking into using a preexisting bike mechanism to turn the axle... See my lastest post for more information :)

Thanks again

Mel & Duncan

Hmm, a good suggestion, we'll keep it in mind :) The only thing is, we already have osmething of a design worked out, if we had more time we'd definetly try experimenting with this idea!

Our entire project (prototype, experimentation, write up, research, display) is due on March 4th so we're a little screwed for time...

anyway,

Thanks a bunch for your input, hope to hear more from you soon.

Mel&Duncan

This is quite similar to a concept that i am using - which is to attach a rotary driver to several gas filled dampers that are directly immersed in a fluid filled sleeve that connects via one-way inlet and outlet valving to a much larger fluid filled reservoir - Converting from rotary to rectilinear motion causes the piston rods of the dampers to move in and out . The repeated compressions create heat very nicely.

Simple convection provides the mixing and pumping action - as the hot water in the sleeve rises through the outlet valve and cooler water moves into the sleeve through the inlet valve to replace it.

I am uncertain if there is any benefit to using fluid filled dampers instead of gas - other than not leaking fluid if they are broken or leak .

Hello again,

So I know we said we'd have the prototype done by Friday, boy what a lie that was. However, new developments are underway. We (unsuccessfully) tested the non-newtonian liquid idea: it worked to a point, but when too much pressure was applied it turned into a solid and jammed the mechanism.

Now we're using steel wool as the friction generating medium, and it works quite well, the only problem being an elastic does not have enough force to drive the axle. We only need to do a few modifications to our prototype to have it working ( at the moment it works... in theory) and it should be ready to go. We only need to have some sort of driving mechanism to replace the elastic, with enough force to turn the can. We're thinking of using a bicycle, what would be good ways to attach the axle to the axle of a bike wheel or gear? Any suggestions?

Thats all for now. Thanks.

Melanie & Duncan

<....tested the non-newtonian liquid idea: it worked to a point, but when too much pressure was applied it turned into a solid and jammed the mechanism...>

That's the problem of using non-Newtonian fluids! With this particular one the viscosity went up drastically with increasing shear rate. Such a fluid would work well in some form of turbine clutch mechanism (information for later study).

Tomato ketchup is non-Newtonian, as is wallpaper paste....

Don't forget glorious CUSTARD , it tates better than ketchup or bentonite slurry !

hi Melanie & Duncan

I'd put the bike upside down balanced on the seat and handlebars. Hold your can against the side of the back tyre (you'll need the can held by a bearing of some sort - eg superglued / bolted to your skateboard wheel). Also check out the type of bearing used for a "lazy susan" ( - do a google image search for "lazy susan bearing"). They sell them pretty cheaply at hardware stores - perfect for your purposes.

The rubber bike wheel will grab on the side of the can - no need for any kind of joining mechanism - you will get the can up to some very high rpm by cranking the pedals around with your hands and the bike wheel will act as a flywheel to give you some breathing space.

How you use your fast spinning can to heat the water is up to you!

Yea, I think your right, I put forward this idea early on (#64) and thought it would come up again as soon as practical experiments started. You could also put thick rubber bands on the outside of the can for more grip to increase the efficiency of the drive. I envisaged the bike on a stand with the back wheel off the ground so one could actually pedal. The gears are a big advantage that you will not easily get with other drive systems.

M & D, if you feel there is a future for your device then a easily available drive is a bonus and an area you do not have to spend too much time on, i.e. spend you time on the central function - the water heating part.

Any way, good luck, nice to see it is on its way and you are discovering things, that is the most enjoyable part of engineering, applying your knowledge & self education on the way. I spent several years in R&D and found it incredibly satisfying.

PS: For insulation readily available, easy to work with and good properties - polystyrene, chips or solid cut to shape, from packaging gets my vote.

Thank you very much for your input! I think we may go back to trying the non-newtonian liquid idea. What we've realized is that there wasn't enough force in the elastic to properly turn the can once the liquid solidified, but now that we are using a bicycle to power the mechanism there may be enough.

I think part of the reason we haven't really had any affinity towards the cornstarch solution idea is that it makes one massive non-newtonian mess! But I guess it may be worth it for sanitary water.

Duncan and I will get back to you soon (this goes for everyone) with maybe a video and some test results.

Ciao,
Melanie

Dear Melanie,

I have simply listened all through what I consider a quite remarkable exchange initiated by your and Duncans dynamic 's approach and may I add , inspiring thirst for technical knowledge.

Rather than inhibit your creative approach I will wait to see the result . Given that you did say that your aim was directed towards the third world 's needs, my later contribution may be towards items that, through my experience in remote and very primitive areas , may contribute towards reaching your goals in such areas of the world.

Best regards

Labor Omnia Vincit.

So we've completed construction and lots of testing on the device with no luck.

We are owing much of this to mechanical insufficiencies (the can is leaking, the axle is turning when it shouldn't be, the outer casing is moving and not gripping the bike wheel properly, etc.)

This isn't the end though, Duncan and I won't give up, but we think that we might take a break from this now. Boy engineering sure is exhausting!

We actually have some more questions for future reference (we will take this up again in the summer, I'm sure):

• We have tried using many different materials as the heat generating mediums. These materials range from a non-newtonian liquid solution to twine to steel wool and a stainless steel scouring brush. All of these have been yet unsucessful, and we're sure that if the mechanisms were working entirely as they should, they would probably work, but we definetly want to optimize this aspect of the project. What other materials do you suggest? These materials should have the following properties:
• Fast rate of heat gain and loss
• Strong, durable, won't wreck other apparatus
• Cheap, easily available
• Must be pliable enough to stick in between two cans

Interestingly enough, there's some sort of Can Depot near where duncan and I live. We're going to have to check it out some day! From some rate of heat loss equation we found, we know that the can should have the following properties:

- Thin (but durable)
- Made of a material with good thermal conductivity (e.g. copper, but I suppose we're looking for a cheaper alternative)
- Large surface area

And the outside or insulated can should be the opposite.

When I get a chance I post a picture of our failure mechanism.

Thanks a bunch everyone, we'll start a new post in the summer if we ever get around to making the project work (and work brilliantly at that!)

Melanie (&Duncan)

I'll be checking back periodically for updates, it seems the only emails I get now are from this forum :p

There is so much here that is ambiguous in its meaning that I think your best way forward would be to talk the detail through with your physics teacher (if that fails, a local company or university physics department). Don't be discouraged, however - this is how we should learn, and worse is to be expected at this stage of your knowledge/experience.

A couple of examples:
given that you aren't generating a great deal of heat (power) in the first instance, it is hard to see why you consider specially high thermal conductivity of the cans to be important - are you trying to conduct the heat along the surface of the can instead of through the walls?
you give no indication as to why you want a large surface area for the can. From the aspect of heat loss to the environment, you would want as small an area as possible - so it would appear that the outer can wants to be as small as possible while containing the amount of water you wish to heat.

<......mechanical insufficiencies (the can is leaking, the axle is turning when it shouldn't be, the outer casing is moving and not gripping the bike wheel properly.......engineering sure is exhausting...many different materials as the heat generating mediums......

• Fast rate of heat gain and loss
• Strong, durable, won't wreck other apparatus
• Cheap, easily available
• Must be pliable enough to stick in between two cans

.....>

This is all good, valuable, hands-on engineering practice. Well done!

Bear in mind that the energy balance is the factor that over-sees everything else:

• Input = output + accumulation

And accumulation can be expressed as the rise in temperature within the fluids in the can. If energy can't get in and it does get out, it won't accumulate to give the temperature rise required.

<.....won't give up......>

That's the spirit!

Hi Melanie,

I'm going to try once more to convince you to forget about friction, non Newtonian fluids and the like. This is going to sound rude so I'll apologise in advance and hope you take it as its meant.

There are loads of people on this forum who think they can circumvent the second law of thermodynamics, but, you are the first I've come across who does not believe the first. If you just stir up the water where do you think the energy goes if it doesn't end up as heat?

What you need to do is work out a system of paddles which present an increasing reverse force to the source of the energy (you don't want a setup in which the water just spins faster and faster in the can, although this would work just as well if you could introduce lossless gears between the source and the paddles).

As I said before try to keep it simple.

Hello Melanie.

I just came across this thread and I think it's wonderful for someone your age has such an interest and knowledge of physics. I'm still not sure I believe all this...

However I'll give it a chance and try to leave some general ideas. I haven't read most of the answers so some of my own ideas may not be new.

The water heating problem is mostly a Heat transfer one, and one of the most efficient methods is using Heat Pumps, like air conditioning machines, and a heat exchanger. These machines may easily pump 3 to 4 units of thermal energy for every unit of mechanical energy. They don't convert mechanical to thermal energy, they just transport heat... However, the maximum temperature achieved may not be enough (maybe you will get 40ºC)

You may also consider a solar panel, if there is enough solar radiation where you live, to add heat up to 70ºC. Another heat exchanger will be needed.

A simple Heat exchanger may be a pipe going back and forth inside the water can.

Finally, consider the insulation used and the time it will take to pasteurize the water: no matter how good the insulation, you will always lose some heat to the environment along time. This means more Thermal Power needed, as Power is the Energy transfer rate along time. Keep also in mind that the net Thermal Power (which will actually raise the temperature) is the added power minus the Power loss to the surrounding environment (Pnet=Pin - Pout). This is why the Joule experiment isn't very good for temperature raising in water...

Now somen numbers:

to raise one kg of water (1 litre) from 10 to 70 ºC takes 250 000 Joules

(250kJ=4,18kJ/kg/ºC x 1kg x 60ºC)

If it takes 5 minutes, the Power needed will be

250/(5 min x 60sec/min) = 250/300 = 0,935 kW net Power

It's like a small toaster working for 5 minutes.

If the heating takes longer, more heat will be lost, so more total power will be needed to comensate for the larger heat losses.

Hope to be of any help, especially one year after the last reply.

Hope you're still out there thinking of Great Questions and finding Great Answers.

Bye

Hi Melanie,

I like the sound of your mind.

It is good to be able to think outside of the box, you will make a great scientist/inventor. Always consider the absurd, and combine exsisting ideas to create a new one.

I digress, the tv program EQUINOX had a program about water. And a chap in america was working on a water heater that uses friction caused by a solid alloy drum rotating within a cylinder. The inner surface of the cylinder was ribbed an the outer face of th drum also. The drum had a hollow central core where the water flowed in, this then made its way to the outside of the drum via holes drilled from the center to the outside delivering the water to the 'friction area' by centrifugal force. There it is beaten ad escapes at the end of the cylinder sleeve heated.

Vary the speed of the drum to achieve different temperatures.

The small motor that span the drum used less power than was produced so he was laughed at by the scientific community, however he had the last laugh when he sighned a multimillion dollar deal to heat a hotel chain water system.

I have always wanted to try to build one, but never had the time.

Good luck in your life.

15 eh! You lucky lady.

Simon

oneshotfilms@hotmail.co.uk

He may have signed a multimillion dollar deal and he may have invented a great device to heat water efficiently - in both cases more power to him. What he didn't do was create a machine that produced more energy out than it took energy in.

That's exactly like saying he made a bucket that you can tip 1 litre of water into and then, with no other inputs, tip two litres out.

So if he's laughing, it's at anyone who believed that he really did it :)