Friction Heating Water (again)

Connect a reciprocating shaft to a piston that runs inside a cylinder such that the piston speed and compression result in an exhaust temperature of roughly 500*F. The run the exhaust through a heat exchanger located inside the water tank. Insulate the tank, seal it and install a safety valve to prevent steam build up. It will be slow to heat but once heated it should be fairly easy to maintain a relatively high temperature flow from the tank.

Similar to what I was going to suggest. If maximum efficiency in heating from a mechanical power source is what is needed, try driving a heat pump. That way you will get at least 3 times the input energy into the water. The 2 times extra coming from atmospheric heat. There are plenty of electric heat pump hot water systems, which first have to convert to mechanical energy, so it works.

yep - good thinking...would low rpm present a problem?

That would depend on compressor design, but it is worth thinking about. As an aside the heatpump unit we installed a couple of years ago yields 3.25 kw for 1 kw input, the latest versions are said to yield around 4kw / kw.

machine holes in the tank 180 degrees apart (so that you can slide a pipe through), machine a weld prep onto the holes in the tank(.093 land with a .093 flat that goes into a radius will work well), fit it, then weld it. ***Let the pipe extend out a few inches from these weld preps so that you can machine another welp prep on both ends of the pipe. Then when you are ready, you can weld you exhaust to these weld preps for the final connection.

Seem to ba a great many gung-ho can-do people out there who cut metal before they think. Work is work is work, it doesn't really matter how you put the work into the tank as long the criteria is cost and transfer or coupling efficiency between you wind mill and the tank. It would be very easy to find that stuff outside the tank was absorbing the energy, that's why push bikes still have what appears to be such a crude and simple drive train. Once you get that shaft turning inside the tank, youv'e won! Anything that puts a brake on it will do, but or overall efficiency it is necessary to match the torque/speed characteristics of the work wasting machine to the windmill under varying wind speeds. Just off the top of my head it seems to me that could be something that looks a bit like the windmill, but smaller.

HI!

I'm in the planning stage of this very project and searching for info.

hit on this site.....I have to agree with Andrew: Basically I think that

simple will be the most efficient way to go. Having worked with wind

power in the past I am well aware that having a speed variable paddle

system would be the ideal solution as the drive power will increase to

the square of the wind speed and the "heater" would act as a regulator

for the machine.

drive power will increase to the square of the wind speed and the "heater" would act as a regulator for the machine.

Actually the power goes up with the cube of wind speed. The force on the airfoils (which translates to torque) goes up with the square. So if you double the windspeed, the blades move twice as fast, with four times the force -- thus 8 times the power.

And as you say, water is a great regulator, because the same effect occurs.

I should think the best way to use mechanical motion to heat a liquid will depend on the speed of rotation available as input. If it is very slow then a positive displacement pump forcing the liquid through small diameter pipes as suggested may be best. But if speed is higher a fluid coupling of the sort used on automatic gear automobiles with the output locked will be better. In fact such dynamometers for testing engines or motors exist.

Thanks for the responses...The rotation speed would be slow and the torque quite high - so the pressure pump idea seems to have merit.
This is based on pressurising a small amount of fluid at a time to quite high temperatures, then releasing that back into the tank, where it would be averaged out across the body of fluid. I can see intuitively in that case that the pressure would force the temperature up markedly on each small volume of fluid as it undergoes compression.
However would simply stirring the whole body of fluid (while preventing it all from rotating within the tank) pass the same amount of energy to the fluid? It seems counter-intuitive that stirring alone could heat water to useful temperatures, but the energy must be going somewhere...

Stirring would heat the fluid. But to get enough torque one needs high speed. The drag on the paddles is proportional to the square of the speed. And as you have mentioned there must be a provision to avoid spinning the whole mass of liquid in synch with the paddles.

When the nuclear plants were being built, to test the turbines, the feedwater pumps were ran against closed valve until the water was heated enough to produce enough steam to run the turbine for a few minutes. My vote is a high pressure pump with no outlet.

Pump does not necessarily need to be high pressure. There have been a few instances of centrifugal pumps exploding due to steam pressure when operating in "no-flow" conditions. This is why NFPA stipulates that fire pumps be equipped with pressure relief valves. The trick for generating steam directly from mechanical energy with would be to have more mechanical input than the thermal losses that would radiate off of the machine used. Somewhat easy with a several HP motor driven pump, but more difficult if uses "hand" power.

Interestingly enough, this very concept is the theme of next years ASME Student design competition. The idea is to build a human-powered still that would allow potable water to be obtained from contaminated water in an emergency. Check out the link (1).

Links: (1) http://www.asme.org/Communities/Students/2007_Desi gn_Problem.cfm.

i had to build a student propelled water heater for physics and i found that the metal on metal worked fairly well as long as you could supply some grit. I had welded a bike on a frame and attached a tube that held 750 mL of water by sprokets and chains. On the outside of the tube was another tube that gave a little bit of room between eachother. It didnt heat the water at all like that so i added some sand and tried it again. That worked really well but i would run out of sand. So, i then wellded a funnel to the outer tube that would hold the sand and allow the sand to fall in as other sand left the area. This greatly helped in heating the water. I heated 700 mL about 15 degrees in 5 minutes so that works really well.

Jordan

First post. Hello everyone.

If I were wanting to maximize friction heating of water through rotational means I would first consider vertical counter rotating concentric cylinders. Actually if you used truncated cones you could adjust the gap separation and thus effect a measure of regulation.

Heated water would enter from below and rise out the top.

Would you want to adjust the gap automatically with one of those old fashioned centripetal regulators? IDK just another idea to throw out there.

Any physicists out there have any idea how to calculate the in/out variables of such a system? Example: 2X 10cm high cylinders,diameter 9.5cm and 10.5cm, gap of 1mm between them,and a rotational speed of 100rpm. What quantity of heat would be generated?

Here is an off the wall idea. Would using a spinning magnetic field heat the water?

I am very interested in this topic. I want to use off-the-shelf techology as much as possible.

I am using several gas filled dampers which are directly immersed in a sleeve that is filled with fluid. The dampers are connected to a rotary driver that will rotate at high speed with a high amount of torque. The repeated compressions of the gas filled cylinders should heat up nicely .

the sleeve (with the dampers ) is connected via some one-way valves to a larger fluid tank - so simple convection creates the necessary pumping action.

I haven't determined if there is a decided advantage to using gas filled cylinders or fluid filled cylinders other than the gas filled cylinders don't leak fluid if they rupture or break.