James Joule's heat apparatus is one of the most under-appreciated experiments in science. It's just a paddle wheel in a bucket of water. By demonstrating that the mechanical work done on the water raises its temperature, Joule basically invented the idea of Conservation of Energy.
In tribute to this great moment of science, mitxela's crack team of product designers have invented a mechanical kettle. No, don't worry, there are no paddle wheels involved (that sure would be some paddlin')!
Joule's Kettle makes use of the same technology as the latest waterjet cutters. There are two nozzles, aimed directly at each other. When the flow is turned on, the cold water streams shoot out at terrific speed, collide with each other, and through the magic of Joule heating, hot water lands in your mug.
[Back of envelope: 75C increase would require a pressure of ~46000psi, which is well within the range of high-end waterjet cutters!]-- mitxela, Jun 29 2014 Freeze water with the blow of a hammer http://blog.modernm...eve_it_or_not_0.jpgbottom left [mitxela, Jun 30 2014] Tallboy http://en.m.wikiped...wiki/Tallboy_(bomb)Designed by Sir Barnes Wallis. [8th of 7, Jun 30 2014] Hedgerow http://en.wikipedia...row_(weapon)#DesignOne way of clearing the Germans off the sunbeds ... [8th of 7, Jun 30 2014] Butterfly Bomb http://en.m.wikiped...wiki/Butterfly_BombNot pretty at all. [8th of 7, Jul 04 2014] How about an alternate version.
The MaxCo. Gravity Kettle is essentially a copper cannon-ball with a hole in it. Cold water is placed in the hole, which is then sealed with a lovingly crafted copper kettle stopper*.
To use, simply take the Gravity Kettle to the highest available point, and release. Retrieve the kettle, remove the copper kettle stopper, and pour.
*I defy anyone to conceive a phrase more euphonious than "copper kettle stopper".-- MaxwellBuchanan, Jun 29 2014 but... you already did with "lovingly crafted copper kettle stopper", you just needed a "proper" at the start.
Why doesn't the word proper have two p's anyway?It needs another p.-- 2 fries shy of a happy meal, Jun 29 2014 Far less fun solution than a "Waterjet kettle set" or a "Proper copper kettle stopper": hydraulic piston pump and pressure relief valve. Pump a few times in a continuous circuit, until piston broke.-- Ling, Jun 29 2014 //Why doesn't the word proper have two p's anyway? It needs another p.//
I spell it with two "p" 's and get autocorrected every time. "Proper" should be pronounced "proWper" or "proUGHper" in my mind.
The problem with this idea is people don't have an intrinsic, instinctive understanding of the energy in a water jet stream. The falling kettle ball is maybe a bit better. Maybe a robotic sledgehammer wielding arm flogging crap out of the kettle ball woudl also work.
Copper would work better than perhaps you appreciate - if made out of something particularly rigid or elastic, little energy would be absorbed, whereas something quite maleable like copper will absorb energy from impacts rather well. Lead might be even better, but y'know - lead. Maybe Gold would be the best material?-- Custardguts, Jun 29 2014 The issue with the MaxCo. Gravity Kettle, and indeed almost every type of mechanical kettle, is the unexpectedly large heat capacity of water. You would need to drop it from about 100,000 feet. Flogging it repeatedly could work.
On the subject of sledgehammers and water, it is reputedly possible to freeze water by hitting it, if you believe Ripley's Believe it or Not. I have not been able to find any other sources for this and might try it.-- mitxela, Jun 30 2014 //Copper would work better than perhaps you appreciate// That is why I chose copper. My first choice was lead, but I foresaw issues.
//You would need to drop it from about 100,000 feet// That sounds unlikely. Anything of a sensible size dropped in air will reach terminal velocity after a few thousand feet. We may, of course, need bigger gravity.
A quick calculation. Assume the kettle has terminal velocity of 250mph (that's a guess; about twice as fast as a skydiver in a spread, a bit less fast than a skydiver in a no-lift dive). That's roughly 100m/s.
The mass of the kettle is irrelevant (more mass = more kinetic energy; but equally more heat capacity) so, for simplicity, assume a mass of 1kg.
Hence, k.e. of kettle on impact = 5,000J.
Heat capacity of copper = 385J/°C/kg.
Hence, temperature rise (if landing on a very rigid surface) = 5000/385 = 13°C.
So, yes, a bigger gravity would help. Alternatively, make the kettle more streamlined. If you can increase its terminal velocity about 3- fold, it should be good enough.-- MaxwellBuchanan, Jun 30 2014 //Heat capacity of copper = 385J/°C/kg.
//Hence, temperature rise (if landing on a very rigid surface) = 5000/385 = 13°C.
Um, [Max], we're trying to warm the water not the copper.-- the porpoise, Jun 30 2014 The "Tallboy" bomb (q.v.; <link>) attained supersonic velocities from 22,000 ft.
At that rate of fall, skin heating becomes significant..
Max, you need an aerodynamically shaped package with a thin copper wall and a pressurised interior to maintain the shape. Plus a safety valve …-- 8th of 7, Jun 30 2014 I like the idea of a kettle consisting of a 1kg hollow projectile made of 18 carat gold, hurled aloft by a kitchen-roof-mounted trebuchet.-- pocmloc, Jun 30 2014 //Um, [Max], we're trying to warm the water not the copper// Yes, oh mammalian fishy one. However, the whole system will come to equilibrium fairly quickly. So, assuming that the mass of water is much less than the mass of the copper kettle, it's a fair approximation to use to heat capacity of copper in lieu of the combined heat capacities of the copper-plus-water.
Sheesh. You try and do the right thing and...
// thin copper wall and a pressurised interior// No, just no. The available kinetic energy depends on the total mass of the projectile (for any given velocity). The copper has an energy-hungry heat capacity, but also adds mass. Overall, you're better off with lots of copper and very little water.
Also, a thin-walled vessel full of water will *either* burst on impact or, if it doesn't, will behave elastically and not convert much of the kinetic energy to heat. You want something which deforms plastically on impact. Water is notoriously very much the exact opposite.
Do try to keep the batteries topped up, [8th].-- MaxwellBuchanan, Jun 30 2014 [Max], you're going from potential energy (a 500 m drop), to kinetic energy (100 m/s), to heating the kettle by deformation, to heating the water by conduction. Efficiency losses are going to clobber you.
Here's a suggestion. Put some mixing baffles on the inside of your cannon ball, make the damn thing out of an insulating material (concrete), and add vanes to the outside. That way when you drop it from half a kilometer's altitude, it spins round and round as it falls and the baffles slosh the water around directly heating it. Roll it down a hill even.-- the porpoise, Jun 30 2014 //Efficiency losses are going to clobber you.// Yes, and yet in a more actual way no. I'm only going from kinetic energy to heat (as I mentioned above, terminal velocities will apply, meaning that I've already accepted loss of some of the PE). And if you drop a big lump of copper onto a huge block of, say, granite, most of its KE is going to wind up as heat in the copper (and thence the water).
If there's one thing that energy is good at doing efficiently, it's turning into heat. Hence entropy.-- MaxwellBuchanan, Jun 30 2014 // So, assuming that the mass of water is much less than the mass of the copper kettle, it's a fair approximation to use to heat capacity of copper in lieu of the combined heat capacities of the copper-plus-water.
No, no, no!
The specific heat capacity of water is more than 10 times that of copper. If 250 grams of water is needed for a cup of tea, your 1 kg mass's average specific heat capacity is 1,333 J/°C/kg, which makes your 13 degrees more like 3.-- the porpoise, Jun 30 2014 1 kg of water requires 4.2 x 1000 x 90 = 378 kJ to raise it from 10 C to 100 C.
Kinetic energy = 0.5 x m x v^2
Allowing for 50% conversion efficiency, and the mass of the container is twice that of the water, it follows that
756,000 = 0.5 x 3000 x v^2
v = SQRT(756,000/1500) = 22.5 m/sec = 81 km/h
We postulate a titanium cylinder containing a perforated piston. A thin shaft attached to the piston protrudes from the front. The rear of the cylinder has a tube tail and fins for stability. The assembly resembles a Hedgerow round. <link>
At launch, the container accelerates under gravity. On contacting the ground, the shaft forces the piston from front to rear, and the water is forced through the piston under very high pressure, heating it.
Since v = SQRT ( 2 x g x distance) and v is known to be 22 m/s, the dstance the projectile must fall (neglecting air resistance*) is given by d = (22 ^2) / 20 = 24.2 metres which is not excesive; many existing structures are significantly taller than this.
We suggest an immediate practical research programme into boiling water for tea by throwing heavy metal objects with big sharp** spikes on the front off the top of the Eiffel Tower.
*air resistance can be neglected, since it is clear that Resistance Is Futile.
**There's no technical requirement for the spikes to be sharp, but the idea of skewering a tourist through the cranium with a three-kilo giant titanium dart would add immeasurably to the enjoyment.-- 8th of 7, Jun 30 2014 //The assembly resembles a Hedgerow round.//
I think, if you reflect for a moment, that you'll find that a Demoiselle round with a Franklin sabot would better suit your porpoise.-- MaxwellBuchanan, Jun 30 2014 //24m ...90C// This is not bad, since the PE of 3kg at 24m height is around 600J, isn't it?-- Ling, Jun 30 2014 //a Demoiselle round with a Franklin sabot//
Is that, as my daughters would say, a thing, [MaxwellBuchanan]?-- pertinax, Jul 04 2014 I'm sure [8th] is familiar with 1930's artillery and can confirm this.-- MaxwellBuchanan, Jul 04 2014 For the same reason that throttle plates don't just melt....-- WcW, Jul 04 2014 That's an excellent answer, [WcW]. Has anyone got the question?-- MaxwellBuchanan, Jul 04 2014 // [8th] … can confirm this //
"It is not the policy of Her Majesty's Government to either confirm or deny …"
But for those interested in evolution, the metamorphosis of the line into the "Sprengbombe Dickwandig 2kg" or "SD2" <link> is an instructive study.-- 8th of 7, Jul 04 2014 //Sprengbombe Dickwandig//
You see, [8th], that's why the krauts never really made it big-time. They probably spent a fortune developing their butterfly bomb, and then called it a "Sprengbombe Dickwandig" - the name doesn't even make sense.-- MaxwellBuchanan, Jul 04 2014 random, halfbakery