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Thalita Luna
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According to the Joule experiment, work can increase the temperature of a liquid. Is it possible to boil water simply by stirring it? How much energy would be required?
Practically, too, by cavitation.Drakkith said:Theoretically, yes. But in reality you'd lose enough energy through heat transfer to the environment that it would probably never boil without a very, very specific setup.
Why not do an experiment with a bucket of water, a stirrer and a thermometer?Thalita Luna said:According to the Joule experiment, work can increase the temperature of a liquid. Is it possible to boil water simply by stirring it? How much energy would be required?
It might depend on the starting temperature of the water. Can you say why?Thalita Luna said:Is it possible to boil water simply by stirring it? How much energy would be required?
And atmospheric pressure. It depends on the entire setup of the experiment. @PeroK's bucket is probably doomed to fail, but if you have a vacuum chamber or a submarine, or a small volume with a really fast stirrer ...berkeman said:It might depend on the starting temperature of the water. Can you say why?
YES.Thalita Luna said:Is it possible to boil water simply by stirring it?
You should try doing some calculations for yourself…. make some sensible assumptions about how much power is going into turning the paddles and how much heat escapes from the water…. @Baluncore has given you an example of an extreme case.Thalita Luna said:According to the Joule experiment, work can increase the temperature of a liquid. Is it possible to boil water simply by stirring it? How much energy would be required?
Apparently not!fresh_42 said:@PeroK's bucket is probably doomed to fail, ...
I associated a setup with a real bucket and a painter's stirrer by your description, something like that:PeroK said:
Huh. I wouldn't have thought it would be practical. Looks like I was wrong.Baluncore said:YES.
It happens in centrifugal pumps when you fail to open the outlet valve. The water that remains in the pump does not carry the "inefficiency heat" away, so it increases in temperature, until it boils. The lower steam density then reduces the centrifugal pressure, and the motor power consumption. The pump maintains the steam and boiling water, until the outlet valve is opened.
It is so simple a mistake, that you are unlikely to meet anyone prepared to admit that they have done it. We learn by other's mistakes. The others remain anonymous, but go by the nickname "tea's up".Drakkith said:Huh. I wouldn't have thought it would be practical. Looks like I was wrong.
Drakkith said:Huh. I wouldn't have thought it would be practical. Looks like I was wrong.
Well. it kind of isn't. The effect is nonzero, but remember that the latent heat of vaporization is 540 cal/g - if it weren't for the phase transition, you'd need to heat your water to 640 C )almost 1200 F). It takes a huge amount of energy to boil water.Drakkith said:I wouldn't have thought it would be practical.
-My arm is tired!Vanadium 50 said:Sure, It can be done. I've done it myself. I've done it myself when it was an undesired side effect, in fact. But there's a reason that most people who want steam buy a boiler and not a giant spoon.
Maxwell's Demon House?DrClaude said:I want to brew my coffee!
I analyzed the video from PeroK's post #9 and determined that the effective power input to the water from the blender was about 530 watts. I then googled and discovered that top athletes arms have a maximum continuous output of 30 watts. I decided that Drakkith was correct stating that it was theoretically possible but practically improbable. Can you imagine 18 Arnold Schwarzenegger sized arms trying to stir up 16 ounces of water? That would be quite the contraption to do something like that. I suppose we could give each of them one ounce containers with arm powered blenders specifically designed for the task.DrClaude said:-My arm is tired!
-Shut up and continue stirring. I want to brew my coffee!
7 minutes? You know you're supposed to keep the door closed, right?OmCheeto said:Another interesting thing was that his blender heated the water about as fast as my microwave. It takes my microwave 7 minutes to bring 16 ounces of tap water to a rolling boil.
Legs would be more effective, via a stationary bicycle or a Peloton or similar device. A fit recreational bicycle tourist like I used to be can probably put out 75-100 W for hours. A Google search seems to indicate that a highly fit racer can do 400 W in a sprint.OmCheeto said:I analyzed the video from PeroK's post #9 and determined that the effective power input to the water from the blender was about 530 watts. I then googled and discovered that top athletes arms have a maximum continuous output of 30 watts.
Up to 600W for 30 seconds in the lead in team time trials.jtbell said:Legs would be more effective, via a stationary bicycle or a Peloton or similar device. A fit recreational bicycle tourist like I used to be can probably put out 75-100 W for hours. A Google search seems to indicate that a highly fit racer can do 400 W in a sprint.
And it's actually a thing:jtbell said:Legs would be more effective, via a stationary bicycle or a Peloton or similar device. A fit recreational bicycle tourist like I used to be can probably put out 75-100 W for hours. A Google search seems to indicate that a highly fit racer can do 400 W in a sprint.
I did the experiment on my microwave yesterday and found that it's output is about 400 watts. It's nameplate output is 650 watts. So I googled and found that several sources said that microwave ovens should be replaced every 7 to 10 years due to degradation of the magnetron. I had never heard such a thing.russ_watters said:7 minutes? You know you're supposed to keep the door closed, right?
You spend a lot of time at the neighbor's house apparently...PeroK said:I must confess I've never owned a microwave or a blender.
OmCheeto said:My microwave is 46 years old, which means it's losing about 5½ watts per year. If it continues at the same rate it with be 2036 when it reaches half of its rated value. Perhaps I'll take some load off it by heating my water in my blender, as it's only 34 years old.
I used a power meter ...JT Smith said:I wonder if there's some not-too-complicated way to run it without the controller board?