Tagged Questions
3
votes
1answer
54 views
How can I understand a Vortex Tube and its efficiency?
A Vortex Tube takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. Apparently, it has been described as a Maxwell's Demon.
Both ...
1
vote
0answers
34 views
What temperatures can be reached in an air-to-air thermocompressor nozzle and why?
People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
2
votes
2answers
139 views
Hot Air Balloon and Buoyancy
This is a conceptual question in a solution I am trying to understand.
Problem statement:
I have a balloon with a volume of V $m^3$. The outside air temp is $K$ kelvin
and mass to lift is $m$ kg.
I ...
0
votes
1answer
145 views
Best way to move teaspoon to dissolve sugar in a cup of tea
I know that there is asked questions about something like cooling down cope of coffee..etc, but this one is little different.
My friend was watching TV program of English eating etiquette, and they ...
9
votes
1answer
332 views
Energy from man-made tornadoes
Peter Thiel just paid $300,000 to Canadian inventor Louis Michaud who is working to construct useful "man-made tornadoes" or "atmospheric vortex engines" which could be components of future power ...
3
votes
1answer
144 views
Rayleigh-Benard Convection
I found this nice paper about RB convection. However I am confused by what is going on page 6. In particular why we are suddenly using Helmholtz equation to find spatially periodic solutions. Aren't ...
6
votes
4answers
442 views
What equation of state is needed for liquid states?
I'm familiar with the ideal gas law $$PV=nRT$$ but I don't think it applies to liquids like water. If I'm wrong, please correct me! If I'm right, then what equation of state applies to liquids such ...
1
vote
2answers
205 views
Shock speed in air/vacuum shock tube
Some of you are probably aware of What If, xkcd's blog about interesting physics problems.
One episode, Glass Half Empty, concerns itself with what would happen if a glass of water is half water, ...
3
votes
1answer
311 views
Wind Turbine Impact
OK, I'm not sure this is not a silly question, but here goes.
I've often wondered what the impact is of wind turbines on the weather. My question is, since wind turbines transform wind energy into ...
1
vote
0answers
35 views
What is the fluid approximation for BCS action?
For a system with free fermion gas at finite density (i.e. free Dirac action),
we have an ideal fluid description with rho, p, n.
What is the fluid description for BCS action?
Suppose we have a box ...
1
vote
1answer
171 views
Why are turbines built differently when a change of entropy or temperature is involved?
We are talking about turbines for extraction of energy from a fluid.
Consider a typical wind turbine, or a francis turbin for water - we have one hub with on set of vanes that are driven by the ...
7
votes
1answer
618 views
Why is compressible flow near the choke point so efficient?
Imagine a steady state, one-dimensional, compressible flow in a horizontal pipe of constant cross sectional area. This flow can be isothermal, adiabatic (Fanno), or diabatic (Rayleigh). As an ...
4
votes
1answer
692 views
Why do steam bubbles increase in size as they rise?
In the following video (a customer's review of a glass kettle), we can observe water boiling: http://youtu.be/jByY5I7Xk7w?t=2m55s
As the kettle starts to boil at around 2:55, we can see large steam ...
1
vote
1answer
450 views
How does smoke move in the air and how can I direct it so it will go to a place I want it to go?
Let's assume a close room with 1-2 people who only one of them smoking cigarette.
What is the equation describe the smoking spreading? is it diffusion? what are the parameters is so?
Is there a ...
2
votes
1answer
88 views
How can I calculate the amount of bubbles needed to lift a submerged body?
Our teacher had us come up with our own thermodynamics experiments, so I put a glass of water inside a vacuum-capsule. Inside the glass of water I have placed a non-floating object, a small plastic ...
4
votes
0answers
211 views
What's the efficency of a steam jet pump?
Jet pumps or venturi pumps are often stated as having a "terribly low" efficiency, steam jet pumps specifically are usually describes as "only justifiable when there's an abundant steam supply anyway" ...
0
votes
0answers
123 views
what is the physics just at bubble formation.
ie do a couple of molecules with more energy bang out a volume in the liquid where molecular attraction is overcome and the energetic molecules can move at random?
where can I find out more about ...
1
vote
0answers
280 views
Do the properties of two streams flowing into an engine add together when they mix?
Let's say I have two stream supplys that have separate mass flow rates, enthalpies, and velocities that flow into an engine. Upstream of the engine's inlet, the two streams mix to form one stream that ...
2
votes
2answers
349 views
the form of a kettle
What is the best form for a kettle, that is, to have the water boil the fastest? I am particularly interested in the following case: for one given kettle (whose volume is constant) containing ...
2
votes
1answer
282 views
Coffee cooling in a cup
Will coffee in two differant size styrofoam cups in the same room conditions cool at the same rate? One cup is 8 oz. and the other would be 12 oz.
4
votes
3answers
417 views
What cools a drink?
When you stick ice in a drink, AFAICT (the last physics I took was in high school) two things cool the drink:The ice, being cooler than the drink, gets heat transferred to it from the drink (Newton's ...
