# Tag Info

1

You are way overthinking this. First, you can start with radiative cooling, but that's not the dominant process. At 65 C, in your workshop, convection cooling is the big dog. The total effect will depend on the shape and size of your container, how good a thermal insulator (or conductor, if you prefer) and even details like airflow. Without knowing these, ...

0

You can add Newton's law of cooling in to your model quite easily: So we've said that Newton's Law of cooling tells you that the rate of cooling or temperature change is proportional to the temperature difference. Since your volume is fixed you can just look at this in terms of energy. so your equation for heating power when the power is on is going to be ...

3

Deuterium reacts with low energy neutrons to form tritium, though the cross section is very low. Tritium beta decays to $^3$He with a half life of about 12 years, so the process results in very slow production of $^3$He. The trouble is that $^3$He also reacts with low energy neutrons, but it forms tritium and a free proton rather than $^4$He. So the ...

1

"typical" household freezers don't do minus 20. A premium dedicated freezer (no fridge part) might, but I don't think you want to buy one just for this. For a low-budget solution, get a styrofoam cooler, put your regular-temperature ice in it, and then add 2x mass dry ice. You will eventually get colder ice. Do cut a small drain hole in the bottom of the ...

0

Don't quite know what you mean by "water at -20 degrees", as I would expect ice at these temperatures. But anyways you can reach such temperatures with a cooling bath

1

Some domestic, commercially marketed deep freezers are able to reach that range of temperature. Here is one for example that advertises -20deg F, so almost -30 deg C. It really depends also on the amount of mass you want to lower the temperature to. Whatever device to be considered must provide outward heat flow to compete with whatever heat influx the ...

12

The boiling water is converting liquid water to gas. Unless this gas is continually removed by the pump, it quickly increases the pressure inside the vessel. This increased pressure will stop the boiling. Setting a lid on the jar gives it a one-way valve. Gas can still escape. If you instead put on a full seal so that gas cannot escape, then it will ...

0

In reviewing the answer supplied by troy, The explanation of his increased water pressure on the larger pipe is as follows: The pressure from the tank is based on the height of the tank. A tank on a 25' tower will supply at least 12.5 pounds per square inch. (we don't know the height of the surface of the water.) The 3/4 inch pipe has an area of .44 sq in. ...

0

The force that the seal has to keep water from escaping must have the same force as the balloon being pushed upwards at least, this will cause it to stop the balloon from going upwards and no motion will occur.

0

There is no answer for the total area of the slot. However we can calculate the width of the slot, and as you say this is done with the same method used in How to find out the maximum radius of a hole that can keep water stay in a container by water viscosity?. If we have a cylindrical meniscus then the pressure difference it produces is: $$\Delta P = ... 2 There is no limit to the length of your slot if it is narrow enough. The circumference of the slot determines the total force available to hold the liquid in place - so as long as the ratio of circumference divided by area is above a critical value, you can keep the water in. That ratio scales with radius for a circular hole - but once you allow elliptical / ... 1 From the question you've linked to, I assume you're asking what would happen if a dense and insanely huge water/ice body was to undergo strong gravitational collapse. Stars are made up of Plasma, and Plasma is extremely high energy stuff. The pressure energy density on the molecules during the gravitational collapse process is more than enough to rip ... 0 The effect of salt etc. on the heat capacity is probably negligible, and the question in the header may be misleading. Cooling down water in a beaker is usually driven by convection. Liquid on top of the solution in the beaker cools quickly, and then has a higher density than the hot liquid at the bottom. The cold liquid falls down, hot comes up, cools, ... 2 I tried this on my kitchen sink and it's true. A narrow stream almost separated into many dollops makes a loud resounding thudding, but a thick fast column of water is almost silent on the metal. The reason is that the narrow, weaker, less continuous stream allows the metal to vibrate. The thick, weighty, continuous stream deforms the metal and keeps it ... 1 When more of the drops are separated, as in the first case, the resulting sound is a bunch of little drops pattering against the metal surface, which is relatively loud. When the flow of water is increased, more drops stick together and you have more of a solid stream rather than a series of drops. Since there isn't a separation between subsequent drops, ... 3 Spilling supercooled liquid on your skin would actually be less painful than spilling a similar liquid that wasn't supercooled. This is because when a supercooled liquid freezes it gets warmer due to the latent heat of crystallisation released by the liquid to solid transition. So suppose we had some supercooled water and some other hypothetical fluid at ... 3 The rapidity of heat loss from black body radiation depends only on the temperature of the body and the difference to the temperature of the environment according to the Stefan-Boltzmann law. which describes the power radiated. This will happen in any case for any body immersed (first version of question) in a supercooled liquid if its temperature is higher ... 0 Fourier number is a measure of heat penetration depth. Together with Biot number it characterizes transient aspect of heat conduction. Characteristic time here is the time it takes for temperature difference between the object and the surrounding to drop to 1 \over e (37%) of its value. If initial temperature is T_0, and surrounding temperature is ... -2 It' simple. If the lip profile curls down-ward at the point of pour (or even down and back) the poured liquid cannot dribble, no matter how slowly you pour, because the liquid would have to travel up-wards after leaving the spout in order to do so, and even the most sticky liquid (imagine golden syrup) won't do that. Certain manufacturers of plastic electric ... 2 Azad provides a link to one of the many empirical models that can predict pressure drop, but if you are seriously planning and investing in plumbing a new home - take caution. A general comment to begin is that tubing or pipe in general will create a resistance to the flow of fluid going through the pipe for any given pressure, so the bigger the pipe, the ... 1 I'd say option 1. Doubling the diameter would reduce the pressure loss in that pipe by 32 times in a constant flow rate scenario. Overall pressure loss will also decrease but not that much. Surface area increases 4 times then if the flow rate is constant the flow velocity will decrease by 4 times according to continuity equation. Then we have this ... 0 If you raise 1.2 liter of water (mass 1.2 kg) by 55 cm (h) in 3 minutes (t) against a gravitational acceleration g of 9.81 m/s2, the average power needed is$$\frac{m\cdot g\cdot h}{t} = \frac{1.2\cdot 9.81 \cdot 0.55}{180} < 40 \mathrm{\;mW}. But if the depth of your water is 30 cm, then on average the water needs to be raised just 40 cm, not 55 ...

0

My educated guess is that a large block of ice, delivered to space somehow, would last quite a while. If we assume it is in Earth orbit, the side facing the sun would sublimate (go directly from solid to gas) and dissipate. The rate of sublimination would depend on the insolation (power per unit area), which is about 400 $W/m^2$ and the absorption ...

2

In my first year at secondary school we got to ignite hydrogen in a glass flask, then test the droplets that formed on the wall of the flask to show they were water. That was at age 11. Actually, in this day and age of safety legislation I'm not sure whether pupils are still encouraged to make explosions. Anyhow, making water from hydrogen and air is dead ...

0

H2O at 0°C is Ice. There is a considerable gap between Ice and Water. After 0°C if you increase the temperature by 0.1°C, that is at 273.1K the equlibrium state occures. This state is called the 'Triple point of water'. This is where water, ice and surprisingly water vapour. After this state if you increase the temp by any amount H20 becomes water. Hope this ...

1

At the transition point between two phases, both states are thermodynamically (meta)stable. The actual composition, however, is kinetically determined and will depend on the history of how you got to 0$^\circ$C and how long you wait. For instance, if pure water (no impurities and in a container that does not induce heterogeneous nucleation) is cooled slowly ...

0

I'm assuming 1 atm pressure. It will be a mix of solid and liquid. It takes a certain amount of thermal energy to change the state of water. Until that amount of energy is reached, it will be a mixture of solid and liquid, both at 0°C. With more energy, a higher portion will be water. Once all of it is liquid, any further energy addition will raise its ...

1

You need more information to tell the state. Actually, exactly two more values, the pressure and the volume. With these three you have a fixed point in the phase diagram: But even if you have a fixed point in the diagram, you can still reach a two-phase sitation. Then e.g. water and ice exists at the same time in fitting fractions of the total mass. What ...

1

As water freezes, zones of ice and zones of water form. On the scale of a bubble, the interface might well be a plane. As the water cools, dissolved gasses form bubbles. A bubble can be engulfed as the interface advances past it. As ice freezes more gas comes out of solution. The bubble grows. The part that has been engulfed cannot expand. So the bubble ...

1

If I see this correctly the vertical bubbles seem to be at the top. My guess is that the bubbles were at the top and only surface tension kept the air from being released, when the temperature cooled this surface tension could have been disturbed and the air may have started to escape; this would cause the water to close in from the sides of the bubble but ...

2

Okay, I have a few guesses on what you are trying to say. I've always wondered how much force water exerted through surface tension. By maximum I mean the theoretical pulling/attracting power. If you mean to ask about a water-water interaction similar to that of a magnet-magnet interaction, then surface tension of water has very little to do with ...

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