Water under pressure and temperature effects

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Discussion Overview

The discussion revolves around the effects of applying high pressure to water, specifically how this pressure influences temperature changes and the relationship between work done on the water and heat transfer to the surroundings. Participants explore theoretical implications and practical considerations related to compressibility and energy storage in water under pressure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the temperature of water will continually rise to match the surroundings after heat is given away, and whether the water could end up colder than the surrounding temperature due to heat loss.
  • Another participant suggests that the temperature rise should correlate with the amount of work done to compress the water, noting that the volume change per pressure change is minimal, leading to a small temperature increase.
  • A third participant agrees that there should be little change in temperature but proposes that significant work is needed for even slight compression, and much of this energy may be recoverable upon release, indicating that the energy is stored rather than converted to heat.
  • A fourth participant introduces the concept of bulk modulus, arguing that water is more compressible than commonly perceived and that calculations will show the work done is relatively small.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between work done, temperature change, and heat transfer, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

Some assumptions about the compressibility of water and the nature of energy transfer are not fully explored, and the discussion relies on specific definitions such as bulk modulus, which may not be universally understood among participants.

jamiek
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If you apply tremendous force to water and cause extremely high pressure, it should compress and the temperature should go up - but if the heat is given away to the surroundings, does the water temp continually go up to match the surroundings? does the water temp go down underneath the surrounding temp? I would think that initially the water would give off some heat, but does this mean the water is colder since it has given off heat? And if it's colder, won't it just have to regain the heat again to match the surrounding temp. Seems confusing.
 
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I would think that the temperature rise would be related to the amount of work that one would have to put into the water to compress it. Since the change in volume of water per change in pressure is not very much there would be little work performed and the temperature rise would be very little.
 
256bits said:
I would think that the temperature rise would be related to the amount of work that one would have to put into the water to compress it. Since the change in volume of water per change in pressure is not very much there would be little work performed and the temperature rise would be very little.

I agree there should be very little change in temperature, but for a different reason. Given that large forces are needed to compress water, even a little compression may take significant work. But on release, I believe much of the energy would be recovered. If so, it means the work done was stored in the state of compression rather than as heat.
See e.g. http://www.criticalprocesses.com/Use%20of%20enthalpies%20to%20calculate%20energy%20needed.htm
 
If you are talking about extreme pressures, then water is more compressible than most folks think. If you are not familiar with the concept of a bulk modulus, go look it up. Think of it as a sort of poison ratio for a liquid, and you can use it in a similar manner as calculating strain energy. This is the energy you are talking about. Once you run the numbers, you will see that the amount of work done is relatively small.
 

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