Dynamics of water under pressure/velocity?

In summary, the conversation discusses the freezing point of water under pressure and velocity, specifically in relation to preventing pipes from freezing in a commercial building. The use of antifreeze and the potential effects on the building's chillers is also mentioned as a possible solution. There is also a mention of the Silver Spring metro station and the potential dangers of using velocity to prevent freezing. The use of antifreeze is suggested as the best solution and the relationship between pressure and freezing point is mentioned.
  • #1
HVACtech
2
0
Hello all, new member here. I am an operating engineer of a 10 story commercial office building in Silver Spring, Md. It's actually right across the street from the Discovery Channel Headquarters building, which is neat.

Anyway, I'm trying to understand the affects on the freezing point of water under pressure and velocity. Basically I try to keep my pipes from freezing by leaving the pumps on when the outside temps drop below 32*F. This keeps the water flowing under a pump pressure of approximately 25psig.
I've searched and found phase diagrams of pure water, but I have a hard time comprehending them.
Can someone help me understand this better? Thank you.
 
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  • #2
Pressure doesn't much matter. ASHRAE HOF2006 specifies flowrates to be maintained in the pipe with respect to ambient temperature. Why don't you go for antifreeze?
 
  • #3
You are right by the Silver Spring metro station, red line-to shady grove. :wink:
 
  • #4
cyrusabdollahi said:
You are right by the Silver Spring metro station, red line-to shady grove. :wink:

Yes indeed. 962 Wayne Ave to be exact.

Quark, some building systems are glycol based systems that won't freeze. Ours is not one of them. Plus, I don't think my centrifugal York chillers would react too well to having antifreeze run through them. I really don't know. If we have a leak somewhere in the building I'd prefer to have plain ol' water everywhere and not antifreeze or glycol.:wink:

Thanks guys. I just leave the boilers on overnight when it gets cold.
 
  • #5
Contact your nearest York service rep (or check York's technical info on their website) - I'd be shocked if your York chiller cared whether it had water or water/glycol running through it. The only real downside is the specific heat is lower so either you lose a little capacity or you have to increase your flow rates (odds are, your flow rates are too high anyway). Often, chiller literature will give multiple performance tables based on the working fluid.

To me, using velocity to prevent freezing seems very dangerous. Velocity isn't going to be consistent everywhere and all you need is a little ice forming in an eddy somewhere and before you know it your entire system is frozen solid.
 
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  • #6
i think antifreeze is the best solution. and besides i think freezing point varies with pressure and not with velocity, u can find formulas in physics books about it. the higher the pressure the lower the freezing pt.
 

1. What is the difference between pressure and velocity in water dynamics?

Pressure and velocity are two important factors in the study of water dynamics. Pressure refers to the force exerted by the water on its surroundings, while velocity is the speed at which the water is moving. In simple terms, pressure is a measure of the intensity of the force applied by water, while velocity is a measure of the speed of water.

2. How does pressure affect the behavior of water under different conditions?

Pressure plays a crucial role in determining the behavior of water under different conditions. As pressure increases, the density of water also increases, making it more difficult for the water molecules to move freely. This can lead to changes in the physical properties of water, such as boiling point, freezing point, and surface tension.

3. What is the relationship between water velocity and its ability to erode or transport sediment?

Water velocity is closely related to its ability to erode or transport sediment. Higher velocity means more energy and force, which allows water to pick up and move larger particles. However, if the velocity is too high, it can also lead to erosion and damage to the surrounding environment.

4. How does the shape and size of an object affect the pressure and velocity of water flowing around it?

The shape and size of an object can greatly impact the pressure and velocity of water flowing around it. As water flows around an object, it creates areas of high and low pressure, which can result in changes in the velocity of the water. The shape and size of an object can also affect the path of the water, creating turbulence and eddies that can further impact pressure and velocity.

5. How can understanding the dynamics of water under pressure/velocity be applied in real-world scenarios?

Understanding the dynamics of water under pressure/velocity is crucial in various real-world scenarios, such as designing dams and water turbines, predicting flood patterns, and developing efficient irrigation systems. It can also help in managing and mitigating natural disasters, such as hurricanes and tsunamis, which are caused by the powerful forces of water under high pressure and velocity.

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