Calculating Water Vapor Pressure at 160 F: Understanding Fluid Mechanics

In summary, when a fluid flows through a sharp bend, low pressure may develop in localized regions of the bend. To prevent cavitation, the minimum vapor absolute pressure in psi that can develop must be higher than the saturation pressure of water at 160°F. This can be found by referencing a thermodynamics text or table. When transporting water through a piping system, the lowest pressure must be higher than the saturation pressure to avoid vapor formation.
  • #1
physicsss
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When a fluid flows through a sharp bend, low pressure may develop in localized regions of the bend. Estimate the minimum vapor absolute pressure in psi that can develop without causing cavitation if the fluid is water at 160 F.

How does one calculate the vapor pressure of water when given a temperature? Thanks.
 
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  • #2
I can tell you from a handbook that the VP of water at 160 is 10.9 ft of water = 4.73 psi and at 212 it is 33.9 ft of water.
 
  • #3
I must say that I can't remember ever having to calculate the vapor pressure of something, unless it was a mixture. I'd have to say that I would simply look it up in a table and be done with it.

I am sure there are some thermosynamics texts that would show some correlations.
 
  • #4
physicsss said:
When a fluid flows through a sharp bend, low pressure may develop in localized regions of the bend. Estimate the minimum vapor absolute pressure in psi that can develop without causing cavitation if the fluid is water at 160 F.
How does one calculate the vapor pressure of water when given a temperature? Thanks.
As Fred mentioned, check a thermodynamics text. The only way one can have vapor with a liquid of the same compound is if the mixture is a saturation conditions. So what one would look for is the saturation pressure of water at 160°F.

Ideally water is transported as a compressed liquid, but there the pressure drops along a pipe by friction and when changing direction (momentum) in a fitting, e.g. an 'L'. For a piping system to transport liquid the lowest pressure is obviously at the end, and if the fluid is to remain a liquid, the lowest pressure must be greater than the saturation pressure. This assumes that there is not heat input into the pipe or fluid transport system.
 

Related to Calculating Water Vapor Pressure at 160 F: Understanding Fluid Mechanics

1. How is water vapor pressure calculated at 160°F?

The water vapor pressure at 160°F can be calculated using the Antoine equation, which relates temperature and vapor pressure using experimental constants specific to the substance. The equation is P = 10A - (B / T + C), where P is the vapor pressure in mmHg, T is the temperature in °C, and A, B, and C are the Antoine coefficients for water at 160°F.

2. What is the significance of understanding fluid mechanics in calculating water vapor pressure?

Fluid mechanics is the study of how fluids behave under different conditions, and it is essential in understanding how water vapor pressure is affected by factors such as temperature and pressure. Understanding fluid mechanics allows scientists to accurately predict and calculate water vapor pressure at a specific temperature like 160°F.

3. How does temperature affect water vapor pressure?

Temperature has a direct impact on water vapor pressure. As temperature increases, so does the energy and movement of water molecules, causing more of them to escape into the air as vapor. This results in a higher vapor pressure. On the other hand, lower temperatures lead to lower vapor pressure as fewer water molecules are able to escape into the air.

4. What are some real-world applications of calculating water vapor pressure at 160°F?

Calculating water vapor pressure at 160°F is important in various industries such as meteorology, agriculture, and food and beverage production. It is also crucial in the design and operation of systems that involve water, such as boilers, distillation columns, and refrigeration units.

5. Can water vapor pressure be measured directly at 160°F?

No, water vapor pressure cannot be measured directly at a specific temperature like 160°F. It can only be calculated using the Antoine equation or other empirical methods. However, it can be indirectly measured by using a hygrometer, which measures the relative humidity in the air. The higher the relative humidity, the higher the water vapor pressure at that temperature.

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