What Diameter is Needed for the Tube in this Thermodynamics Problem?

In summary, the task is to determine the diameter of a horizontal tube elevated at 20m above sea level, through which oil with a density of 850 kg/m^3 is flowing at a velocity of 20 m/s. The rate of mechanical energy for the oil is 60000 J/s. The equation used is dE/dt = \frac{ρv∏D2}{4} * (\frac{P}{ρ} + \frac{202}{2} + 9.81 * 20) = 60,000, and the question is whether the P in the equation should be taken as gage or absolute pressure. However, it is noted that this distinction will not affect the final result.
  • #1
Jay9313
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0
ρ

Homework Statement


Oil with a density of 850 kg/m^3 is flowing at a velocity of 20 m/s at the atmospheric pressure in a horizontal tube elevated at 20m above the sea level. Please determine the diameter of the tube if the rate of mechanical energy for oil is 60000 J/s


Homework Equations





The Attempt at a Solution


dE/dt = [itex]\frac{ρv∏D2}{4}[/itex] * ([itex]\frac{P}{ρ}[/itex] + [itex]\frac{202}{2}[/itex] + 9.81 * 20) = 60,000

Now, my question is, P/ρ. I was told that it is at atmospheric pressure, but the pressure I use for that equation, is it absolute or gage?


EDIT: It's not coming out properly, I just need to know if the P in P/ρ is gage or absolute or should it matter? I did it both ways and got a diameter difference of about 20mm
 
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  • #2
it won't make any difference on gage or absolute
 
Last edited:

FAQ: What Diameter is Needed for the Tube in this Thermodynamics Problem?

What is thermodynamics?

Thermodynamics is a branch of physics that deals with the relationship between heat and other forms of energy.

How does energy play a role in thermodynamics?

Energy is a fundamental concept in thermodynamics as it is the driving force for all physical and chemical processes. It can exist in various forms, such as heat, light, and mechanical work.

What are the laws of thermodynamics?

The four laws of thermodynamics are: 1) The law of conservation of energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. 2) The second law, which states that the total entropy (disorder) of a closed system will never decrease over time. 3) The third law, which states that the entropy of a perfect crystal at absolute zero temperature is zero. 4) The zeroth law, which states that if two systems are in thermal equilibrium with a third system, then they are also in thermal equilibrium with each other.

What is the difference between heat and work in thermodynamics?

In thermodynamics, heat refers to the transfer of thermal energy between two systems, while work refers to the transfer of mechanical energy. Heat is a form of energy that flows from a higher temperature to a lower temperature, while work is the product of a force acting over a distance.

How is thermodynamics used in everyday life?

Thermodynamics has many practical applications in our daily lives, such as in the design and operation of engines, refrigerators, and air conditioners. It also plays a crucial role in fields such as chemistry, biology, and environmental science.

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