Pressure drops and Temperature changes

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SUMMARY

The discussion focuses on the temperature changes experienced by a fluid undergoing a pressure drop from 3500 psi to atmospheric pressure at an upstream temperature of 120°C. The fluids in question are either methanol or oil. It is established that when throttling an incompressible fluid, the temperature will rise due to the conversion of pressure energy to internal energy, maintaining total enthalpy. The relationship between internal energy and temperature is defined by the equation u = cT, where c represents specific heat.

PREREQUISITES
  • Understanding of thermodynamics, specifically the principles of pressure and temperature relationships.
  • Familiarity with the concept of enthalpy in fluid dynamics.
  • Knowledge of specific heat capacity for fluids like methanol and oil.
  • Experience with fluid mechanics, particularly the behavior of incompressible fluids under pressure changes.
NEXT STEPS
  • Research the thermodynamic properties of methanol and oil, focusing on specific heat capacities.
  • Study the principles of enthalpy and its application in fluid dynamics.
  • Learn about the differences between throttling, turbines, and nozzles in fluid systems.
  • Explore pressure vs. temperature charts for various fluids to make meaningful comparisons.
USEFUL FOR

This discussion is beneficial for chemical engineers, fluid dynamics specialists, and anyone involved in thermodynamic analysis of fluids under pressure changes.

hpcycling2010
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Hello,

I have a fluid that is going through a pressure drop (3500psi down to atmospheric) and its around 120C at the upstream temp.
The fluid can be either methanol or oil.
What kind of temperature change will I see? I am assuming it will cool down, but by how much?

Help! and Thanks ahead of time!
 
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I have no idea. However, I know that pressure vs. temperature charts for water are quite common and that you might be able to make some meaningful comparisons between them. I would assume that water is harder to heat up than both methanol or oil.
 
hpcycling2010 said:
Hello,

I have a fluid that is going through a pressure drop (3500psi down to atmospheric) and its around 120C at the upstream temp.
The fluid can be either methanol or oil.
What kind of temperature change will I see? I am assuming it will cool down, but by how much?

Help! and Thanks ahead of time!

By "going through a pressure drop" do you mean a pressure drop like in a turbine, like in a nozzle, or like in a throttle? Turbines and nozzles are thermodynamically similar, but throttles are different.

If you throttle an incompressible fluid, the temperature will rise as the pressure energy converts to internal energy. You can find the temperature rise in a throttle by noting that the fluid passing through the throttle maintains its total enthalpy, h=u+P/ρ. The internal energy u=cT for an incompressible fluid, where c is the specific heat.

BBB
 

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