Throttling Process & Joule Thomson Effect

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SUMMARY

The throttling process is defined as an isenthalpic process where the enthalpy remains constant (h1 = h2), leading to changes in internal energy when pressure is altered. The Joule-Thomson effect describes the temperature change of a gas when it expands, with hydrogen being an exception as it heats up during expansion. In the context of compressed natural gas (CNG) systems, the pressure drop from 300 bar to 4 bar in a pressure regulator exemplifies the throttling process, resulting in a temperature decrease. Understanding these concepts is crucial for safe and efficient gas handling.

PREREQUISITES
  • Understanding of thermodynamic processes, specifically isenthalpic processes.
  • Familiarity with the Joule-Thomson effect and its implications on gas behavior.
  • Knowledge of pressure regulation in gas systems, particularly CNG applications.
  • Basic principles of fluid dynamics related to throttling valves.
NEXT STEPS
  • Research the Joule-Thomson coefficient for various gases, including methane.
  • Study the design and operation of throttling valves in gas systems.
  • Explore the thermodynamic properties of hydrogen and its unique behavior during expansion.
  • Learn about safety measures and best practices in handling compressed gases.
USEFUL FOR

Engineers, safety professionals, and technicians involved in gas handling, particularly those working with compressed natural gas (CNG) systems and thermodynamic applications.

ahmad.hasan
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dear all

What is the throttling Process?
what is Joule homson Effect?
 
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A throttling process is a process that is isenthalpic. Thus, h_1 = h_2. This means that the following is also true, u_1 + P_1 v_1 = u_2 + P_2 v_2. So if you drop pressure in a throttling value, you increase the internal energy, and vise versa.

The Joule -thomson- effect deals with the fact that as you expand a gas it looses temperature. Note that for hydrogen; however, it gains temperaturee as it expands. This makes hyrdogen particularly dagnerous.
 
Pressure drops in CNG kit Pressure regulator from 300 bar to 4 bar in 1st chamber due to expansion is it throttling process? temperature also drops in it.
 
Yes, that is exactly what it is.

Edit: wait, what do you mean by expansion? Is it going through a nozzle?
 
no it is going throug valve (sloninoid valve) from storage cylinder through high pressure pipe into solinoid valve and then in the 1st stage chamber of pressure regulator.
 
Yes, it is a throttling valve.
 
what is the value of joule-thomson coefficient for methane
 

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