THE EXPANSION AND COOLING OF GAS

The Joules-Tompson Effect (J-T) is the cooling effect of the expansion of a real gas.

This cooling occurs where a reduction in flow and pressure is induced at a choke, valve or restriction in the system.

The temperature depression is a function of gas composition, initial pressure and temperature upstream of restriction and delta P across restriction.

Curves are available for temperature reduction from the expansion natural gas but these do not take into account high percentages of components such as CO2, H2S etc. which will cause deviation from the basic curve.

Trianglia calculations will include ALL components of the gas.

Accurate prediction of this temperatures is a safety critical issue

In certain operations such as the opening a cold shut in well into a depressured system, initial flowing temperatures can be below the design temperature of pipe work and components

i.e. SIWHP 3000 psi at ambient temperature - resultant downstream gas temperature on opening circa (minus) -120°F.

In some cases relief system pipe work can encounter very low temperatures

For the prediction of hydrate formation

Accurate temperature prediction is also necessary for determining injection rates for the depression of hydrate formation temperature.