Joule-Thomson throttling effect

Temperature changes as pressure is reduced when a flowing stream of gas passes through a throttle, i.e., a valve, choke, or perforations in casing. This is called the Joule-Thomson effect. The change in temperature is directly related to the attraction of die molecules for each other. 

The temperature of the gas thus falls. The cooled air enters the chamber E from below and then goes up as shown. Thus, the gas cools the portion of the compressed air passing down the coil CE. This chilled gas then passes through a jet or throttle J and is further cooled by Joule-Thomson effect on account of expansion. This process goes on till the gas is converted into the liquid state. 

The Linde cycle is a simple cryogenic process based on Joule-Thompson effect. It is composed of different steps the gas is first compressed, then preliminarily cooled in a heat exchanger using liquid nitrogen, finally it passes through a lamination throttle valve to exploit the benefits of Joule-Thomson expansion. Some liquid is produced, and the vapour is separated from the liquid phase and returns back to the compressor through the heat exchanger. A simplified scheme of the overall process is reported in Fig. 2.9. 

In the Heatric process, the warm wet pressurised gas from the inlet separator is pre-cooled in the PCHE and then throttled in a Joule-Thomson (JT) valve to a lower pressure. The drop in pressure produces a cooling effect and both hydrocarbon liquids and water condense out of the gas. The two-phase stream passes to a separator where the liquids are removed. The cold dry gas from the separator is returned to the exchanger to chill the incoming warm, wet gas (Figure 9.3). Refrigeration... 

Collaborated with James Joule to discover the Joule-Thomson effect that describes changes in the temperature of a gas that is expanded through a throttling valve. 

---