11524

# Throttling High-Pressure Water

Water at high pressure expands adiabatically to a lower pressure (throttled) through a partially closed valve. You can vary the inlet temperature and outlet pressure . If the exit stream is a compressed liquid, then the outlet temperature is slightly higher than the inlet temperature. If the exit stream is a vapor-liquid mixture, then the outlet temperature is the saturation temperature at the outlet pressure. An energy balance () determines the temperature and the fractions of liquid and vapor in the exit stream, which are shown in the bar graph.

### DETAILS

Water at high pressure undergoes Joule–Thomson expansion when passing through a throttling valve. This process is assumed to be adiabatic, so the enthalpy change is zero.
, so , where is the inlet enthalpy and is the exit enthalpy.
When two phases are present, the saturated vapor enthalpy and the saturated liquid enthalpy are used to determine the fraction of the exit stream that is vapor. For the conditions chosen, liquid and vapor exit the throttle at saturation conditions, because .
The steam quality is calculated by:
,
so that .
When only liquid is present and .
The screencast video at [1] explains how to use this Demonstration.
Reference

### PERMANENT CITATION

 Share: Embed Interactive Demonstration New! Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details » Download Demonstration as CDF » Download Author Code »(preview ») Files require Wolfram CDF Player or Mathematica.

#### Related Topics

 RELATED RESOURCES
 The #1 tool for creating Demonstrations and anything technical. Explore anything with the first computational knowledge engine. The web's most extensive mathematics resource. An app for every course—right in the palm of your hand. Read our views on math,science, and technology. The format that makes Demonstrations (and any information) easy to share and interact with. Programs & resources for educators, schools & students. Join the initiative for modernizing math education. Walk through homework problems one step at a time, with hints to help along the way. Unlimited random practice problems and answers with built-in step-by-step solutions. Practice online or make a printable study sheet. Knowledge-based programming for everyone.