ANS:B - adiabatic expansion through a throttle valve (Joule-Thomson expansion).

The correct answer is: adiabatic expansion through a throttle valve (Joule-Thomson expansion).

Explanation:

The Linde process uses the Joule-Thomson effect, where a gas is allowed to expand adiabatically through a throttle valve, leading to a temperature drop and facilitating gas liquefaction.

Adiabatic expansion through a throttle valve, also known as Joule-Thomson expansion, is a thermodynamic process used in gas liquefaction and refrigeration. Here’s how it works:

1. Concept of Adiabatic Expansion

• Adiabatic Process: In an adiabatic process, there is no heat exchange with the surroundings. The system is thermally insulated, meaning any energy change occurs solely due to work done on or by the system.
• Expansion: When a gas expands without heat exchange, its internal energy changes, which can lead to a drop in temperature.

2. Throttle Valve Mechanism

• Throttle Valve: A throttle valve is a device that allows a gas to pass through while reducing its pressure. It creates a sudden drop in pressure, which facilitates expansion.
• Joule-Thomson Effect: When a gas expands through the throttle valve, it experiences a decrease in pressure. Depending on the gas and its initial conditions, this can result in a temperature drop, which is the essence of the Joule-Thomson effect.

3. Process Steps

1. Compression: The gas is initially compressed, raising its temperature and pressure.
2. Cooling: The compressed gas is then cooled, often through heat exchange with a colder stream, to prepare it for expansion.
3. Expansion: The cooled, high-pressure gas is allowed to expand through the throttle valve, causing a drop in pressure and temperature.
4. Liquefaction: If the temperature drops sufficiently, the gas can condense into a liquid state.

4. Applications

• Gas Liquefaction: This process is fundamental in the liquefaction of gases such as oxygen, nitrogen, and natural gas.
• Refrigeration Systems: It is also used in refrigeration and cryogenic applications to achieve low temperatures.

Summary

Adiabatic expansion through a throttle valve (Joule-Thomson expansion) involves the rapid expansion of a gas through a throttle, leading to a drop in pressure and temperature without heat exchange. This process is essential for gas liquefaction and is widely used in various industrial applications.