Positive Displacement Compressor

Definition

A positive displacement compressor is a type of mechanical device that increases the pressure of a gas by trapping a fixed volume of gas and forcing it into a smaller space. These compressors operate on the principle of creating a pressure difference to move the gas, making them essential for various industrial applications where consistent and reliable gas compression is required.

5 Must Know Facts For Your Next Test

1. Positive displacement compressors are widely used in industries such as refrigeration, air conditioning, and pneumatic tools due to their ability to deliver high pressures.
2. The two main types of positive displacement compressors are reciprocating and rotary, each with its own design features and applications.
3. These compressors can handle a wide range of gases, including air, natural gas, and refrigerants, making them versatile for different processes.
4. Operating at low speeds helps reduce wear and tear on components in positive displacement compressors, contributing to longer service life.
5. Unlike dynamic compressors, which rely on high-speed rotating blades, positive displacement compressors maintain constant flow rates regardless of discharge pressure.

Review Questions

• Compare the operational principles of reciprocating compressors and rotary screw compressors as types of positive displacement compressors.
  • Reciprocating compressors operate by utilizing a piston that moves back and forth within a cylinder to compress the gas. In contrast, rotary screw compressors use two interlocking helical screws to compress the gas continuously as it moves through the machine. While both are classified as positive displacement compressors, their mechanisms lead to different performance characteristics, such as efficiency, noise levels, and maintenance needs.
• Discuss how the design differences between positive displacement compressors and dynamic compressors influence their applications in industrial settings.
  • Positive displacement compressors create pressure by mechanically trapping and compressing gas within a chamber, making them ideal for applications requiring high pressures at lower flow rates. On the other hand, dynamic compressors generate pressure through high-speed rotating blades, providing higher flow rates but less efficiency at high pressures. This design distinction results in positive displacement compressors being used for tasks like refrigeration and pneumatic tools while dynamic compressors suit applications needing large volumes of compressed gas, like in HVAC systems.
• Evaluate the impact of compressor efficiency on the operational costs of positive displacement compressors in industrial applications.
  • Compressor efficiency directly affects the operational costs associated with running positive displacement compressors. Higher efficiency means less energy is wasted during the compression process, leading to lower energy bills and reduced environmental impact. Conversely, inefficient compressors consume more power, increasing operational expenses and potentially leading to frequent maintenance issues. By evaluating and optimizing compressor efficiency, industries can significantly reduce costs while maintaining effective gas compression.

Related terms

Reciprocating Compressor: A type of positive displacement compressor that uses a piston to compress the gas by moving back and forth within a cylinder.

Rotary Screw Compressor: A positive displacement compressor that uses two interlocking helical screws to compress the gas as it moves through the unit.

Compressor Efficiency: A measure of how effectively a compressor converts input power into useful work for compressing gas, often expressed as a percentage.