Which of the following statements are correct for...

Name: Problem 21, Chapter 12: Thermal Engineering
Uploaded: 2021-11-26T20:45:02-08:00
Duration: 1 min 11 s
Channel: Hunza Gilgit
Description: Which of the following statements are correct for multi-staging in a reciprocating air compressor? 1. It decreases the volumetric efficiency 2. The work done can be reduced 3. A small high-pressure cylinder is required. 4. The size of flywheel is reduced. Select the correct answer using the code given below: (a) 1,2 and 3 (b) 2,3 and 4 (c) 1,3 and 4 (d) 1,2 and 4

Which of the following statements are correct for multi-staging in a reciprocating air compressor? 1. It decreases the volumetric efficiency 2. The work done can be reduced 3. A small high-pressure cylinder is required. 4. The size of flywheel is reduced. Select the correct answer using the code given below: (a) 1,2 and 3 (b) 2,3 and 4 (c) 1,3 and 4 (d) 1,2 and 4

Which of the following statements are correct for multi-staging in a reciprocating air compressor?
1. It decreases the volumetric efficiency
2. The work done can be reduced
3. A small high-pressure cylinder is required.
4. The size of flywheel is reduced. Select the correct answer using the code given below:
(a) 1,2 and 3
(b) 2,3 and 4
(c) 1,3 and 4
(d) 1,2 and 4

Key Concepts

Volumetric Efficiency

Volumetric efficiency is a measure of the effectiveness with which an engine or compressor draws in the working fluid relative to its displacement. In compressors, factors such as clearance volume and the method of compression (single or multi-stage) influence the volumetric efficiency, thereby affecting the amount of air that is actually compressed in each cycle.

Flywheel Design

Flywheels in reciprocating compressors serve to smooth out the pulsating motion of the piston and maintain steady rotational energy. In multi-stage compressors, due to the distributed compression work and reduced individual pressure fluctuations, the design may allow for a reduction in the size or mass of the flywheel needed to stabilize the engine's operation.

Cylinder Sizing

In multi-stage reciprocating compressors, different stages can be optimized separately; often, the cylinder handling the highest pressure is designed to be smaller due to factors such as reduced volumetric flow rate at higher pressures. This design choice helps manage mechanical stresses and enhances the efficiency of the compression process.

Multi-stage Compression

Multi-stage compression involves compressing air in two or more successive stages with intercooling between the stages. This method helps to reduce the overall energy consumption by lowering the work required for each individual compression stage as the air is cooled between stages, leading to improved thermal efficiency.

Work Reduction in Compression

Reducing the work done in the compression process is one of the benefits of multi-stage compression. By inter-cooling the air between stages, the process approximates an isothermal compression rather than an adiabatic process, which in turn reduces the energy required for compression and enhances overall efficiency.

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