Author: Haroon Khalil

Fixed Vane Type Compressors These compressors belong to the category of positive displacement type as compression is achieved by reducing the volume of the gas. In this type of compressors, the rotating shaft of the roller has its axis of rotation that matches with the centre line of the cylinder; however, it is eccentric with…

P−V and T−S diagrams for multistage compression are shown in Figure 10.6. Figure 10.6 ρ−V and T−S Diagrams for Multistage Compressor If P1, T1 and delivery pressure P3 are fixed, the optimum value of the intermediate pressure P2 for minimum work can be obtained by setting the derivative dW/dP2 = 0. For perfect cooling,  In general, if there are N stages, the pressure ratio for each stage will be given by, Heat Rejected During…

Number of stages required depends on the pressure to be developed in compressor. Normally, following relationships are used with pressure and number of stages. Advantages of Multistage Compression Assumption in Multistage Compression: The following assumptions are usually made in calculation of work done in multistage compression:

The volumetric efficiency of a compressor is the ratio of actual free air delivered to the displacement of the compressor. Substituting the value of V4 in Eq. (10.1), we get Where ∈ is clearance ratio  and r is pressure ratio  Example 10.1: A single cylinder, single acting air compressor has a cylinder diameter of 150 mm and stroke of 300 mm. It…

Figure 10.5 Reciprocating Compressor with Clearance Volume

In isothermal compression work done is minimum and it is maximum for adiabatic compression.

Area 0−1−2−3 in Figure 10.4 represents the net work done, when the compression follows the polytropic law. Net work on air per cycle = Area 0−1−2−3 = Work done during compression (1−2) + Work done during air delivery (2−3) − Work done during suction (0−1). Similarly, for isentropic compression

In these compressors, the gas volume decreases and pressure increases due to the action of one or more reciprocating piston moving axially in one or more cylinders. It may be single acting or double acting, single cylinder or multicylinder and single stage or multistage compressors. Figure 10.2 shows the schematic of a reciprocating compressor. Reciprocating compressors…

Compressors can be classified on the basis of range of pressures, capacity, pressure ratio and design, and principle of operations. Figure 10.1 Classification of Compressors Positive Displacement Compressor: In this compressor, pressure is raised by decreasing the volume of gas, i.e., positive displacement of gas. Dynamic Compressor: In this compressor, the kinetic energy imparted to the gas by…

The function of compressor is to compress the gases and vapours from low pressure to high pressure. According to second law of thermodynamics this is only possible when work is done on the system, i.e., on the gas or vapour. Compressors have wide industrial and domestic applications such as compression of refrigerants in refrigerators and…