3.1.2.1.1.Working principle of Reciprocating compressor

Unit 3 - Parts of refrigeration systems

3.1.2.1.1.Working principle of Reciprocating compressor

Resiprocating compressor

Let us consider that the piston is at the top of its stroke fig (a). This is called top dead centre position of the piston. In this position the suction valve is held closed because of the pressure in the clearance space between the top of the piston and the cylinder head. The discharge valve is also held closed because of the cylinder head pressure acting on the top of it.

When the piston moves down word (i.e during suction stroke) as shown in Fig (b) the refrigerant left in the clearance space expands. Thus the volume of the cylinder increases and the pressure inside the cylinder decreases. When the pressure becomes slightly less than the suction pressure or atmosphere pressure, the suction valve gets opened and the vapour refrigerant flows into the cylinder. This flow continues until the piston reaches the bottom of its stroke (i.e. Bottom Dead Centre). At the bottom of the stroke, as shown in Fig (c), the suction valve closes because of spring action. Now when the piston moves upward (i.e, during compression stroke) as shown in fig (d), the volume of the cylinder decrease and the pressure inside the cylinder increases. When the pressure inside the cylinder becomes greater than that on the top of the discharge valve, the discharged valve gets opened and the vapour refrigerant is discharged into the condenser and the cycle is repeated.
Last modified: Monday, 22 August 2011, 11:01 AM