Important Terms

1. Suction pressure.  It is the absolute pressure of refrigerant at the inlet of a compressor. 
2. Discharge pressure.  It is the absolute pressure of refrigerant at the outlet of a compressor. 
3. Compression ratio (or pressure ratio).  It is the ratio of absolute discharge pressure to the absolute suction pressure. Since the absolute discharge pressure is always more than the absolute iuction pressure, therefore, the value of compression ratio is more than unity.