AIR REFRIGERATION CYCLES

There are two types of air refrigeration cycles.

1. Open air refrigeration cycle.
2. Closed (or dense) air refrigeration cycle.

1 Open Air Refrigeration Cycle

In an open air refrigeration cycle, the air is directly (at atmospheric pressure) led to the space to be cooled (i.e. refrigerator). The air is then allowed to circulate through the cooler and returned to the compressor to start another cycle. This requires size of the compressor and expander to be large. The moisture is regularly carried away by the air circulated through the refrigerator. This leads to the formation of frost at the end of expansion process and clog the line. Therefore, a drier is required in the open cycle system.

2 Closed (or dense) Air Refrigeration Cycle

In a closed air refrigeration cycle, the air is passed through the pipes and components parts of the system at all times. The air is used for absorbing heat from the other fluid (say brine) which is circulated into the space to be cooled. The air does not come in contact directly with the space to be cooled.

This system has the following advantages over the open cycle:

1. The suction pressure is higher than that of atmospheric pressure Therefore, the volume of air handled by the compressor and expander is smaller.
2. The operating pressure ratio can be reduced, which results in higher coefficient of performance.