Air Refrigeration System

Working Principle of Air Refrigeration System

The Air refrigeration system is normally working on the bell- Coleman cycle. The bell-Coleman air refrigerator and its cycle. In this cycle, constant pressure processes have replaced the isothermal heat absorption and rejection of the Carnot cycle.

During the outward stroke of the expander, the air from the cooler is drawn into the expander and expanded adiabatically (1-2) where the temperature of the air falls. During the inward stroke of the expander, the low-temperature air is pushed into the cold chamber where it takes the heat from the space of the cold chamber. This heat addition is a constant pressure process. (2-3)

During the outward stroke of the compressor, the air is drawn into the compressor and compressed adiabatically (3-4). During the inward stroke of the compressor, the compressed air is delivered to the cooler. In the cooler, the air is cooled at constant pressure (4-1).

Open air system of refrigeration

In an open-air refrigeration system, the refrigerant (air) comes in direct contact with the substance/matter/or space to be cooled.

The operation in the open system is only at atmospheric pressure, due to which, the size of the unit increases for producing the same refrigerating effect as produced by the closed system.

Closed air system of refrigeration

In a closed-air refrigeration system, the refrigerant (air) does not come in direct contact with the substance/matter/or the space to be cooled. usually, the coils carrying cold air are kept in a brine tank. The air absorbs heat from the brine is kept in a brine which then circulates through the refrigerating chamber.

Open-air system vs Closed-air system

S.N.Open system Closed system
1.For a specific refrigerating effect, the size of the system is large.For the same refrigerating effect, the size of the system is small.
2.Chocking of valves due to moisture mix-up with air.No chocking of valves because air does not mix with moisture.
3.Dense air could not be usedDense air could be used to produce a more refrigerating effect.

Advantages and disadvantages of air refrigeration systems

Advantages

1. The working fluid (air) is free and easily available, the system is cheaper.

2. No environmental impact (Non-toxic, non-flammable) hence totally safe.

3. Air being light in weight, the system is quite suitable for aircraft.

4. Air cycle equipment is extremely reliable than others.

5. Low maintenance cost.

6. Low running cost.

7. Reduced system downtime.

8. Leakage (air) will not cause any problem.

Disadvantages

1. The weight of air required is more compared to other refrigerants.

2. The COP is very low as compared to other systems.

3. If the open system is used, the air mix-up with moisture. This moisture may freeze during expansion and may choke the valves.

Also Read:

Thermodynamics state of a pure substance
Mechanism of production of cooling in refrigeration
Reversed Carnot Cycle [Working Principle]


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