During the start-up operation of an air conditioner or refrigerator, warm air enters into the compressor through its suction nozzle for several reasons:
Pressure equalization: The compressor is the heart of the refrigeration cycle and is responsible for compressing the refrigerant gas. During the off cycle or when the unit is not running, the refrigerant pressure equalizes with the ambient pressure. When the compressor starts, it needs to create a pressure difference between the low-pressure (suction) side and the high-pressure (discharge) side of the system. Allowing warm air into the suction nozzle helps in achieving this pressure difference and initiates the compression process.
Preventing liquid slugging: In a refrigeration system, the refrigerant exists as a mixture of liquid and vapor. Liquid slugging occurs when liquid refrigerant enters the compressor during the start-up, which can be detrimental to the compressor's operation. By allowing warm air into the suction nozzle, any liquid refrigerant present in the system tends to vaporize due to the heat, reducing the risk of liquid slugging.
Lubrication and cooling: Compressors rely on lubrication to ensure smooth operation and reduce wear and tear on moving parts. During the start-up, the compressor may have been idle for some time, and warm air entering the suction nozzle helps to warm up the lubricant and improve its flow, ensuring adequate lubrication during the initial stages of operation. Additionally, the warm air helps in cooling the compressor, preventing overheating during the start-up phase.
System stabilization: When the air conditioner or refrigerator starts, the system goes through various pressure and temperature fluctuations until it stabilizes. Allowing warm air into the compressor's suction nozzle helps in this stabilization process and prevents abrupt temperature and pressure changes that could be harmful to the system.
Once the compressor starts running and the refrigerant circulation is established, the warm air will be pushed out of the system, and the cooling process will begin as the refrigerant absorbs heat from the conditioned space (in the case of an air conditioner) or from the refrigerator compartment (in the case of a refrigerator).