Defrost Process

The defrost process in refrigeration systems is crucial for the correct operation of the equipment and allows the removal of the frost generated after dehumidification and subsequent freezing of the humidity in the air.

First, we plan a defrost schedule, where we agree on the frequency of defrosting. Initially, by closing the refrigerant solenoid valve to prevent the refrigerant from entering the evaporator, the compressor sucks the remaining refrigerant until it stops due to low pressure. This process allows the system to completely and safely empty the evaporator. During defrosting, in general, both compressors and fans are switched off to minimize the flow of hot air into the refrigerated chamber.

Defrosts involve providing sufficient heat to melt the accumulated ice, using different heat sources depending on the method employed, such as air, water, electric heaters or hot gas from the compressor. The defrost ends when a probe detects that the temperature is above 0°C or when a predefined time has elapsed, ensuring that the process is effective and consistent.

In addition to these steps, it is essential to consider delay times such as drip, dry-out, drain or injection time to allow water to drain and the evaporator to cool, reducing thermal shock and stabilising conditions inside the chamber. These practices not only improve the energy efficiency and operation of refrigeration systems, but also extend the life of the equipment, maintaining optimal and safe product preservation.

Types of defrost

In refrigeration systems, the effectiveness of defrost will depend on the ability of the method used to generate sufficient heat to melt the accumulated ice, minimising energy consumption and time required. The most common methods include air defrost, electric resistance defrost, hot gas defrost, hot glycol defrost and reverse cycle defrost. Each has its particularities and should be selected based on efficiency as well as its impact on the stored products.