As an important component of the cold storage refrigeration system, the air cooler begins to frost on the evaporator surface when the air cooler works at a temperature below 0℃ and below the air dew point. As the operating time increases, the frost layer will become thicker and thicker. Reasons for frosting of the air cooler (evaporator)
1. Insufficient air supply, including blockage of the return air duct, blockage of the filter, blockage of the fin gap, fan failure or reduced speed, etc., resulting in insufficient heat exchange, reduced evaporation pressure, and reduced evaporation temperature;
2. Problems with the heat exchanger itself. The heat exchanger is often used, and the heat exchange performance decreases, which reduces the evaporation pressure;
3. The external temperature is too low. Civil refrigeration generally does not fall below 20℃, refrigeration in a low temperature environment will cause insufficient heat exchange and low evaporation pressure;
4. The expansion valve is clogged or the pulse motor system that controls the opening is damaged. In a long-term running system, some debris will block the expansion valve port and make it unable to work normally, reducing the refrigerant flow and lowering the evaporation pressure. Abnormal opening control will also cause a decrease in flow and pressure;
5. Secondary throttling, pipe bending or debris blockage inside the evaporator causes secondary throttling, which causes the pressure and temperature to drop in the part after the secondary throttling;
6. Poor system matching. To be precise, the evaporator is small or the compressor operating condition is too high. In this case, even if the evaporator performance is fully utilized, the high compressor operating condition will cause low suction pressure and a drop in evaporation temperature;
7. Lack of refrigerant, low evaporation pressure and low evaporation temperature ;
8. The relative humidity in the warehouse is high, or the evaporator is installed in the wrong position or the cold storage door is opened and closed frequently;
9. Incomplete defrosting. Due to insufficient defrosting time and unreasonable position of the defrost reset probe, the evaporator is started when it is not completely defrosted. After multiple cycles, the local frost layer of the evaporator freezes into ice and accumulates and becomes larger.
Cold storage defrosting methods 1. Hot air defrosting – suitable for defrosting the pipes of large, medium and small cold storages: Directly let the hot high-temperature gaseous condensing agent enter the evaporator without interception, and the evaporator temperature rises, causing the frost layer and the pipe joint to melt or then peel off. Hot air defrosting is economical and reliable, easy to maintain and manage, and its investment and construction difficulty are not large. 2. Water spray defrosting – mostly used for defrosting large and medium-sized air coolers: Regularly use normal temperature water to spray and cool the evaporator to melt the frost layer. Although water spray defrosting has a good defrosting effect, it is more suitable for air coolers and is difficult to operate for evaporating coils. You can also use a solution with a higher freezing point temperature, such as 5% to 8% concentrated brine, to spray the evaporator to prevent frost from forming. 3. Electric defrosting – electric heating tubes are mostly used for medium and small air coolers: Electric heating wires are mostly used for electric heating defrosting of aluminum pipes in medium and small cold storages. It is simple and easy to use for air coolers; but for aluminum pipe cold storages, the construction difficulty of installing electric heating wires on aluminum fins is not small, and the failure rate in the future is also relatively high, maintenance and management are difficult, economic efficiency is poor, and the safety factor is relatively low. 4. Mechanical manual defrosting – small cold storage pipe defrosting is applicable: Manual defrosting of cold storage pipes is more economical and the original defrosting method. It is unrealistic to use manual defrosting for larger cold storages. It is difficult to operate with the head tilted up, and the physical energy is consumed too quickly. It is harmful to health to stay in the warehouse for too long. It is not easy to defrost thoroughly, which may cause the evaporator to deform, and may even damage the evaporator and cause a refrigerant leakage accident.
Post time: Jul-17-2025