Choose The Right Evaporator For Your Cold Room

The evaporator is an important and indispensable component of the refrigeration system. As the most commonly used evaporator in cold storage, the proper selection of the chiller directly affects the efficiency of the refrigeration system.

The Impact Of Frosting On The Refrigeration System

During the normal operation of the refrigeration system of the cold storage, the surface temperature of the evaporator is far lower than the dew point temperature of the air, and the moisture in the air will precipitate and condense on the pipe wall. If the pipe wall temperature is lower than 0℃, the dew will condense into frost. The frosting is also the result of the normal operation of the refrigeration system, so a small amount of frosting is allowed on the surface of the evaporator.

Because the thermal conductivity of frost is too small, it is one percent or even one-hundredth of that of metal, so the frost layer forms a large thermal resistance. Especially when the frost layer is thick, it is like heat preservation, so that the cold in the evaporator is not easy to be distributed, which affects the refrigeration effect of the evaporator, and finally makes the cold room unable to reach the required temperature. At the same time, the evaporation of refrigerant in the evaporator will also be weakened, and the incompletely evaporated refrigerant may be sucked in by the compressor thus causing liquid strike accident. Therefore, we must try to remove the frost layer, otherwise, the frost layer will be thicker and thicker, and the chilling effect will be worse and worse.

How To Choose The Right Evaporator?

As we all know, depending on the required ambient temperature, the air cooler (evaporator) will use different fin spacing.

The most commonly used air coolers in the refrigeration industry have fin pitches of 4mm, 4.5mm, 6~8mm, 10mm, 12mm, as well as those with front and rear variable fin pitches. If the air chiller has a small fin pitch, this chiller is suitable for use in high-temperature environments; the lower the temperature of the cold storage, the greater the spacing of the air chiller fins. If an improper air chiller is selected, the fins will frost too fast, and the air outlet channel of the air cooler will soon be blocked by the icing, which will cause the temperature in the cold room to cool down slowly. Once the compressor refrigeration efficiency cannot be fully utilized, As a result, the power consumption of the refrigeration system will eventually increase.

According to our company’s years of experience in cold storage engineering construction, we have summarized the following types of air chillers suitable for different types of cold storage for different use environments.

High-temperature storage room (0℃~20℃): For example, workshop air conditioning, cooler room, cold storage corridor, fresh-keeping storage, temperature-controlled environment, ripening chamber, etc., generally use air chillers with the fin spacing of 4mm~4.5mm ；

Low-temperature cold room (-16℃~-25℃): For example, low-temperature freezing and refrigeration and cold-chain logistics storage, should choose the air chiller with the fin spacing of 6mm~8mm;

Quick-freezing cold room (-25℃~-35℃): generally choose chillers with fin spacing of 10mm~12mm. If the quick-freezing cold storage requires high humidity of the goods, you should choose the chiller with variable fin pitch, and the inlet side fin pitch can reach 16mm.

However, for some special-purpose cold storage, it is not possible to select the air chiller fin spacing based on the temperature in the cold storage, for example, rapid pre-cooling and acid discharge of meat and vegetables, although the temperature of the cold storage room is generally set above 0℃, because of the high incoming temperature, fast cooling speed, and high humidity of the goods, it is not appropriate to choose a chiller with a fin spacing of 4mm or 4.5mm. You must choose the air chiller with fin spacing of 8mm~10mm.

There are also fresh-keeping warehouses similar to garlic, apple, and other fruits and vegetables. The suitable storage temperature is generally – 2 ℃. For such fresh-keeping or air-controlled warehouses with storage temperatures below 0 ℃, it is also necessary to select air chillers with fin spacing of not less than 8 mm to avoid air duct blockage and increase power consumption that caused by a rapid frosting of air chillers.