Defrosting Heating Tubes in Refrigeration Devices

When refrigeration devices such as cold storage air coolers and frozen & refrigerated display cabinets are in use, frost may form on the surface of the evaporator. Since the frost layer can narrow the flow channels, reduce the air volume, and even completely block the evaporator, seriously hindering the air flow. If the frost layer is too thick, it will deteriorate the cooling effect of the refrigeration device, increase power consumption. Therefore, some refrigeration devices use electric defrosting to defrost regularly.

Electric defrosting uses the electric heating tubes arranged inside the equipment to heat the frost layer adhering to the surface of the equipment, melting it to achieve the purpose of defrosting. This kind of electric heating tube belongs to one type of metal tubular electric heating elements, also known as defrosting heating tubes or frost - melting heating tubes. The electric heating tube takes a metal tube as the outer shell, an alloy electric heating wire as the heating element, has lead rods (wires) at one or both ends, and fills the metal tube with dense magnesium oxide powder insulation medium to fix the heating element.

Due to the characteristics of high indoor humidity, low temperature, and frequent thermal shock when the freezing equipment is working, the defrosting heating tube is generally based on the tubular electric heating element.

It uses high - quality modified magnesium oxide as the filler and stainless steel as the shell. After tube shrinking, the wiring end is sealed by special rubber pressing, enabling the electric heating tube to be used normally in the freezing equipment. It can be bent into any shape according to user needs, and is relatively convenient to be embedded on the fins inside the air cooler, or on the surface of the freezer evaporator, or at the bottom of the water - receiving tray, etc. for defrosting. There are approximately four basic structures of the electric heating tube:
(1) There are lead rods at both ends, and each end is connected to the outer shell.
(2) The leads are at both ends, with one end connected to the outer shell.
(3) Two lead rods are led out from one end, and the two lead rods are parallel.
(4) One end is led out, the lead rod is coaxial, and a part of the tail at the other end does not generate heat.

Among them:
a) Lead rods (wires): They are metal conductive parts connected to the heating element for connecting the element to the power supply and connecting elements to each other.
b) Outer shell tube material: Generally 304 stainless steel, which has good corrosion resistance.
c) Internal heating wire: Nickel - chromium alloy resistance wire, or iron - chromium - aluminum wire.
d) The port of the electric heating tube is sealed with vulcanized rubber.

Regarding the connection of the heating tubes, if the connection method of the defrosting electric heating tube is marked with Y, it is a star connection, and Y must be connected to the neutral line. If not marked, it is a Δ delta connection. For example, the heating tubes of the air cooler are generally 220V. One end of each heating tube is connected to the live wire, and the other ends are connected together to the neutral wire.

In addition, the input power marked on the outer shell of the heating tube is generally the rated power of the heating tube.

The method of electric defrosting has a simple system and is more convenient to operate. However, the power of the defrosting electric heating tube is generally large. If the quality of the heating tube is poor or it has been used for a long time, it is likely to burn out and even cause a fire. Therefore, the method of electric defrosting has serious potential safety hazards and requires regular inspections. The common damages of electric heating tubes are as follows: