Cold Mold Sweat Dehumidifier

In the plastic injection molding cycle, while chilling water being introduced, there will be moisture condensation on mould’s surface, since the surface temperature of mould is lower than the surrounding air temperature after being cooled by chilling water. Moisture condensation may severely affect products’ quality and production efficiency. The most simple and effective way to avoid moisture condensation is to make the temperature of air surround the mould’s surface lower than the one of mould’s surface. Using dehumidifier can achieve this aim. The following are instructions of several main industrial dehumidifiers on market.

Types of Industrial Dehumidifiers

According to working principles, it can be sorted into the following types: Cold Mold Sweat Dehumidifier, Honeycomb Rotor Dehumidifier, Compressed Air Dehumidifier, Lithium Bromide Adsorption Type Liquid Dehumidifier.

Dehumidifier with refrigerating system achieves the effect of dehumidification by cooling the air to lower dew-point temperature and separate out moisture from air. It can be applied to extremely wide fields and is easy and simple to operate. Honeycomb rotor dehumidifier achieves the effect of dehumidification by using its molecular sieve and silica gel to adsorb moisture in air, the dehumidification effect of this type is good. Its dew-point temperature can reach to lower than -40℃. Compressed air dehumidifier compress air and lower the air dew-point temperature to separate out moisture from air so as to dehumidify. However, this type of dehumidifier is just suitable for application when the air quantity is small, since it adopts the way of compressing air. Lithium bromide adsorption type liquid dehumidifier makes use of the strong water-absorbing ability of lithium chloride liquid to absorb moisture in air. However, this device is quite large and requires change of absorption liquid. The operating cost is high.

Above all being said, frozen type and honeycomb rotor are the main humidifying types. The following will simply introduce.

Working Principles

One working principle of Cold Mold Sweat Dehumidifier is to apply double refrigerating system. Air exchanges heat with refrigerant through evaporator 1 to take away some heat. Next, the air goes through evaporator 2 to further exchanging heat with refrigerant to lower temperature to the required dew-point temperature.  During this procedure, moisture in air dissolves out and then the air absorbs heat while getting through the fin style condenser to raise the air temperature. Finally, the air blower gets the air to appointed place.

Another working principle of Cold Mold Sweat Dehumidifier is to apply combination of single refrigerating system and cold water coil. Air gets initial cooling by exchanging heat with chilling water in the cold water coil to release some heat. Next, the temperature of air will decrease continuously to meet the required dew-point temperature by exchanging heat with refrigerant through evaporator. Then, the condenser gets air temperature up. Finally, the air blower gets the air to appointed place.

Comparison of systems

Dehumidifier with refrigerating system of different working principles has their own advantages and disadvantages. Dehumidifier with double refrigerating system doesn’t require external cold water machine to offer chilling water and can finish the whole dehumidifying process alone. Besides, its internal structure of pipes is simple and it doesn’t require insulation treatment toward its system of water pipes as well as can avoid leakage. Cold Mold Sweat Dehumidifier SMD-R, which was currently developed by Shini, is the one using double refrigerating system.

Cold sweat dehumidifier of applying combination of single refrigerating system and cold water coil has advantage of small temperature fluctuation, since it cool air temperature by chilling water. If a cooling-water machine is available in factory, the machine cost of this dehumidifier is competitive, since it has only one refrigerating system. Otherwise, the cost may raise quite a lot. The pipeline of water system and operation are more complicated, since it adjusts its cooling capacity by controlling water flow through cold water coil by solenoid valve.

Above all being said, choice of different types of dehumidifiers should depend on clients’ conditions so as to make full use of dehumidifiers.

Application Range of Shini Freezing Dehumidifier

Shini Cold Mold Sweat Dehumidifier SCMD-R-W Series is mainly applied in plastic molding, especially suitable for PET preform injection. Condensation trouble, which occurs when using cold water to shorten molding cycle, affects products’ quality and production efficiency as well as corrodes moulds’ surfaces and then brings environmental pollution. However, this dehumidifier using refrigerating system to dehumidify can keep a low dew-point temperature reach to about 2℃~8℃, which helps moulds avoid condensation trouble and not to be affected by seasonal change. It can largely reduce defective rate.which helps moulds avoid condensation trouble and not to be affected by seasonal change. It can largely reduce defective rate.