Reasons why freeze dryers cannot dry

　　Freeze drying machines have been widely used nowadays, playing a prominent role in food and chemical industries. A freeze dryer is a cold drying device that first freezes water containing substances into a solid state, and then sublimates the water in the solid state into a gaseous state to remove the water and preserve the substance. The reason why the compressor of the freeze dryer runs normally without cooling or insufficient cooling is mainly due to the refrigeration unit itself. Let's analyze the reasons why the freeze dryer does not cool?

　　1. Insufficient refrigerant addition in the freeze-drying mechanism, the observation mirror should be able to see fully transparent liquid refrigerant flow under normal conditions. If there is thin frost at the inlet of the expansion valve (capillary) and evaporator, it indicates that the refrigerant is insufficient and needs to be added.

　　2. If there is ice blockage or dirty blockage in the expansion valve (capillary), it will cause the system friction resistance or flash vapor to increase, resulting in a decrease in the total refrigerant flow rate, a decrease in suction working pressure, and a decrease in the cooling capacity of the evaporator.

　　3. Malfunction of the centrifugal fan in the air-cooled condenser, insufficient cooling water output or high water seepage temperature in the water-cooled condenser, and excessive dust accumulation on the heat transfer surface of the condenser can cause an increase in the working pressure of the refrigerant exhaust pipe, resulting in a decrease in cooling capacity.

　　4. If the suction working pressure is high and the evaporator and condenser of the freeze dryer are operating normally, and there are no obvious abnormalities in the operating current of the compressor, it may be due to damage to the gate valve in the compressor or generator set, or insufficient cooling capacity for specific applications (i.e. high load); If the operating current of the compressor is significantly lower than the factory nameplate value, it will remind that the suction spring inside the compressor is damaged or the crankshaft is broken, and the compressor should be replaced.

　　Reasons and solutions for poor cooling effect (insufficient or no cooling capacity) of freeze-drying mechanism:

　　Causes:

　　① The expansion valve is opened too much, and at this time, the temperature of the shelf or water vapor condenser has not dropped to the set value, while the compressor is severely frosted.

　　② The expansion valve is too small to lower the temperature, but the compressor temperature is high and there is no frost at the suction valve. The suction pressure and the evaporation temperature corresponding to the shelf or water vapor condenser are much lower than the temperature of the shelf or water vapor condenser.

　　2. The refrigeration system is blocked and not smooth, such as filter blockage, valve failure, solenoid valve malfunction, expansion valve blockage, etc.

　　3. Insufficient refrigerant charging results in the inability to lower the temperature, low suction pressure, and no frost formation at the suction valve.

　　4. The paper pads on the upper part of the compressor valve plate or the lower part of the cylinder are punctured or broken, or the suction and exhaust valve plates of the compressor are broken.

　　Exclusion method:

　　(1) Adjust the expansion valve.

　　(2) Clear the refrigeration system and replace the components.

　　(3) Fill refrigerant.

　　(4) Replace the paper pad or valve plate.

　　We have briefly introduced the reasons why freeze dryers cannot dry. The above is the analysis of the reasons why freeze dryers do not cool. If you want to learn more about related content, you can follow us more! We are a professional manufacturer of refrigerated dryers and suction dryers, including freeze dryers, adsorption dryers, air filters, pressure swing adsorption nitrogen generators, and other products. If you have any needs, please feel free to contact us!

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