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Precautions when adjusting the temperature of food freeze dryer

July 28, 2022

The freeze-drying technology of freeze-drying machine has a wide range of applications in the fields of bioengineering, food industry, pharmaceutical industry, material science and deep processing of agricultural and sideline products. In use, it is necessary to adjust the temperature to the appropriate temperature according to the specific food, but pay attention to the following matters:

In order to add a refrigeration branch that can supply appropriate cooling capacity around the refrigeration system pipeline that supplies cooling to the front box of the food freeze dryer under the premise that the cooling capacity of the refrigeration compressor is sufficient to meet the cooling capacity demand during temperature adjustment;


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At the same time, when the temperature is adjusted, the refrigeration compressor is supplying cooling to two evaporators with different evaporating temperatures, and the difference in working conditions may have a greater impact on the refrigeration compressor due to the lag of the expansion valve control. The defect caused by the hydraulic shock of the refrigeration compressor requires a good grasp of the control of the return steam pressure.


The technicians added an electromagnetic valve to the return steam pipeline of the front box evaporator, and the pressure controller controls the pressure of the electromagnetic valve before and after. Poor monitoring to control the opening or closing of the valve to reduce the load impact during temperature adjustment and ensure the smooth operation of the compressor;

In order to avoid the pressure rise in the front box evaporator caused by the closing of the electromagnetic valve, and the temperature adjustment effect cannot be ensured, the technician added a return steam branch pipe to the return steam pipeline before the electromagnetic valve, which is connected to the refrigeration compressor.


The second-stage compressed suction pipe of the machine, through the practice on many food freeze dryers, has proved that this treatment plan is feasible. The selected capillary temperature regulation constitutes an unsatisfactory temperature regulation effect and a load impact on the compressor.