In the freeze-drying process of the freeze dryer, the temperature of the liquid items is pre-frozen and the subsequent sublimation of the moisture in the solid items needs to be controlled within a certain range of process requirements, which requires the freeze dryer to have a certain degree of temperature regulation Features. How to solve the temperature adjustment problem of the freeze dryer without setting the temperature adjustment unit, the specific scheme is as follows:
1. Under the premise of surplus cooling capacity of the refrigeration compressor, add a cooling branch that can provide appropriate cooling capacity next to the refrigeration system piping that supplies the front box of the freeze dryer to meet the cooling capacity needs during temperature adjustment;
2. At the same time, when the temperature is adjusted, the refrigeration compressor is cooling two evaporators with different evaporation temperatures. The difference in operating conditions may cause a greater impact on the refrigeration compressor due to the lag of the expansion valve control. It will lead to the failure of the liquid compressor of the refrigeration compressor, which needs to grasp the control of the return steam pressure. Now the technical staff has added an electromagnetic valve on the return steam line of the front tank evaporator, and the electromagnetic valve is controlled by the pressure controller. Monitoring the pressure difference between the front and back to control the opening or closing of the valve to reduce the load shock during temperature adjustment and ensure the smooth operation of the compressor;
3. In order to prevent the pressure in the front tank evaporator from rising due to the closing of the electromagnetic valve, the temperature adjustment effect cannot be guaranteed, and the technician has added a steam return branch pipe to the steam return line in front of the solenoid valve, which is connected to The suction tube of the secondary compression of the refrigeration compressor, through the practice on multiple freeze dryers, the result proves that this treatment scheme is practical and feasible, it can not only avoid the cost increase of the additional temperature regulating unit, but also solve the current The commonly used capillary temperature adjustment results in unsatisfactory temperature adjustment effects and impact on the load of the compressor.