Energy-saving control method of twin-stage compression type heat pump vacuum freeze drying combined device

Abstract

The present invention relates to an energy-saving control method of a twin-stage compression type heat pump vacuum freeze drying combined device. The energy-saving control method of a control system is characterized by comprising the steps that according to the requirements of the food drying processes, temperature T1 of a heating medium entering drying chamber heating division plates is determined; according to the vacuum degree requirements of the combined device and the changes of the thickness of a frost layer on the surface of a water catcher in the operation process of the combined device, a functional expression of the change of an evaporation temperature T4 of the water catcher with an operation time t during the operation process of the combined device is determined; according to the evaporation temperature T4 of the water catcher in a low-pressure stage refrigeration system and a condensing temperature T2 of a high-pressure stage condenser, an optimum intermediate temperature T3 of an intercooler is determined; according to the functional expression of the change of the evaporator temperature T4 of the water catcher with the operation time t, the temperature is realized by adjusting the opening degree of a low-pressure stage throttle valve and the rotation speed of a low-pressure stage compressor; and according to the calculation of a functional expression, the optimal intermediate temperature T3 of the intercooler is determined and realized by adjusting the opening degree of a high-pressure stage throttle valve and the rotation speed of a high-pressure compressor. The advantages are as follows: the heat supply temperature and heat of the drying chamber can be adjusted, the optimum evaporation temperature of the water catcher can be determined, and the optimum intermediate temperature of the intercooler can be determined, and the combined device is energy-saving in operation.

Description

technical field [0001] The invention relates to an energy-saving control method of a double-stage compression heat pump vacuum freeze-drying combined equipment. Background technique [0002] The quality of food dried by vacuum freeze drying equipment is better than that of other drying methods, but the energy consumption in the process of processing is large. During the operation of vacuum freeze-drying equipment, on the one hand, the sublimation of the water in the dried food requires a lot of heat, and on the other hand, the desublimation of the water in the water trap requires a lot of cooling. Because the refrigeration system that provides cooling capacity for vacuum freeze-drying equipment emits a large amount of heat during the refrigeration process, and this heat is greater than the heat required for food drying, therefore, some researchers have proposed to use the heat of the condenser of the refrigeration system as Food drying heat source, resulting in heat pump va...

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Problems solved by technology

At the same time, since the temperature required for heating the drying chamber is generally around 60°C, and the evaporation temperature of the refrigeration system is around -40°C, the refrigeration system must use cascade refrigeration, two-stage compression refrigeration or air jet enthalpy-enhancing refrigeration to meet the requirements, but this It also increases the difficulty of controlling the combined equipment

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