Energy-saving control method for cascade type heat pump vacuum freeze drying combination equipment

Abstract

The invention relates to an energy-saving control method for cascade type heat pump vacuum freeze drying combination equipment. The energy-saving control method for a control system is characterized by comprising the steps that the temperature T1 of a heating medium entering a heating partition plate of a drying chamber is determined according to food drying technological requirements; according to the vacuum degree requirements of the combination equipment and thickness changes of the frost layer on the surface of a water catcher in the combination equipment operation process, the functional expression of the evaporation temperature T5, changing along with operation time t, of the water catcher in the combination equipment operation process is determined; according to the evaporation temperature T5 of a low-pressure stage refrigeration system water catcher and the condensation temperature T2 of a high-pressure stage condenser, the high-pressure stage evaporation temperature T3 of a condensation evaporator and the functional expression of the high-pressure stage evaporation temperature T3 changing along with the evaporation temperature T5 and the condensation temperature T2 are determined; according to the functional expression of the evaporation temperature T5, changing along the operation time t, of the water catcher, the determined high-pressure stage evaporation temperature T3 is calculated, and energy saving is achieved by adjusting the opening degree of a high-pressure stage throttling valve and adjusting the rotating speed of a high-pressure stage compressor. The method has the advantages that the evaporation temperature of the low-pressure stage water catcher can be dynamically adjusted according to the thickness changes of the frost on the surface of the water catcher, energy-saving operation of the cascade type refrigeration system is achieved, and more energy is saved in the operation process.

Description

technical field [0001] The invention relates to an energy-saving control method of a cascade 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, some researchers have proposed to use the heat of the condenser of the refrigeration system as a food drying method. Heat source, so there has been a combination of heat pum...

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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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