Energy-saving control method for dual-stage compression heat pump vacuum freeze-drying combined equipment

Abstract

An energy-saving control method for a vacuum freezing and drying combined device for a double-stage compression heat pump comprises the steps of: according to requirements of a food drying technology, determining the temperature T1 of a heating medium entering heating division plates (8) of a drying chamber; according to vacuum degree requirements of the combined device and changes of the thickness of a frost layer on the surface of a water catcher (12) in the operation process of the combined device, determining a functional expression of the change of the evaporation temperature T4 of the water catcher (12) along with an operation time t during the operation process of the combined device; according to the evaporation temperature T4 of the water catcher (12) in a low-pressure-stage refrigeration system and a condensing temperature T2 of a high-pressure-stage condenser (7), determining an optimal intermediate temperature T3 of an intercooler (10); according to the functional expression of the change of the evaporation temperature T4 of the water catcher (12) with the operation time t, achieving the temperature by adjusting the opening degree of a low-pressure-stage throttling valve (11) and the rotation speed of a low-pressure-stage compressor (2); and according to the calculation of a functional expression, determining the optimal intermediate temperature T3 of the intercooler (10), and achieving the temperature by adjusting the opening degree of a high-pressure-stage throttling valve (9) and the rotation speed of a high-pressure-stage compressor (3). The advantages are as follows: the heat supply temperature and heat of the drying chamber can be adjusted, the optimal evaporation temperature of the water catcher (12) can be determined, and the optimal intermediate temperature of the intercooler (10) can be determined, and the combined device saves energy 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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