Multi-stage heat pump drying system and control method thereof

Abstract

The invention discloses a multi-stage heat pump drying system and a control method thereof and relates to the technical field of heat pump drying. The system comprises a multi-stage heat pump circulating subsystem and a drying medium circulating subsystem. The multi-stage heat pump circulating subsystem comprises an R410a heat pump circulating subsystem, an R134a heat pump circulating subsystem, an R744 heat pump circulating subsystem and a heat pipe circulating subsystem. By the adoption of the control method of the system, opening and closing of an air volume adjusting valve are controlled,and six working modes of drying box up and down air supply, condenser front and rear bypass, evaporator front and rear fresh air and the like can be achieved for drying media. Starting and stopping ofall stages of compressors are controlled, and a first-stage dehumidifying, heating and drying mode, a second-stage dehumidifying, heating and drying mode and a third-stage dehumidifying, heating anddrying mode can be achieved. The rotating speed of the multiple variable frequency compressors is controlled, and evaporation and condensation temperature of different units reach the optimal match relation. The problems that the compression ratio of compressors of a single-stage heat pump drying system is large, and efficiency is low are solved, drying time is shortened, and energy consumption isreduced.

Description

technical field [0001] The invention relates to the technical field of heat pump drying, in particular to a multi-stage heat pump drying system and a control method thereof. Background technique [0002] Drying is a process with high energy consumption. In China, the energy consumption of drying equipment accounts for 12% of the total energy consumption of GDP, but the energy utilization rate of drying technology is only 40% to 50%. Traditional hot air drying is widely used due to its low cost, and currently occupies a dominant position in my country. Because the air with high temperature and high humidity is continuously discharged through replacement, it has disadvantages such as large energy consumption and slow drying speed, and the drying room The uniformity of temperature and humidity is poor, and the hot and humid environment formed is not easy to control. The heat pump can recover the energy of the waste heat of the waste gas in the drying process, recycle it and reu...

AI Technical Summary

Problems solved by technology

However, its equipment consumes a lot of energy, requiring multiple compressors to run in series, and the system consumes a lot of energy

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