CN111023622A - Multistage heat pump drying system and control method thereof - Google Patents

Multistage heat pump drying system and control method thereof Download PDF

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Publication number
CN111023622A
CN111023622A CN201911336022.4A CN201911336022A CN111023622A CN 111023622 A CN111023622 A CN 111023622A CN 201911336022 A CN201911336022 A CN 201911336022A CN 111023622 A CN111023622 A CN 111023622A
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pipe
compressor
valve
air
air volume
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CN201911336022.4A
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CN111023622B (en
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金旭
王宝瑞
刘忠彦
洪文鹏
章罕伶
刘卓然
杜可丰
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Northeast Electric Power University
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Northeast Dianli University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
    • F26B21/08—Humidity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/02—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
    • F26B21/10—Temperature; Pressure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

The invention discloses a multistage heat pump drying system and a control method thereof, relating to the technical field of heat pump drying, wherein the system comprises a multistage heat pump circulation subsystem and a drying medium circulation subsystem; the multistage heat pump circulation subsystem comprises an R410a heat pump circulation subsystem, an R134a heat pump circulation subsystem, an R744 heat pump circulation subsystem and a heat pipe circulation subsystem. The control method of the system controls the opening and closing of the air volume regulating valve, and 6 working modes of up-and-down air supply of the drying box, front-and-back bypass of the condenser, front-and-back fresh air of the evaporator and the like can be realized for the drying medium; the start and stop of each stage of compressor are controlled, and a first-stage dehumidification heating drying mode, a second-stage dehumidification heating drying mode and a third-stage dehumidification heating drying mode can be realized; and controlling the rotating speeds of the variable frequency compressors to enable the evaporating and condensing temperatures of different units to reach the optimal matching relationship. The problems of large compressor pressure ratio and low efficiency of the single-stage heat pump drying system are solved, the drying time is shortened, and the energy consumption is saved.

Description

Multistage heat pump drying system and control method thereof
Technical Field
The invention relates to the technical field of heat pump drying, in particular to a multistage heat pump drying system and a control method thereof.
Background
Drying is a high-energy-consumption process, and in China, the energy consumption of drying equipment accounts for 12% of the total GDP energy consumption, but the energy utilization rate of the drying technology is only 40% -50%. The traditional hot air drying has lower cost and is widely applied, the traditional hot air drying occupies a leading position in China at present, the defects of high energy consumption, low drying speed and the like exist because the high-temperature and high-humidity air is continuously discharged in a replacement mode, the uniformity of the temperature and the humidity in a drying chamber is poor, and the formed hot and wet environment is not easy to control. The heat pump can recover the energy of the waste heat of the waste gas in the drying process, and the energy can be recycled and recycled, so that the energy consumption in the drying process can be reduced. The drying operation is not limited by the temperature and the humidity of the environment any more, the quality of the dried product is well maintained, the yield and the quality of the product are improved, and the method is particularly suitable for heat-sensitive foods and medicines. However, the single-stage heat pump compressor has large pressure, generally low latent heat recovery rate of the moisture-removing exhaust gas and low energy utilization rate.
The invention patent with publication number CN109945631A adopts indoor and outdoor double evaporators, and the compressor adopts double compression cylinders to recover heat exhausted by the system and outdoor air heat, thereby improving heat recovery efficiency, but the temperature difference between the inlet and the outlet of the heat exchanger is large, the pressure ratio of the compressor is increased, so that the power consumption of the compressor is increased, and the energy efficiency of the system is low.
The invention provides a heat pump type grain drying tower capable of recovering waste gas heat, and the whole system forms a loop, so that the purposes of energy conservation and environmental protection are achieved by recovering latent heat in waste gas. However, the energy consumption of the equipment is huge, a plurality of compressors are required to be connected in series for operation, and the energy consumption of the system is very high.
Disclosure of Invention
The invention aims to provide a multistage heat pump drying system and a control method thereof, which are used for solving the problems in the prior art, so that the heat pump drying system has high stability during operation, the utilization rate of latent heat energy of the moisture-discharging waste gas in the drying process is improved, the drying requirements of different materials under different working conditions are met, and the heating efficiency of a heat pump is effectively improved.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a multistage heat pump drying system, which comprises a multistage heat pump circulation subsystem and a drying medium circulation subsystem;
the multistage heat pump circulation subsystem comprises an R410a heat pump circulation subsystem, an R134a heat pump circulation subsystem, an R744 heat pump circulation subsystem and a heat pipe circulation subsystem; the R410a heat pump circulation subsystem comprises an R410a compressor, an R410a condenser, an R410a electronic expansion valve and an R410a evaporator which are sequentially connected in series in a closed manner; the R134a heat pump circulation subsystem comprises an R134a compressor, a refrigerant pipeline at the outlet of the R134a compressor is respectively connected with a refrigerant pipeline at the inlet of an R134a external condenser and a refrigerant pipeline at the inlet of an R134a internal condenser, a refrigerant pipeline at the outlet of an R134a external condenser and a refrigerant pipeline at the outlet of an R134a internal condenser are connected with a refrigerant pipeline at the inlet of an R134a electronic expansion valve after being intersected, a refrigerant pipeline at the outlet of an R134a electronic expansion valve is connected with a refrigerant pipeline at the inlet of an R134a evaporator, and an outlet of an R134a evaporator is connected with a refrigerant pipeline at the inlet of an R134a compressor; the R744 heat pump cycle subsystem includes an R744 compressor; the outlet of the R744 compressor is connected with a refrigerant pipeline at the inlet of the first gas cooler, the outlet of the first gas cooler is connected with a refrigerant pipeline at the inlet of the second gas cooler, the outlet of the second gas cooler is connected with a refrigerant pipeline at the inlet of the R744 electronic expansion valve, the outlet of the R744 electronic expansion valve is connected with a refrigerant pipeline at the inlet of the R744 evaporator, and the outlet of the R744 evaporator is connected with a refrigerant pipeline at the inlet of the R744 compressor; the heat pipe circulation subsystem comprises a fluorine pump, a heat pipe condenser and a heat pipe evaporator which are sequentially connected in series in a closed manner;
the drying medium circulation subsystem comprises a first horizontal ventilation pipe and a drying box; the upper part of the drying box is connected with the first ventilation transverse pipe at a point a, and the lower part of the drying box is connected with the fourth ventilation transverse pipe at a point b; the left end of the first ventilation horizontal pipe is connected with the point c at the upper end of the first ventilation vertical pipe, and the lower end of the first ventilation vertical pipe is connected with the point d at the left end of the fourth ventilation horizontal pipe; the right end of the first ventilating horizontal pipe and the upper end of the second ventilating vertical pipe are connected to a point e, and the lower end of the second ventilating vertical pipe and the right end of the fourth ventilating horizontal pipe are connected to a point f; a second ventilating horizontal pipe is arranged at the position 800mm below the first ventilating horizontal pipe, a third ventilating horizontal pipe is arranged at the position 1100mm above the fourth ventilating horizontal pipe, the right end of the second ventilating horizontal pipe and the second ventilating vertical pipe are connected to a g point, and an exhaust fan is arranged at the left end of the second ventilating horizontal pipe; the left end of the third ventilation horizontal pipe is connected with the first ventilation vertical pipe at a point h, and the right end of the third ventilation horizontal pipe is provided with a fresh air fan; a first bypass vertical pipe, a second bypass vertical pipe and a third bypass vertical pipe are arranged between the second ventilating horizontal pipe and the third ventilating horizontal pipe, the upper end of the first bypass vertical pipe and the second ventilating horizontal pipe are connected to a point i, the lower end of the first bypass vertical pipe and the third ventilating horizontal pipe are connected to a point j, the upper end of the second bypass vertical pipe and the second ventilating horizontal pipe are connected to a point k, the lower end of the second bypass vertical pipe and the third ventilating horizontal pipe are connected to a point l, the upper end of the third bypass vertical pipe and the second ventilating horizontal pipe are connected to a point m, and the third bypass vertical pipe and the third ventilating horizontal pipe are connected to a point n; a seventh air volume adjusting valve is arranged between the exhaust fan and the point i at the upper end of the first bypass vertical pipe; a first bypass valve is arranged on the first bypass vertical pipe, a second bypass valve is arranged on the second bypass vertical pipe, and a third bypass valve is arranged on the third bypass vertical pipe; a fresh air pipe is arranged on the third air transverse pipe, the left end of the fresh air pipe is connected with the third air transverse pipe at a point o, the right end of the fresh air pipe is connected with the third air transverse pipe at a point p, and a sixth air volume adjusting valve is arranged on the fresh air pipe; a fifth air volume regulating valve is arranged between the point p at the right end of the fresh air pipe and the point n at the lower end of the third bypass vertical pipe, a third air volume regulating valve is arranged between the points c and h, and a fourth air volume regulating valve is arranged between the points h and d; a first air volume adjusting valve is arranged between the two points e and g of the second ventilating vertical pipe, and a second air volume adjusting valve is arranged between the two points g and f; a heat pipe evaporator and a first circulating fan are sequentially arranged in a second ventilation transverse pipe between a third bypass vertical pipe and a second ventilation vertical pipe from left to right, and a second circulating fan and an electric heater are sequentially arranged in a third ventilation transverse pipe between the first bypass vertical pipe and the first ventilation vertical pipe from left to right; and a first gas cooler, an R134a built-in condenser, an R410a condenser, a second gas cooler and a heat pipe condenser are sequentially arranged in the air channel between j and l points on the third air-connecting transverse pipe from left to right, and an R410a evaporator, an R134a evaporator and an R744 evaporator are sequentially arranged in the air channel between o and n points from left to right.
Optionally, a second circulating fan, an electric heater, a first gas cooler, an R134a built-in condenser, an R410a condenser, a second gas cooler, a heat pipe condenser, an R410a evaporator, an R134a evaporator, an R744 evaporator, and a fresh air fan are sequentially arranged in the third ventilation transverse pipe from left to right.
Optionally, the first circulating fan, the second circulating fan, the fresh air fan and the exhaust fan are all variable frequency fans; the R410a compressor, the R134a compressor and the R744 compressor are all frequency conversion compressors.
The invention also provides a control method of the multistage heat pump drying system, which comprises a control method of a multistage heat pump circulation subsystem, wherein the control method of the multistage heat pump circulation subsystem comprises the following steps:
step one; first-stage dehumidification, heating and drying, namely R410a combined with heat pipe single-stage dehumidification and heating, R134a combined with heat pipe single-stage dehumidification and heating or R744 combined with heat pipe single-stage dehumidification and heating;
r410a combines heat pipe single-stage dehumidification heating including: the R134a electronic expansion valve and the R744 electronic expansion valve are not electrified, the R134a compressor and the R744 compressor are not started, and the R410a compressor, the R410a electronic expansion valve and the fluorine pump are started;
r134a combines heat pipe single-stage dehumidification heating and includes: the R410a electronic expansion valve and the R744 electronic expansion valve are not electrified, the R410a compressor and the R744 compressor are not started, and the R134a compressor, the R134a electronic expansion valve and the fluorine pump are started;
r744 combines the single-stage dehumidification heating of heat pipe to include: the R134a electronic expansion valve and the R410a electronic expansion valve are not electrified, the R134a compressor and the R410a compressor are not started, and the R744 compressor, the R744 electronic expansion valve and the fluorine pump are started;
step two; secondary dehumidification and heating drying, namely combining R410a with R134a and heat pipe secondary dehumidification and heating, combining R410a with R744 and heat pipe secondary dehumidification and heating or combining R134a with R744 and heat pipe secondary dehumidification and heating;
r410a and R134a combine the heat pipe secondary dehumidification heating to include: the R744 electronic expansion valve and the R744 compressor are not electrified, the R134a electronic expansion valve and the R410a electronic expansion valve are electrified, and the R134a compressor, the R410a compressor and the fluorine pump are started;
r410a combines R744 and heat pipe two-stage dehumidification heating to include: the R134a electronic expansion valve and the R134a compressor are not electrified, the R410a electronic expansion valve and the R744 electronic expansion valve are electrified, and the R410a compressor, the R744 compressor and the fluorine pump are started;
r134a combines R744 and heat pipe two-stage dehumidification heating to include: the R410a electronic expansion valve and the R410a compressor are not electrified, the R134a electronic expansion valve and the R744 electronic expansion valve are electrified, and the R134a compressor, the R744 compressor and the fluorine pump are started;
step three; and the three-stage dehumidification, heating and drying comprises the simultaneous energization of an R410a electronic expansion valve, an R134a electronic expansion valve and an R744 electronic expansion valve, and the simultaneous opening of an R410a compressor, an R134a compressor, an R744 compressor and a fluorine pump.
Optionally, the method also comprises a control method of the drying medium circulation subsystem; the control method of the drying medium circulation subsystem comprises a closed circulation up-feeding and down-returning air supply control method, a closed circulation down-feeding and up-returning air supply control method, a closed circulation condenser front air bypass method, a closed circulation condenser rear air bypass method, a semi-open evaporator front fresh air introducing method or a semi-open evaporator rear fresh air introducing method;
the method for controlling the air supply of the closed-cycle upper air supply and the closed-cycle lower air supply comprises the following steps: the first circulating fan and the second circulating fan are started, the second air volume adjusting valve, the third bypass valve and the third air volume adjusting valve are opened, and the rest air volume adjusting valves are closed;
the air supply control method for the closed circulation of downward supply and upward return comprises the following steps: the first circulating fan and the second circulating fan are started, the first air volume adjusting valve, the third bypass valve and the fourth air volume adjusting valve are opened, and the rest air volume adjusting valves are closed;
the method for bypassing air before the closed cycle condenser comprises the following steps: the first circulating fan and the second circulating fan are started, the first air volume adjusting valve, the third bypass valve, the second bypass valve and the fourth air volume adjusting valve are opened, and the rest air volume adjusting valves are closed;
the method for bypassing air after the closed cycle condenser comprises the following steps: the first circulating fan and the second circulating fan are started, the first air volume regulating valve, the third bypass valve, the first bypass valve and the fourth air volume regulating valve are opened, and the rest air volume regulating valves are closed;
the method for introducing fresh air in front of the semi-open evaporator comprises the following steps: the first circulating fan, the second circulating fan, the fresh air fan and the exhaust fan are started, the first air volume adjusting valve, the seventh air volume adjusting valve, the third bypass valve, the fifth air volume adjusting valve and the fourth air volume adjusting valve are opened, and the rest air volume adjusting valves are closed;
the method for introducing fresh air behind the semi-open evaporator comprises the following steps: and the first circulating fan, the second circulating fan, the fresh air fan and the exhaust fan are started, the first air volume regulating valve, the seventh air volume regulating valve, the third bypass valve, the sixth air volume regulating valve and the fourth air volume regulating valve are opened, and the rest air volume regulating valves are closed.
Compared with the prior art, the invention has the following technical effects:
the invention provides a multi-stage heat pump drying system and a control method thereof, which solve the problems of the existing heat pump drying system, adopt an air supply mode of up-feeding, down-feeding and up-feeding, a multi-evaporator and a condenser simultaneously carry out cooling, dehumidifying and dry heating processes on dry air based on an air duct, and simultaneously realize multiple ventilation modes of air bypass at the front and the back of the condenser, fresh air introduced at the front and the back of the evaporator and the like, so that the dry air is reasonably treated, the performance of the heat pump system is improved, the temperature and humidity of the dry air supply are effectively controlled, and the material drying quality is ensured. The working modes of the heat pump units with different stages reduce the compression ratio of the single-stage heat pump unit, improve the heating efficiency of the heat pump and the quality stability of a drying product, can meet the requirements of a continuous drying process, and improve the production capacity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of the structural layout of a multi-stage heat pump drying system according to the present invention;
description of reference numerals: 1-R410a compressor; 2-R410a condenser; 3-R410a electronic expansion valve; 4-R410a evaporator; 5-R134a compressor; 6-R134a external condenser; 7-R134a is internally provided with a condenser; 8-R134a electronic expansion valve; 9-R134a evaporator; 10-R744 compressor; 11 a-a first gas cooler; 11 b-a second gas cooler; 12-R744 electronic expansion valve; 13-R744 evaporator; 14-a fluorine pump; 15-a heat pipe condenser; 16-a heat pipe evaporator; 17-a first horizontal ventilation duct; 18-a second ventilating horizontal pipe; 19-a third ventilating horizontal pipe; 20-a fourth cross air duct; 21-a first ventilation riser; 22-a second vent riser; 23-a first bypass riser; 24-a second bypass riser; 25-a third bypass riser; 26-a fresh air pipe; 27-drying box; 28-a first circulation fan; 29-a second circulation fan; 30-a fresh air fan; 31-an exhaust fan; 32-a first air volume adjusting valve; 33-a second air volume adjusting valve; 34-a third air volume adjusting valve; 35-a fourth air volume adjusting valve; 36-a fifth air volume adjusting valve; 37-sixth air volume adjusting valve; 38-seventh air volume adjusting valve; 39-a first bypass valve; 40-a second bypass valve; 41-a third bypass valve; 42-electric heater.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a multistage heat pump drying system and a control method thereof, which are used for solving the problems in the prior art, so that the heat pump drying system has high stability during operation, the utilization rate of latent heat energy of the moisture-discharging waste gas in the drying process is improved, the drying requirements of different materials under different working conditions are met, and the heating efficiency of a heat pump is effectively improved.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a multistage heat pump drying system, as shown in fig. 1, comprising a multistage heat pump circulation subsystem and a drying medium circulation subsystem, wherein the multistage heat pump circulation subsystem consists of an R410a heat pump circulation subsystem, an R134a heat pump circulation subsystem and an R744 heat pump circulation subsystem; wherein, R410a is a novel environment-friendly refrigerant, does not destroy the ozone layer, has the working pressure about 1.6 times that of the common R22 air conditioner, and has high refrigerating (heating) efficiency. The R410a new refrigerant is composed of two quasi-azeotropic mixtures R32 and R125 of 50% respectively, mainly composed of hydrogen, fluorine and carbon elements (indicated as hfc), and has the characteristics of stability, no toxicity, excellent performance and the like. R134a (1, 1, 1, 2-tetrafluoroethane) is a widely used medium-low temperature environment-friendly refrigerant, has good comprehensive performance, becomes a very effective and safe substitute of R12 (dichlorodifluoromethane), and can be applied to most fields using R12 refrigerant. R744 is a novel refrigerant, the main component being carbon dioxide.
The R410a heat pump cycle subsystem includes R410a compressor 1, R410a condenser 2, R410a electronic expansion valve 3, R410a evaporator 4; the R134a heat pump circulation subsystem comprises a R134a compressor 5, a R134a external condenser 6, a R134a internal condenser 7, a R134a electronic expansion valve 8 and a R134a evaporator 9; the R744 heat pump circulation subsystem comprises an R744 compressor 10, a first gas cooler 11a, a second gas cooler 11b, an R744 electronic expansion valve 12 and an R744 evaporator 13; the heat pipe circulation subsystem comprises a fluorine pump 14, a heat pipe condenser 15 and a heat pipe evaporator 16; the drying medium circulation subsystem comprises a first ventilation transverse pipe 17, a second ventilation transverse pipe 18, a third ventilation transverse pipe 19, a fourth ventilation transverse pipe 20, a first ventilation vertical pipe 21, a second ventilation vertical pipe 22, a first bypass vertical pipe 23, a second bypass vertical pipe 24, a third bypass vertical pipe 25, a fresh air pipe 26, a drying box 27, a first circulating fan 28, a second circulating fan 29, a fresh air fan 30, an exhaust fan 31, a first air volume regulating valve 32, a second air volume regulating valve 33, a third air volume regulating valve 34, a fourth air volume regulating valve 35, a fifth air volume regulating valve 36, a sixth air volume regulating valve 37, a seventh air volume regulating valve 38, a first bypass valve 39, a second bypass valve 40, a third bypass valve 41 and an electric heater 42, wherein specifically, the upper part of the drying box 27 is connected with the first ventilation transverse pipe 17 at a point, and the lower part of the drying box is connected with the fourth ventilation transverse pipe 20 at b point; the left end of the first ventilation horizontal pipe 17 is connected with the point c at the upper end of the first ventilation vertical pipe 21, and the lower end of the first ventilation vertical pipe 21 is connected with the point d at the left end of the fourth ventilation horizontal pipe 20; the right end of the first ventilating horizontal pipe 17 is connected with the upper end of the second ventilating vertical pipe 22 at a point e, and the lower end of the second ventilating vertical pipe 22 is connected with the right end of the fourth ventilating horizontal pipe 20 at a point f; a second ventilating horizontal pipe 18 is arranged at the position 800mm below the first ventilating horizontal pipe 17, a third ventilating horizontal pipe 19 is arranged at the position 1100mm above the fourth ventilating horizontal pipe 20, the right end of the second ventilating horizontal pipe 18 is connected with a second ventilating vertical pipe 22 at a g point, and an exhaust fan 31 is arranged at the left end; the left end of the third ventilation horizontal pipe 19 is connected with the first ventilation vertical pipe 21 at a point h, and the right end is provided with a fresh air fan 30; a first bypass vertical pipe 23, a second bypass vertical pipe 24 and a third bypass vertical pipe 25 are arranged between the second ventilating transverse pipe 18 and the third ventilating transverse pipe 19, the upper end of the first bypass vertical pipe 23 is connected with the second ventilating transverse pipe 18 at a point i, the lower end of the first bypass vertical pipe 23 is connected with the third ventilating transverse pipe 19 at a point j, the upper end of the second bypass vertical pipe 24 is connected with the second ventilating transverse pipe 18 at a point k, the lower end of the second bypass vertical pipe 24 is connected with the third ventilating transverse pipe 19 at a point l, the upper end of the third bypass vertical pipe 25 is connected with the second ventilating transverse pipe 18 at a point m, and the third bypass vertical pipe 25 is connected with the third ventilating transverse pipe 19 at a point n; a seventh air volume adjusting valve 38 is arranged between the exhaust fan 31 and the point i at the upper end of the first bypass vertical pipe 23; a first bypass valve 39 is arranged on the first bypass riser 23, a second bypass valve 40 is arranged on the second bypass riser 24, and a third bypass valve 41 is arranged on the third bypass riser 25; the third horizontal ventilation pipe 19 is provided with a fresh air pipe 26, the left end of the fresh air pipe is connected with the third horizontal ventilation pipe 19 at a point o, the right end of the fresh air pipe is connected with the third horizontal ventilation pipe 19 at a point p, and the fresh air pipe 26 is provided with a sixth air volume adjusting valve 37; a fifth air volume adjusting valve 36 is arranged between a point p at the right end of the fresh air pipe 26 and a point n at the lower end of the third bypass vertical pipe 25, a third air volume adjusting valve 34 is arranged between the points 21c and h, and a fourth air volume adjusting valve 35 is arranged between the points h and d; a first air volume adjusting valve 32 is arranged between the two points of the second ventilating vertical pipe 22e and g, and a second air volume adjusting valve 33 is arranged between the two points g and f; a heat pipe evaporator 16 and a first circulating fan 28 are sequentially arranged in the second ventilating cross pipe 18 between the third bypass vertical pipe 25 and the second ventilating vertical pipe 22 from left to right, and a second circulating fan 29 and an electric heater 42 are sequentially arranged in the third ventilating cross pipe 19 between the first bypass vertical pipe 23 and the first ventilating vertical pipe 21 from left to right; a first air cooler 11a, an R134a built-in condenser 7, an R410a condenser 2, a second air cooler 11b and a heat pipe condenser 15 are sequentially arranged in the air channel between j and l points on the third air passing transverse pipe 19 from left to right, and an R410a evaporator 4, an R134a evaporator 9 and an R744 evaporator 13 are sequentially arranged in the air channel between o and n points; the outlet of the R410a compressor 1 is connected with the refrigerant pipeline of the inlet of the R410a condenser 2, the outlet of the R410a condenser 2 is connected with the refrigerant pipeline of the inlet of the R410a electronic expansion valve 3, the outlet of the R410a electronic expansion valve 3 is connected with the refrigerant pipeline of the inlet of the R410a evaporator 4, and the outlet of the R410a evaporator 4 is connected with the refrigerant pipeline of the inlet of the R410a compressor 1; the refrigerant pipeline at the outlet of the R134a compressor 5 is divided into two branches, wherein one branch is connected with the refrigerant pipeline at the inlet of the R134a external condenser 6, the other branch is connected with the refrigerant pipeline at the inlet of the R134a internal condenser 7, the refrigerant pipelines at the outlets of the R134a external condenser 6 and the R134a internal condenser 7 are connected with the refrigerant pipeline at the inlet of the R134a electronic expansion valve 8 after being intersected, the refrigerant pipeline at the outlet of the R134a electronic expansion valve 8 is connected with the refrigerant pipeline at the inlet of the R134a evaporator 9, and the outlet of the R134a evaporator 9 is connected with the refrigerant pipeline at the inlet of the R134a compressor 5; the outlet of the R744 compressor 10 is connected with the refrigerant pipeline of the inlet of the first gas cooler 11a, the outlet of the first gas cooler 11a is connected with the refrigerant pipeline of the inlet of the second gas cooler 11b, the outlet of the second gas cooler 11b is connected with the refrigerant pipeline of the inlet of the R744 electronic expansion valve 12, the outlet of the R744 electronic expansion valve 12 is connected with the refrigerant pipeline of the inlet of the R744 evaporator 13, and the outlet of the R744 evaporator 13 is connected with the refrigerant pipeline of the inlet of the R744 compressor 10.
In this example, the first circulating fan 28, the second circulating fan 29, the fresh air fan 30 and the exhaust fan 31 are all variable frequency fans; the R410a compressor 1, the R134a compressor 5 and the R744 compressor 10 are all frequency conversion compressors.
In this example, the second circulating fan 29, the electric heater 42, the first gas cooler 11a, the R134a built-in condenser 7, the R410a condenser 2, the second gas cooler 11b, the heat pipe condenser 15, the R410a evaporator 4, the R134a evaporator 9, the R744 evaporator 13, and the fresh air fan 30 are sequentially arranged in the third ventilating cross duct 19 from left to right.
In this example, the control method for the drying medium circulation subsystem includes the following modes:
(1) and (3) an air supply control mode of closed cycle upper air supply and lower air return: the first circulating fan 28 and the second circulating fan 29 are started, the second air volume adjusting valve 33, the third bypass valve 41 and the third air volume adjusting valve 34 are opened, and the rest air volume adjusting valves are closed;
(2) and (3) an air supply control mode of closed circulation downward feeding and upward returning: the first circulating fan 28 and the second circulating fan 29 are started, the first air volume adjusting valve 32, the third bypass valve 41 and the fourth air volume adjusting valve 35 are opened, and the rest air volume adjusting valves are closed;
(3) closed cycle condenser front air bypass mode: the first circulating fan 28 and the second circulating fan 29 are started, the first air volume adjusting valve 32, the third bypass valve 41, the second bypass valve 40 and the fourth air volume adjusting valve 35 are opened, and the rest air volume adjusting valves are closed;
(4) closed cycle condenser rear air bypass mode: the first circulating fan 28 and the second circulating fan 29 are started, the first air volume regulating valve 32, the third bypass valve 41, the first bypass valve 39 and the fourth air volume regulating valve 35 are opened, and the rest air volume regulating valves are closed;
(5) introduce the new trend mode before the semi-open type evaporimeter: the first circulating fan 28, the second circulating fan 29, the fresh air fan 30 and the exhaust fan 31 are started, the first air volume adjusting valve 32, the seventh air volume adjusting valve 38, the third bypass valve 41, the fifth air volume adjusting valve 36 and the fourth air volume adjusting valve 35 are opened, and the rest air volume adjusting valves are closed;
(6) introduce the new trend mode behind the semi-open evaporimeter: the first circulating fan 28, the second circulating fan 29, the fresh air fan 30 and the exhaust fan 31 are started, the first air volume adjusting valve 32, the seventh air volume adjusting valve 38, the third bypass valve 41, the sixth air volume adjusting valve 37 and the fourth air volume adjusting valve 35 are opened, and the rest air volume adjusting valves are closed;
in this example, for the heat pump cycle subsystem, the control method includes the following modes:
(1) first-stage dehumidification heating drying mode
R410a + heat pipe single-stage dehumidification heating mode: the R134a electronic expansion valve 8 and the R744 electronic expansion valve 12 are not electrified, the R134a compressor 5 and the R744 compressor 10 are not started, and the R410a compressor 1, the R410a electronic expansion valve 3 and the fluorine pump 14 are started;
r134a + heat pipe single-stage dehumidification heating mode: the R410a electronic expansion valve 3 and the R744 electronic expansion valve 12 are not electrified, the R410a compressor 1 and the R744 compressor 10 are not started, and the R134a compressor 5, the R134a electronic expansion valve 8 and the fluorine pump 14 are started;
r744+ heat pipe single-stage dehumidification heating mode: the R134a electronic expansion valve 8 and the R410a electronic expansion valve 3 are not electrified, the R134a compressor 5 and the R410a compressor 1 are not started, and the R744 compressor 10, the R744 electronic expansion valve 12 and the fluorine pump 14 are started.
In this example, (2) two-stage dehumidification heating drying mode
R410a + R134a + heat pipe secondary dehumidification heating mode: the R744 electronic expansion valve 12 and the R744 compressor 10 are not electrified, the R134a electronic expansion valve 8 and the R410a electronic expansion valve 3 are electrified, and the R134a compressor 5, the R410a compressor 1 and the fluorine pump 14 are started;
r410a + R744+ heat pipe secondary dehumidification heating mode: the R134a electronic expansion valve 8 and the R134a compressor 5 are not electrified, the R410a electronic expansion valve 3 and the R744 electronic expansion valve 12 are electrified, and the R410a compressor 1, the R744 compressor 10 and the fluorine pump 14 are started;
and c, R134a + R744+ heat pipe secondary dehumidification heating mode: the R410a electronic expansion valve 3 and the R410a compressor 1 are not electrified, the R134a electronic expansion valve 8 and the R744 electronic expansion valve 12 are electrified, the R134a compressor 5, the R744 compressor 10 and the fluorine pump 14 are started
In this example, (3) three-stage dehumidification heating drying mode
The R410a electronic expansion valve 3, the R134a electronic expansion valve 8 and the R744 electronic expansion valve 12 are electrified simultaneously, and the R410a compressor 1, the R134a compressor 5, the R744 compressor 10 and the fluorine pump 14 are started simultaneously;
in this example, the multi-stage heat pump drying system operating modes include the following:
multistage bypass and multistage dehumidification heat pump drying system are equipped with ten air regulating valves and four frequency conversion fans altogether, and this system still can regulate and control the fan amount of wind through air regulating valve's aperture and converter, realizes that closed, semi-open air cycle and dry railway carriage or compartment are from top to bottom, are sent from top to bottom and are returned equal air current tissue mode to satisfy the required drying condition of different materials, reasonable utilization air supply air current is to the influence of drying process, improves dry material quality effectively, practices thrift the energy consumption.
(1) Closed circulation upper and lower air supply mode
In order to realize different air supply modes in the drying box, meet different drying processes of different materials and improve the energy utilization rate, the control method of the multistage heat pump drying system can realize two air circulation switching modes of upward feeding, downward returning and upward feeding and upward returning of a drying medium in the drying box.
a. Closed cycle feed-up and return-down mode: as shown in fig. 1, the second air volume adjusting valve 33, the third bypass valve 41 and the third air volume adjusting valve 34 are opened, and the rest air volume adjusting valves are closed, the high-temperature and high-humidity air after the drying of the materials is discharged from the lower part of the drying box 27 and flows through the heat pipe evaporator 16 for primary cooling and dehumidification under the action of the first circulating fan 28 through the second air volume adjusting valve 33, the air passes through the R744 evaporator 13, the R134a evaporator 9, the R410a evaporator 4, the heat pipe condenser 15, the two gas cooler 11b, the R410a condenser 2 and the R134a built-in condenser 7, the first gas cooler 11a and the electric heater 42 along the third air volume adjusting valve 19 in sequence to perform step-by-step cooling and dehumidification and step-by-step heating on the air, the processed air passes through the third air volume adjusting valve 34 under the action of the second circulating fan 29 and enters the drying box 27 along the first air volume adjusting valve 17 to dry the materials, and a drying mode of closed circulation up-feeding and down-returning is completed.
b. Closed cycle feed-back-up mode: as shown in fig. 1, the first air volume adjusting valve 32, the third bypass valve 41 and the fourth air volume adjusting valve 35 are opened, and the rest air volume adjusting valves are closed, the high-temperature and high-humidity air after the drying of the materials is discharged from the upper part of the drying box 27, flows through the heat pipe evaporator 16 for primary cooling and dehumidification under the action of the first air volume adjusting valve 32 under the action of the first circulating fan 28, sequentially passes through the R744 evaporator 13, the R134a evaporator 9, the R410a evaporator 4, the heat pipe condenser 15, the two gas cooler 11b, the R410a condenser 2, the built-in condenser 7 of the R134a, the first gas cooler 11a and the electric heater 42 along the third air cross pipe 19 to perform step-by-step cooling and dehumidification and step-by-step heating on the air, and the treated air passes through the fourth air volume adjusting valve 35 under the action of the second circulating fan 29 and enters the drying box 27 along the fourth air cross pipe 20 to dry the materials, so as to complete a closed cycle up-feeding-down-returning drying mode.
(2) Closed cycle multiple bypass mode
In order to improve the drying effect, the multistage heat pump drying system is provided with two-stage bypass, and bypass air can be mixed with system circulating air respectively in front of a condenser and behind the condenser.
a. Condenser front air bypass mode: as shown in fig. 1, the third bypass valve 41, the second bypass valve 40, the first air volume adjusting valve 32, and the fourth air volume adjusting valve 35 are opened, and the remaining air volume adjusting valves are closed. When the wet air is discharged from the upper part of the drying box 27 and flows through the heat pipe evaporator 16 for primary cooling and dehumidification under the action of the first air volume adjusting valve 32 under the action of the first circulating fan 28, a part of the circulating air enters the evaporation section of the heat pump subsystem for cooling and dehumidification through the third bypass valve 41, the other part of the bypass air is mixed with the circulating air through the second bypass valve 40 in front of the condenser, the mixed air enters the condensation section together for heating and warming, and then is sent into the drying box 27 under the action of the second circulating fan 29, the temperature of the air entering the condensation section can be effectively increased along with the change of the air bypass rate, the heat load is reduced, the humidity of the air sent into the drying box can be effectively regulated, and the phenomenon that the air humidity is too high and the quality of dried products is.
b. Condenser rear air bypass mode: as shown in fig. 1, when the first air volume adjusting valve 32, the third bypass valve 41, the first bypass valve 39 and the fourth air volume adjusting valve 35 are opened, after the humid air is discharged from the upper part of the drying box 27 and passes through the first air volume adjusting valve 32 and flows through the heat pipe evaporator 16 under the action of the first circulating fan 28 for primary cooling and dehumidification, a part of the circulating air enters the evaporation section of the heat pump subsystem through the third bypass valve 41 for cooling and dehumidification and then passes through the condensation section for heating and warming, and the other part of the bypass air passes through the first bypass valve 39 and is mixed with the circulating air after passing through the condensation section, and then is sent into the drying box 27 under the action of the second circulating fan 29, so that the humidity and the temperature of the air sent into the drying box can be effectively controlled along. Avoid the evaporation stage not have the moisture to condense and separate out and cause the energy waste.
(3) Semi-open type multi-stage fresh air mode
When the heat pump drying system works at a high-temperature section, the performance of the heat pump system is reduced due to overhigh temperature of circulating air, and the quality of dried materials can be influenced. Therefore, by introducing the fresh air of the outdoor environment, the exhaust temperature of the compressor can be effectively reduced, the service life is prolonged, and the air supply temperature can be controlled.
a. Introducing fresh air in front of the evaporator: as shown in fig. 1, the first circulation fan 28, the second circulation fan 29, the fresh air fan 30 and the exhaust fan 31 are started, the first air volume adjusting valve 32, the seventh air volume adjusting valve 38, the third bypass valve 41, the fifth air volume adjusting valve 36 and the fourth air volume adjusting valve 35 are opened, the remaining air volume adjusting valves are closed, when the humid air is discharged from the upper part of the drying box 27 and flows through the heat pipe evaporator 16 under the action of the first circulation fan 28 through the first air volume adjusting valve 32 to perform primary cooling and dehumidification, part of the humid air is discharged to the outside through the seventh air volume adjusting valve 38 under the action of the exhaust fan 31, and the other part of the circulating air passes through the third bypass valve 41 and enters the front end of the heat pump evaporation section. Outdoor fresh air enters the front section of the evaporator under the action of the fresh air fan 30 to be mixed with circulating air, and then enters the evaporation section and the condensation section together to be subjected to corresponding air treatment. The fresh air introduced in front of the evaporator can reduce the temperature of the waste gas entering the heat pump subsystem and reduce the temperature of the evaporator.
b. Introducing fresh air behind the evaporator: as shown in fig. 1, the first circulation fan 28, the second circulation fan 29, the fresh air fan 30 and the exhaust fan 31 are started, the first air volume adjusting valve 32, the seventh air volume adjusting valve 38, the third bypass valve 41, the sixth air volume adjusting valve 37 and the fourth air volume adjusting valve 35 are opened, the remaining air volume adjusting valves are closed, when the humid air is discharged from the upper part of the drying box 27, passes through the first air volume adjusting valve 32 and flows through the heat pipe evaporator 16 under the action of the first circulation fan 28 for primary cooling and dehumidification, part of the humid air is discharged to the outside through the seventh air volume adjusting valve 38 under the action of the exhaust fan 31, and the other part of the circulating air passes through the third bypass valve 41 and enters the front end of the heat pump evaporation section. Outdoor fresh air enters the rear end of the evaporator under the action of the fresh air fan 22, is mixed with circulating air which is cooled and dehumidified by the evaporator section, and enters the condensation section together for heating and temperature rise.
According to the invention, through the air regulating valve on the regulating air duct, the closed circulation of dry air is realized or the dry waste gas is discharged and introduced into fresh air to form a semi-open system, and the air bypass of the front part and the rear part of the condenser can be realized, so that the temperature, humidity and air volume of the drying box are regulated. The multi-stage heat pumps are connected in parallel, so that the compression ratio of the single-stage heat pump unit is reduced, and the heating efficiency of the heat pumps is improved. The quality stability of the dried product is improved, the requirements of a continuous drying process can be met, and the production capacity is improved.
The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (5)

1. A multistage heat pump drying system characterized in that: the system comprises a multi-stage heat pump circulation subsystem and a drying medium circulation subsystem;
the multistage heat pump circulation subsystem comprises an R410a heat pump circulation subsystem, an R134a heat pump circulation subsystem, an R744 heat pump circulation subsystem and a heat pipe circulation subsystem; the R410a heat pump circulation subsystem comprises an R410a compressor (1), an R410a condenser (2), an R410a electronic expansion valve (3) and an R410a evaporator (4) which are sequentially connected in series in a closed manner; the R134a heat pump circulation subsystem comprises an R134a compressor (5), a refrigerant pipeline at the outlet of the R134a compressor (5) is respectively connected with a refrigerant pipeline at the inlet of an R134a external condenser (6) and a refrigerant pipeline at the inlet of an R134a internal condenser (7), a refrigerant pipeline at the outlet of an R134a external condenser (6) and an R134a internal condenser (7) is connected with a refrigerant pipeline at the inlet of an R134a electronic expansion valve (8) after being intersected, a refrigerant pipeline at the outlet of the R134a electronic expansion valve (8) is connected with a refrigerant pipeline at the inlet of an R134a evaporator (9), and an outlet of an R134a evaporator (9) is connected with a refrigerant pipeline at the inlet of an R134a compressor (5); the R744 heat pump cycle subsystem includes an R744 compressor (10); the outlet of the R744 compressor (10) is connected with a refrigerant pipeline at the inlet of a first gas cooler (11a), the outlet of the first gas cooler (11a) is connected with a refrigerant pipeline at the inlet of a second gas cooler (11b), the outlet of the second gas cooler (11b) is connected with a refrigerant pipeline at the inlet of an R744 electronic expansion valve (12), the outlet of the R744 electronic expansion valve (12) is connected with a refrigerant pipeline at the inlet of an R744 evaporator (13), and the outlet of the R744 evaporator (13) is connected with a refrigerant pipeline at the inlet of the R744 compressor (10); the heat pipe circulation subsystem comprises a fluorine pump (14), a heat pipe condenser (15) and a heat pipe evaporator (16) which are sequentially connected in series in a closed manner;
the drying medium circulation subsystem comprises a first horizontal ventilation pipe (17) and a drying box (27); the upper part of the drying box (27) is connected with a first ventilation transverse pipe (17) at a point a, and the lower part of the drying box is connected with a fourth ventilation transverse pipe (20) at a point b; the left end of the first ventilation horizontal pipe (17) is connected with the point c at the upper end of the first ventilation vertical pipe (21), and the lower end of the first ventilation vertical pipe (21) is connected with the point d at the left end of the fourth ventilation horizontal pipe (20); the right end of the first ventilation horizontal pipe (17) is connected with the upper end of the second ventilation vertical pipe (22) at a point e, and the lower end of the second ventilation vertical pipe (22) is connected with the right end of the fourth ventilation horizontal pipe (20) at a point f; a second ventilating transverse pipe (18) is arranged at the position 800mm below the first ventilating transverse pipe (17), a third ventilating transverse pipe (19) is arranged at the position 1100mm above the fourth ventilating transverse pipe (20), the right end of the second ventilating transverse pipe (18) is connected with a second ventilating vertical pipe (22) at a g point, and an exhaust fan (31) is arranged at the left end; the left end of the third ventilation transverse pipe (19) is connected with the first ventilation vertical pipe (21) at a point h, and the right end is provided with a fresh air fan (30); a first bypass vertical pipe (23), a second bypass vertical pipe (24) and a third bypass vertical pipe (25) are arranged between the second ventilating transverse pipe (18) and the third ventilating transverse pipe (19), the upper end of the first bypass vertical pipe (23) is connected with the second ventilating transverse pipe (18) at a point i, the lower end of the first bypass vertical pipe (23) is connected with the third ventilating transverse pipe (19) at a point j, the upper end of the second bypass vertical pipe (24) is connected with the second ventilating transverse pipe (18) at a point k, the lower end of the second bypass vertical pipe (24) is connected with the third ventilating transverse pipe (19) at a point l, the upper end of the third bypass vertical pipe (25) is connected with the second ventilating transverse pipe (18) at a point m, and the third bypass vertical pipe (25) is connected with the third ventilating transverse pipe (19) at a point n; a seventh air volume adjusting valve (38) is arranged between the exhaust fan (31) and the point i at the upper end of the first bypass vertical pipe (23); a first bypass valve (39) is arranged on the first bypass vertical pipe (23), a second bypass valve (40) is arranged on the second bypass vertical pipe (24), and a third bypass valve (41) is arranged on the third bypass vertical pipe (25); a fresh air pipe (26) is arranged on the third cross ventilation pipe (19), the left end of the fresh air pipe is connected with the third cross ventilation pipe (19) at a point o, the right end of the fresh air pipe is connected with the third cross ventilation pipe (19) at a point p, and a sixth air volume adjusting valve (37) is arranged on the fresh air pipe (26); a fifth air volume adjusting valve (36) is arranged between the p point at the right end of the fresh air pipe (26) and the n point at the lower end of the third bypass vertical pipe (25), a third air volume adjusting valve (34) is arranged between the c point and the h point of the first ventilation vertical pipe (21), and a fourth air volume adjusting valve (35) is arranged between the h point and the d point; a first air volume adjusting valve (32) is arranged between the two points of the second ventilating vertical pipe (22) e and g, and a second air volume adjusting valve (33) is arranged between the two points g and f; a heat pipe evaporator (16) and a first circulating fan (28) are sequentially arranged in a second ventilating cross pipe (18) between a third bypass vertical pipe (25) and a second ventilating vertical pipe (22) from left to right, and a second circulating fan (29) and an electric heater (42) are sequentially arranged in a third ventilating cross pipe (19) between a first bypass vertical pipe (23) and a first ventilating vertical pipe (21) from left to right; a first gas cooler (11a), an R134a built-in condenser (7), an R410a condenser (2), a second gas cooler (11b) and a heat pipe condenser (15) are sequentially arranged between j and l points on the third air-passing transverse pipe (19) from left to right in an air channel, and an R410a evaporator (4), an R134a evaporator (9) and an R744 evaporator (13) are sequentially arranged between o and n points in the air channel from left to right.
2. The multi-stage heat pump drying system of claim 1, wherein: and a second circulating fan (29), an electric heater (42), a first gas cooler (11a), a built-in condenser (7) of R134a, a condenser (2) of R410a, a second gas cooler (11b), a heat pipe condenser (15), an evaporator (4) of R410a, an evaporator (9) of R134a, an evaporator (13) of R744 and a fresh air fan (30) are sequentially arranged in the third air passing transverse pipe (19) from left to right.
3. The multi-stage heat pump drying system of claim 1, wherein: the first circulating fan (28), the second circulating fan (29), the fresh air fan (30) and the exhaust fan (31) are all variable frequency fans; the R410a compressor (1), the R134a compressor (5) and the R744 compressor (10) are all frequency conversion compressors.
4. A control method of a multistage heat pump drying system is characterized in that: the method comprises a control method of a multistage heat pump circulation subsystem, and the control method of the multistage heat pump circulation subsystem comprises the following steps:
step one; first-stage dehumidification, heating and drying, namely R410a combined with heat pipe single-stage dehumidification and heating, R134a combined with heat pipe single-stage dehumidification and heating or R744 combined with heat pipe single-stage dehumidification and heating;
r410a combines heat pipe single-stage dehumidification heating including: the R134a electronic expansion valve (8) and the R744 electronic expansion valve (12) are not electrified, the R134a compressor (5) and the R744 compressor (10) are not started, and the R410a compressor (1), the R410a electronic expansion valve (3) and the fluorine pump (14) are started;
r134a combines heat pipe single-stage dehumidification heating and includes: the R410a electronic expansion valve (3) and the R744 electronic expansion valve (12) are not electrified, the R410a compressor (1) and the R744 compressor (10) are not started, and the R134a compressor (5), the R134a electronic expansion valve (8) and the fluorine pump (14) are started;
r744 combines the single-stage dehumidification heating of heat pipe to include: the R134a electronic expansion valve (8) and the R410a electronic expansion valve (3) are not electrified, the R134a compressor (5) and the R410a compressor (1) are not started, and the R744 compressor (10), the R744 electronic expansion valve (12) and the fluorine pump (14) are started;
step two; secondary dehumidification and heating drying, namely combining R410a with R134a and heat pipe secondary dehumidification and heating, combining R410a with R744 and heat pipe secondary dehumidification and heating or combining R134a with R744 and heat pipe secondary dehumidification and heating;
r410a and R134a combine the heat pipe secondary dehumidification heating to include: the R744 electronic expansion valve (12) and the R744 compressor (10) are not electrified, the R134a electronic expansion valve (8) and the R410a electronic expansion valve (3) are electrified, and the R134a compressor (5), the R410a compressor (1) and the fluorine pump (14) are started;
r410a combines R744 and heat pipe two-stage dehumidification heating to include: the R134a electronic expansion valve (8) and the R134a compressor (5) are not electrified, the R410a electronic expansion valve (3) and the R744 electronic expansion valve (12) are electrified, and the R410a compressor (1), the R744 compressor (10) and the fluorine pump (14) are started;
r134a combines R744 and heat pipe two-stage dehumidification heating to include: the R410a electronic expansion valve (3) and the R410a compressor (1) are not electrified, the R134a electronic expansion valve (8) and the R744 electronic expansion valve (12) are electrified, and the R134a compressor (5), the R744 compressor (10) and the fluorine pump (14) are started;
step three; the three-stage dehumidification and heating drying device comprises an R410a electronic expansion valve (3), an R134a electronic expansion valve (8) and an R744 electronic expansion valve (12) which are electrified simultaneously, and an R410a compressor (1), an R134a compressor (5), an R744 compressor (10) and a fluorine pump (14) are started simultaneously.
5. The multistage heat pump drying system control method according to claim 4, characterized in that: also includes a drying medium circulation subsystem control method; the control method of the drying medium circulation subsystem comprises a closed circulation up-feeding and down-returning air supply control method, a closed circulation down-feeding and up-returning air supply control method, a closed circulation condenser front air bypass method, a closed circulation condenser rear air bypass method, a semi-open evaporator front fresh air introducing method or a semi-open evaporator rear fresh air introducing method;
the method for controlling the air supply of the closed-cycle upper air supply and the closed-cycle lower air supply comprises the following steps: the first circulating fan (28) and the second circulating fan (29) are started, the second air volume adjusting valve (33), the third bypass valve (41) and the third air volume adjusting valve (34) are opened, and the rest air volume adjusting valves are closed;
the air supply control method for the closed circulation of downward supply and upward return comprises the following steps: the first circulating fan (28) and the second circulating fan (29) are started, the first air volume adjusting valve (32), the third bypass valve (41) and the fourth air volume adjusting valve (35) are opened, and the rest air volume adjusting valves are closed;
the method for bypassing air before the closed cycle condenser comprises the following steps: the first circulating fan (28) and the second circulating fan (29) are started, the first air volume adjusting valve (32), the third bypass valve (41), the second bypass valve (40) and the fourth air volume adjusting valve (35) are opened, and the rest air volume adjusting valves are closed;
the method for bypassing air after the closed cycle condenser comprises the following steps: the first circulating fan (28) and the second circulating fan (29) are started, the first air volume regulating valve (32), the third bypass valve (41), the first bypass valve (39) and the fourth air volume regulating valve (35) are opened, and the rest air volume regulating valves are closed;
the method for introducing fresh air in front of the semi-open evaporator comprises the following steps: the first circulating fan (28), the second circulating fan (29), the fresh air fan (30) and the exhaust fan (31) are started, the first air volume adjusting valve (32), the seventh air volume adjusting valve (38), the third bypass valve (41), the fifth air volume adjusting valve (36) and the fourth air volume adjusting valve (35) are opened, and the rest air volume adjusting valves are closed;
the method for introducing fresh air behind the semi-open evaporator comprises the following steps: the first circulating fan (28), the second circulating fan (29), the fresh air fan (30) and the exhaust fan (31) are started, the first air volume adjusting valve (32), the seventh air volume adjusting valve (38), the third bypass valve (41), the sixth air volume adjusting valve (37) and the fourth air volume adjusting valve (35) are opened, and the rest air volume adjusting valves are closed.
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