Heat pump type drying device

Abstract

The invention discloses a heat pump type drying device, relates to the technical field of drying equipment, and aims to solve the problems that in the prior art, the moisture absorption capacity of dry air is limited, the efficiency is low, and the drying difficulty is high in a high-humidity environment. Comprising a first-stage refrigeration unit, a second-stage refrigeration unit, a drying chamber and an air supply system. The first-stage refrigeration unit forms a circulation loop by a first-stage compressor, a first-stage condenser, a first-stage evaporator and the like; the second-stage refrigeration unit is similar in structure. The first-stage evaporator shell, the first-stage condenser shell, the second-stage condenser shell, the air feeder and the drying chamber are sequentially connected in series through an air supply pipeline to form a closed air circulation path. Through the synergistic effect of the two stages of refrigeration units, accurate regulation and control over the temperature and humidity of a drying medium are achieved, the air moisture absorption capacity and the drying efficiency are remarkably improved, and the device is particularly suitable for low-temperature drying of heat-sensitive materials such as seeds and the like and has the advantages of being low in energy consumption and good in stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of drying equipment, in particular to a heat pump type drying device. BACKGROUND

[0002] Moisture content is a key factor affecting the safe storage of seeds. Seeds that need to be stored for a long time must be dried to a safe moisture content after harvesting. Currently, common drying methods include natural air drying, hot air drying (electric heating, coal heating, biomass heating, heat pump heating), infrared drying, microwave drying, etc. Among them, heat pump drying is a clean and efficient drying method, especially suitable for high-temperature areas. When the ambient temperature is high, the heat efficiency of the heat pump is high.

[0003] However, the existing heat pump drying device has limited moisture absorption capacity of the air provided at low temperature (temperature ≤ 60℃), resulting in low drying efficiency. Moreover, high-temperature environments are usually accompanied by high humidity, but when the ambient humidity is high, it will greatly increase the difficulty of drying, especially when the seeds are harvested and encounter rainy weather, which requires timely drying to prevent seed mold and loss of activity. SUMMARY

[0004] The purpose of the present application is to provide a heat pump type drying device to solve the problems existing in the prior art and to realize comprehensive regulation of drying temperature and humidity and improve drying efficiency.

[0005] To achieve the above purpose, the present application provides the following solutions: The present application provides a heat pump drying device, comprising: A first refrigeration unit, the first refrigeration unit comprises a first compressor, a first condenser, a first liquid tank, a first drying filter, a first expansion valve, a first evaporator and a first gas-liquid separator which are sequentially connected, the gas outlet of the first gas-liquid separator is communicated with the gas inlet of the first compressor; the shell of the first evaporator is a first shell, and the shell of the first condenser is a second shell; A second refrigeration unit, the second refrigeration unit comprises a second compressor, a second condenser, a second liquid tank, a second drying filter, a second expansion valve, a second evaporator and a second gas-liquid separator which are sequentially connected, the gas outlet of the second gas-liquid separator is communicated with the gas inlet of the second compressor; the shell of the second condenser is a third shell; A drying chamber, the drying chamber is a closed shell; The air supply system comprises a first connecting pipe, a second connecting pipe, a third connecting pipe, an air supply fan, an air supply pipe, an air return pipe, an air return fan and a fourth connecting pipe; one end of the first connecting pipe is communicated with the first shell and the other end is communicated with the second shell; one end of the second connecting pipe is communicated with the second shell and the other end is communicated with the third shell; one end of the third connecting pipe is communicated with the third shell and the other end is communicated with the air suction port of the air supply fan; the air outlet of the air supply fan is communicated with the drying chamber through the air supply pipe; the drying chamber is communicated with the air return fan through the air return pipe; the air return fan is communicated with the first shell through the fourth connecting pipe.

[0006] Preferably, the primary evaporator comprises a drying filter screen, a fin heat exchanger and a water baffle arranged in the first shell; the drying filter screen, the fin heat exchanger and the water baffle are sequentially connected; the drying filter screen is closer to the communication port of the first shell and the fourth connecting pipe than the fin heat exchanger; and the water baffle is closer to the communication port of the first shell and the first connecting pipe than the fin heat exchanger.

[0007] Preferably, the air supply fan is a variable frequency fan.

[0008] Preferably, the bottom end of the drying chamber is provided with an air inlet; and the end of the air supply pipe close to the drying chamber is communicated with the air inlet.

[0009] Preferably, the top end of the drying chamber is provided with an air return port; and the end of the air return pipe close to the drying chamber is communicated with the air return port.

[0010] Preferably, a door body is hinged on the side wall of the drying chamber; and the door body is in sealing connection with the side wall of the drying chamber when the door body is closed.

[0011] Preferably, the air supply system further comprises a controller; the first connecting pipe, the second connecting pipe, the third connecting pipe and the air return pipe are respectively provided with a temperature and humidity sensor; the frequency converter of the air supply fan and all the temperature and humidity sensors are respectively signal connected with the controller.

[0012] Preferably, the end of the drying chamber close to the air inlet is provided with a trapezoidal cavity; and the smaller end of the trapezoidal cavity is communicated with the air inlet.

[0013] Preferably, the drying chamber is in a cylindrical shape.

[0014] Preferably, the first connecting pipe, the second connecting pipe, the third connecting pipe, the air supply pipe and the air return pipe are all wrapped with a heat preservation layer.

[0015] The present application has the following technical effects compared with the prior art: The heat pump type drying device of the present application realizes the accurate control of the temperature and humidity of the drying medium through the cooperation of the primary refrigeration unit and the secondary refrigeration unit, and the series design of the primary evaporator, the primary condenser and the secondary condenser. The combination of the drying filter screen, the finned heat exchanger and the water baffle in the primary evaporator effectively removes the moisture in the return air and recovers the latent heat. The primary condenser preliminarily heats the air, and the secondary condenser further heats the air, so that the air in the drying chamber has significantly enhanced moisture absorption capacity. The air is dehumidified before drying to eliminate the influence of environmental humidity, which can improve the drying efficiency and realize the comprehensive regulation of the drying temperature and humidity, and create a stable drying condition. Seeds have high requirements for drying temperature as heat-sensitive materials, and need to be dried at low temperature. Reducing the drying humidity is beneficial to improve the moisture absorption of the drying air, shorten the low-temperature drying time and reduce the energy consumption of the drying process. Therefore, the heat pump type drying device of the present application is especially suitable for seed drying. The air supply system adopts a frequency conversion fan, which cooperates with a temperature and humidity sensor and a controller to dynamically adjust the air volume and temperature and humidity parameters according to the characteristics of the material, so as to realize the whole-process constant temperature and humidity drying, reduce the environmental influence and avoid excessive drying or energy waste. The closed design of the drying chamber and the pipeline system wrapped by the heat preservation layer reduce heat loss and prevent external moisture from entering, further ensuring the drying stability. Through the trapezoidal cavity design, the hot air distribution is more uniform, and the material is heated uniformly. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0017] Fig. 1 FIG. 1 is a structural schematic diagram of the heat pump type drying device of the present application; Fig. 2 FIG. 2 is a partial structural schematic diagram of the primary evaporator in the heat pump type drying device of the present application; Fig. 3 FIG. 3 is a partial structural schematic diagram of the drying chamber in the heat pump type drying device of the present application; In the diagram: 1. First-stage compressor; 2. First-stage condenser; 3. First-stage liquid tank; 4. First-stage dryer filter; 5. First-stage expansion valve; 6. First-stage evaporator; 7. First-stage gas-liquid separator; 8. Second-stage compressor; 9. Second-stage condenser; 10. Second-stage liquid tank; 11. Second-stage dryer filter; 12. Second-stage expansion valve; 13. Second-stage evaporator; 14. Second-stage gas-liquid separator; 15. First housing; 16. Second housing; 17. Third housing; 18. First connecting pipe; 19. Second connecting pipe; 20. Third connecting pipe; 21. Blower; 22. Frequency converter; 23. Blower duct; 24. Drying chamber; 25. Return air duct; 26. Return air fan; 27. Fourth connecting pipe; 28. Dryer filter screen; 29. ​​Finned heat exchanger; 30. Water baffle; 31. Air inlet; 32. Trapezoidal cavity. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The purpose of this invention is to provide a heat pump type drying device to solve the problems existing in the prior art, achieve comprehensive control of drying temperature and humidity, and improve drying efficiency.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figs. 1 to 3 As shown, this embodiment provides a heat pump type drying device, which is mainly used for low-temperature drying of heat-sensitive materials such as seeds. Through the synergistic effect of two-stage refrigeration units, it achieves comprehensive control of the temperature and humidity of the drying air, thereby improving drying efficiency and reducing energy consumption. The heat pump type drying device of this embodiment includes a primary refrigeration unit, a secondary refrigeration unit, a drying chamber 24, and an air supply system.

[0022] The primary refrigeration unit consists of a primary compressor 1, a primary condenser 2, a primary liquid tank 3, a primary dryer filter 4, a primary expansion valve 5, a primary evaporator 6, and a primary gas-liquid separator 7, which are connected sequentially through pipes to form a closed loop (the outlet of the primary gas-liquid separator 7 is connected to the inlet of the primary compressor 1). The housing of the primary evaporator 6 is the first housing 15, and the housing of the primary condenser 2 is the second housing 16.

[0023] The structure of the secondary refrigeration unit is similar to that of the primary refrigeration unit, and a circulation system is formed by sequentially connecting a secondary compressor 8, a secondary condenser 9, a secondary liquid tank 10, a secondary dry filter 11, a secondary expansion valve 12, a secondary evaporator 13 and a secondary gas-liquid separator 14 (the gas outlet of the secondary gas-liquid separator 14 is communicated with the gas inlet of the secondary compressor 8), and the shell of the secondary condenser 9 is a third shell 17.

[0024] The drying chamber 24 is a closed container for containing seeds or other materials to be dried.

[0025] The air supply system comprises a first connecting pipe 18, a second connecting pipe 19, a third connecting pipe 20, an air supply fan 21, an air supply pipe 23, an air return pipe 25, an air return fan 26 and a fourth connecting pipe 27. The first connecting pipe 18 is communicated with the first shell 15 and the second shell 16, the second connecting pipe 19 is communicated with the second shell 16 and the third shell 17, the third connecting pipe 20 is communicated with the third shell 17 and the air suction port of the air supply fan 21, the air outlet of the air supply fan 21 is connected to the drying chamber 24 through the air supply pipe 23, the drying chamber 24 is communicated with the air return fan 26 through the air return pipe 25, and the air return fan 26 is connected with the first shell 15 through the fourth connecting pipe 27, so as to form a complete air circulation path.

[0026] In the optional scheme of the embodiment, preferably, the primary evaporator 6 is internally provided with a drying filter screen 28, a fin heat exchanger 29 and a water baffle 30, which are sequentially arranged along the air flow direction. The drying filter screen 28 is close to the interface between the fourth connecting pipe 27 and the first shell 15, and is used for preliminarily filtering impurities in the air; the fin heat exchanger 29 is used as a main heat exchange component to realize air cooling and dehumidification; and the water baffle 30 is used for separating the condensed water in the air to prevent it from entering the subsequent process.

[0027] In the embodiment, the air supply fan 21 preferably adopts a variable frequency fan to adjust the air volume according to the needs of the drying stage. The bottom of the drying chamber 24 is provided with an air inlet 31 connected with the air supply pipe 23, and the top of the drying chamber 24 is provided with an air return port connected with the air return pipe 25. A door body that can be sealed and opened is installed on the side wall of the drying chamber 24 to facilitate loading and unloading of the materials. The air supply system further comprises a controller, and temperature and humidity sensors are respectively arranged on the first connecting pipe 18, the second connecting pipe 19, the third connecting pipe 20 and the air return pipe 25. The frequency converter 22 of the air supply fan 21, the air return fan 26 and all the temperature and humidity sensors are respectively signal-connected with the controller.

[0028] In the optional scheme of the embodiment, preferably, to optimize the air flow distribution, one end of the drying chamber 24 close to the air inlet 31 can be designed as a trapezoidal cavity 32 to make the hot air uniformly diffuse. The drying chamber 24 as a whole can adopt a cylindrical structure to reduce the air flow dead angle. The outer surfaces of all the connecting pipes and the air supply pipe 23 and the air return pipe 25 are covered with a heat preservation layer to reduce heat loss.

[0029] The specific working principle of the heat pump type drying device of the present embodiment is as follows: When working, the wet air from the drying chamber 24 enters the first shell 15 through the return air pipe 25, the return air fan 26 and the fourth connecting pipe 27, and flows through the primary evaporator 6. In the primary evaporator 6, the air is cooled, and the water is condensed and separated out, realizing preliminary dehumidification; at the same time, the latent heat of the air is recovered by the primary refrigeration unit. Subsequently, the dehydrated air enters the second shell 16 through the first connecting pipe 18, and is preliminarily heated by absorbing heat in the primary condenser 2. Then, the air enters the third shell 17 through the second connecting pipe 19, and is further heated in the secondary condenser 9, and after the temperature is increased, its moisture absorption capacity is significantly enhanced. Finally, the dry hot air is pumped into the drying chamber 24 by the supply air fan 21 to dry the materials. During the drying process, the temperature and humidity sensors arranged on the connecting pipes monitor the air state in real time and transmit the signals to the controller; the controller adjusts the frequency of the supply air fan 21 according to the preset parameters, so as to dynamically control the air volume and temperature and humidity, and ensure the efficient and stable drying process. This series connection type multi-stage processing method effectively overcomes the adverse effects of high humidity environment on drying, and is especially suitable for low-temperature drying of temperature-sensitive materials such as seeds, which reduces energy consumption while ensuring quality.

[0030] Specific implementation case 1 When tail heat recovery drying is adopted, the temperature of the recovered tail heat air is 38℃, and the relative humidity is 90%. Combined with formulas (1), (2) and (3), it can be calculated that the absolute humidity of the air at this time is 41.6 g / m 3 . After being cooled by the primary evaporator 6, the air temperature is 8℃, and the relative humidity is 100%. Combined with formulas (1), (2) and (3), it can be calculated that the absolute humidity of the air at this time is 8.3 g / m 3 . Then the air flows through the primary condenser 2 and is heated to 40℃, at which time the absolute humidity of the air does not change, and the relative humidity decreases. The air continues to flow into the secondary condenser 9 and is heated to 50℃, at which time the absolute humidity of the air does not change. Combined with formulas (1), (4) and (5), it can be calculated that the relative humidity is 9.9%. If the recovered temperature is 38℃, and the relative humidity of the hot tail gas is 90%, and the temperature is directly heated to 50℃, the absolute humidity does not change, and combined with formulas (1), (4) and (5), it can be calculated that the relative humidity is 50%. Obviously, after being cooled and dehydrated by the recovered hot tail gas, the humidity of the air is significantly reduced, and the moisture absorption capacity of the air is improved, which is beneficial to shorten the drying time and maintain the drying activity of the seeds.

[0031] Saturation water vapor pressure calculation formula: (1) In the formula: t represents saturated water vapor pressure, in hPa; t represents air temperature, in °C.

[0032] Formula for calculating water vapor partial pressure based on relative humidity: (2) In the formula: RH is the partial pressure of water vapor, expressed in hPa; RH is the relative humidity of air.

[0033] absolute humidity calculation formula: (3) In the formula: α represents absolute humidity, with units of g / m³. 3 ; t is the gas constant of dry air (287.05 J / (kg·K)); T is the absolute temperature of air (K, T = t + 273.15).

[0034] Calculate the partial pressure of water vapor based on absolute humidity: (4) In the formula: α is the partial pressure of water vapor, in Pa; α is the absolute humidity, in g / m³. 3 ; t is the gas constant of dry air (287.05 J / (kg·K)); T is the absolute temperature of air (K, T = t + 273.15).

[0035] Relative humidity calculation formula: (5) In the formula: RH is the relative humidity; This is the partial pressure of water vapor, expressed in Pa. This is the saturated water vapor pressure, expressed in Pa.

[0036] Specific Implementation Case 2 When hot exhaust gas is difficult to recover and ambient air is used for drying, and the ambient air is in a high temperature and high humidity state during rainy weather, taking a temperature of 25℃ and relative humidity of 90% as an example, after cooling by the first-stage evaporator 6, the air temperature is 6℃ and the relative humidity is 100%. Combining the above formulas (1), (2), and (3), it can be calculated that the absolute humidity of the air at this time is 7.26 g / m³. 3Then, the air flows through the first-stage condenser 2 and is heated to 28°C. At this point, the absolute humidity of the air remains unchanged, but the relative humidity decreases. The air continues to flow forward into the second-stage condenser 9 and is heated to 50°C. At this point, the absolute humidity of the air remains unchanged. Using formulas (1), (4), and (5) above, the relative humidity is calculated to be 8.7%. If the ambient air is directly heated to 50°C, using formulas (1), (4), and (5) above, the relative humidity is calculated to be 24.9%. Similarly, if the final target temperature is 40°C, using formulas (1), (4), and (5) above, the relative humidity of the cooled air is 14.2%, while the relative humidity of the directly heated air is 40.5%. By reducing the air humidity, the moisture absorption capacity of the air during drying is greatly improved, which is beneficial for shortening the drying time and reducing energy consumption.

[0037] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A heat pump drying device, characterized in that, include: A primary refrigeration unit includes a primary compressor, a primary condenser, a primary liquid tank, a primary dryer filter, a primary expansion valve, a primary evaporator, and a primary gas-liquid separator connected in sequence. The outlet of the primary gas-liquid separator is connected to the inlet of the primary compressor. The housing of the primary evaporator is a first housing, and the housing of the primary condenser is a second housing. A secondary refrigeration unit includes a secondary compressor, a secondary condenser, a secondary liquid tank, a secondary dryer filter, a secondary expansion valve, a secondary evaporator, and a secondary gas-liquid separator connected in sequence. The outlet of the secondary gas-liquid separator is connected to the inlet of the secondary compressor. The housing of the secondary condenser is a third housing. A drying chamber, wherein the drying chamber is a sealed shell; An air supply system is provided, comprising a first connecting pipe, a second connecting pipe, a third connecting pipe, a blower, an air supply duct, a return air duct, a return air blower, and a fourth connecting pipe. One end of the first connecting pipe is connected to the first housing and the other end is connected to the second housing. One end of the second connecting pipe is connected to the second housing and the other end is connected to the third housing. One end of the third connecting pipe is connected to the third housing and the other end is connected to the air intake of the blower. The air outlet of the blower is connected to the drying chamber through the air supply duct. The drying chamber is connected to the return air blower through the return air duct. The return air blower is connected to the first housing through the fourth connecting pipe.

2. The heat pump drying device according to claim 1, characterized in that: The primary evaporator includes a drying filter, a finned heat exchanger, and a baffle plate disposed within the first housing. The drying filter, the finned heat exchanger, and the baffle plate are connected in sequence. The drying filter is closer to the connection port between the first housing and the fourth connecting pipe than the finned heat exchanger, and the baffle plate is closer to the connection port between the first housing and the first connecting pipe than the finned heat exchanger.

3. The heat pump drying device according to claim 1, characterized in that: The blower is a variable frequency blower.

4. The heat pump drying device according to claim 1, characterized in that: An air inlet is provided at the bottom of the drying chamber, and the end of the air supply pipe near the drying chamber is connected to the air inlet.

5. The heat pump drying device according to claim 1, characterized in that: The top of the drying chamber is provided with a return air vent, and the end of the return air duct near the drying chamber is connected to the return air vent.

6. The heat pump drying device according to claim 1, characterized in that: A door is hinged to the side wall of the drying chamber, and the door is sealed to the side wall of the drying chamber when closed.

7. The heat pump drying device according to claim 3, characterized in that: The air supply system also includes a controller. Temperature and humidity sensors are respectively installed on the first connecting pipe, the second connecting pipe, the third connecting pipe and the return air pipe. The frequency converter of the air supply fan and all the temperature and humidity sensors are respectively connected to the controller.

8. The heat pump drying device according to claim 4, characterized in that: The drying chamber is configured as a trapezoidal cavity at one end near the air inlet, and the smaller end of the trapezoidal cavity is connected to the air inlet.

9. The heat pump drying device according to claim 1, characterized in that: The drying chamber is cylindrical.

10. The heat pump drying device according to claim 1, characterized in that: The first connecting pipe, the second connecting pipe, the third connecting pipe, the air supply pipe, the return air pipe, and the fourth connecting pipe are all wrapped with an insulation layer.

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