A grain drying heat pump system

Abstract

The utility model relates to the field of cereal drying, and specifically discloses a cereal drying heat pump system, the cereal drying heat pump system includes air inlet pipe, heat pump and drying bin, the heat pump includes condenser and evaporimeter, and the evaporimeter, condenser and drying bin are sequentially arranged along the airflow direction in the air inlet pipe on the air inlet pipe, the drying bin is equipped with the exhaust pipe, the heat exchange device and preheating device are equipped on the air inlet pipe and located the front of evaporimeter, the heat exchange device is used for exchanging heat between the air flowing out of the exhaust pipe and the air flowing into the air inlet pipe, the preheating device is used for preheating the air circulating in the air inlet pipe, and the fan is arranged on the air inlet pipe. The utility model solves the problems of slow air temperature rise in the initial drying stage, low heat pump heating temperature, low heat pump starting efficiency, waste heat discharge through the exhaust pipe and energy waste in the prior art.

Description

Technical Field

[0001] This utility model relates to the field of grain drying, and specifically to a grain drying heat pump system. Background Technology

[0002] Grain drying is a crucial step in ensuring the quality of stored grains and reducing post-harvest losses. Grains such as corn, wheat, and rice need to have their moisture content rapidly reduced to safe storage standards after harvest. Traditional grain drying methods mostly use coal-fired or oil-fired boilers for heating or natural sun-drying. Natural sun-drying is not only greatly affected by weather but also inefficient; while coal-fired or oil-fired methods suffer from high energy consumption, severe pollution, and low thermal efficiency.

[0003] Heat pump drying technology is gradually being applied to the grain drying field due to its advantages such as energy saving and environmental protection. In the existing technology, the grain drying heat pump system includes an air inlet pipe, a heat pump, and a drying chamber; the heat pump and the drying chamber are connected by the air inlet pipe, and the heat pump is equipped with an exhaust pipe; the heat pump includes a compressor, a condenser, an expansion valve, and an evaporator connected in sequence through a refrigerant circulation pipeline.

[0004] Existing grain drying heat pump systems have the following problems: slow air temperature rise in the initial stage of drying, low heat pump start-up efficiency in low-temperature environments; moreover, the heating temperature of the heat pump dryer is too low, and the drying cycle is too long for grains with high moisture content, such as corn and rice, which cannot meet the needs of large-scale production; in addition, after the grain is dried in the drying chamber, the residual heat is discharged through the exhaust pipe, resulting in energy waste. Utility Model Content

[0005] The purpose of this invention is to provide a grain drying heat pump system to address the above-mentioned problems, thereby solving the issues of slow air temperature rise during the initial drying stage, low heat pump heating temperature, low heat pump start-up efficiency, and energy waste caused by waste heat being discharged through the exhaust pipe in the existing technology.

[0006] To achieve the above objectives, this utility model discloses a grain drying heat pump system, which includes an air inlet pipe, a heat pump, and a drying chamber. The heat pump includes a condenser and an evaporator, which are arranged sequentially on the air inlet pipe along the airflow direction. The drying chamber is located at the air outlet of the air inlet pipe and has an exhaust pipe. A heat exchange device and a preheating device are provided on the air inlet pipe in front of the evaporator. The heat exchange device is used to exchange heat between the air flowing out of the exhaust pipe and the air flowing in through the air inlet pipe. The preheating device is used to preheat the air flowing through the air inlet pipe. A fan is installed on the air inlet pipe.

[0007] With the above structure, the hot, humid air discharged from the drying chamber after drying the grain is discharged through the exhaust pipe, and waste heat is recovered and utilized through a heat exchange device. The preheating device preheats the air before it flows through the evaporator during the initial drying stage, raising the air temperature and thus increasing the heating temperature and start-up efficiency of the heat pump. The heat exchange device exchanges heat between the hot air in the exhaust pipe and the cold air in the intake pipe, recovering the waste heat discharged from the exhaust pipe and avoiding energy waste; it also further preheats the cold air entering the grain drying heat pump system, increasing the intake temperature and thus improving the COP value of the heat pump and reducing energy consumption. The evaporator absorbs heat from the air and transfers it to the refrigerant. The fan not only delivers the dry, hot air heated by the condenser into the drying chamber but also drives air circulation throughout the entire grain drying heat pump system, ensuring full contact between the grain and the dry, hot air and removing moisture from the grain, thus improving drying efficiency.

[0008] As a further improvement of this utility model, the preheating device is located in front of the heat exchange device, and the air flowing through the intake pipe first flows through the preheating device and then through the heat exchange device. With this structure, the air entering the intake pipe is first preheated by the preheating device, and then further preheated by the heat exchange device. This two-stage preheating of the air by the preheating device and the heat exchange device improves preheating efficiency and increases the heating temperature of the heat pump, thereby enhancing the start-up efficiency of the heat pump system.

[0009] As a further improvement of this utility model, the heat exchange device is located at the junction of the intake pipe and the exhaust pipe. With this structure, the heat exchange device exchanges heat between the hot air in the exhaust pipe and the cold air in the intake pipe, thereby recovering the waste heat discharged from the exhaust pipe and preheating the cold air entering the intake pipe, increasing the intake air temperature, and thus improving the COP value of the heat pump and reducing energy consumption.

[0010] As a further improvement of this utility model, the heat exchanger is provided with two air passages; the section of the inlet pipe between the preheating device and the heat exchanger is the inlet section, and the section of the inlet pipe between the heat exchanger and the evaporator is the connecting section; the section of the exhaust pipe near the heat exchanger is the exhaust section; the heat exchanger is provided with an outlet for discharging the air after heat exchange; the inlet section and the connecting section are connected to one air passage of the heat exchanger, and the exhaust section and the outlet are connected to the other air passage of the heat exchanger. With this structure, the air flowing in through the inlet pipe and the air discharging through the exhaust pipe can both enter the heat exchanger, making the heat exchange between the hot air in the exhaust pipe and the cold air in the inlet pipe more complete, improving waste heat recovery, and reducing heat loss.

[0011] As a further improvement of this utility model, the preheating device is located inside the air intake pipe.

[0012] This structure allows the heat from the preheating device to be released directly inside the intake pipe, resulting in less heat loss and faster preheating. Moreover, the structure is more compact, saving installation space.

[0013] As a further improvement of this invention, the preheating device is a PTC heater. Using this structure, the PTC heater material is a high-temperature resistant ceramic matrix composite material, which not only provides higher safety and reliability, but also gives the PTC heater adaptive adjustment capability, resulting in higher preheating stability.

[0014] As a further improvement of this invention, the drying chamber is equipped with a multi-layered grain-supporting mesh. This structure effectively increases the contact area between the grain and the hot, dry air, allowing for full contact between the two and improving drying efficiency.

[0015] As a further improvement of this utility model, a fan is positioned between the evaporator and the condenser to deliver air heated by the condenser into the drying chamber. With this structure, the fan can directly blow air onto the condenser, effectively avoiding resistance to airflow from other components and allowing the airflow to fully penetrate the entire condenser. Furthermore, the fan's rotation increases the flow rate of the hot, dry air within the drying chamber, resulting in more thorough contact between the grain and the hot, dry air, thus effectively improving the drying efficiency of the grain within the drying chamber.

[0016] As a further improvement of this utility model, the grain drying heat pump system also includes a controller; temperature and humidity sensors electrically connected to the controller are installed inside the air inlet pipe, drying chamber, and exhaust pipe; actuators electrically connected to the controller are installed on the preheating device, heat pump, and fan. With this structure, the temperature and humidity sensors can collect real-time data on grain temperature and humidity, as well as the temperature and humidity of the inlet and outlet air; the controller can control the heating power of the preheating device, the operating frequency of the heat pump, and the speed of the fan; the actuators can receive commands from the controller and execute corresponding operations to achieve precise control of the drying temperature.

[0017] In summary, the beneficial effects of this utility model are as follows: By installing a preheating device on the air inlet pipe, the air is preheated before it flows through the evaporator during the initial drying stage, thereby increasing the heating temperature and start-up efficiency of the heat pump; it can meet the drying needs of various high-moisture grains such as corn, wheat, and rice, and shorten the drying cycle. By installing a heat exchange device on the air inlet pipe in front of the evaporator, the waste heat discharged from the exhaust pipe is recovered, avoiding energy waste; it also further preheats the cold air in the air inlet pipe, increasing the intake air temperature, significantly improving the COP value of the heat pump system, and reducing energy consumption. The evaporator can absorb heat from the air and transfer it to the refrigerant. By installing a fan on the air inlet pipe, hot dry air can be sent into the drying chamber; in addition, the fan can drive the air circulation throughout the entire grain drying heat pump system. The integrated design of each module results in a compact structure, convenient installation and maintenance, and suitability for large-scale grain drying scenarios, with significant economic and environmental benefits. This invention solves the problems of slow air temperature rise during the initial drying stage, low heat pump heating temperature, low heat pump start-up efficiency, and energy waste caused by waste heat being discharged through the exhaust pipe in existing technologies. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of this utility model.

[0019] The arrows in the diagram indicate the airflow direction in intake pipe 1; here, we define the end where air enters intake pipe 1 as the front and the end where air enters drying chamber 3 as the rear. Air in intake pipe 1 flows from front to back and enters drying chamber 3.

[0020] In the diagram: 1. Inlet pipe, 11. Inlet section, 12. Connecting section, 2. Heat pump, 21. Refrigerant circulation pipeline, 22. Compressor, 23. Condenser, 24. Throttling element, 25. Evaporator, 3. Drying chamber, 4. Exhaust pipe, 41. Discharge section, 42. Discharge outlet, 5. Heat exchange device, 6. Preheating device, 7. Fan, 8. Controller, 9. Sensor. Detailed Implementation

[0021] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0022] Reference Figure 1In some embodiments of this utility model, the grain drying heat pump system includes an air inlet pipe 1, a heat pump 2, and a drying chamber 3. The heat pump 2 includes a compressor 22, a condenser 23, a throttling element 24, and an evaporator 25 connected in sequence through a refrigerant circulation pipe 21, forming a complete heat pump circulation system to realize the absorption, compression, and release of heat. The evaporator 25 and the condenser 23 are arranged in sequence on the air inlet pipe 1 along the airflow direction in the air inlet pipe 1. The condenser 23 is located on the air inlet side of the drying chamber 3 and is used to transfer the heat of the refrigerant to the air entering the drying chamber 3 to generate dry hot air. The drying chamber 3 is located at the air outlet end of the air inlet pipe 1 and is equipped with an exhaust pipe 4. A preheating device 6 and a heat exchange device 5 are provided on the air inlet pipe 1 in front of the evaporator 25. The preheating device 6 is used to preheat the air flowing in the air inlet pipe 1. The heat exchange device 5 is used to exchange heat between the air flowing out of the exhaust pipe 4 and the air flowing in of the air inlet pipe 1. A fan 7 is provided on the air inlet pipe 1. The refrigerant used is R134a, a high-efficiency and environmentally friendly refrigerant, or other high-efficiency alternatives such as R410A, R290, and R245fa. The compressor 22 is preferably a variable-frequency scroll compressor, capable of adjusting its operating frequency according to drying requirements. The throttling element 24 is preferably an electronic expansion valve, capable of precisely controlling the refrigerant flow.

[0023] Through the above structure, the preheating device 6 preheats the air before it flows through the evaporator 25 during the initial drying stage, raising the air temperature to a certain level, preferably 15-25°C, thereby increasing the heating temperature and start-up efficiency of the heat pump 2. When the hot, humid air generated after drying the grain in the drying chamber 3 is discharged through the exhaust pipe 4, waste heat is recovered and utilized through the heat exchange device 5. The heat exchange device 5 exchanges heat between the hot air in the exhaust pipe 4 and the cold air in the intake pipe 1, recovering the waste heat discharged from the exhaust pipe 4 and avoiding energy waste; it also further preheats the cold air entering the grain drying heat pump system, increasing the intake temperature and thus improving the COP value of the heat pump 2 and reducing energy consumption. The evaporator 25 can absorb heat from the air and transfer it to the refrigerant. The fan 7 can not only send the dry hot air generated by the condenser 23 into the drying chamber 3, but also drive the air circulation in the entire grain drying heat pump system, so that the grain can fully contact the dry hot air and remove the moisture in the grain, thereby improving the drying efficiency.

[0024] Reference Figure 1In some embodiments of this utility model, the heat exchange device 5 is located in front of the preheating device 6, and the air flowing through the intake pipe 1 first flows through the heat exchange device 5, and then through the preheating device 6. In another embodiment, the preheating device 6 is located in front of the heat exchange device 5, and the air flowing through the intake pipe 1 first flows through the preheating device 6, and then through the heat exchange device 5. The second embodiment is preferred. With this structure, the air entering the intake pipe 1 is first preheated by the preheating device 6, and then further preheated by the heat exchange device 5. By combining the two-stage preheating of the air by the preheating device 6 and the heat exchange device 5, the preheating efficiency is improved, and the heating temperature of the heat pump is increased, thereby improving the start-up efficiency of the heat pump system.

[0025] Reference Figure 1 In some embodiments of this utility model, the heat exchange device 5 is located at the junction of the air inlet pipe 1 and the exhaust pipe 4. In a first embodiment, the heat exchange device 5 is located inside the air inlet pipe 1, preferably a tubular heat exchanger. The hot air flowing out of the exhaust pipe 4 enters the tubular heat exchanger and exchanges heat with the air flowing in from the air inlet pipe 1 inside the air inlet pipe 1. In the second embodiment, the heat exchange device 5 is located outside the inlet pipe 1 and the exhaust pipe 4, preferably a plate heat exchanger. The heat exchange device 5 has two air passages. The section of the inlet pipe 1 between the preheating device 6 and the heat exchange device 5 is the inlet section 11, and the section of the inlet pipe 1 between the heat exchange device 5 and the evaporator 25 is the connecting section 12. The section of the exhaust pipe 4 near the heat exchange device 5 is the discharge section 41. The heat exchange device 5 has an outlet 42 for discharging the heat-exchanged air. The inlet section 11 and the connecting section 12 are connected to one air passage of the heat exchange device 5, and the discharge section 41 and the outlet 42 are connected to the other air passage of the heat exchange device 5. The hot air flowing out of the exhaust pipe 4 and the cold air flowing in from the inlet pipe 1 exchange heat in the two air passages within the plate heat exchanger. This is the preferred embodiment. With this structure, the air flowing in through the intake pipe 1 can completely enter the heat exchanger 5 through the intake section 11. After being preheated by the heat exchanger 5, it flows through the preheating device 6 through the connecting section 12. The air discharged through the exhaust pipe 4 can completely enter the heat exchanger 5 through the exhaust section 41. After recovering some of the waste heat through the heat exchanger 5, it is discharged through the exhaust outlet 42. This makes the heat exchange between the hot air in the exhaust pipe 4 and the cold air in the intake pipe 1 more complete, reducing heat loss.

[0026] Reference Figure 1In some embodiments of this utility model, the preheating device 6 can be sleeved outside the intake pipe 1 or disposed inside the intake pipe 1. Preferably, the preheating device 6 is disposed inside the intake pipe 1. The preheating device 6 is preferably cylindrical in shape to fit the inner diameter of the intake pipe, and a gas channel is provided inside the preheating device 6. Through this structure, the heat generated by the preheating device 6 is directly released inside the intake pipe 1, resulting in less heat loss from the pipeline and faster preheating speed; moreover, this structure is more compact and saves installation space.

[0027] Reference Figure 1 In some embodiments of this utility model, the preheating device 6 can be a resistance wire heater, a PTC heater, etc., preferably a PTC heater, with a rated power preferably of 5-15kW. Through this structure, the PTC heater uses a high-temperature resistant ceramic matrix composite material and has heat dissipation fins on its surface to improve heat exchange efficiency, resulting in higher safety and reliability. Furthermore, the PTC heater has adaptive adjustment capabilities, allowing it to adjust the heating power according to the inlet air temperature, thus improving preheating stability.

[0028] Reference Figure 1 In some embodiments of this invention, the drying chamber 3 is equipped with a multi-layer grain-supporting mesh. This structure increases the contact area between the grain and the hot, dry air, allowing for full contact between the two and improving drying efficiency.

[0029] Reference Figure 1 In some embodiments of this utility model, the fan 7 can be located at the inlet end of the air inlet pipe 1, between the evaporator 25 and the condenser 23, or at other locations in the entire system. Preferably, the fan 7 is located between the evaporator 25 and the condenser 23 to deliver the air heated by the condenser 23 into the drying chamber 3; the fan 7 is preferably a centrifugal fan. With this structure, the fan 7 can directly blow air onto the condenser 23, effectively avoiding resistance to airflow from other components, allowing the airflow to fully penetrate the entire condenser 23; moreover, it increases the flow rate of the hot dry air in the drying chamber 3, allowing the grain to come into more thorough contact with the hot dry air, effectively improving the drying efficiency of the grain in the drying chamber 3.

[0030] Reference Figure 1In some embodiments of this utility model, the grain drying heat pump system further includes a controller 8, which is preferably a PLC programmable controller. Sensors 9 electrically connected to the controller 8 are installed inside the air inlet pipe 1, the drying chamber 3, and the exhaust pipe 4. These sensors 9 include temperature and humidity sensors. Actuators electrically connected to the controller 8 are installed on the preheating device 6, the compressor 22, and the fan 7. (This protection only covers the entire grain drying heat pump system apparatus, not the method or algorithm). Through this structure, the temperature and humidity sensors can collect real-time data on grain temperature and humidity, as well as the temperature and humidity of the inlet and outlet air. The PLC programmable controller has a built-in library of drying process parameters for various grains such as corn, wheat, and rice. Based on the grain type and the real-time monitoring data from the temperature and humidity sensors, it can control the preheating power of the preheating device 6, the frequency of the compressor 22, and the speed of the fan 7. The actuators can receive commands from the controller 8 and execute corresponding operations to achieve precise control of the drying temperature.

[0031] The working principle of this invention is as follows: During the drying process, cold outside air first enters the preheating device 6 through the air inlet section 11 of the air inlet pipe 1, where the preheating device 6 preheats the air. Then, the air flows through the heat exchange device 5 via the air inlet pipe 1. The cold air exchanges heat with the hot air discharged from the exhaust pipe 4 within the heat exchange device 5, thus recovering the waste heat from the humid air discharged from the exhaust pipe 4. In addition, the heat exchange device 5 can further preheat the air. The air, after secondary preheating, flows through the evaporator 25. The refrigerant in the evaporator 25 absorbs heat and rises in temperature, then is compressed and heated by the compressor 22. The condenser 23 releases heat, generating dry hot air at 45-65°C. This dry hot air enters the drying chamber 3 under the action of the fan 7, fully contacting the grain and removing moisture, forming humid hot air. Under the action of the fan 7, the humid hot air flows through the discharge section 41 and then through the heat exchange device 5. After the heat exchange device 5 recovers the waste heat, the air is discharged through the discharge outlet 42. The controller 8 controls the preheating power of the preheating device 6, the frequency of the compressor 22, and the speed of the fan 7 based on the real-time monitoring data of the sensor 9, so as to ensure that the drying process meets the process requirements of the corresponding grain.

[0032] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A grain drying heat pump system, comprising an air inlet pipe (1), a heat pump (2), and a drying chamber (3); said heat pump (2) comprising a condenser (23) and an evaporator (25), characterized in that, The evaporator (25) and condenser (23) are arranged sequentially on the inlet pipe (1) along the airflow direction in the inlet pipe (1); the drying chamber (3) is located at the outlet end of the inlet pipe (1), and the drying chamber (3) is provided with an exhaust pipe (4); a heat exchange device (5) and a preheating device (6) are provided in front of the evaporator (25) on the inlet pipe (1); the heat exchange device (5) is used to exchange heat between the air flowing out of the exhaust pipe (4) and the air flowing in of the inlet pipe (1); the preheating device (6) is used to preheat the air flowing in the inlet pipe (1); a fan (7) is provided on the inlet pipe (1).

2. The grain drying heat pump system as described in claim 1, characterized in that, The preheating device (6) is located in front of the heat exchange device (5). The air flowing through the air inlet pipe (1) first flows through the preheating device (6) and then through the heat exchange device (5).

3. The grain drying heat pump system as described in claim 2, characterized in that, The heat exchange device (5) is located at the intersection of the air inlet pipe (1) and the exhaust pipe (4).

4. The grain drying heat pump system as described in claim 3, characterized in that, The heat exchange device (5) is provided with two air passages; the section of the inlet pipe (1) between the preheating device (6) and the heat exchange device (5) is the inlet section (11), and the section of the inlet pipe (1) between the heat exchange device (5) and the evaporator (25) is the connecting section (12); the section of the exhaust pipe (4) near the heat exchange device (5) is the discharge section (41); the heat exchange device (5) is provided with an outlet (42) for discharging the air after heat exchange; the inlet section (11) and the connecting section (12) are connected to one air passage of the heat exchange device (5), and the discharge section (41) and the outlet (42) are connected to the other air passage of the heat exchange device (5).

5. The grain drying heat pump system as described in claim 1, characterized in that, The preheating device (6) is located inside the air inlet pipe (1).

6. The grain drying heat pump system as described in claim 5, characterized in that, The preheating device (6) is a PTC heater.

7. The grain drying heat pump system as described in claim 1, characterized in that, The drying chamber (3) is equipped with a multi-layer grain support net inside.

8. The grain drying heat pump system as described in claim 1, characterized in that, The fan (7) is located between the evaporator (25) and the condenser (23) and is used to send the air heated by the condenser (23) into the drying chamber (3).

9. The grain drying heat pump system according to any one of claims 1 to 8, characterized in that, The grain drying heat pump system also includes a controller (8); the air inlet pipe (1), drying chamber (3) and exhaust pipe (4) are all equipped with temperature sensors and humidity sensors that are electrically connected to the controller (8); the preheating device (6), heat pump (2) and fan (7) are all equipped with actuators that are electrically connected to the controller (8).

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