High-temperature heat pump waste heat recovery energy-saving system

Abstract

During the cycle of a conventional high-temperature heat pump system, the refrigerant passing through the evaporator directly enters the compressor, where it is pressurized and heated, and then sent to the condenser to heat the drying air. A prominent problem arising from this is that the compressor always operates at a high temperature, seriously affecting its working efficiency and lifespan. By adding a heat exchanger and placing it in the air inlet channel, since the temperature in the air inlet channel is much lower than that in the air outlet channel, the heat exchange speed is accelerated, the heat exchange capacity of the heat exchanger is increased, and more waste heat is recovered; the temperature of the refrigerant entering the compressor is reduced by 15 to 30 °C compared to before; combined with an automatic temperature control circuit, regardless of the external ambient temperature, the working temperature of the compressor is maintained within a suitable temperature range, solving the problem of the compressor's efficiency, lifespan decline, or even burnout caused by high temperature.

Description

Technical Field

[0001] The present invention relates to a high-temperature heat pump drying system, and more particularly to a high-temperature heat pump exhaust gas waste heat recovery and energy-saving system. Background Art

[0002] A heat pump is essentially a heat transfer device. A high-temperature heat pump drying system utilizes the reverse Carnot principle to extract heat from the surrounding environment and transfer it to the object to be heated (a higher-temperature object). Due to its excellent energy efficiency ratio, waste heat recovery ability, dehumidification effect, and clean zero emissions, the heat pump heating system is widely used in industrial production heating and drying processes with large energy consumption, especially in the drying process of the food processing industry.

[0003] The drying process is characterized by a high required output drying working temperature, even exceeding 100°C, so the temperature of the exhaust gas discharged is also very high, even exceeding 80°C. At this time, the excellent waste heat recovery ability of the heat pump system plays a great role. The evaporator in the heat pump system absorbs a large amount of waste heat from the exhaust gas and recovers and reuses it through the thermodynamic cycle process of the refrigerant driven by the compressor.

[0004] During waste heat recovery, due to the high waste heat temperature, the temperature of the refrigerant after being preheated by the evaporator is also very high, sometimes even exceeding 60°C. In the cycle process of a conventional heat pump system, the refrigerant passing through the evaporator directly enters the compressor for pressurization and temperature rise, and then is sent to the condenser to heat the drying air. This leads to a prominent problem that the compressor always works at a high temperature, seriously affecting the working efficiency and service life of the compressor. When the working temperature of the compressor exceeds 75°C, the internal resistance of its coil increases, the internal power consumption of the compressor increases, the temperature rises, forming a vicious cycle; at the same time, the quality of the lubricating oil deteriorates at high temperatures, which will cause lubrication failure, dry friction and temperature rise between the rotating parts, and they will fuse together, and even burn out the compressor.

[0005] Therefore, when designing a high-temperature heat pump system, how to reduce and maintain the working temperature of the compressor while recovering waste heat under the ambient temperatures in different seasons and improving the working conditions of the compressor in the high-temperature heat pump system has become an urgent problem to be solved. Summary of the Invention

[0006] The problem to be solved by the present invention is to keep the compressor of the high-temperature heat pump system working within a suitable temperature range for different ambient temperatures while recovering waste heat.

[0007] The present invention provides a high-temperature heat pump exhaust gas waste heat recovery and energy-saving system, including:

[0008] A drying air duct, which includes an air inlet channel, a high-temperature drying chamber, and an air exhaust channel;

[0009] A heat pump cycle circuit, which includes a compressor, a condenser, an expansion valve, an evaporator, a heat exchanger, a refrigerant and pipelines; the evaporator is placed in the exhaust air duct, and the heat exchanger and the condenser are placed in the intake air duct; the heat exchanger is upstream of the condenser;

[0010] An automatic temperature control circuit for maintaining the temperature of the refrigerant at the inlet of the compressor within the range of 35 - 45 °C, which includes:

[0011] 1) A temperature sensor, which is placed at the inlet of the compressor to measure the temperature of the refrigerant at the inlet;

[0012] 2) A control module, which controls the following adjustment actuator according to the temperature value measured by the temperature sensor according to a preset rule;

[0013] 3) The adjustment actuator includes two schemes, where:

[0014] In Scheme 1, the adjustment actuator is an electric control valve, and the electric control valve is connected to the outlet of the evaporator and the inlet of the compressor through pipelines respectively, and the control module controls the opening degree of the electric control valve according to the temperature value measured by the temperature sensor;

[0015] In Scheme 2, the adjustment actuator is an electric air damper, which is located upstream of the heat exchanger in the intake air duct, and the angle of the electric air damper is adjustable to adjust the air volume passing through the heat exchanger, and the control module controls the deflection angle of the electric air damper according to the temperature value measured by the temperature sensor.

[0016] Preferably, in the high-temperature heat pump waste heat recovery and energy-saving system, an electric heater is provided downstream of the condenser in the intake air duct.

[0017] The effects achieved by the present invention: Adding a heat exchanger and placing it in the intake air duct. Since the temperature in the intake air duct is much lower than that in the exhaust air duct, the heat exchange speed is accelerated, the heat exchange amount of the heat exchanger is increased, and more waste heat is recovered; the temperature of the refrigerant entering the compressor is reduced by 15 to 30 °C compared with before; combined with the automatic temperature control circuit, no matter what the external environmental temperature is, the working temperature of the compressor is maintained within a suitable temperature range, solving the problems of reduced efficiency, shortened life and even burnout caused by the high temperature of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of an embodiment of Scheme 1 of the high-temperature heat pump waste heat recovery and energy-saving system of the present invention;

[0019] Figure 2 is a schematic structural diagram of an embodiment of Scheme 2 of the high-temperature heat pump waste heat recovery and energy-saving system of the present invention;

[0020] Figure 3 is Figure 2 a schematic diagram of the local detailed structure;

[0021] Figure 4 is a schematic diagram of another embodiment of the first solution of the high-temperature heat pump waste heat recovery and energy-saving system of the present invention.

[0022] In the figure: 1. Evaporator; 2. Heat exchanger; 3. Compressor; 4. Temperature sensor; 5. Regulation module; 6. Electric control valve; 7. Expansion valve; 8. Air inlet channel; 9. Exhaust air channel; 10. Condenser; 11. Electric heater; 12. High-temperature drying chamber; 13. Electric air damper. Specific embodiments

[0023] Now in combination with Figure 1 explain the specific embodiments of the technical solution proposed by the present invention. The high-temperature heat pump waste heat recovery and energy-saving system includes:

[0024] A drying air path, which includes an air inlet channel 8, a high-temperature drying chamber 12, and an exhaust air channel 9; a heat pump circulation loop, which includes a compressor 3, a condenser 10, an expansion valve 7, an evaporator 1, a heat exchanger 2, refrigerant, and pipelines; the evaporator 1 is placed in the exhaust air channel 9, and the heat exchanger 2 and the condenser 10 are placed in the air inlet channel 8; the heat exchanger 2 is upstream of the condenser 10; the connection sequence of the heat pump circulation loop is compressor 3 > condenser 10 > expansion valve 7 > evaporator 1 > heat exchanger 2 > back to compressor 3; wherein the evaporator 1 is placed in the exhaust air channel 9 of the drying air path, and the heat exchanger 2 is placed upstream of the condenser 10 in the air inlet channel 8 of the drying air path. Fresh outdoor environmental air enters the air inlet channel 8 and is preheated by the heat exchanger 2, and then heated by the condenser 10. After the temperature is raised to the drying working temperature, it enters the high-temperature drying chamber 12. The hot air discharged from the high-temperature drying chamber 12 is discharged to the outdoor environment after recovering part of the heat energy through the evaporator 1 in the exhaust air channel 9; since the temperature in the air inlet channel 8 is lower than the temperature in the exhaust air channel 9, and the heat exchanger 2 is placed in the air inlet channel 8 of the drying air path, it is more conducive to the refrigerant in it to reduce the temperature; at the same time, the heat reduced due to the temperature reduction is not wasted, but is absorbed by the air in the air inlet channel 8 and the temperature is increased. By adopting this technical solution, not only the waste heat is recovered, but also the temperature at the inlet of the compressor 3 is reduced, and at the same time, the working efficiency and service life of the compressor 3 are improved, and the compressor 3 is prevented from being burned out due to high temperature.

[0025] After repeated practical summaries and comprehensively considering factors such as overall energy consumption, system cost, and the life of the compressor 3, the optimal temperature range at the inlet of the compressor 3 is 35 - 45 °C, and at this time, the working temperature of the compressor 3 is lower than 60 °C.

[0026] The technical solution provided by the present invention sets up an automatic temperature regulation loop for automatically regulating the temperature of the refrigerant at the inlet of the compressor 3 and maintaining the temperature of the refrigerant at the inlet of the compressor 3 within the range of 35 - 45°C. It includes:

[0027] 1) A temperature sensor 4 placed at the inlet of the compressor 3 for measuring the temperature of the refrigerant at the inlet.

[0028] 2) A regulation module 5 that regulates the following adjustment execution device according to the temperature value measured by the temperature sensor 4 according to a preset rule.

[0029] 3) The adjustment execution device includes two solutions, where:

[0030] Solution 1, as Figure 1 shown, the adjustment execution device is an electric control valve 6, and the electric control valve 6 is connected to the outlet of the evaporator 1 and the inlet of the compressor 3 through pipelines respectively; the opening degree of the electric control valve 6 is adjusted by the regulation module 5 according to the temperature of the refrigerant at the inlet of the compressor 3 measured by the temperature sensor 4; when the temperature at the inlet of the compressor 3 exceeds the set value, the regulation module 5 controls the electric control valve 6 to reduce the opening degree, reducing the flow rate of the refrigerant flowing through the electric control valve 6 and increasing the flow rate of the refrigerant passing through the heat exchanger 2, thereby reducing the temperature at the inlet of the compressor 3 and reducing the working temperature of the compressor 3; conversely, it acts in the opposite direction to achieve automatic adjustment. The automatic temperature regulation loop automatically adjusts only referring to the temperature of the refrigerant at the inlet of the compressor 3, can keep the temperature of the refrigerant at the inlet within 35 - 45°C, and thus ensures that the compressor 3 works at a suitable temperature without being affected by the external environmental temperature.

[0031] Solution 2, as Figure 2 and 3 shown, the adjustment execution device is an electric air damper 13 located upstream of the heat exchanger 2 in the air inlet passage 8, and the angle of the air damper 13 is adjustable; the regulation module 5 regulates the deflection angle of the air damper 13 according to the temperature value measured by the temperature sensor 4, thereby changing the magnitude of the air volume passing through the heat exchanger 2, changing the magnitude of the refrigerant heat dissipation and cooling amount, and finally changing the temperature of the refrigerant at the inlet of the compressor 3 and changing the working temperature of the compressor 3. The automatic temperature regulation loop automatically adjusts only referring to the temperature of the refrigerant at the inlet of the compressor 3, can keep the temperature of the refrigerant at the inlet within 35 - 45°C, and thus ensures that the compressor 3 works at a suitable temperature without being affected by the external environmental temperature.

[0032] During the system startup phase, before the waste heat is recovered, it takes a relatively long time to raise the temperature in the high-temperature drying chamber 12 to the required working temperature relying only on the compressor 3. To quickly reach the working temperature required for the drying process, an electric heater 11 is provided downstream of the condenser 10 in the air inlet passage 8. During the system startup phase, the hot air output by the system can reach the required working temperature within 5 minutes. After the system thermal cycle is formed, the thermal compensation of the electric heater 11 automatically cuts off the power.

[0033] Figure 4 This is another embodiment of the first solution of the present invention. Among them, the numerical control system includes the functions of the regulation module 5.

[0034] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A high-temperature heat pump waste heat recovery and energy-saving system, characterized in that Comprising: A drying air path, which includes an air inlet channel (8), a high-temperature drying chamber (12), and an air exhaust channel (9); A heat pump cycle circuit, which includes a compressor (3), a condenser (10), an expansion valve (7), an evaporator (1), a heat exchanger (2), a refrigerant, and pipes; The evaporator (1) is disposed in the air exhaust channel (9), and the heat exchanger (2) and the condenser (10) are disposed in the air inlet channel (8); The heat exchanger (2) is upstream of the condenser (10); The connection sequence of the heat pump cycle circuit is: the compressor (3) is sequentially connected to the condenser (10), the expansion valve (7), the evaporator (1), the heat exchanger (2), and finally returns to the compressor (3); The high-temperature drying chamber (12) is disposed at the rear end of the condenser (10), and the evaporator (1) is disposed at the rear end of the high-temperature drying chamber (12); An automatic temperature control circuit for maintaining the temperature of the refrigerant at the inlet of the compressor (3) within the range of 35-45 °C, which includes: a temperature sensor (4), which is disposed at the inlet of the compressor (3) for measuring the temperature of the refrigerant at the inlet; A control module (5), which controls the following adjustment actuator according to a preset rule based on the temperature value measured by the temperature sensor (4); An electric control valve (6), which is connected to the outlet of the evaporator (1) and the inlet of the compressor (3) through pipes respectively; An adjustment actuator, where: The control module (5) controls the opening degree of the electric control valve (6) according to the temperature value measured by the temperature sensor (4); or, The adjustment actuator is an electric air damper (13), which is located upstream of the heat exchanger (2) in the air inlet channel (8). The angle of the electric air damper (13) is adjustable for adjusting the air volume passing through the heat exchanger (2). The control module (5) controls the deflection angle of the electric air damper (13) according to the temperature value measured by the temperature sensor (4).

2. The high-temperature heat pump waste heat recovery and energy-saving system according to claim 1, characterized in that An electric heater (11) is provided downstream of the condenser (10) in the air inlet channel (8).

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