Dual-system multi-mode air source heat pump system for tobacco leaf curing and curing method

Abstract

The invention belongs to the technical field of heat pump systems, and particularly relates to a dual-system multi-mode air source heat pump system for tobacco leaf curing and a curing method. The system comprises a double-circulation evaporator, a cascade compressor, a flash evaporator, a gas-liquid separator, a parallel condenser, a liquid storage device, a multi-pressure-stage throttling valve, a plurality of check valves, a plurality of electromagnetic valves and a plurality of one-way valves. The double-circulation evaporator comprises an outer circulation evaporator and an inner circulation evaporator; the cascade compressor comprises a first-stage compressor and a second-stage compressor; the system comprises two independent refrigerating or heating systems, stable heating can be achieved even in the low-temperature environment, and the problems that a traditional air source heat pump is poor in reliability and low in operation efficiency are solved. The invention further provides a method for baking tobacco leaves by using the dual-system multi-mode air source heat pump system for tobacco leaf baking.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat pump systems, and particularly relates to a dual-system multi-mode air-source heat pump system for tobacco leaf baking and a baking method. Background Art

[0002] A single-system mode air-source heat pump system has only one system with a fixed operating mode. Once a component fails, it may affect the operation of the entire system, and it is difficult to maintain the basic heating function by switching to other standby modes. Therefore, the heating reliability is poor. At the same time, during the maintenance process, due to the simplicity of the system, maintenance personnel may need to spend more time and effort to accurately determine the fault point, and operations such as replacing components may be relatively complex, which all lead to a continuous increase in maintenance costs and impose an economic burden on users.

[0003] In a low-temperature environment, the operating efficiency of a single-system mode air-source heat pump system will drop significantly. An air-source heat pump realizes the heating function by absorbing heat from the air. When the outside air temperature decreases, the available heat in the air decreases, and the heating capacity of the heat pump unit weakens accordingly. Moreover, it is difficult to achieve efficient regulation when such a system operates at partial load. The heating capacity and stability of traditional air-source heat pumps are insufficient. For example, the heating effect of the unit under cloudy, rainy, or snowy weather conditions is inferior to that under sunny conditions. Summary of the Invention

[0004] The present invention solves the problems of poor heating reliability and low operating efficiency of traditional air-source heat pumps, and provides a dual-system multi-mode air-source heat pump system for tobacco leaf baking.

[0005] The technical solution claimed by the present invention is as follows:

[0006] A dual-system multi-mode air-source heat pump system for tobacco leaf baking, comprising: a dual-cycle evaporator, a cascade compressor, a flash tank, a gas-liquid separator, a parallel condenser, a liquid receiver, a multi-stage throttle valve, a plurality of check valves, a plurality of solenoid valves, and a plurality of one-way valves; the dual-cycle evaporator includes an outer-cycle evaporator and an inner-cycle evaporator; the cascade compressor includes a first-stage compressor and a second-stage compressor; the multi-stage throttle valve includes a low-pressure throttle valve and a high-pressure throttle valve; the outer-cycle evaporator and the inner-cycle evaporator are connected in parallel and share the gas-liquid separator and the flash tank; the first-stage compressor and the second-stage compressor are connected in series to form a cascade compressor and are connected between the gas-liquid separator and the parallel condenser;

[0007] The gaseous refrigerant outlet end of the double-cycle evaporator is connected to the gaseous refrigerant inlet end of the gas-liquid separator through a check valve. The gaseous refrigerant outlet end of the gas-liquid separator is connected to the gaseous refrigerant inlet end of the first-stage compressor. The gaseous refrigerant outlet end of the first-stage compressor is connected to the gaseous refrigerant inlet end of the parallel condenser through a solenoid valve. The liquid refrigerant outlet end of the parallel condenser is sequentially connected to the inlet liquid refrigerant end of the flash evaporator through a liquid receiver, a drier filter, and a high-pressure throttle valve. The liquid refrigerant outlet end of the flash evaporator returns to the inlet liquid refrigerant end of the double-cycle evaporator through a low-pressure throttle valve and a check valve to form a main heating circuit;

[0008] On the basis of the main heating circuit, the gaseous refrigerant outlet end of the first-stage compressor is connected to the gaseous refrigerant inlet end of the second-stage compressor through a solenoid valve and further connected to the gaseous refrigerant inlet end of the parallel condenser through the gaseous refrigerant outlet end of the second-stage compressor. The gaseous refrigerant outlet end of the flash evaporator is connected to the gaseous refrigerant inlet end of the second-stage compressor through a check valve to form a branch jet enthalpy-increasing circuit.

[0009] Preferably, the air source heat pump system further includes a variable-frequency circulating fan and an electric auxiliary heater respectively arranged on the air inlet side and the air outlet side of the parallel condenser.

[0010] Preferably, the air source heat pump system further includes a water receiving tray arranged below the inner-cycle evaporator to receive the condensed water generated by the inner-cycle evaporator; a drain pipe extending outside the water receiving tray is arranged in the water receiving tray to drain the water in the water receiving tray.

[0011] In a specific embodiment of the present invention, the air source heat pump system is used to provide heat for a tobacco barn; the outer-cycle evaporator uses outdoor ambient air and indoor moisture exhaust port air as heat sources; the inner-cycle evaporator uses the air at the return air inlet flowing unidirectionally from bottom to top in the tobacco barn as a heat source.

[0012] In a specific embodiment of the present invention, the flash evaporator participates in switching between the main heating circuit and the branch jet enthalpy-increasing circuit of the parallel condenser; the evaporator relies on a check valve to control the liquid flow direction of the refrigerant to achieve the switching of the working mode; the compressor relies on a solenoid valve to control the steam flow direction of the refrigerant to achieve the switching of the working mode.

[0013] In a specific embodiment of the present invention, the electric auxiliary heater is configured with a temperature sensor at the condenser air outlet; the temperature sensor is arranged at both ends of the electric auxiliary heater.

[0014] The present invention also provides a method for baking tobacco leaves using the double-system multi-mode air source heat pump system for tobacco leaf baking, including the following steps:

[0015] S1: During the yellowing period of tobacco leaves, the air source heat pump system operates under low-temperature conditions, specifically: the external evaporator circulates, the first-stage compressor, the parallel condenser, and the multi-stage throttle valve loop operate independently for heating;

[0016] S2: During the color-fixing period of tobacco leaves, the air source heat pump system operates under medium-temperature conditions, specifically: the internal evaporator, the first-stage compressor, the parallel condenser, and the multi-stage throttle valve loop operate independently for heating;

[0017] S3: During the stem-drying period of tobacco leaves, the air source heat pump system operates under high-temperature conditions, specifically: the internal evaporator, the first-stage compressor, the second-stage compressor, the parallel condenser, the flash tank, the multi-stage throttle valve multi-loop, and the electric auxiliary heater operate in a coupled manner for heating.

[0018] In the above method, the tobacco leaves are difficult-to-cure tobacco leaves formed under special flue-cured tobacco varieties and field climate conditions.

[0019] In the above method, the specific heating process in S1 is as follows: Refrigerant circulation route: First, the check valves (21), (22) and the solenoid valve (25) are energized and normally open, the check valves (23), (24), (91) and the solenoid valve (26) are de-energized and normally closed. The low-temperature and low-pressure liquid refrigerant enters the external evaporator through the check valve (21), absorbs heat and forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (22) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensation pressure. It sequentially passes through the solenoid valve (25) and the check valve (51) and enters the parallel condenser to release heat and form a high-temperature and high-pressure liquid refrigerant. Then, it passes through the liquid receiver and the dryer filter in sequence, enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash tank for gas-liquid separation, and continues to enter the low-pressure throttle valve as a medium-temperature and medium-pressure liquid refrigerant for re-throttling and increasing the enthalpy difference. Finally, a low-temperature and low-pressure liquid refrigerant with an evaporation pressure is formed, and it returns to the external evaporator through the check valve (21) to absorb heat for a new round of cyclic heating;

[0020] Air circulation route: The low-temperature and low-humidity gas in the curing barn forms a high-temperature and low-humidity gas after condensing and releasing heat in the parallel condenser, and is forced into the curing barn by the variable-frequency circulation fan. After the gas in the curing barn flows, it enters the heating chamber through the return air duct, exchanges heat with the external evaporator again, and starts a new round of heating cycle.

[0021] In the above method, for the method of baking tobacco leaves with a dual-system and multi-mode air source heat pump system, when the internal evaporator, the first-stage compressor, the parallel condenser, and the multi-stage throttle valve loop operate independently for heating in S2, the specific process includes:

[0022] Refrigerant circulation route: Gradually energize the check valves (23), (24) and the solenoid valve (25) to be normally open, and de-energize the check valves (21), (22), (91) and the solenoid valve (26) to be normally closed. The low-temperature and low-pressure liquid refrigerant enters the built-in evaporator through the check valve (23), absorbs heat, and then forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (24) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensation pressure. It successively passes through the solenoid valve (25) and the one-way valve (51) and enters the parallel condenser to release heat and form a high-temperature and high-pressure liquid refrigerant. Then it successively passes through the liquid receiver and the dryer filter, enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash evaporator for gas-liquid separation. It continues to enter the low-pressure throttle valve as a medium-temperature and medium-pressure liquid refrigerant for further throttling and increasing the enthalpy difference. Finally, it forms a low-temperature and low-pressure liquid refrigerant with an evaporation pressure, returns to the built-in evaporator through the check valve (23) to absorb heat and starts a new round of cycle for heating;

[0023] Air circulation route: The medium-temperature and high-humidity gas in the baking room is absorbed by heat through the built-in evaporator to form condensed water and low-temperature and low-humidity gas. Among them, the condensed water drips along the fins onto the water receiving tray and is discharged from the baking room along the drain pipe; the low-temperature and low-humidity gas is condensed and releases heat through the parallel condenser to form a high-temperature and low-humidity gas. The high-temperature and low-humidity gas is forced into the baking room by the variable-frequency circulation fan. The medium-temperature and high-humidity gas in the baking room enters the heating chamber through the return air duct, exchanges heat with the built-in evaporator again, and then starts a new round of heating cycle.

[0024] In the above method, when the built-in evaporator, the first-stage compressor, the second-stage compressor, the parallel condenser, the flash evaporator, the multi-stage throttle valve multi-loop and the electric auxiliary heater work in a coupled manner for heating in S3, it specifically includes:

[0025] Refrigerant circulation route: Keep the check valves (23), (24), (91) and the solenoid valve (26) energized and normally open, and keep the check valves (21), (22) and the solenoid valve (25) de-energized and normally closed. The low-temperature and low-pressure liquid refrigerant enters the built-in evaporator (12) through the check valve (23), absorbs heat and forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (24) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensation pressure. Then, it enters the second-stage compressor through the solenoid valve (26) and is compressed again to form a high-temperature and high-pressure gaseous refrigerant with a higher enthalpy value. After passing through the one-way valve (52), it enters the parallel condenser to release heat and form a high-temperature and high-pressure liquid refrigerant. Then, it successively passes through the liquid receiver and the dryer filter, and enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant. Then, it passes through the flash evaporator for gas-liquid separation. Among them: a part of the gaseous refrigerant is sprayed back to the second-stage compressor through the check valve (91) to increase the intake air volume entering the parallel condenser to improve the heat exchange efficiency; another part of the liquid refrigerant increases the degree of subcooling, continues to enter the low-pressure throttle valve for throttling again and increases the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with an evaporation pressure, and returns to the built-in evaporator through the check valve (23) to absorb heat for a new round of cycle heating;

[0026] Air circulation route: The medium-temperature and low-humidity gas in the baking room is absorbed by heat through the built-in evaporator to form a low-temperature and low-humidity gas, and then is condensed and releases heat through the parallel condenser to form a high-temperature and low-humidity gas. The high-temperature and low-humidity gas is forced into the baking room by the variable-frequency circulation fan. After the air in the baking room flows, it enters the air return port, and the air in the baking room returns to the heating chamber again to exchange heat with the built-in evaporator and the parallel condenser.

[0027] Beneficial effects:

[0028] The present invention provides a dual-system multi-mode air source heat pump system for tobacco leaf baking, which includes a dual-cycle evaporator, a cascade compressor, a flash evaporator, a gas-liquid separator, a parallel condenser, a liquid receiver, a multi-stage throttle valve, a plurality of check valves and a plurality of one-way valves; the dual-cycle evaporator includes an outer-cycle evaporator and an inner-cycle evaporator; the cascade compressor includes a first-stage compressor and a second-stage compressor; the system includes two independent refrigeration or heating systems, which can achieve flexible collaborative operation under different working conditions, avoiding the energy waste caused by frequent start-stop or inefficient operation of traditional single-system units during low-load operation, and can stably heat even in a low-temperature environment, solving the problems of poor reliability and low operating efficiency of traditional air source heat pumps; when the indoor heat load is small, only one of the systems needs to be turned on and operated at a low power to accurately match the demand and maintain a comfortable indoor temperature, which can greatly reduce energy consumption compared with single-system units. In addition, the system can switch modes according to the indoor and outdoor environmental temperature, humidity and user settings. The dual-system multi-mode unit can better adapt to complex and changeable environmental conditions and improve the stability of heating through optimized system design and control strategies. And the unit can be well integrated with other HVAC systems or building equipment. The refrigeration and heating capabilities of the unit can be further improved by adding modules or upgrading the control system, etc.

[0029] The system adopts first-stage compression and second-stage compression respectively according to different tobacco baking stages, and has two sets of evaporators. In the low-temperature yellowing stage, medium-temperature color-fixing stage and high-temperature dry-leaf stage of tobacco baking, the outer-cycle evaporator, inner-cycle evaporator and dual-cycle evaporator working modes are respectively enabled. On the one hand, the two sets of equipment can be used as spares for each other, improving the stability and reliability of the system; on the other hand, different evaporators can be used according to the different requirements of the indoor environment in different tobacco baking stages, greatly improving the adaptability of the system and the performance of the equipment. And, an electric auxiliary heater is arranged at the outlet of the parallel condenser, and a condenser air outlet temperature sensor is configured to accurately control the air supply temperature and adjust the indoor temperature. Brief Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the dual-system multi-mode air source heat pump system for tobacco leaf baking in an embodiment of the present invention.

[0031] In the figure: 11, external evaporator; 12, internal evaporator; 101, low-pressure throttle valve; 102, high-pressure throttle valve; 21-24, check valves; 25-26, solenoid valves; 3, gas-liquid separator; 41, first-stage compressor; 42, second-stage compressor; 51-52, one-way valves; 6, parallel condenser; 7, liquid receiver; 8, drying filter; 9, flash evaporator; 91, check valve; 10, water receiving tray. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] The first group of embodiments: a dual-system multi-mode air source heat pump system for tobacco leaf baking

[0034] This group of embodiments provides a dual-system multi-mode air source heat pump system for tobacco leaf baking, as Figure 1 shown, including: a dual-cycle evaporator, a cascade compressor, a flash tank, a gas-liquid separator, a parallel condenser, an electric auxiliary heater, a liquid receiver, a multi-stage throttle valve, a plurality of check valves, a plurality of solenoid valves, a variable-frequency circulating fan, a dryer filter, a water receiving tray, and a plurality of one-way valves;

[0035] The dual-cycle evaporator includes an outer-cycle evaporator and an inner-cycle evaporator, and the outer-cycle evaporator and the inner-cycle evaporator share a gas-liquid separator and a flash tank in parallel; in a specific embodiment of the present invention, the outer-cycle evaporator uses outdoor ambient air and indoor dehumidification port air as heat sources, and the inner-cycle evaporator uses the return air from the bottom to the top of the curing barn as a heat source.

[0036] The cascade compressor includes a first-stage compressor and a second-stage compressor, and the first-stage compressor and the second-stage compressor are connected in series to form a cascade compressor and are connected between the gas-liquid separator and the parallel condenser.

[0037] The gaseous refrigerant end of the dual-cycle evaporator is connected to the gaseous refrigerant inlet end of the gas-liquid separator through a check valve, the gaseous refrigerant end of the gas-liquid separator is connected to the gaseous refrigerant inlet end of the first-stage compressor, the gaseous refrigerant end of the first-stage compressor is connected to the gaseous refrigerant inlet end of the parallel condenser through a solenoid valve, the liquid refrigerant outlet end of the parallel condenser is sequentially connected to the flash tank through a liquid receiver, a dryer filter, and a high-pressure throttle valve, and the liquid refrigerant outlet end of the flash tank returns to the liquid refrigerant inlet end of the dual-cycle evaporator through a low-pressure throttle valve and a check valve to form a main heating circuit;

[0038] On the basis of the main heating circuit, the gaseous refrigerant end of the first-stage compressor is connected to the gaseous refrigerant inlet end of the second-stage compressor through a solenoid valve and further connected to the gaseous refrigerant inlet end of the parallel condenser through the gaseous refrigerant end of the second-stage compressor, and the gaseous refrigerant end of the flash tank is connected to the gaseous refrigerant inlet end of the second-stage compressor through a check valve to form a branch jet enthalpy-increasing circuit.

[0039] In a specific embodiment of the present invention, the refrigerant passing through the main refrigerant heating circuit enters the high-pressure throttle valve and is depressurized to a medium-pressure gas-liquid mixture. After entering the flash evaporator, it directly enters the low-pressure throttle valve and is depressurized again to a low-pressure liquid, and then enters the double-cycle evaporator to absorb heat and evaporate into a low-pressure steam. It then enters the gas-liquid separator and the cascade compound compressor to start the cycle; the refrigerant passing through the refrigerant branch jet enthalpy-increasing circuit enters the high-pressure throttle valve and is depressurized to a medium-pressure gas-liquid. After entering the flash evaporator, the gaseous refrigerant after gas-liquid separation is injected into the compression chamber of the compressor in the form of inter-stage air supplement through an electromagnetic check valve. After converging with the refrigerant in the main heating circuit, it is further compressed to form a high-pressure steam and repeats the cycle for heating.

[0040] In a specific embodiment of the present invention, the participation of the flash evaporator in switching between the main heating circuit and the branch jet enthalpy-increasing circuit of the parallel condenser is determined by the temperature conditions required in different baking stages; the main heating circuit mode operates throughout the entire baking cycle, and the branch jet enthalpy-increasing circuit mode only operates as an auxiliary when high-temperature conditions are required in the later color-fixing stage and the stem-drying stage; on the one hand, the flash evaporator supplies air to the compressor to increase the subcooling degree of the liquid refrigerant in the main heating circuit before entering the low-pressure throttle valve, so as to absorb more heat from the medium in the evaporator, and on the other hand, to increase the exhaust volume of the parallel condenser, so as to increase the amount of refrigerant for heat exchange.

[0041] The multi-stage throttle valve includes a low-pressure throttle valve and a high-pressure throttle valve.

[0042] The water receiving tray is arranged below the inner-cycle evaporator to receive the condensed water generated by the inner-cycle evaporator; a drain pipe extending outside the water receiving tray is arranged in the water receiving tray to drain the water in the water receiving tray.

[0043] The electric auxiliary heater is equipped with a temperature sensor at the outlet of the condenser. When the temperature detected by the temperature sensor is lower than the temperature set by the baking room controller, it starts to work and stops working after the air supply temperature is stabilized.

[0044] Second group of embodiments: A method for baking tobacco leaves using a dual-system multi-mode air source heat pump system for tobacco leaf baking

[0045] This group of embodiments provides a method for baking tobacco leaves using the dual-system multi-mode air source heat pump system for tobacco leaf baking described in the first group of embodiments, including the following steps:

[0046] S1: During the yellowing period of tobacco leaves, the air source heat pump system operates under low-temperature conditions. Specifically: the external evaporator circulates, the first-stage compressor, the parallel condenser, and the multi-stage throttle valve loop operate independently for heating; in a specific embodiment of the present invention, the specific heating process is as follows: Refrigerant circulation route: First, the check valves 21, 22, and the solenoid valve 25 are energized and normally open, and the check valves 23, 24, 91, and the solenoid valve 26 are de-energized and normally closed. The low-temperature and low-pressure liquid refrigerant enters the external evaporator through the check valve 21, absorbs heat, and then forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve 22 for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensation pressure. It sequentially passes through the solenoid valve 25 and the one-way valve 51 and enters the parallel condenser to release heat and form a high-temperature and high-pressure liquid refrigerant. Then, it successively passes through the liquid receiver and the dryer filter, enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash evaporator for gas-liquid separation. It continues to enter the low-pressure throttle valve with the medium-temperature and medium-pressure liquid refrigerant for re-throttling and increasing the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with an evaporation pressure, and returns to the external evaporator through the check valve 21 to absorb heat for a new round of cycle heating;

[0047] Air circulation route: The low-temperature and low-humidity gas in the tobacco barn forms a high-temperature and low-humidity gas after being condensed and releasing heat by the parallel condenser, and is forced into the tobacco barn by the variable-frequency circulation fan. After the gas in the tobacco barn flows, it enters the heating chamber through the return air duct, exchanges heat with the external evaporator again, and then starts a new round of heating cycle.

[0048] S2: During the color-fixing period of tobacco leaves, the dual-system and multi-mode air source heat pump system for tobacco leaf baking operates under medium-temperature conditions. Specifically: the internal evaporator, the first-stage compressor, the parallel condenser, and the multi-stage throttle valve loop operate independently for heating; in a specific embodiment of the present invention, the specific heating process is as follows: Refrigerant circulation route: Gradually energize the check valves 23, 24, and the solenoid valve 25 to be normally open, and de-energize the check valves 21, 22, 91, and the solenoid valve 26 to be normally closed. The low-temperature and low-pressure liquid refrigerant enters the internal evaporator through the check valve 23, absorbs heat, and then forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve 24 for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensation pressure. It sequentially passes through the solenoid valve 25 and the one-way valve 51 and enters the parallel condenser to release heat and form a high-temperature and high-pressure liquid refrigerant. Then, it successively passes through the liquid receiver and the dryer filter, enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash evaporator for gas-liquid separation. It continues to enter the low-pressure throttle valve with the medium-temperature and medium-pressure liquid refrigerant for re-throttling and increasing the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with an evaporation pressure, and returns to the internal evaporator through the check valve 23 to absorb heat for a new round of cycle heating;

[0049] Air circulation route: The medium-temperature and high-humidity gas in the baking room is absorbed by the built-in evaporator to form condensed water and low-temperature and low-humidity gas. Among them, the condensed water drips along the fins into the water receiving tray and is discharged from the baking room along the drain pipe; the low-temperature and low-humidity gas is condensed and releases heat through the parallel condenser to form high-temperature and low-humidity gas, and the high-temperature and low-humidity gas is forced into the baking room by the variable-frequency circulation fan. The medium-temperature and high-humidity gas in the baking room enters the heating chamber through the air return port, exchanges heat with the built-in evaporator again, and then starts a new round of heating cycle.

[0050] S3: During the dry leaf vein period, the dual-system and multi-mode air source heat pump system for tobacco leaf baking operates under high-temperature conditions. Specifically, the built-in evaporator, the first-stage compressor, the second-stage compressor, the parallel condenser, the flash evaporator, the multi-stage throttle valve multi-loop, and the electric auxiliary heater are coupled to work for heating. In a specific embodiment of the present invention, the specific heating process is as follows: Refrigerant circulation route, keep the check valves 23, 24, 91 and the solenoid valve 26 energized and normally open, and keep the check valves 21, 22 and the solenoid valve 25 de-energized and normally closed. The low-temperature and low-pressure liquid refrigerant enters the built-in evaporator through the check valve 23, absorbs heat, and forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve 24 for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with condensation pressure. Then, it enters the second-stage compressor through the solenoid valve 26 for further compression to form a high-temperature and high-pressure gaseous refrigerant with a higher enthalpy value. After passing through the one-way valve 52, it releases heat in the parallel condenser to form a high-temperature and high-pressure liquid refrigerant, and then passes through the liquid storage tank and the dryer filter in sequence, and enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant. Then, it passes through the flash evaporator for gas-liquid separation. Among them, a part of the gaseous refrigerant is sprayed back to the second-stage compressor through the check valve 91 to increase the intake air volume entering the parallel condenser to improve the heat exchange efficiency; the other part of the liquid refrigerant increases the subcooling degree, continues to enter the low-pressure throttle valve for further throttling and increases the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with evaporation pressure, and returns to the built-in evaporator through the check valve 23 to absorb heat for a new round of cyclic heating;

[0051] Air circulation route: The medium-temperature and low-humidity gas in the baking room is absorbed by the built-in evaporator to form low-temperature and low-humidity gas, and then is condensed and releases heat through the parallel condenser to form high-temperature and low-humidity gas. The high-temperature and low-humidity gas is forced into the baking room by the variable-frequency circulation fan. After the air in the baking room flows, it enters the air return port, and the air in the baking room returns to the heating chamber again under the traction action to exchange heat with the built-in evaporator and the parallel condenser again. In a specific embodiment of the present invention, when the baking process needs to increase the temperature, the electric auxiliary heater is added and turned on for auxiliary heating to ensure uniform temperature increase and long-term stable temperature.

[0052] In a specific embodiment of the present invention, the tobacco leaves are difficult-to-cure tobacco leaves formed under special flue-cured tobacco varieties and field climate conditions; in a specific embodiment of the present invention, the fresh tobacco leaf quality and baking characteristics of this type of tobacco leaves are poor, and it is easy to appear green-roasted tobacco, ash-hung tobacco, black and rotten tobacco, etc. during the baking process; the special flue-cured tobacco varieties refer to two flue-cured tobacco varieties enjoying national price policy subsidies: Honghua Dajinyuan and Cuibi No. 1, and the special field climate conditions refer to climates such as rainy and less sunny, long-term rainfall during the maturity period, drought and high temperature, etc.; the difficult-to-cure tobacco leaves are formed by the combination of one or more of the above situations.

[0053] It should be noted that the above specific embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way. Therefore, although this specification has described the present invention in detail with reference to the drawings and embodiments, those skilled in the art should understand that the present invention can still be modified or equivalently replaced. In short, all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the patent of the present invention.

Claims

1. A dual-system multi-mode air source heat pump system for tobacco leaf baking, characterized in that: include: A dual-circulation evaporator, a cascade compressor, a flash evaporator, a gas-liquid separator, a parallel condenser, a liquid storage device, a multi-pressure stage throttle valve, a plurality of check valves, a plurality of solenoid valves and a plurality of one-way valves; the dual-circulation evaporator comprises an outer circulation evaporator and an inner circulation evaporator; the cascade compressor comprises a primary compressor and a secondary compressor; the multi-pressure stage throttle valve comprises a low-pressure throttle valve and a high-pressure throttle valve; the outer circulation evaporator and the inner circulation evaporator share a gas-liquid separator and a flash evaporator by being connected in parallel with each other; The primary compressor and the secondary compressor are connected in series to form a cascade compressor and are connected between the gas-liquid separator and the parallel condenser; The gaseous refrigerant outlet of the dual-cycle evaporator is connected to the gaseous refrigerant inlet of the gas-liquid separator through a check valve, the gaseous refrigerant outlet of the gas-liquid separator is connected to the gaseous refrigerant inlet of the primary compressor, the gaseous refrigerant outlet of the primary compressor is connected to the gaseous refrigerant inlet of the parallel condenser through a solenoid valve, the liquid refrigerant outlet of the parallel condenser is connected to the liquid refrigerant inlet of the flash evaporator through a liquid storage device, a drying filter and a high-pressure throttle valve in sequence, and the liquid refrigerant outlet of the flash evaporator returns to the liquid refrigerant inlet of the dual-cycle evaporator through a low-pressure throttle valve and a check valve to form a main line heating circuit; On the basis of the main line heating circuit, the gaseous refrigerant outlet end of the primary compressor is connected to the gaseous refrigerant inlet end of the secondary compressor through a solenoid valve and is further connected to the gaseous refrigerant inlet end of the parallel condenser through the gaseous refrigerant outlet end of the secondary compressor, and the gaseous refrigerant outlet end of the flash evaporator is connected back to the gaseous refrigerant inlet end of the secondary compressor through a check valve to form a branch jet reheat increase circuit.

2. The dual-system multi-mode air source heat pump system for tobacco leaf baking according to claim 1, characterized in that: The air source heat pump system further comprises a variable frequency circulation fan and an electric auxiliary heater respectively arranged on the air inlet side and the air outlet side of the parallel condenser.

3. The dual-system multi-mode air source heat pump system for tobacco leaf baking according to claim 2, characterized in that: The air source heat pump system also includes a water receiving pan arranged below the internal circulation evaporator to receive condensed water generated by the internal circulation evaporator; a drain pipe extending outside the water receiving pan to drain water from the water receiving pan is arranged in the water receiving pan.

4. The dual-system multi-mode air source heat pump system for tobacco leaf baking according to claim 2, characterized in that: The air source heat pump system is used to provide heat source for the baking room; the external circulation evaporator uses outdoor ambient air and indoor dehumidification outlet air as heat source; the internal circulation evaporator uses the return air outlet air of the baking room that unidirectionally convects from bottom to top as heat source.

5. The dual-system multi-mode air source heat pump system for tobacco leaf baking according to claim 2, characterized in that: The flash evaporator participates in the parallel condenser switching between the main heating circuit and the branch jet enthalpy increase circuit; the evaporator relies on a check valve to control the refrigerant to split the liquid flow direction to achieve working mode switching; the compressor relies on a solenoid valve to control the refrigerant to split the steam flow direction to achieve working mode switching.

6. The dual-system multi-mode air source heat pump system for tobacco leaf baking according to claim 2, characterized in that: The electric auxiliary heater is equipped with a condenser air outlet temperature sensor; the temperature sensor is arranged at both ends of the electric auxiliary heater.

7. A method for baking tobacco leaves using the dual-system multi-mode air source heat pump system for baking tobacco leaves according to any one of claims 1 to 6, characterized in that: The steps include: S1: During the yellowing period of tobacco leaves, the air source heat pump system operates under low temperature conditions, specifically: the external evaporator cycle, the first-stage compressor, the parallel condenser and the multi-pressure stage throttle valve circuit independently circulate to heat; S2: During the tobacco leaf color fixing period, the air source heat pump system operates under medium temperature conditions, specifically: the built-in evaporator, the first-stage compressor, the parallel condenser and the multi-pressure stage throttle valve circuit work independently to generate heat; S3: During the tobacco leaf drying period, the air source heat pump system operates under high temperature conditions, specifically: the built-in evaporator, the first-stage compressor, the second-stage compressor, the parallel condenser, the flash evaporator, the multi-pressure stage throttle valve, the multi-circuit and the electric auxiliary heater are coupled to work for heating; The tobacco leaves are difficult to cure due to special flue-cured tobacco varieties and field climate conditions.

8. The method for baking tobacco leaves using a dual-system multi-mode air source heat pump system for baking tobacco leaves according to claim 7, characterized in that: The specific heating process described in S1 is as follows: Refrigerant circulation route: first, the check valves (21), (22) and the solenoid valve (25) are powered on and normally open, and the check valves (23), (24), (91) and the solenoid valve (26) are powered off and normally closed, and the low-temperature and low-pressure liquid refrigerant enters the external evaporator through the check valve (21) to absorb heat and then forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (22) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with condensation pressure, in sequence. After entering the parallel condenser through the solenoid valve (25) and the one-way valve (51) to release heat, a high-temperature and high-pressure liquid refrigerant is formed. Then, the refrigerant passes through the liquid storage device and the drying filter in sequence, and enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant. Then, the refrigerant passes through the flash evaporator for gas-liquid separation, and continues to enter the low-pressure throttle valve as a medium-temperature and medium-pressure liquid refrigerant for throttling again and increasing the enthalpy difference, finally forming a low-temperature and low-pressure liquid refrigerant with evaporation pressure, and returns to the external evaporator through the check valve (21) to absorb heat for a new round of heating cycle; Air circulation route: The low-temperature and low-humidity gas in the baking room is condensed and released through the parallel condenser to form high-temperature and low-humidity gas, which is forced into the baking room by the variable frequency circulation fan. The gas in the baking room flows into the heating chamber through the return air port, and then exchanges heat with the external evaporator again to start a new round of heating cycle.

9. The method for baking tobacco leaves using a dual-system multi-mode air source heat pump system for baking tobacco leaves according to claim 7, characterized in that: When the built-in evaporator, the primary compressor, the parallel condenser and the multi-pressure stage throttle valve circuit described in S2 work independently for heating, the specific process includes: Refrigerant circulation route: gradually turn on the check valves (23), (24) and the solenoid valve (25) to open them normally, turn off the check valves (21), (22), (91) and the solenoid valve (26) to close them normally, and the low-temperature and low-pressure liquid refrigerant enters the built-in evaporator through the check valve (23) to absorb heat and then forms a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (24) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with condensing pressure, which passes through the solenoid valves (2 5) After entering the parallel condenser through the one-way valve (51) to release heat, a high-temperature and high-pressure liquid refrigerant is formed, and then it passes through the liquid storage tank and the drying filter in sequence, and enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash evaporator for gas-liquid separation, and continues to enter the low-pressure throttle valve as a medium-temperature and medium-pressure liquid refrigerant to throttle again and increase the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with evaporation pressure, and returns to the built-in evaporator through the check valve (23) to absorb heat for a new round of cycle heating; Air circulation route: The medium-temperature and high-humidity gas in the baking room absorbs heat through the built-in evaporator to form condensed water and low-temperature and low-humidity gas, among which: the condensed water drips along the fins to the water receiving tray, and the water is discharged from the baking room along the drain pipe; the low-temperature and low-humidity gas is condensed and releases heat through the parallel condenser to form high-temperature and low-humidity gas, which is forcibly sent into the baking room through the variable frequency circulation fan. The medium-temperature and high-humidity gas in the baking room enters the heating chamber through the return air port, and starts a new round of heating cycle after heat exchange with the built-in evaporator again.

10. The method for baking tobacco leaves using a dual-system multi-mode air source heat pump system for baking tobacco leaves according to claim 7, characterized in that: When the built-in evaporator, the primary compressor, the secondary compressor, the parallel condenser, the flash evaporator, the multi-pressure stage throttle valve, the multi-circuit and the electric auxiliary heater described in S3 are coupled to perform heating, it specifically includes: In the refrigerant circulation route, the check valves (23), (24), (91) and the solenoid valve (26) are energized and normally open, and the check valves (21), (22) and the solenoid valve (25) are de-energized and normally closed. The low-temperature and low-pressure liquid refrigerant enters the built-in evaporator (12) through the check valve (23) to absorb heat to form a low-temperature and low-pressure gaseous refrigerant, which enters the gas-liquid separator through the check valve (24) for gas-liquid separation, and then enters the first-stage compressor for compression to form a high-temperature and high-pressure gaseous refrigerant with a condensing pressure, and then enters the second-stage compressor through the solenoid valve (26) for compression again to form a high-temperature and high-pressure gaseous refrigerant with a higher enthalpy value, and enters through the one-way valve (52) After the parallel condenser releases heat, a high-temperature and high-pressure liquid refrigerant is formed, and then it passes through the liquid storage tank and the drying filter in sequence, and enters the high-pressure throttle valve for the first throttling to form a medium-temperature and medium-pressure gas-liquid mixed refrigerant, and then passes through the flash evaporator for gas-liquid separation, wherein: a part of the gaseous refrigerant is ejected back to the secondary compressor through the check valve (91), increasing the air intake entering the parallel condenser to improve the heat exchange efficiency; the other part of the liquid refrigerant has a higher degree of supercooling, continues to enter the low-pressure throttle valve for throttling again and increasing the enthalpy difference, and finally forms a low-temperature and low-pressure liquid refrigerant with evaporation pressure, and returns to the built-in evaporator through the check valve (23) to absorb heat for a new round of cycle heating; Air circulation route: The medium-temperature and low-humidity gas in the baking room absorbs heat through the built-in evaporator to form low-temperature and low-humidity gas, and then condenses and releases heat through the parallel condenser to form high-temperature and low-humidity gas. The high-temperature and low-humidity gas is forcibly sent into the baking room through the variable frequency circulation fan. The air in the baking room flows into the return air port, and the air in the baking room returns to the heating room to exchange heat with the built-in evaporator and parallel condenser again.

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