An aircraft ground air conditioning unit with multi-stage refrigeration and heating and its control method

Abstract

The present invention belongs to the field of air-conditioning units, and relates to a multi-stage refrigeration and heating aircraft ground air-conditioning unit and its control method, including a first-stage module, a second-stage module, a third-stage module, a fourth-stage module and a air supply section; the first-stage module, the second-stage module, the third-stage module, the fourth-stage module and the air supply section are sequentially connected through an air-conditioning air supply channel. The first-stage module includes an indirect evaporative cooler, and the indirect evaporative cooler is provided with a cooling water pipeline; the second-stage module includes an absorption refrigeration unit, a solar collector and a gas-oil heat exchanger. The solar collector is respectively connected in a cycle with the absorption refrigeration unit and the gas-oil heat exchanger through a heat-conducting oil pipeline, and the cooling water pipeline is connected to the absorption refrigeration unit; the third-stage module uses a vapor compression refrigeration unit; the fourth-stage module uses an electric heater; the air supply section includes a blower and a fresh air supply opening, and the fresh air supply opening is communicated to the outside of the aircraft ground air-conditioning unit. It can utilize solar energy and dry air energy to form multi-stage refrigeration and heating, reducing energy consumption.

Description

Technical Field

[0001] The invention belongs to the field of air-conditioning units, and relates to a multi-stage refrigerating and heating aircraft ground air-conditioning unit and a control method thereof. Background Art

[0002] An aircraft ground air conditioner is a special air-conditioning unit for regulating the air inside the aircraft cabin on the airport ground, also known as a pre-treatment air-conditioning unit. It uses refrigeration technology to filter, cool, dehumidify or heat the inhaled air, and conveys the processed air to the internal space of the aircraft parked on the ground according to the air flow and pressure specified for the aircraft model. This equipment is mostly used during the stage from when the aircraft is parked to when it takes off. Without relying on the aircraft's own auxiliary power unit, it can still provide a good cabin environment for the crew, airport staff, passengers, etc.

[0003] The refrigeration and heating processes of traditional aircraft ground air conditioners are single. Steam compression refrigeration is used for refrigeration, and electric heaters are used for heating. In most areas of northwest, northeast, southwest, etc. in China, the climate is dry and hot, and the temperature on the apron is above 40°C, but the wet bulb temperature is very low, only about 22°C. In some areas, the wet bulb temperature can reach below 20°C. Traditional aircraft ground air conditioners do not make full use of this dry air energy, resulting in low efficiency of the unit. At the same time, there is no shelter on the apron in summer, and the solar heat radiation is very large, but the existing aircraft ground air conditioners do not consider this part of free solar energy, resulting in waste of energy. Summary of the Invention

[0004] The purpose of the invention is to overcome the above-mentioned disadvantages of the prior art, and provide a multi-stage refrigerating and heating aircraft ground air-conditioning unit and a control method thereof, which can utilize solar energy and dry air energy to form multi-stage refrigeration and heating, improve the efficiency of the aircraft ground air-conditioning unit, and reduce energy consumption.

[0005] To achieve the above purpose, the invention adopts the following technical solutions:

[0006] A multi-stage refrigerating and heating aircraft ground air-conditioning unit includes a first-stage module, a second-stage module, a third-stage module, a fourth-stage module and a air supply section;

[0007] The first-stage module, the second-stage module, the third-stage module, the fourth-stage module and the air supply section are sequentially connected through an air-conditioning air supply channel. The first-stage module includes an indirect evaporative cooler, and the indirect evaporative cooler is provided with a cooling water pipeline;

[0008] The second-stage module includes an absorption refrigeration unit, a solar collector and an air-oil heat exchanger. The solar collector is respectively connected in a cycle with the absorption refrigeration unit and the air-oil heat exchanger through heat-conducting oil pipelines, and the cooling water pipeline is connected to the absorption refrigeration unit;

[0009] The third - level module adopts a steam compression refrigeration unit; the fourth - level module adopts an electric heater; the air supply section includes a blower and a fresh air supply outlet, and the fresh air supply outlet is connected to the outside of the aircraft ground air conditioner unit.

[0010] Preferably, the indirect evaporative cooler includes a fresh air inlet, a secondary air inlet, an air filter, an evaporative cooling exhaust fan, a water filter, a sprayer, an indirect evaporative cooling pipe, and a water collecting tray; the outlets of both the fresh air inlet and the secondary air inlet are connected to the air filter, the evaporative cooling exhaust fan, the water filter, the sprayer, the indirect evaporative cooling pipe, and the water collecting tray are arranged in sequence from top to bottom, the indirect evaporative cooling pipe is located at the outlet of the air filter, the fresh air inlet is connected to the inside of the indirect evaporative cooling pipe, and the secondary air inlet is connected to the outside of the indirect evaporative cooling pipe and the evaporative cooling exhaust fan; the water collecting tray is connected to the inlet of the cooling water pipeline, the sprayer is connected to the outlet of the cooling water pipeline, the cooling water pipeline is provided with two loops, and electric valves are arranged at the inlets and outlets of both loops.

[0011] Preferably, a first temperature sensor is arranged between the first - level module and the second - level module, a second temperature sensor is arranged between the second - level module and the third - level module, a third temperature sensor is arranged between the third - level module and the fourth - level module, and a fourth temperature sensor is arranged inside the air supply section.

[0012] Preferably, the absorption refrigeration unit includes a generator; the solution outlet of the generator is sequentially connected with an absorber, a solution pump, a solution heat exchanger, and the solution inlet of the generator through a solution pipeline to form a solution circulation pipeline; the steam outlet of the generator is sequentially connected with a first - stage condenser, a first - stage evaporator, and the steam inlet of the absorber through a steam - water pipeline; both the absorber and the first - stage condenser are connected with a cooling water pipeline; the heat - conducting oil pipeline is connected to the generator.

[0013] Preferably, the fresh air inlets of the gas - oil heat exchanger and the first - stage evaporator are respectively connected with a first electric airtight valve and a second electric airtight valve; the first electric airtight valve and the second electric airtight valve are arranged one above the other to block the air - conditioning air supply channel.

[0014] Preferably, the steam compression refrigeration unit includes a compressor, a second - stage condenser, a liquid receiver, a second - stage evaporator, and a gas - liquid separator that are connected in a circulating sequence.

[0015] Preferably, the generator includes a closed outer shell, an inner tank is arranged inside the outer shell, a solution is arranged in the inner tank, the top of the inner tank is open, the bottom of the inner tank is slidably and sealedly arranged with the inner wall of the outer shell, a solution outlet is arranged at the bottom of the inner tank of the generator, the solution outlet is connected to the outside of the outer shell of the generator through a solution outlet pipeline, and the parts of the heat - conducting oil pipeline connected to the generator and the second - stage condenser are both located in the inner tank.

[0016] A multi - stage refrigeration and heating control method for the aircraft ground air conditioner unit described above includes the following processes:

[0017] Under the refrigeration condition, the indirect evaporative cooler, the absorption refrigeration unit and the vapor compression refrigeration unit are sequentially started, and the gas-oil heat exchanger and the electric heater are closed;

[0018] When the temperature of the medium in the heat transfer oil pipeline is higher than the set temperature, the flow rate of the medium in the heat transfer oil pipeline is increased. When the temperature of the medium in the heat transfer oil pipeline is lower than the set temperature, the connection between the heat transfer oil pipeline and the absorption refrigeration unit is cut off. When the temperature of the medium in the heat transfer oil pipeline is higher than the set temperature, the heat transfer oil pipeline and the absorption refrigeration unit are reconnected;

[0019] Under the heating condition, the gas-oil heat exchanger and the electric heater are started, and the indirect evaporative cooler, the absorption refrigeration unit and the vapor compression refrigeration unit are closed;

[0020] When the temperature of the medium in the heat transfer oil pipeline is higher than the set temperature, the flow rate of the medium in the heat transfer oil pipeline is increased. When the temperature of the medium in the heat transfer oil pipeline is lower than the air temperature after the fresh air passes through the indirect evaporative cooler, the gas-oil heat exchanger is closed and the power of the electric heater is increased.

[0021] Preferably, the absorption refrigeration unit includes a generator; the solution outlet of the generator is sequentially connected with an absorber, a solution pump, a solution heat exchanger and the solution inlet of the generator through a solution pipeline to form a solution circulation pipeline; the steam outlet of the generator is sequentially connected with a primary condenser, a primary evaporator and the steam inlet of the absorber through a steam-water pipeline; the vapor compression refrigeration unit includes a compressor, a secondary condenser, a liquid receiver, a secondary evaporator and a gas-liquid separator connected in sequence; the generator includes a closed outer shell, an inner tank is arranged inside the outer shell, a solution is arranged in the inner tank, the top of the inner tank is open, the bottom of the inner tank is slidably and sealed with the inner wall of the outer shell, a solution outlet is arranged at the bottom of the inner tank, and the solution outlet is connected to the outside of the outer shell through a solution outlet pipeline, and the secondary condenser is located in the inner tank;

[0022] After the secondary module operates normally, when there is liquid water in the steam in the outlet pipeline of the primary evaporator, the flow rate on the pipeline of the steam outlet of the generator is reduced, so that the flow rate of the high-pressure steam entering the primary condenser is reduced, and the steam generated in the generator will accumulate, increasing the pressure above the solution liquid level in the inner tank of the generator, pushing the inner tank of the generator downward, exposing the secondary condenser out of the solution surface, thereby reducing the heating amount of the solution by the secondary condenser. As the heating amount of the solution gradually decreases, the outlet pressures of the secondary condenser and the compressor gradually increase. When the outlet pressure of the compressor reaches 90% of the overpressure alarm pressure, the power of the compressor is reduced;

[0023] As the amount of heat supplied to the solution gradually decreases, the evaporation rate of the solution in the generator also decreases. At this time, the amount of liquid water in the pipeline at the outlet of the primary evaporator gradually decreases until it disappears. By increasing the flow rate in the pipeline at the steam outlet of the generator, the pressure above the liquid level of the solution in the inner tank of the generator will decrease, causing the inner tank to move upward, submerging the secondary condenser in the solution again to continue heating the solution to promote evaporation. The outlet pressures of the secondary condenser and the compressor gradually decrease. When the outlet pressure of the compressor drops to 110% of the minimum allowable pressure, the power of the compressor is increased.

[0024] Preferably, a constant-frequency pump is used as the solution pump; the concentration and temperature of the concentrated solution at the solution outlet of the generator are obtained, and the flow rate and temperature of the dilute solution at the solution outlet of the absorber are obtained. Since the solution pump is a constant-frequency pump, the flow rate remains constant all the time, and the flow rate of the concentrated solution is equal to that of the dilute solution; through heat exchange calculation, the critical temperature at which the dilute solution enters the solution heat exchanger is obtained.

[0025] When the temperature of the dilute solution entering the solution heat exchanger is higher than the critical temperature, the outlet temperature of the concentrated solution will not be lower than the saturation temperature at its own concentration, and the concentrated solution will not crystallize. At this time, the temperature of the medium in the cooling water pipeline is reduced.

[0026] When the temperature of the dilute solution entering the solution heat exchanger is lower than the critical temperature, the outlet temperature of the concentrated solution will also be lower than the saturation temperature at its own concentration, and the concentrated solution will crystallize. At this time, the temperature of the medium in the cooling water pipeline is increased.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention uses an indirect evaporative cooler as the primary refrigeration, making full use of the dry air energy on the apron and improving the efficiency of the unit. An absorption refrigeration unit is used as the secondary refrigeration. By combining a solar collector and an absorption refrigeration unit, the high-temperature medium obtained based on solar energy is used as the heat source of the absorption refrigeration unit, improving the efficiency of the absorption refrigeration unit. Moreover, the combination of the solar collector and the gas-oil heat exchanger is used as the primary heating, the vapor compression refrigeration unit is used as the tertiary refrigeration, and the electric heater is used as the secondary heating. Finally, the unit of the present invention realizes multi-stage refrigeration and heating, improves the efficiency of the aircraft ground air-conditioning unit, and reduces energy consumption.

[0029] The present invention recovers and utilizes the waste heat of the vapor compression refrigeration unit as the heat source of the absorption refrigeration unit, further improving the efficiency of the absorption refrigeration unit.

[0030] In the present invention, the inner container of the generator moves up and down along the outer shell of the generator according to the pressure brought by different evaporation amounts of water vapor, adjusting the volume of the inner container, so as to keep the pressure above the liquid level of the solution constant. Moreover, the up and down movement of the inner container can adjust the immersion depth of the secondary condenser in the solution, thereby automatically adjusting the heating amount of the solution, and further adjusting the evaporation amount of water vapor, so that the refrigeration effect of the primary evaporator is always in the optimal state, achieving independent, rapid and stepless adjustment of the refrigerating capacity, while greatly reducing the frequent adjustment and low-load operation of the compressor power.

[0031] In the present invention, the temperature and concentration of the strong solution entering the solution heat exchanger are known, and the temperature and flow rate of the weak solution entering the solution heat exchanger are also known. Since the solution pump is a constant-frequency pump, the flow rate remains unchanged. And because it is the same pipeline, the flow rates of the strong solution entering the solution heat exchanger and the weak solution entering the solution heat exchanger are equal. Through heat exchange calculation, the critical temperature of the weak solution entering the solution heat exchanger can be obtained. According to whether the temperature of the weak solution entering the solution heat exchanger is higher than the critical temperature, the temperature of the medium in the cooling water pipeline is controlled, and the cooling capacity of the medium in the cooling water pipeline is adjusted, so as to achieve the purpose of reducing the crystallization of the solution in the solution heat exchanger by accurately controlling the temperature of the medium in the cooling water pipeline, and neither conservatively increasing the temperature of the medium in the cooling water pipeline nor rashly reducing the temperature of the medium in the cooling water pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of a multi-stage refrigeration and heating aircraft ground air-conditioning unit according to Embodiment 1 of the present invention;

[0033] Figure 2 is a schematic structural diagram of the secondary module and the tertiary module according to Embodiment 1 of the present invention;

[0034] Figure 3 is a schematic internal structure diagram of the generator according to Embodiment 2 of the present invention;

[0035] Figure 4 is a schematic diagram of the upward movement of the inner container of the generator according to Embodiment 2 of the present invention;

[0036] Figure 5 is an enthalpy-humidity diagram of the refrigeration process of a traditional aircraft ground air-conditioning unit and a multi-stage refrigeration and heating aircraft ground air-conditioning unit according to Embodiment 2 of the present invention;

[0037] Figure 6 is an enthalpy-humidity diagram of the heating process of a multi-stage refrigeration and heating aircraft ground air-conditioning unit according to Embodiment 2 of the present invention.

[0038] Wherein: 1. Fresh air inlet, 2. Secondary air inlet, 3. Air filter, 4. Indirect evaporative cooling pipeline, 5. Evaporative cooling exhaust fan, 6. Water filter, 7. Spray water device, 8. Cooling water pump, 9. Cooling water filter, 10. Electric valve of the first cooling water pipeline, 11. Electric valve of the second cooling water pipeline, 12. Electric valve of the third cooling water pipeline, 13. Electric valve of the fourth cooling water pipeline, 14. Electric valve of the first heat transfer oil pipeline, 15. Electric valve of the second heat transfer oil pipeline, 16. Gas-oil heat exchanger, 17. First electric airtight damper, 18. Primary evaporator, 19. Second electric airtight damper, 20. Solar collector, 21. Electric valve of the third heat transfer oil pipeline, 22. Electric valve of the fourth heat transfer oil pipeline, 23. Heat transfer oil pump, 24. Heat transfer oil pipeline temperature sensor, 25. Primary condenser, 26. Absorber, 27. Generator, 28. Solution pump, 29. Solution heat exchanger, 30. Compressor, 31. Secondary condenser, 32. Expansion valve, 33. Liquid receiver, 34. Secondary evaporator, 35. Gas-liquid separator, 36. Refrigerant pipeline, 37. Electric heater, 38. Supply fan, 39. Fresh air supply outlet, 40. Cooling water pipeline, 41. Heat transfer oil pipeline, 42. Water collection tray, 43. Solution pipeline, 44. First temperature sensor, 45. Second temperature sensor, 46. Third temperature sensor, 47. Fourth temperature sensor, 48. Baffle, 49. Air conditioning supply air channel, 50. Conductivity meter, 51. Solenoid valve, 52. Heat transfer oil heat exchange coil, 53. Shunt plate, 54. First solution temperature sensor, 55. Second solution temperature sensor, 56. Solution concentration sensor, 57. Flow sensor, 58. Steam-water pipeline, 59. Outer shell, 60. Inner tank, 61. Primary module, 62. Secondary module, 63. Tertiary module, 64. Quaternary module, 65. Supply air section. Specific embodiments

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0040] Example 1:

[0041] As Figure 1 shown, this embodiment provides an aircraft ground air conditioning unit with multi-stage refrigeration and heating, including a primary module 61, a secondary module 62, a tertiary module 63, a quaternary module 64 and a supply air section 65 connected in sequence.

[0042] In this embodiment, the primary module 61 is used for primary refrigeration. The primary module 61 adopts an indirect evaporative cooler, which includes a fresh air inlet 1, a secondary air inlet 2, an air filter 3, an indirect evaporative cooling pipeline 4, an evaporative cooling exhaust fan 5, a water filter 6, a sprayer 7, a cooling water pump 8, a cooling water filter 9 and a water collection tray 42. The fresh air inlet 1 and the secondary air inlet 2 are arranged vertically in parallel, with the fresh air inlet 1 above the secondary air inlet 2. The outlets of both the fresh air inlet 1 and the secondary air inlet 2 are connected to the air filter 3. The indirect evaporative cooling pipeline 4 is arranged at the outlet of the air filter 3. The water collection tray 42 is arranged below the indirect evaporative cooling pipeline 4. The sprayer 7 is located above the indirect evaporative cooling pipeline 4. The water filter 6 is located above the sprayer 7. The evaporative cooling exhaust fan 5 is located above the water filter 6. The fresh air inlet 1 corresponds to the position of the indirect evaporative cooling pipeline 4, and the fresh air inlet 1 is connected to the inside of the indirect evaporative cooling pipeline 4. The secondary air inlet 2 corresponds to the position below the indirect evaporative cooling pipeline 4, and the secondary air inlet 2 is connected to the outside of the indirect evaporative cooling pipeline 4 and the evaporative cooling exhaust fan 5. Below the indirect evaporative cooling pipeline 4, a plurality of shunt plates 53 with different lengths are arranged along the height direction. Each shunt plate 53 is arranged obliquely in the horizontal direction. Each shunt plate 53 is located behind the secondary air inlet 2. The shunt plates 53 are used to shunt the ambient air entering from the secondary air inlet 2, so that the air can evenly contact different positions of the indirect evaporative cooling pipeline 4. The shunt plates 53 are all provided with slopes, and the slope direction is the same as the air inlet direction to facilitate drainage.

[0043] The evaporative cooling exhaust fan 5 sucks the ambient air from the secondary air inlet 2. A baffle 48 is arranged between the fresh air inlet 1 and the secondary air inlet 2. The water collection tray 42 is connected to the inlet of the cooling water pipeline 40 through the cooling water filter 9. The sprayer 7 is connected to the outlet of the cooling water pipeline 40 through the cooling water pump 8. The cooling water pipeline 40 is used for the circulating flow of cooling water. The cooling water pipeline 40 is provided with two loops, and electric valves are arranged at the inlets and outlets of both loops, including a first cooling water pipeline electric valve 10, a second cooling water pipeline electric valve 11, a third cooling water pipeline electric valve 12 and a fourth cooling water pipeline electric valve 13. The four electric valves are used to control the on-off and switching of the cooling water pipeline 40. The structural form of the indirect evaporative cooling pipeline 4 includes but is not limited to horizontal elliptical tube type, vertical tube type, inner groove vertical tube type, polymer plate type and aluminum foil brazing plate type. The refrigeration process is realized through the indirect evaporative cooler.

[0044] In this embodiment, the secondary module 62 is used for secondary refrigeration and primary heating. The secondary module 62 includes an absorption refrigeration unit, a solar collector 20 and a gas-oil heat exchanger 16. The solar collector 20 is respectively connected to the absorption refrigeration unit and the gas-oil heat exchanger 16 in a circulating manner through a heat transfer oil pipeline 41. The solar collector 20 is used as one of the heat sources of the absorption refrigeration unit, such as Figure 2As shown in the figure, the secondary module 62 specifically includes a solar collector 20, a heat-conducting oil pump 23, a generator 27, a primary condenser 25, an expansion valve 32, a primary evaporator 18, a conductivity meter 50, an absorber 26, a flow sensor 57, a second solution temperature sensor 55, a solution heat exchanger 29, a solution pump 28, a solution concentration sensor 56, a first solution temperature sensor 54, a first electric airtight valve 17, a second electric airtight valve 19, an air-oil heat exchanger 16, a first electric valve for the heat-conducting oil pipeline 14, a second electric valve for the heat-conducting oil pipeline 15, a third electric valve for the heat-conducting oil pipeline 21, a fourth electric valve for the heat-conducting oil pipeline 22, a heat-conducting oil pipeline temperature sensor 24, and a heat-conducting oil heat exchange coil 52.

[0045] The solar collector 20 is of the concentrating type and is made of frosted material to prevent reflection from affecting the pilot's line of sight. The heat-collecting medium inside it is heat-conducting oil. The solar collector 20, the heat-conducting oil pump 23, the heat-conducting oil heat exchange coil 52, the air-oil heat exchanger 16, the first electric valve for the heat-conducting oil pipeline 14, the second electric valve for the heat-conducting oil pipeline 15, the third electric valve for the heat-conducting oil pipeline 21, the fourth electric valve for the heat-conducting oil pipeline 22, and the heat-conducting oil pipeline temperature sensor 24 are connected by a heat-conducting oil pipeline 41. The heat-conducting oil pipeline 41 is used for the circulation of heat-conducting oil. The heat-conducting oil heat exchange coil 52 is arranged inside the solution of the generator 27 and is used for heating the solution inside the generator 27. The heat-conducting oil pipeline temperature sensor 24 controls the connection and disconnection between the heat-conducting oil pipeline 41 and the heat-conducting oil heat exchange coil 52 or the air-oil heat exchanger 16 according to the collected temperature of the heat-conducting oil. By controlling the opening and closing of the first electric valve for the heat-conducting oil pipeline 14, the second electric valve for the heat-conducting oil pipeline 15, the third electric valve for the heat-conducting oil pipeline 21, and the fourth electric valve for the heat-conducting oil pipeline 22, the winter and summer working conditions of the heat-conducting oil pipeline 41 are switched.

[0046] The heat-conducting oil pipeline 41 between the solar collector 20 and the heat-conducting oil heat exchange coil 52 is connected or disconnected through the second electric valve for the heat-conducting oil pipeline 15 and the third electric valve for the heat-conducting oil pipeline 21. The heat-conducting oil pipeline 41 between the solar collector 20 and the air-oil heat exchanger 16 is connected or disconnected through the first electric valve for the heat-conducting oil pipeline 14 and the fourth electric valve for the heat-conducting oil pipeline 22. When refrigerating, the solar collector 20 is connected to the heat-conducting oil heat exchange coil 52. At this time, the first electric valve for the heat-conducting oil pipeline 14 is closed, the second electric valve for the heat-conducting oil pipeline 15 is opened, the fourth electric valve for the heat-conducting oil pipeline 22 is closed, and the third electric valve for the heat-conducting oil pipeline 21 is opened. When heating, it is just the opposite. At that time, the solar collector 20 is connected to the air-oil heat exchanger 16.

[0047] The first electric airtight damper 17 and the second electric airtight damper 19 are arranged vertically at the very front of the secondary module 62, blocking the air supply channel 49 of the air conditioner. The gas-oil heat exchanger 16 and the primary evaporator 18 are arranged vertically behind the first electric airtight damper 17 and the second electric airtight damper 19. The fresh air inlets of the gas-oil heat exchanger 16 and the primary evaporator 18 are respectively connected to the outlets of the first electric airtight damper 17 and the second electric airtight damper 19. The rear end of the first electric airtight damper 17 is connected to the gas-oil heat exchanger 16, and the rear end of the second electric airtight damper 19 is connected to the primary evaporator 18. By controlling the opening and closing of the first electric airtight damper 17 and the second electric airtight damper 19, the channel through which the air flow passes is controlled, thereby switching between winter and summer operating conditions.

[0048] The solution outlet of the generator 27, the solution concentration sensor 56, the absorber 26, the flow sensor 57, the solution pump 28, the solution heat exchanger 29 and the solution inlet of the generator 27 are sequentially connected through the solution pipeline 43 to form a solution circulation pipeline; the steam outlet of the generator 27, the solenoid valve 51, the primary condenser 25, the expansion valve 32, the primary evaporator 18, the conductivity meter 50 and the steam inlet of the absorber 26 are sequentially connected through the steam-water pipeline 58; both the absorber 26 and the primary condenser 25 are connected with the cooling water pipeline 40. The heat of the absorber 26 and the primary condenser 25 is taken away through the cooling water pipeline 40 to improve the refrigeration efficiency of the secondary module 62 and reduce energy consumption. The heat taken away is finally dissipated through the evaporation of the external cooling water in the indirect evaporative cooling pipeline 4.

[0049] As Figure 3 and Figure 4 shown, the generator 27 includes a closed outer shell 59. Inside the outer shell 59, there is a silicone rubber bladder-type inner liner 60. A solution is arranged in the inner liner 60. The inner liner 60 and the outer shell 59 of the generator 27 form a structure similar to a pneumatic cylinder. The top of the inner liner 60 is open, and the bottom of the inner liner 60 is slidably and sealedly arranged with the inner wall of the outer shell 59. A solution outlet is arranged at the bottom of the inner liner 60 of the generator 27. The solution outlet is connected to the outside of the outer shell 59 of the generator 27 through a solution outlet pipeline. The solution outlet pipeline uses a telescopic carbon steel pipe. A solution inlet and a steam outlet are arranged at the top of the outer shell 59 of the generator 27. The heat transfer oil heat exchange coil 52 is connected in parallel to the heat transfer oil pipeline 41. The heat transfer oil heat exchange coil 52 is located inside the generator 27 and immersed in the solution of the inner liner 60 of the generator 27. The secondary condenser 31 is located inside the generator 27 and immersed in the solution of the inner liner 60 of the generator 27. The top heights of the heat transfer oil heat exchange coil 52 and the secondary condenser 31 are different, and the bottom heights are the same.

[0050] The inner tank 60 of the generator 27 moves up and down in the outer shell 59 to keep the water vapor pressure above the solution level in the inner tank constant. By adjusting the height of the inner tank 60 through this constant pressure, the solution level is adjusted, and then the immersion depth of the secondary condenser 31 in the solution is adjusted. Finally, the heating amount of the secondary condenser 31 to the solution is adjusted. The heating amount of the solution is proportional to the immersion depth of the secondary condenser 31 in the solution. The solution pump 28 is a constant-frequency pump. A solution concentration sensor 56 and a first solution temperature sensor 54 are provided on the solution pipeline 43 at the bottom outlet of the generator 27. A flow sensor 57 and a second solution temperature sensor 55 are provided on the solution pipeline 43 at the outlet of the absorber 26.

[0051] In this embodiment, a first temperature sensor 44 is provided between the first-stage module 61 and the second-stage module 62. A second temperature sensor 45 is provided behind the air-oil heat exchanger 16 and the first-stage evaporator 18.

[0052] In this embodiment, the third-stage module 63 is used for three-stage refrigeration. The third-stage module 63 adopts a vapor compression refrigeration unit, which includes a compressor 30, a secondary condenser 31, a liquid reservoir 33, a secondary evaporator 34, and a gas-liquid separator 35 connected in sequence through a refrigerant pipeline 36.

[0053] In this embodiment, the fourth-stage module 64 is used for two-stage heating. The fourth-stage module 64 adopts an electric heater 37, which includes heating fresh air through the electric heater 37. A third temperature sensor 46 is provided between the third-stage module 63 and the fourth-stage module 64.

[0054] In this embodiment, the air supply section 65 includes a fourth temperature sensor 47, a blower 38, and a fresh air supply outlet 39. The blower 38 communicates from the inside of the aircraft ground air-conditioning unit to the fresh air inlet 1. The fresh air supply outlet 39 can be connected to facilities such as an external air supply hose of the aircraft ground air-conditioning unit to supply the processed fresh air to the aircraft. The fresh air is sucked from the fresh air inlet 1 by the blower 38 and enters the air-conditioning air supply passage 49.

[0055] In this embodiment, an air-conditioning air supply passage 49 communicating from the front end to the rear end is provided inside the aircraft ground air-conditioning unit. The indirect evaporative cooling pipeline 4, the first-stage evaporator 18, the air-oil heat exchanger 16, the secondary evaporator 34, the electric heater 37, and the blower 38 are all in the air-conditioning air supply passage 49. Equipment components other than the above-mentioned equipment components are separated from the air-conditioning air supply passage 49 by partitions.

[0056] The specific working process of the refrigeration condition in this embodiment is as follows: When starting to work, turn on the evaporative cooling exhaust fan 5, suck in the ambient air through the secondary air inlet 2, turn on the cooling water pump 8, turn on the first cooling water pipeline electric valve 10 and the third cooling water pipeline electric valve 12, close the second cooling water pipeline electric valve 11 and the fourth cooling water pipeline electric valve 13, pump the cooling water in the water collecting tray 42 to the sprayer 7, and sprinkle it outside the indirect evaporative cooling pipeline 4 through the sprayer 7. Turn on the supply fan 38, suck in the fresh air through the fresh air inlet 1 into the air supply channel 49 of the air conditioner, and enter the inside of the indirect evaporative cooling pipeline 4. The ambient air promotes the evaporation of the cooling water sprinkled outside the indirect evaporative cooling pipeline 4, absorbs the heat of the fresh air in the indirect evaporative cooling pipeline 4, and achieves the purpose of cooling the fresh air.

[0057] Specifically, there is a baffle 48 between the fresh air inlet 1 and the secondary air inlet 2. The fresh air only flows inside the indirect evaporative cooling pipeline 4, and the ambient air flows outside the indirect evaporative cooling pipeline 4. The ambient air is discharged outside the aircraft ground air conditioner unit through the evaporative cooling exhaust fan 5. The fresh air and the ambient air do not contact or mix.

[0058] Specifically, in order to prevent the water sprayed by the sprayer 7 from being blown outside by the evaporative cooling exhaust fan 5, this embodiment blocks the water through the water filter 6 to reduce the ineffective loss of water.

[0059] Specifically, the cooling water flows between the water collecting tray 42, the cooling water filter 9, and the sprayer 7 through the cooling water pump 8 to cool the fresh air.

[0060] In this embodiment, the fresh air cooled once by the first-stage module 61 enters the second-stage module 62. After the temperature is measured by the first temperature sensor 44 and reaches the set temperature, the first cooling water pipeline electric valve 10 and the third cooling water pipeline electric valve 12 are closed, the second cooling water pipeline electric valve 11 and the fourth cooling water pipeline electric valve 13 are opened, so that the cooling water enters the absorber 26 and the first-stage condenser 25, and then enters the sprayer 7. At the same time, the heat conduction oil pump 23 is turned on, the first heat conduction oil pipeline electric valve 14 and the fourth heat conduction oil pipeline electric valve 22 are closed, the second heat conduction oil pipeline electric valve 15 and the third heat conduction oil pipeline electric valve 21 are opened, the solution pump 28 is turned on, and then the first electric airtight valve 17 is closed, the second electric airtight valve 19 is opened, so that the fresh air flows through the first-stage evaporator 18 for secondary cooling.

[0061] Specifically, the first cooling water pipeline electric valve 10, the second cooling water pipeline electric valve 11, the third cooling water pipeline electric valve 12, the fourth cooling water pipeline electric valve 13, the first heat conduction oil pipeline electric valve 14, the second heat conduction oil pipeline electric valve 15, the third heat conduction oil pipeline electric valve 21, and the fourth heat conduction oil pipeline electric valve 22 all adopt solenoid valves.

[0062] Specifically, the solution can be a lithium bromide - aqueous solution, and the solution flows between the generator 27, the absorber 26, and the solution heat exchanger 29 under the action of the solution pump 28.

[0063] Specifically, the heat - conducting oil flows between the concentrating solar collector 20 and the heat - conducting oil heat - exchange coil 52 located inside the generator 27 under the action of the heat - conducting oil pump 23. The heat - conducting oil is heated up in the concentrating solar collector 20. After entering the heat - conducting oil heat - exchange coil 52 located inside the generator 27, it transfers heat to the solution in the generator 27, causing the water in the solution in the generator 27 to vaporize into high - pressure and high - temperature water vapor. The high - pressure and high - temperature water vapor goes to the primary condenser 25, releases heat and condenses into a high - pressure liquid after being cooled by the cooling water in the primary condenser 25, and then becomes a low - pressure and low - temperature gas - liquid two - phase flow after throttling through the expansion valve 32. After entering the coil inside the primary evaporator 18, it evaporates and absorbs heat, taking away the heat of the fresh air outside the coil of the primary evaporator 18 to achieve the purpose of cooling the fresh air. Finally, the low - temperature and low - pressure water vapor enters the absorber 26 through the water - vapor inlet of the absorber 26, enters the coil inside the absorber 26, is cooled by the cooling water outside the coil of the absorber 26, and then redissolves into the solution inside the coil of the absorber 26. The solution is boosted in pressure by the solution pump 28, passes through the solution heat exchanger 29, and finally returns to the generator 27, and this cycle repeats.

[0064] Specifically, the heat - conducting oil heat - exchange coil 52 transfers heat to the solution in the generator 27, causing the water in the solution in the generator 27 to vaporize into high - pressure and high - temperature water vapor. At this time, both the temperature and concentration of the solution in the generator 27 increase, becoming a high - temperature and concentrated solution. The high - temperature and concentrated solution enters the solution heat exchanger 29 under the action of the solution pump 28, exchanges heat with the low - temperature and dilute solution from the absorber 26, and then enters the absorber 26, absorbs the low - temperature and low - pressure water vapor from the primary evaporator 18, forms a low - temperature and dilute solution, enters the solution heat exchanger 29, and finally returns to the generator 27, and this cycle repeats.

[0065] Specifically, after the switching of the four cooling - water pipeline electric valves, the cooling water is changed to flow between the water collecting tray 42, the cooling - water filter 9, the absorber 26, the primary condenser 25, and the indirect evaporation cooling pipeline 4 by the cooling water pump 8, taking away not only the heat of the fresh air but also the heat of the absorber 26 and the primary condenser 25.

[0066] In this embodiment, the fresh air after being cooled twice by the primary evaporator 18 enters the tertiary module 63. After the temperature is measured by the second temperature sensor 45 and reaches the set temperature, the compressor 30 is turned on so that the tertiary module 63 starts to work. After the fresh air enters the secondary evaporator 34, it is cooled again.

[0067] After the third-level module 63 is turned on, the heat generated by the secondary condenser 31 inside the generator 27 will also be transferred to the solution in the generator 27, causing the water vapor in the solution in the generator 27 to vaporize into high-pressure and high-temperature water vapor. The high-pressure and high-temperature water vapor goes to the primary condenser 25, releases heat after being cooled by the cooling water in the primary condenser 25 and condenses into a high-pressure liquid. Then, after throttling by the expansion valve 32, it becomes a low-pressure and low-temperature gas-liquid two-phase flow, enters the coil inside the primary evaporator 18 and evaporates to absorb heat, and then takes away the fresh air heat outside the coil of the primary evaporator 18, achieving the purpose of cooling the fresh air again. Finally, the low-temperature and low-pressure water vapor enters the coil inside the absorber 26, is cooled by the cooling water outside the coil of the absorber 26, and then redissolves into the solution inside the coil of the absorber 26. After being boosted by the solution pump 28, it returns to the generator 27 after passing through the solution heat exchanger 29, and so on in a cycle.

[0068] In this embodiment, after measuring the temperature by the third temperature sensor 46, the third-level module 63 adjusts the refrigeration output of the third-level module 63 by adjusting the rotation speed of the compressor 30.

[0069] As Figure 5 shown, the thick line is the enthalpy-humidity diagram of the refrigeration process of the aircraft ground air-conditioning unit in this embodiment. Point W is the state point of the outdoor air in summer, point W1 is the state point after being cooled by the first-level module 61, point W2 is the state point after being cooled by the second-level module 62, and point O is the state point after being cooled by the third-level module 63; the thin line is the refrigeration process of the traditional aircraft ground air-conditioning unit, and the fresh air is processed from point W to point O through vapor compression refrigeration. The enthalpy value corresponding to point W is 58 kJ / (kg·°C), the enthalpy value corresponding to point W1 is 54 kJ / (kg·°C), the enthalpy value corresponding to point W2 is 44 kJ / (kg·°C), and the enthalpy value corresponding to point O is 12 kJ / (kg·°C). In the refrigeration process of this embodiment, the cooling capacity utilized from point W to point W1 is provided by the indirect evaporative cooler, making full use of the dry air energy, and the energy efficiency is about 3 times that of the traditional vapor compression refrigeration unit. In the refrigeration process of the aircraft ground air-conditioning unit in this embodiment, the cooling capacity utilized from point W1 to point W2 is provided by the absorption refrigeration unit. The heat sources of the absorption refrigeration unit are the solar collector 20 and the secondary condenser 31 in the third-level module 63, both of which are free energy. Therefore, compared with the traditional unit, the aircraft ground air-conditioning unit in this embodiment utilizes multiple free energy sources and can significantly reduce energy consumption.

[0070] The specific working process of the heating condition in this embodiment is as follows: When starting to work, turn on the supply fan 38 to allow fresh air to enter the air supply channel 49 of the air conditioner through the fresh air inlet 1. Turn off the evaporative cooling exhaust fan 5 and the cooling water pump 8 in the first-stage module 61, and close the first cooling water pipeline electric valve 10, the second cooling water pipeline electric valve 11, the third cooling water pipeline electric valve 12, and the fourth cooling water pipeline electric valve 13 to make the first-stage module 61 not work. At the same time, turn on the heat conduction oil pump 23, open the first heat conduction oil pipeline electric valve 14 and the fourth heat conduction oil pipeline electric valve 22, close the second heat conduction oil pipeline electric valve 15 and the third heat conduction oil pipeline electric valve 21, and turn off the solution pump 28 to make the second-stage module 62 shut down the refrigeration work. Then open the first electric airtight valve 17 and close the second electric airtight valve 19 to allow the fresh air to flow through the air-oil heat exchanger 16 for heating up.

[0071] Specifically, the heat collected by the concentrating solar collector 20 is transferred to the heat conduction oil, and the heat conduction oil enters the air-oil heat exchanger 16 through the heat conduction oil pipeline 41 to transfer the heat to the fresh air, so that the fresh air is heated for the first time.

[0072] When the temperature of the fresh air after the second-stage module 62 measured by the second temperature sensor 45 is lower than the set temperature, adjust the power of the electric heater 37 of the fourth-stage module 64 to make the final outlet air temperature meet the requirements.

[0073] As Figure 6 shown, it is the enthalpy-humidity diagram of the heating process of the aircraft ground air conditioner unit in this embodiment. Point W is the state point of the outdoor air in winter, point W1 is the state point after preheating by the second-stage module 62, and point O is the state point after heating up by the fourth-stage module 64. The traditional aircraft ground air conditioner unit uses an electric heater to heat the outdoor air from point W to point O. The enthalpy value corresponding to point W is 11 kJ / (kg·°C), the enthalpy value corresponding to point W1 is 14 kJ / (kg·°C), and the enthalpy value corresponding to point O is 51 kJ / (kg·°C). In the heating process of the aircraft ground air conditioner unit in this embodiment, the free heat obtained by the solar collector 20 is used from point W to point W1. Therefore, compared with the traditional aircraft ground air conditioner unit, the heating energy consumption of this embodiment is expected to be reduced by (14 - 11) / (51 - 11) = 7.5%.

[0074] Embodiment 2:

[0075] This embodiment provides a control method for a multi-stage refrigeration and heating aircraft ground air conditioner unit, which is applied to the aircraft ground air conditioner unit provided in Embodiment 1. The control method of the aircraft ground air conditioner unit includes the following processes:

[0076] Refrigeration condition:

[0077] Before picking up the machine, first turn on the cooling water pump 8 and the evaporative cooling exhaust fan 5 to start the operation of the first-stage module 61, and turn on the supply fan 38 to cool the fresh air for the first time.

[0078] Specifically, before picking up the machine, open the electric valve 10 of the first cooling water pipeline and the electric valve 12 of the third cooling water pipeline, and close the electric valve 11 of the second cooling water pipeline and the electric valve 13 of the fourth cooling water pipeline.

[0079] After the first temperature sensor 44 measures the temperature, when the temperature of the fresh air reaches the preset temperature, turn on the heat conduction oil pump 23, close the electric valve 10 of the first cooling water pipeline and the electric valve 12 of the third cooling water pipeline, and open the electric valve 11 of the second cooling water pipeline and the electric valve 13 of the fourth cooling water pipeline, so that the second-stage module 62 starts to operate for secondary refrigeration.

[0080] Specifically, at the same time, close the first electric airtight valve 17 and open the second electric airtight valve 19 to make the fresh air flow through the first-stage evaporator 18 for secondary cooling.

[0081] The fresh air after being secondary cooled by the first-stage evaporator 18 of the second-stage module 62 enters the third-stage module 63. After the second temperature sensor 45 measures the temperature and reaches the preset temperature, turn on the compressor 30, so that the third-stage module 63 starts to operate. After the fresh air enters the second-stage evaporator 34, the fresh air is cooled three times.

[0082] Specifically, after the third-stage module 63 measures the temperature according to the third temperature sensor 46, it adjusts the refrigeration output of the third-stage module 63 by adjusting the speed of the compressor 30.

[0083] After normal operation, when the air temperature after the first-stage module 61 is higher than the set temperature, by controlling to increase the speeds of the cooling water pump 8 and the evaporative cooling exhaust fan 5, so that the first-stage module 61 increases the refrigeration output until the processed air temperature meets the requirements.

[0084] When the temperature shown by the heat conduction oil pipeline temperature sensor 24 is higher than the set temperature, it indicates that the solar irradiance on that day is higher than the predetermined value. At this time, by increasing the speed of the heat conduction oil pump 23, the output of the second-stage module 62 is increased.

[0085] When the temperature shown by the heat conduction oil pipeline temperature sensor 24 is lower than the set temperature, it indicates that the solar irradiance on that day is relatively low and does not meet the requirement of the operating energy efficiency ratio. Close the heat conduction oil pump 23, cut off the heat conduction oil flow in the heat conduction oil pipeline 41 and the heat conduction oil heat exchange coil 52. When the temperature of the medium in the heat conduction oil pipeline 41 is higher than the set temperature, reopen the heat conduction oil pump 23 and reconnect the heat conduction oil pipeline 41 and the heat conduction oil heat exchange coil 52.

[0086] When the air temperature after the tertiary module 63 is higher than the set temperature, the output of the tertiary module 63 is increased by increasing the rotational speed of the compressor 30 in the tertiary module 63 to meet the air temperature requirement after the tertiary module 63.

[0087] Specifically, after the secondary module 62 operates normally, when the conductivity meter 50 on the outlet pipe of the primary evaporator 18 measures that there is liquid water in the outlet pipe of the primary evaporator 18, it indicates that the primary evaporator 18 has not completely evaporated the incoming liquid water, which means that the cooling load demand of the primary evaporator 18 is decreasing; at this time, the opening of the solenoid valve 51 on the pipe of the steam outlet of the generator 27 is adjusted smaller through the signal sent by the conductivity meter 50.

[0088] After the opening of the solenoid valve 51 is adjusted smaller, the flow rate of the high-pressure steam entering the primary condenser 25 decreases, and the steam generated in the generator 27 will accumulate, increasing the pressure above the liquid level of the solution in the inner tank 60 of the generator 27, pushing the inner tank 60 of the generator 27 downward, exposing the secondary condenser 31 out of the solution surface, as Figure 3 shown, thereby reducing the heating amount of the solution by the secondary condenser 31. As the heating amount of the solution gradually decreases, the outlet pressures of the secondary condenser 31 and the compressor 30 gradually increase.

[0089] Specifically, when the outlet pressure of the compressor 30 reaches 90% of the overpressure alarm pressure, the power of the compressor 30 is reduced.

[0090] As the heating amount of the solution gradually decreases, the evaporation amount of the solution in the generator 27 also decreases accordingly. At this time, the conductivity meter 50 on the outlet pipe of the primary evaporator 18 measures that the liquid water there gradually decreases until it disappears, and the opening of the solenoid valve 51 is adjusted larger, increasing the flow rate of the high-pressure steam entering the primary condenser 25 from the generator 27. The pressure above the liquid level of the solution in the inner tank 60 of the generator 27 will decrease accordingly, and the inner tank 60 will move upward, submerging the secondary condenser 31 in the solution again to continue heating the solution to promote the evaporation of the solution, as Figure 4 shown, and the outlet pressures of the secondary condenser 31 and the compressor 30 gradually decrease.

[0091] When the outlet pressure of the compressor 30 decreases to 110% of the minimum allowable pressure, the power of the compressor 30 is increased, and so on in a cycle.

[0092] During the whole process, the heat transfer oil heat exchange coil 52 is always completely immersed in the solution, which is used to ensure the output of the aircraft ground air conditioning unit under low load, avoid the low-load operation of the compressor 30, and can realize the independent, fast and stepless adjustment of the refrigerating capacity of the absorption refrigeration unit. At the same time, the frequent adjustment and low-load operation of the power of the compressor 30 are greatly reduced.

[0093] Heating condition:

[0094] When the operating condition of the aircraft ground air conditioning unit changes from the refrigeration condition to the heating condition, the cooling water pump 8 and the evaporative cooling exhaust fan 5 are turned off, the electric valves 10, 11, 12, and 13 of the first, second, third, and fourth cooling water pipelines are closed to shut down the first-stage module 61, the electric valves 14 and 22 of the first and fourth heat transfer oil pipelines are opened, the electric valves 15 and 21 of the second and third heat transfer oil pipelines are closed, the solution pump 28 is turned off, the heat transfer oil pump 23 is turned on, the first electric airtight damper 17 is opened, and the second electric airtight damper 19 is closed. The fresh air flows through the air-oil heat exchanger 16 for heating up, and the heating function of the second-stage module 62 is enabled.

[0095] When the temperature shown by the heat transfer oil pipeline temperature sensor 24 is higher than the set temperature, it indicates that the solar illuminance on that day is higher than the predetermined value. At this time, by increasing the rotation speed of the heat transfer oil pump 23, the heating output of the second-stage module 62 is increased.

[0096] When the temperature shown by the heat transfer oil pipeline temperature sensor 24 is lower than the fresh air temperature measured by the first temperature sensor 44, it indicates that the solar illuminance on that day is too low. At this time, the heat transfer oil pump 23 is turned off, and the air-oil heat exchanger 16 is closed to reduce the ineffective loss of fresh air heat.

[0097] When the fresh air temperature measured by the second temperature sensor 45 after passing through the second-stage module 62 is lower than the set temperature, the power of the electric heater 37 of the fourth-stage module 64 is increased to make the final outlet air temperature meet the requirements.

[0098] Specifically, the control system adopted by the control method of the multi-stage refrigeration and heating aircraft ground air conditioning unit in this embodiment is a PLC control system.

[0099] Embodiment 3:

[0100] This embodiment provides a control method for preventing crystallization of the solution in the solution heat exchanger 29. The control method is applied to the aircraft ground air conditioning unit described in Embodiment 1 and specifically includes the following process:

[0101] Since the water vapor pressure above the solution liquid level in the inner tank 60 of the generator 27 is constant, and the concentrated solution side of the solution heat exchanger 29 is connected to the inside of the generator 27, the pressure of the concentrated solution in the solution heat exchanger 29 and the generator 27 is the same and constant. At this time, the saturation concentration of the solution is only related to the solution temperature. In this way, the traditional problem of the solution saturation concentration being coupled with two factors, namely the solution temperature and the internal pressure of the generator 27, is adjusted to a problem only related to a single factor of the solution temperature. Then, the saturation concentration of the solution at different temperatures is determined. As long as it is ensured that the temperature of the solution at a certain determined concentration is not lower than the saturation temperature corresponding to this concentration, the solution can be ensured not to crystallize.

[0102] The concentration of the concentrated solution at the solution outlet of the generator 27 is measured by the solution concentration sensor 56 provided thereon, and the saturation temperature corresponding to this concentration is calculated.

[0103] The temperature of the concentrated solution at the solution outlet of the generator 27 is measured by the first solution temperature sensor 54 provided thereon.

[0104] The flow rate of the solution pump 28 and the temperature of the dilute solution are respectively measured by the flow sensor 57 and the second solution temperature sensor 55 provided at the solution outlet of the absorber 26.

[0105] Then, at this time, the temperature and concentration of the concentrated solution entering the solution heat exchanger 29 are known, and the temperature and flow rate of the dilute solution entering the solution heat exchanger 29 are also known. Since the solution pump 28 is a constant-frequency pump, the flow rate remains unchanged, and since it is the same pipeline, the flow rate of the concentrated solution entering the solution heat exchanger 29 is equal to the flow rate of the dilute solution entering the solution heat exchanger 29, so the flow rate of the concentrated solution entering the solution heat exchanger 29 is also known.

[0106] Through heat transfer calculation, the critical temperature of the dilute solution entering the solution heat exchanger 29 can be obtained.

[0107] When the temperature of the dilute solution entering the solution heat exchanger 29 is higher than the critical temperature, the outlet temperature of the concentrated solution will not be lower than the saturation temperature at its own concentration. At this time, the concentrated solution will not crystallize. The rotational speeds of the evaporative cooling exhaust fan 5 and the cooling water pump 8 should be increased to lower the temperature of the cooling water, improve the cooling capacity of the cooling water, and thus improve the refrigeration efficiency of the unit.

[0108] When the temperature of the dilute solution entering the solution heat exchanger 29 is lower than the critical temperature, the outlet temperature of the concentrated solution will also be lower than the saturation temperature at its own concentration. At this time, the concentrated solution will crystallize. The rotational speeds of the evaporative cooling exhaust fan 5 and the cooling water pump 8 should be decreased to increase the temperature of the cooling water, reduce the cooling capacity of the cooling water, and prevent crystallization.

[0109] Finally, by accurately controlling the temperature of the cooling water, the purpose of reducing the crystallization of the concentrated solution in the solution heat exchanger 29 is achieved on the premise of ensuring the refrigeration efficiency of the unit, and neither conservatively increasing the temperature of the cooling water nor aggressively decreasing the temperature of the cooling water.

[0110] Embodiment 4:

[0111] This embodiment provides a design method for a multi-stage refrigeration and heating aircraft ground air-conditioning unit, which is applied to the aircraft ground air-conditioning unit provided in this embodiment 1. The aircraft ground air-conditioning unit design method includes the following steps:

[0112] S1: By querying local meteorological parameters, including the summer outdoor design dry-bulb temperature and the summer outdoor design wet-bulb temperature of the air conditioner, calculate the enthalpy value of the outdoor air through the formula h = 1.01t + d(2500 + 1.84t). Here, h is the enthalpy value of the outdoor air, with the unit of kJ / kg; 1.01 is the specific heat at constant pressure of dry air, with the unit of kJ / (kg·°C); d is the moisture content of the outdoor air, with the unit of kg / kg of dry air; 2500 is the latent heat of vaporization required for every kilogram of water at 0°C to become water vapor at 0°C, with the unit of kJ / kg; 1.84 is the specific heat at constant pressure of water vapor, with the unit of kJ / (kg·°C); t is the dry-bulb temperature of the outdoor air, with the unit of °C.

[0113] S2: Determine the wet-bulb efficiency η of the indirect evaporative cooling pipe 4. In areas where the wet-bulb temperature is below 23°C, the wet-bulb efficiency is taken as 0.75; when the wet-bulb temperature is 23 - 26°C, the wet-bulb efficiency is taken as 0.65; when the wet-bulb temperature is greater than 26°C, the wet-bulb efficiency is taken as 0.6.

[0114] S3: Calculate T wg through the formula η = (T w1g - T wg ) / (T w1s - T w1g ); where T wg represents the dry-bulb temperature of the fresh air entering the indirect evaporative cooler, with the unit of °C, and T w1g represents the dry-bulb temperature of the fresh air leaving the indirect evaporative cooler, with the unit of °C; T w1s represents the wet-bulb temperature of the outdoor ambient air, with the unit of °C.

[0115] S4: Calculate the cooling capacity P of the indirect evaporative cooling pipe 4 through the formula P = 1.01·ρ·V·(T wg - T w1g ), with the unit of kW; where ρ is the air density at the dry-bulb temperature of the fresh air entering, with the unit of kg / m³, V is the volume flow rate of the fresh air entering, with the unit of m³ / s, and 1.01 is the specific heat at constant pressure of dry air, with the unit of kJ / (kg·°C).

[0116] S5: Calculate the total cooling capacity Q required for various types of models in this area through the formula Q = ρ·V / (1 + d0)·(h1 - h2 - c0·t·Δd), with the unit of kW; where d0 is the moisture content of the supply air, with the unit of g / kg of dry air, h1 represents the enthalpy value of the air entering the air conditioner unit, with the unit of kJ / kg, h2 represents the enthalpy value of the fresh air leaving the aircraft ground air conditioner unit, with the unit of kJ / kg, c0 represents the specific heat at constant pressure of water, with the unit of kJ / (kg·°C), which can be taken as 4.18 kJ / (kg·°C), and Δd represents the difference in moisture content between the inlet and outlet of the fresh air flow, with the unit of g / kg of dry air.

[0117] S6: Based on the calculation results of S4 and S5, calculate the cooling capacity P1 required to be provided by the secondary module 62 and the tertiary module 63 through the formula P1 = Q - P, with the unit of kW.

[0118] S7: Select models for the absorption refrigeration unit of the secondary module 62 and the vapor compression refrigeration unit of the tertiary module 63 according to P1 obtained through S6.

[0119] S8: Determine the area S of the concentrating solar collector 20, with the unit of m², according to the unit sizes of the absorption refrigeration unit and the vapor compression refrigeration unit.

[0120] S9: According to the local solar irradiance M, with the unit of kW / m 2 , combined with the thermal conversion efficiency η1 of the solar collector 20 and the effective irradiation rate η2 per unit area, obtain the convertible heat Q1 of the solar collector 20 through the formula Q1 = M·η1·η2·S, with the unit of kW.

[0121] S10: Recheck and optimize the model selection of the absorption refrigeration unit of the secondary module 62 according to Q1 obtained through S9.

[0122] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An aircraft ground air conditioning unit with multi-stage refrigeration and heating, characterized in that, It includes a first-level module (61), a second-level module (62), a third-level module (63), a fourth-level module (64) and an air supply section (65); The first-level module (61), the second-level module (62), the third-level module (63), the fourth-level module (64) and the air supply section (65) are sequentially connected through an air-conditioning air supply channel (49). The first-level module (61) includes an indirect evaporative cooler, and the indirect evaporative cooler is provided with a cooling water pipeline (40); The second-level module (62) includes an absorption refrigeration unit, a solar collector (20) and a gas-oil heat exchanger (16). The solar collector (20) is respectively connected in a cycle with the absorption refrigeration unit and the gas-oil heat exchanger (16) through a heat-conducting oil pipeline (41), and the cooling water pipeline (40) is connected to the absorption refrigeration unit; The third-level module (63) uses a vapor compression refrigeration unit; the fourth-level module (64) uses an electric heater (37); the air supply section (65) includes a blower (38) and a fresh air supply opening (39), and the fresh air supply opening (39) communicates to the outside of the aircraft ground air-conditioning unit; The absorption refrigeration unit includes a generator (27); the solution outlet of the generator (27) is sequentially connected with an absorber (26), a solution pump (28), a solution heat exchanger (29) and the solution inlet of the generator (27) through a solution pipeline (43) to form a solution circulation pipeline; the steam outlet of the generator (27) is sequentially connected with a solenoid valve (51), a first-stage condenser (25), a first-stage evaporator (18), a conductivity meter (50) and the steam inlet of the absorber (26) through a steam-water pipeline (58); both the absorber (26) and the first-stage condenser (25) are connected with a cooling water pipeline (40); the heat-conducting oil pipeline (41) is connected to the generator (27); The vapor compression refrigeration unit includes a compressor (30), a second-stage condenser (31), a liquid receiver (33), a second-stage evaporator (34) and a gas-liquid separator (35) that are sequentially connected in a cycle; The generator (27) includes an enclosed outer shell (59), an inner tank (60) is arranged inside the outer shell (59), a solution is arranged in the inner tank (60), the top of the inner tank (60) is open, the bottom of the inner tank (60) is slidably and sealedly arranged with the inner wall of the outer shell (59), a solution outlet is arranged at the bottom of the inner tank (60) of the generator (27), and the solution outlet is connected to the outside of the outer shell (59) of the generator (27) through a solution outlet pipeline. The part of the heat-conducting oil pipeline (41) connected to the generator (27) and the second-stage condenser (31) are both located in the inner tank (60); The heat-conducting oil heat exchange coil (52) has a different height from the top of the second-stage condenser (31) and the same height from the bottom. The heat-conducting oil heat exchange coil (52) is always completely immersed in the solution; the solution pump (28) is a constant-frequency pump.

2. The multi-stage refrigeration and heating aircraft ground air conditioning unit according to claim 1, characterized in that The indirect evaporative cooler includes a fresh air inlet (1), a secondary air inlet (2), an air filter (3), an evaporative cooling exhaust fan (5), a water filter (6), a spray water device (7), an indirect evaporative cooling duct (4), and a water collection tray (42); the outlets of the fresh air inlet (1) and the secondary air inlet (2) are both connected to the air filter (3), the evaporative cooling exhaust fan (5), the water filter (6), the spray water device (7), the indirect evaporative cooling duct (4), and the water collection tray (42) are arranged in sequence from top to bottom, the indirect evaporative cooling duct (4) is located at the outlet of the air filter (3), the fresh air inlet (1) is connected to the inside of the indirect evaporative cooling duct (4), and the secondary air inlet (2) is connected to the outside of the indirect evaporative cooling duct (4) and the evaporative cooling exhaust fan (5); the water collection tray (42) is connected to the inlet of a cooling water pipeline (40), the spray water device (7) is connected to the outlet of the cooling water pipeline (40), the cooling water pipeline (40) is provided with two loops, and electric valves are arranged at the inlets and outlets of the two loops.

3. The multi-stage refrigeration and heating aircraft ground air conditioning unit according to claim 2, characterized in that, A first temperature sensor (44) is arranged between the first-stage module (61) and the second-stage module (62), a second temperature sensor (45) is arranged between the second-stage module (62) and the third-stage module (63), a third temperature sensor (46) is arranged between the third-stage module (63) and the fourth-stage module (64), and a fourth temperature sensor (47) is arranged in the air supply section (65).

4. The multi-stage refrigeration and heating aircraft ground air conditioning unit according to claim 1, characterized in that, The fresh air inlets of the gas-oil heat exchanger (16) and the first-stage evaporator (18) are respectively connected with a first electric airtight valve (17) and a second electric airtight valve (19); the first electric airtight valve (17) and the second electric airtight valve (19) are arranged one above the other, blocking the air supply passage (49) of the air conditioner.

5. A multi-stage refrigeration and heating control method for an aircraft ground air conditioning unit according to any one of claims 1-4, characterized in that, It includes the following processes: Under the refrigeration condition, the indirect evaporative cooler, the absorption refrigeration unit, and the vapor compression refrigeration unit are sequentially started, and the gas-oil heat exchanger (16) and the electric heater (37) are closed; When the temperature of the medium in the heat transfer oil pipeline (41) is higher than the set temperature, the flow rate of the medium in the heat transfer oil pipeline (41) is increased. When the temperature of the medium in the heat transfer oil pipeline (41) is lower than the set temperature, the connection between the heat transfer oil pipeline (41) and the absorption refrigeration unit is cut off. When the temperature of the medium in the heat transfer oil pipeline (41) is higher than the set temperature, the heat transfer oil pipeline (41) and the absorption refrigeration unit are reconnected; Under the heating condition, the gas-oil heat exchanger (16) and the electric heater (37) are started, and the indirect evaporative cooler, the absorption refrigeration unit, and the vapor compression refrigeration unit are closed; When the temperature of the medium in the heat transfer oil pipeline (41) is higher than the set temperature, the flow rate of the medium in the heat transfer oil pipeline (41) is increased. When the temperature of the medium in the heat transfer oil pipeline (41) is lower than the air temperature after the fresh air passes through the indirect evaporative cooler, the gas-oil heat exchanger (16) is closed, and the power of the electric heater (37) is increased.

6. The multi-stage refrigeration and heating control method according to claim 5, characterized in that, The absorption refrigeration unit includes a generator (27); the solution outlet of the generator (27) is sequentially connected to an absorber (26), a solution pump (28), a solution heat exchanger (29) and the solution inlet of the generator (27) through a solution pipeline (43) to form a solution circulation pipeline; the water vapor outlet of the generator (27) is sequentially connected to a primary condenser (25), a primary evaporator (18) and the water vapor inlet of the absorber (26) through a steam-water pipeline (58); the vapor compression refrigeration unit includes a compressor (30), a secondary condenser (31), a liquid receiver (33), a secondary evaporator (34) and a gas-liquid separator (35) that are sequentially and circularly connected; the generator (27) includes an enclosed outer shell (59), an inner container (60) is arranged inside the outer shell (59), a solution is arranged in the inner container (60), the top of the inner container (60) is open, the bottom of the inner container (60) is slidably and sealed with the inner wall of the outer shell (59), a solution outlet is arranged at the bottom of the inner container (60), and the solution outlet is connected to the outside of the outer shell (59) through a solution outlet pipeline, and the secondary condenser (31) is located in the inner container (60); After the secondary module (62) operates normally, when there is liquid water in the water vapor in the outlet pipeline of the primary evaporator (18), the flow rate on the pipeline of the water vapor outlet of the generator (27) is reduced, so that the flow rate of the high-pressure water vapor entering the primary condenser (25) is reduced, and the water vapor generated in the generator (27) will accumulate, increasing the pressure above the solution liquid level in the inner container (60) of the generator (27), pushing the inner container (60) of the generator (27) downward, exposing the secondary condenser (31) from the solution surface, thereby reducing the heating amount of the solution by the secondary condenser (31). As the heating amount of the solution gradually decreases, the outlet pressures of the secondary condenser (31) and the compressor (30) gradually increase. When the outlet pressure of the compressor (30) reaches 90% of the overpressure alarm pressure, the power of the compressor (30) is reduced; As the heating amount of the solution gradually decreases, the evaporation amount of the solution in the generator (27) also decreases accordingly. At this time, the liquid water in the outlet pipeline of the primary evaporator (18) gradually decreases until it disappears. The flow rate on the pipeline of the water vapor outlet of the generator (27) is increased, and the pressure above the solution liquid level in the inner container (60) of the generator (27) will decrease accordingly, and the inner container (60) moves upward, so that the secondary condenser (31) is immersed in the solution again to continue heating the solution to promote solution evaporation, and the outlet pressures of the secondary condenser (31) and the compressor (30) gradually decrease; when the outlet pressure of the compressor (30) decreases to 110% of the minimum allowable pressure, the power of the compressor (30) is increased.

7. The multi-stage refrigeration and heating control method according to claim 6, characterized in that, The solution pump (28) is a fixed-frequency pump; the concentration and temperature of the concentrated solution at the solution outlet of the generator (27) are obtained, and the flow rate and temperature of the dilute solution at the solution outlet of the absorber (26) are obtained. Since the solution pump (28) is a fixed-frequency pump, the flow rate remains constant all the time, and the flow rate of the concentrated solution is equal to the flow rate of the dilute solution; through heat transfer calculation, the critical temperature of the dilute solution entering the solution heat exchanger (29) is obtained; When the temperature of the dilute solution entering the solution heat exchanger (29) is higher than the critical temperature, the outlet temperature of the concentrated solution will not be lower than the saturation temperature at the concentration of the concentrated solution itself, and the concentrated solution will not crystallize. At this time, the temperature of the medium in the cooling water pipeline is reduced; When the temperature of the dilute solution entering the solution heat exchanger (29) is lower than the critical temperature, the outlet temperature of the concentrated solution will also be lower than the saturation temperature at the concentration of the concentrated solution itself, and the concentrated solution will crystallize. At this time, the temperature of the medium in the cooling water pipeline is increased.

Images