Commercial vehicle thermal management system using carbon dioxide refrigerant and control method

Abstract

According to the commercial vehicle heat management system using the carbon dioxide refrigerant and the control method, the high-pressure side of a compressor is connected with a first port of a four-way valve through a bypass valve, a second port of the four-way valve is connected with an exterior heat exchanger, and the exterior heat exchanger is connected with an interior heat exchanger through a first electronic expansion valve and a third one-way valve; the other end of the in-vehicle heat exchanger is connected with a third port of the four-way valve, the refrigerant is connected to the heat regenerator through a fourth port of the four-way valve, the heat regenerator is connected with the gas-liquid separator, and the gas-liquid separator is connected to the low-pressure side of the compressor; the bypass valve is connected with the hot water heat exchanger in parallel; the air outlet side of the heat regenerator is connected with a first electronic expansion valve through a fourth one-way valve and enters the outside-vehicle heat exchanger through the first electronic expansion valve. And a second one-way valve is arranged on a pipeline between the first electronic expansion valve and the second electronic expansion valve. The refrigerating capacity of the air conditioner is improved, battery heat management is achieved, meanwhile, waste heat of a whole vehicle system is recycled through a water path, and the heating capacity of the air conditioner is improved.

Description

Technical Field

[0001] The invention belongs to the field of passenger car air conditioning, and in particular relates to a commercial vehicle thermal management system and a control method using carbon dioxide refrigerant. Background Art

[0002] Carbon dioxide has gradually entered the mainstream due to its environmental protection characteristics and low temperature adaptability. In the automotive industry, more and more vehicle manufacturers and air-conditioning companies are developing and producing vehicle air-conditioning and thermal management systems that use carbon dioxide as a refrigerant. However, due to poor refrigeration performance and high system pressure, carbon dioxide air-conditioning systems have the disadvantages of poor vehicle cooling performance and high refrigerant system costs in actual applications.

[0003] In the specific use scenario of new energy buses, the air conditioning system itself needs to take into account both cooling and heating performance, and at the same time, it needs to be able to link the driver's heating and cooling defrost for the driver and defrost and defog the front windshield, and must have the function of battery thermal management. Therefore, the application of carbon dioxide air conditioning systems in bus scenarios has high requirements for system performance and functional richness, and the cost must be optimized while meeting these requirements.

[0004] With the development of the new energy industry, how to improve energy utilization, reduce vehicle energy consumption, and reduce user mileage anxiety has become one of the work priorities and main research directions of various OEMs and parts suppliers.

[0005] For new energy buses, due to the actual needs of the vehicle design, various thermal management devices (air conditioners, defrosters, motor radiators, water pumps, heating equipment, heaters, etc.) are scattered in various parts of the vehicle. Therefore, when building the system, the components that need to serve specific needs (such as battery heating and cooling) are often designed as independent circulation systems. Therefore, the degree of correlation between components is low, making it difficult to achieve integrated energy management of the vehicle.

[0006] When the carbon dioxide air conditioning system is used in buses, there is an industry pain point that its refrigeration performance is insufficient and affects the cooling of the entire vehicle. It is necessary to build an air conditioning enhanced heat dissipation function mode based on the current carbon dioxide air conditioning system. Since the bus is large in height and length, and the front windshield is large, the driver has characteristic cooling and heating needs. However, due to the high pressure of carbon dioxide refrigerant and the high cost of system pipelines, it is difficult to achieve related functions by passing the refrigerant to the driver's area defroster (inside the air conditioner). Therefore, the current thermal management system of new energy buses adopts distributed independent control, which is mainly divided into air conditioning, car heating equipment, driver defroster, motor drive cooling system, and battery cooling system. Each component is independent of each other, and the independent control is not related, and requires the use of independent sensors and controllers for adjustment.

[0007] Although from the perspective of functional realization, the current vehicle thermal management system solution with multiple independent circulation systems can meet the vehicle's usage requirements, it still has the following problems: 1. Since the related systems are designed completely independently, components with the same functions are required in each independent system. In actual design, multiple components with the same functions (such as cabin heater, defroster heater, battery heater) need to be selected, which makes it difficult to integrate effectively and the cost is also high. 2. Due to the space limitation of the whole vehicle, the compactness of the air conditioning system design is required to be high. Therefore, under the given size, the same technical route is difficult to support the air conditioning system to further improve its shortcomings in cooling performance; 3. Since the carbon dioxide air conditioning system has high pressure and is prone to leakage, the existing refrigerant pipe connection form and design scheme cannot be used in the current bus production and processing. When connecting the driver defroster (driver air conditioner) and the air conditioner with pipes, special high-pressure pipes and welding processes are required, and the production and manufacturing costs are extremely high. Summary of the invention

[0008] The technical problem to be solved by the present invention is: how to reduce the manufacturing cost of the whole vehicle thermal management system assembly, realize the reuse of whole vehicle parts, improve the overall performance, and provide a new energy commercial vehicle thermal management system using carbon dioxide refrigerant and its control method.

[0009] To achieve the above object, the present invention is achieved through the following technical solutions: A commercial vehicle thermal management system using carbon dioxide refrigerant includes a compressor, a high-pressure side of the compressor is connected to a first port of a four-way valve through a bypass valve, a second port of the four-way valve is connected to an external heat exchanger, the external heat exchanger is connected to an internal heat exchanger through a first electronic expansion valve and a third one-way valve, the other end of the internal heat exchanger is connected to a third port of the four-way valve, the refrigerant is connected to a regenerator through a fourth port of the four-way valve, the regenerator is connected to a gas-liquid separator, and the gas-liquid separator is connected to a low-pressure side of the compressor; The bypass valve is connected in parallel with the hot water heat exchanger; The outlet side of the regenerator is connected to the first electronic expansion valve through the fourth one-way valve, and enters the outdoor heat exchanger through the first electronic expansion valve; The off-vehicle heat exchanger is also connected to the cold water heat exchanger through a drying filter, a first non-return valve, and a second electronic expansion valve, and the other end of the cold water heat exchanger is connected to the regenerator; A second one-way valve is arranged on the pipeline between the first electronic expansion valve and the second electronic expansion valve.

[0010] The external heat exchanger is provided with an external fan, and the internal heat exchanger is provided with an internal fan.

[0011] A method for controlling hot and cold water using the commercial vehicle thermal management system, during a refrigeration cycle, if the bypass valve is closed, the high-temperature and high-pressure refrigerant at the compressor outlet will enter the hot water heat exchanger, and after the water circuit of the entire vehicle is connected to the hot water heat exchanger, the refrigerant will release heat to the water circuit; after the refrigerant is cooled and liquefied by the off-vehicle heat exchanger, under the action of the first one-way valve and the second one-way valve, one path of the refrigerant will flow through the first one-way valve to the second electronic expansion valve, and at this time, the second electronic expansion valve is opened, and the throttled low-temperature and low-pressure refrigerant will flow through the cold water heat exchanger, and the refrigerant will cool the water circuit of the entire vehicle connected to the cold water heat exchanger; another path of the refrigerant will flow through the first electronic expansion valve, and under the action of the third one-way valve and the fourth one-way valve, it will bypass the regenerator through the third one-way valve and enter the on-vehicle heat exchanger, thereby avoiding excessively high exhaust temperature during the refrigeration cycle; During the heating cycle, if the bypass valve is closed, the high-temperature and high-pressure refrigerant at the compressor outlet will enter the hot water heat exchanger. After the water circuit of the entire vehicle is connected to the hot water heat exchanger, the refrigerant will release heat to the water circuit. After the refrigerant is cooled and liquefied by the heat exchanger in the vehicle, it will flow into the regenerator and flow through the fourth one-way valve under the action of the third one-way valve and the fourth one-way valve. The regenerator will heat the refrigerant in front of the gas-liquid separator at this time to ensure that the system has a certain degree of superheat during low-temperature heating to avoid compressor liquid hammer. Later, under the action of the first one-way valve and the second one-way valve, the refrigerant will flow through the second one-way valve to the second electronic expansion valve. At this time, the second electronic expansion valve is opened, and the low-temperature and low-pressure refrigerant after throttling will flow through the cold water heat exchanger, and the refrigerant will cool the water circuit of the entire vehicle connected to the cold water heat exchanger.

[0012] A linkage control method using the commercial vehicle thermal management system and vehicle components, comprising a multi-way water valve body, the multi-way water valve body being respectively connected to a carbon dioxide refrigerant thermal management system, a defroster, a motor electronic control system, a motor radiator and a vehicle compartment heating device, and a hot water interface and a cold water interface being provided between the carbon dioxide refrigerant thermal management system and the multi-way water valve body; The motor and electronic control require liquid cooling; Batteries require liquid cooling when the ambient temperature is high and liquid heating when the ambient temperature is low; The motor radiator dissipates heat outside the vehicle and cools the water circuit; Carriage heating equipment: When the ambient temperature is low, the carbon dioxide refrigerant thermal management system supplies hot water to the carriage heating equipment through the hot water interface; Defroster: When the ambient temperature is high, the CO2 refrigerant thermal management system uses cold water through the cold water interface to cool the driver and defog with cold air. When the ambient temperature is low, hot water is used through the hot water interface to heat the driver and defrost with hot air. When the cold water circuit is working, the second electronic expansion valve works.

[0013] When the hot water circuit is working, the bypass valve is closed.

[0014] The multi-channel water valve body comprises 14 flow channels and 7 pairs of interfaces.

[0015] Compared with the prior art, the present invention has the following beneficial effects: when conditions permit, the present invention can utilize the heat dissipation components of the vehicle's three-electric system to dissipate heat from the air conditioning system, thereby improving the air conditioning refrigeration capacity, and can also recover the waste heat of the vehicle system through the water circuit while achieving battery thermal management, thereby improving the air conditioning heating capacity. At the same time, by preparing hot and cold water, the needs of cabin heating, battery heating, and driver area cooling can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the refrigerant system of the present invention; Figure 2 It is a schematic diagram of the linkage control of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0019] like Figure 1 As shown, a thermal management system for a commercial vehicle using carbon dioxide refrigerant includes a compressor 1, a high-pressure side of the compressor 1 is connected to a first port of a four-way valve 3 through a bypass valve 2, a second port of the four-way valve 3 is connected to an external heat exchanger 4, the external heat exchanger 4 is connected to an internal heat exchanger 7 through a first electronic expansion valve 5 and a third one-way valve 6, the other end of the internal heat exchanger 7 is connected to the third port of the four-way valve 3, the refrigerant is connected to a regenerator 8 through a fourth port of the four-way valve 3, the regenerator 8 is connected to a gas-liquid separator 9, and the gas-liquid separator 9 is connected to the low-pressure side of the compressor 1.

[0020] The bypass valve 2 is connected in parallel with the hot water heat exchanger 10 .

[0021] Furthermore, an outdoor fan 11 is provided on the outdoor heat exchanger 4 , and an indoor fan 12 is provided on the indoor heat exchanger 7 .

[0022] Furthermore, the air outlet side of the regenerator 8 is connected to the first electronic expansion valve 5 via the fourth one-way valve 13 , and enters the outdoor heat exchanger 4 via the first electronic expansion valve 5 .

[0023] Furthermore, the off-vehicle heat exchanger 4 is also connected to the cold water heat exchanger 17 via the drying filter 14 , the first one-way valve 15 , and the second electronic expansion valve 16 , and the other end of the cold water heat exchanger 17 is connected to the regenerator 8 .

[0024] Furthermore, a second one-way valve 18 is provided on the pipeline between the first electronic expansion valve 5 and the second electronic expansion valve 16 .

[0025] Thus, functionally, the refrigerant system has two cycles: cooling and heating.

[0026] The refrigeration cycle flow is: compressor 1—bypass valve 2 / hot water heat exchanger 10—four-way valve 3—outside vehicle heat exchanger 4—first electronic expansion valve 5—third one-way valve 6—inside vehicle heat exchanger 7—four-way valve 3—regenerator 8—gas-liquid separator 9—compressor 1.

[0027] The heating cycle flow is: compressor 1—bypass valve 2 / hot water heat exchanger 10—four-way valve 3—in-vehicle heat exchanger 7—regenerator 8—fourth one-way valve 13—first electronic expansion valve 5—out-vehicle heat exchanger 7—four-way valve 3—regenerator 8—gas-liquid separator 9—compressor 1.

[0028] The present invention provides a method for controlling hot and cold water in a thermal management system of a new energy commercial vehicle using carbon dioxide refrigerant: During the refrigeration cycle, if the bypass valve 2 is closed, the high-temperature and high-pressure refrigerant at the outlet of the compressor 1 will enter the hot water heat exchanger 10. After the water circuit of the whole vehicle is connected to the hot water heat exchanger 10, the refrigerant will release heat to the water circuit. After the refrigerant is cooled and liquefied by the external heat exchanger 4, under the action of the first one-way valve 15 and the second one-way valve 18, one path of the refrigerant will flow through the first one-way valve 15 to the second electronic expansion valve 16. At this time, the second electronic expansion valve 16 is opened, and the throttled low-temperature and low-pressure refrigerant will flow through the cold water heat exchanger 17. The refrigerant cools down the water circuit of the whole vehicle connected to the cold water heat exchanger 17. Another path of the refrigerant will flow through the first electronic expansion valve 5, and under the action of the third one-way valve 6 and the fourth one-way valve 13, it will bypass the regenerator 8 through the third one-way valve 6 and enter the internal heat exchanger 7 to avoid excessive exhaust temperature during the refrigeration cycle.

[0029] During the heating cycle, if the bypass valve 2 is closed, the high-temperature and high-pressure refrigerant at the compressor outlet will enter the hot water heat exchanger 10. After the water circuit of the whole vehicle is connected to the hot water heat exchanger 10, the refrigerant will release heat to the water circuit. After the refrigerant is cooled and liquefied by the in-vehicle heat exchanger 7, it will flow into the regenerator 8 and pass through the fourth one-way valve 13 under the action of the third one-way valve 6 and the fourth one-way valve 13. At this time, the regenerator 8 will heat the refrigerant before the gas-liquid separator 9 to ensure that the system has a certain degree of superheat during low-temperature heating to avoid liquid hammering of the compressor 1. Later, under the action of the first one-way valve 15 and the second one-way valve 18, one path of refrigerant will flow through the second one-way valve 18 to the second electronic expansion valve 16. At this time, the second electronic expansion valve 16 is opened, and the low-temperature and low-pressure refrigerant after throttling will flow through the cold water heat exchanger 17, and the refrigerant will cool down the water circuit of the whole vehicle connected to the cold water heat exchanger 17.

[0030] Therefore, no matter what mode the refrigerant system is in, the system can always provide cooling water or heating water to the entire vehicle to meet the cooling and heating needs of the vehicle components.

[0031] In addition, for the refrigeration cycle, the thermal management system dissipates heat through both the hot water heat exchanger and the external heat exchanger at the same time, which can improve the system's cooling capacity and reduce the impact of the insufficient cooling capacity of the carbon dioxide refrigeration system; under the heating cycle, the thermal management system dissipates heat through both air and water sources, which can further leverage the advantages of the carbon dioxide system's strong heating capacity; through the cold water heat exchanger, heat can be absorbed from other systems in the vehicle, which can further improve the heating capacity of the thermal management system.

[0032] In extremely low temperature conditions, the refrigerant system cannot absorb heat from the environment, and can enter the pure water circuit heat absorption mode. At this time, the carbon dioxide thermal management system is in a heating cycle, but the first electronic expansion valve 5 is closed, and the second electronic expansion valve 16 is opened, using the cold water interface to recover the heat of the three-electric (battery electric drive and electronic control) system.

[0033] Since the thermal management module itself has the function of heat pump air conditioning, the following functional subdivisions exist in the actual system control: 1. When the cold water circuit is working, if the thermal management system is in the heating cycle but there is no heating demand (the vehicle interior reaches the target temperature), the system needs to switch to the refrigeration cycle and operate in accordance with the refrigeration cycle mode; if the thermal management system is in the refrigeration cycle but there is no refrigeration demand (the vehicle interior reaches the target temperature), the first electronic expansion valve 5 can be closed, and the vehicle interior fan can be turned off or enter the circulating air mode; 2. When the hot water circuit is working, if the thermal management system is in the refrigeration cycle but there is no cooling demand (the target temperature in the vehicle is reached), the system needs to switch to the heating cycle and operate in accordance with the heating cycle mode; if the thermal management system is in the heating cycle and there is no heating demand (the target temperature in the vehicle is reached), the temperature can be judged first to determine the working mode of the first electronic expansion valve 5. At this time, the fan in the vehicle is turned off or enters the circulating air mode.

[0034] 3. When there is a dehumidification demand and the thermal management system is in heating demand, the system switches to the refrigeration cycle and both the cold and hot water circuits work, and operates in accordance with the refrigeration cycle mode; the bypass valve 2 is closed and the first electronic expansion valve 5 is opened. At this time, the temperature of the in-vehicle heat exchanger 7 is lower than the in-vehicle temperature, the moisture in the air condenses on its surface, and low-temperature dry air is blown into the vehicle; the hot water in the hot water heat exchanger 10 is passed into the in-vehicle heating equipment to provide heat in the vehicle for maintaining the in-vehicle temperature.

[0035] like Figure 2 As shown, a linkage control method for a thermal management system of a new energy commercial vehicle using carbon dioxide refrigerant and vehicle components includes a multi-way water valve body 20, which is respectively connected to the carbon dioxide refrigerant thermal management system, a defroster, a motor electronic control system, a motor radiator and a vehicle compartment heating equipment. The multi-way water valve body 20 includes 14 flow channels and 7 pairs of interfaces, and a hot water interface 21 and a cold water interface 22 are provided between the carbon dioxide refrigerant thermal management system and the multi-way water valve body 20.

[0036] The linkage control method of the present invention is for the thermal management system of new energy vehicles. The components that need to receive cold and hot water to implement the functions and the corresponding requirements / functions are as follows: The motor and electronic control require liquid cooling; Batteries require liquid cooling when the ambient temperature is high and liquid heating when the ambient temperature is low; The motor radiator dissipates heat outside the vehicle and cools the water circuit; Carriage heating equipment, when the ambient temperature is low, the carbon dioxide refrigerant thermal management system supplies hot water to the carriage heating equipment through the hot water interface 21; Defroster: When the ambient temperature is high, the carbon dioxide refrigerant thermal management system introduces cold water through the cold water interface 22 to cool the driver and defog with cold air. When the ambient temperature is low, hot water is introduced through the hot water interface 21 to heat the driver and defrost with hot air; When the cold water circuit is working, the second electronic expansion valve 16 is working.

[0037] When the hot water circuit is working, bypass valve 2 is closed.

[0038] The specific association working mode is shown in Table 1.

[0039] Table 1.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, which should also be regarded as the scope of protection of the present invention.

Claims

1. A thermal management system for commercial vehicles using carbon dioxide refrigerant, characterized in that: The invention comprises a compressor (1), wherein the high-pressure side of the compressor (1) is connected to the first port of a four-way valve (3) via a bypass valve (2), the second port of the four-way valve (3) is connected to an external heat exchanger (4), the external heat exchanger (4) is connected to an internal heat exchanger (7) via a first electronic expansion valve (5) and a third one-way valve (6), the other end of the internal heat exchanger (7) is connected to the third port of the four-way valve (3), the refrigerant is connected to a regenerator (8) via a fourth port of the four-way valve (3), the regenerator (8) is connected to a gas-liquid separator (9), and the gas-liquid separator (9) is connected to the low-pressure side of the compressor (1); The bypass valve (2) is connected in parallel with the hot water heat exchanger (10); The outlet side of the regenerator (8) is connected to the first electronic expansion valve (5) via a fourth one-way valve (13), and enters the off-vehicle heat exchanger (4) via the first electronic expansion valve (5); The off-vehicle heat exchanger (4) is also connected to a cold water heat exchanger (17) via a drying filter (14), a first non-return valve (15), and a second electronic expansion valve (16); the other end of the cold water heat exchanger (17) is connected to a regenerator (8); A second one-way valve (18) is provided on the pipeline between the first electronic expansion valve (5) and the second electronic expansion valve (16).

2. A commercial vehicle thermal management system using carbon dioxide refrigerant according to claim 1, characterized in that: The external heat exchanger (4) is provided with an external fan (11), and the internal heat exchanger (7) is provided with an internal fan (12).

3. A method for controlling hot and cold water using the commercial vehicle thermal management system according to claim 1 or 2, characterized in that: During the refrigeration cycle, if the bypass valve (2) is closed, the high-temperature and high-pressure refrigerant at the outlet of the compressor (1) will enter the hot water heat exchanger (10). After the water circuit of the entire vehicle is connected to the hot water heat exchanger (10), the refrigerant will release heat to the water circuit. After the refrigerant is cooled and liquefied by the off-vehicle heat exchanger (4), under the action of the first one-way valve (15) and the second one-way valve (18), one path of the refrigerant will flow through the first one-way valve (15) to the second electronic expansion valve (16). At this time, the second electronic expansion valve (16) is opened, and the throttled low-temperature and low-pressure refrigerant will flow through the cold water heat exchanger (17). The refrigerant cools the water circuit of the entire vehicle connected to the cold water heat exchanger (17). Another path of the refrigerant will flow through the first electronic expansion valve (5), and under the action of the third one-way valve (6) and the fourth one-way valve (13), it will bypass the regenerator (8) through the third one-way valve (6) and enter the on-vehicle heat exchanger (7), thereby avoiding excessively high exhaust temperature during the refrigeration cycle. During the heating cycle, if the bypass valve (2) is closed, the high-temperature and high-pressure refrigerant at the compressor outlet will enter the hot water heat exchanger (10). After the water circuit of the vehicle is connected to the hot water heat exchanger (10), the refrigerant will release heat to the water circuit. After the refrigerant is cooled and liquefied by the in-vehicle heat exchanger (7), it will flow into the regenerator (8) and pass through the fourth regenerator (13) under the action of the third one-way valve (6) and the fourth one-way valve (13). At this time, the regenerator (8) will release heat to the gas-liquid separator (9). The refrigerant is heated to ensure that the system has a certain degree of superheat during low-temperature heating, thereby avoiding liquid hammer in the compressor (1); then, under the action of the first one-way valve (15) and the second one-way valve (18), a path of refrigerant will flow through the second one-way valve (18) to the second electronic expansion valve (16). At this time, the second electronic expansion valve (16) is opened, and the throttled low-temperature and low-pressure refrigerant will flow through the cold water heat exchanger (17), and the refrigerant will cool the water circuit of the entire vehicle connected to the cold water heat exchanger (17).

4. A linkage control method for a commercial vehicle thermal management system and vehicle components using the thermal management system of claim 1 or 2, characterized in that: The multi-way water valve body (20) is respectively connected to a carbon dioxide refrigerant thermal management system, a defroster, a motor electronic control system, a motor radiator and a vehicle compartment heating device, and a hot water interface (21) and a cold water interface (22) are provided between the carbon dioxide refrigerant thermal management system and the multi-way water valve body (20); The motor and electronic control require liquid cooling; Batteries require liquid cooling when the ambient temperature is high and liquid heating when the ambient temperature is low; The motor radiator dissipates heat outside the vehicle and cools the water circuit; The vehicle compartment heating device, when the ambient temperature is low, the carbon dioxide refrigerant thermal management system supplies hot water to the vehicle compartment heating device through the hot water interface (21); Defroster: when the ambient temperature is high, the carbon dioxide refrigerant thermal management system introduces cold water through the cold water interface (22) to cool the driver and defog with cold air; when the ambient temperature is low, hot water is introduced through the hot water interface (21) to heat the driver and defrost with hot air; When the cold water circuit is working, the second electronic expansion valve (16) is working; When the hot water circuit is operating, the bypass valve (2) is closed.

5. The linkage control method of the commercial vehicle thermal management system and vehicle components according to claim 4 is characterized in that: The multi-channel waterway valve body (20) comprises 14 flow channels and 7 pairs of ports.

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