Variable air volume air source heat pump unit with double-layer heat exchanger and control method thereof

Abstract

The application discloses a variable air volume air source heat pump unit with double-layer heat exchangers and a control method thereof, which comprises a compressor, a water-side heat exchanger tank and an air-side heat exchanger, wherein the air-side heat exchanger comprises multiple groups of air-side heat exchanger assemblies, each group of air-side heat exchanger assemblies comprises two air-side heat exchanger assemblies, each air-side heat exchanger assembly comprises an upper first heat exchanger, an upper second heat exchanger, a lower first heat exchanger and a lower second heat exchanger, the four heat exchangers of the air-side heat exchanger assembly enclose an exhaust air cavity, and the upper second heat exchanger and the lower second heat exchanger of the two air-side heat exchanger assemblies enclose an air inlet cavity; the width of each group of air-side heat exchanger assemblies is kept unchanged, the width of the exhaust air cavity gradually increases from bottom to top, and the width of the air inlet cavity is small at the top and large at the bottom. The application adopts upper and lower double-layer heat exchangers, optimizes the arrangement angle of the upper and lower heat exchangers, can greatly improve the heating capacity per unit floor area of the heat pump unit, appropriately increases the width of the exhaust air cavity along the exhaust air direction, and ensures the air volume of the air passing through the lower heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of renewable energy utilization technology, and more specifically, to a variable air volume air source heat pump unit with a double-layer heat exchanger and its control method. Background Technology

[0002] Air source heat pumps, as one of the simplest ways to utilize renewable energy, have advantages such as convenient heat source acquisition, easy operation and maintenance, and no direct carbon emissions. They have a current status and prospect of widespread application in Chinese buildings.

[0003] Due to the low heat transfer coefficient of the air-side heat exchanger in air source heat pump units, the heat exchange capacity per unit area is limited, making it difficult to increase the heating capacity of a single heat pump unit. Currently, the largest single-unit heating capacity of mainstream brand air source heat pump units on the market is usually between 1400kW and 1600kW. The equipment size of this capacity unit reaches 13.5m to 18m in length, about 2.3m in width, and about 2.5m in height, which seriously restricts the application of air source heat pump units in medium and large-scale projects. There is an urgent need to take effective measures to improve the heating capacity of the unit without changing the floor space occupied. This is of great significance for saving outdoor land and promoting the application of air source heat pumps.

[0004] Compared to heat exchange tower systems or water-cooled chiller systems, which often have heat exchange towers exceeding 5 meters in height, air source heat pump units, with an equipment height of only 2.5 meters, make insufficient use of outdoor space. Therefore, increasing the height of the air-side heat exchanger in an air source heat pump unit to increase the heating capacity per unit area is an effective measure to improve the heating capacity of a single heat pump unit. There are generally two approaches to increasing the heat exchanger area by increasing the height. One approach is to overlap two single-layer heat exchangers, which doubles the heat exchanger area without increasing the width. However, this method creates a very narrow channel between the upper and lower heat exchangers, significantly limiting the airflow through the lower heat exchanger, resulting in a limited increase in heat exchange capacity despite doubling the heat exchange area. The other approach is to extend a V-shaped single-layer heat exchanger directly in the height direction. This method significantly increases the heat exchanger area with minimal impact on the heat exchange capacity per unit area, but it leads to a substantial increase in the width of the unit. Therefore, it is extremely important to develop a structural design that has a smaller impact on the heat exchange capacity per unit area of ​​the heat pump unit's heat exchanger and the width of the equipment.

[0005] The operating energy consumption of an air source heat pump unit consists of two parts: compressor energy consumption and fan energy consumption. When the air source heat pump unit is operating under partial load, the two parts restrict each other. The larger the air volume through the heat exchanger, the greater the fan energy consumption, but the better the heat exchange effect, which helps to reduce compressor energy consumption. Therefore, researching an air source heat pump unit operation control method based on the lowest comprehensive energy consumption is of great significance for reducing the operating energy consumption of heat pumps.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] To address existing technical problems and fill gaps in the field, this invention aims to provide a variable air volume (VAV) air source heat pump unit with a double-layer heat exchanger and its control method. The unit employs a double-layer heat exchanger structure and optimizes the arrangement angle of the upper and lower heat exchangers. By appropriately increasing the width of the exhaust cavity along the exhaust direction, a sharply narrowing "throat" between the upper and lower heat exchangers is avoided, ensuring sufficient airflow through the lower heat exchanger and thus significantly increasing the heating capacity per unit area of ​​the heat pump unit.

[0008] This invention is achieved through the following technical solution:

[0009] In a first aspect, the present invention provides a variable air volume air source heat pump unit with a double-layer heat exchanger, including a compressor and a water-side heat exchanger box disposed at the lower part and an air-side heat exchanger disposed at the upper part. The air-side heat exchanger includes multiple sets of air-side heat exchanger assemblies arranged sequentially along the length direction. Each set of air-side heat exchanger assemblies includes two air-side heat exchanger assemblies symmetrically arranged along the plane containing the width midline.

[0010] The air-side heat exchanger assembly includes an upper heat exchanger and a lower heat exchanger;

[0011] The upper heat exchanger includes an upper first heat exchanger disposed on the side away from the other wind-side heat exchanger assembly and an upper second heat exchanger disposed on the side closer to the other wind-side heat exchanger assembly.

[0012] The lower heat exchanger includes a lower first heat exchanger disposed on the side away from the other air-side heat exchanger assembly and a lower second heat exchanger disposed on the side closer to the other air-side heat exchanger assembly.

[0013] An exhaust chamber is formed between the upper and lower heat exchangers of the air-side heat exchanger assembly, and an air inlet chamber is formed between the upper second heat exchanger and the lower second heat exchanger of the two air-side heat exchanger assemblies in the same group.

[0014] While ensuring that the width of each group of air-side heat exchanger components remains unchanged, the width of the exhaust cavity gradually increases from bottom to top, while the width of the inlet cavity is smaller at the top and larger at the bottom.

[0015] In one specific embodiment, the upper end of the upper second heat exchanger is inclined away from the upper first heat exchanger, and the lower end of the lower first heat exchanger is inclined towards the lower second heat exchanger.

[0016] In one specific embodiment, both the upper first heat exchanger and the lower second heat exchanger are arranged vertically.

[0017] This invention adopts a double-layer heat exchanger structure, and by optimizing the arrangement angle of the upper and lower heat exchangers and appropriately increasing the width of the exhaust cavity along the exhaust direction, it avoids the "throat" that narrows sharply between the upper and lower heat exchangers, thus ensuring the air volume passing through the lower heat exchanger and significantly increasing the heating capacity per unit area of ​​the heat pump unit.

[0018] Specifically, the upper second heat exchanger and the lower first heat exchanger are arranged at an angle to increase the heat exchange area. The lower second heat exchanger is arranged vertically to increase the cross-sectional area of ​​the air inlet cavity, ensuring the air volume in the middle. The upper first heat exchanger is arranged vertically so that the cross-sectional area of ​​the exhaust cavity gradually increases along the exhaust direction, which facilitates balancing the air volume passing through the upper and lower heat exchangers.

[0019] In one specific embodiment, it also includes a duct set at the top of the exhaust cavity, a fan is installed inside the duct, the upper ends of the two upper second heat exchangers of each group of air-side heat exchanger assemblies are connected by a first splicing plate (10), and the lower ends of the two lower second heat exchangers are connected by a second splicing plate (11).

[0020] The fan adopts a permanent magnet direct drive frequency conversion structure, which can maintain high-efficiency output at a load rate of 30% to 100%, overcoming the problems of low efficiency and severe motor heat generation when the asynchronous motor is running at low load. It can realize efficient and wide-range frequency conversion regulation of the air source heat pump unit under partial load conditions. The upper end of the air duct has a flow guiding structure, which can prevent exhaust backflow from causing short circuit of the air intake. The width of the first splicing plate and the second splicing plate can be linearly adjusted according to the air-side heat exchange components spliced ​​in the length direction to match the appropriate middle air intake cavity area, so as to ensure the air intake volume of the air-side heat exchange components located in the middle of the heat pump unit.

[0021] In one specific embodiment, because the upper heat exchanger is closer to the fan, air preferentially passes through it, resulting in a lower airflow to the lower heat exchanger. Considering that the heat exchange capacity and airflow resistance per unit area of ​​the heat exchanger are directly related to the airflow and thickness, but the influence of airflow and thickness on heat exchange capacity and airflow resistance differs, with airflow having a greater impact on heat exchange capacity and thickness having a greater impact on airflow resistance. Therefore, in this invention, the upper heat exchanger is 20% thicker than the lower heat exchanger. This thickened upper heat exchanger design balances the airflow and heat exchange capacity between the upper and lower heat exchangers.

[0022] In one specific implementation, the compressor and water-side heat exchanger box are enclosed by removable sound-absorbing and heat-insulating panels to isolate the unit's operating noise. When the external environment is high and the compressor needs to dissipate heat, the sound-absorbing and heat-insulating panels can be removed to partially open the ventilation area.

[0023] In one specific embodiment, the air-side heat exchanger assembly is mounted on a frame above the compressor and the water-side heat exchanger box.

[0024] Secondly, the present invention also provides a control method for a variable air volume air source heat pump unit with a double-layer heat exchanger, comprising the following steps:

[0025] S1. Based on the principle of minimizing the combined energy consumption of the air source heat pump unit's compressor and fan, determine the total air volume through the air-side heat exchanger, i.e., the number and frequency of the fan in operation.

[0026] S2, during winter heating, monitors the inlet air temperature T of the air-side heat exchanger. h The operating load rate ζ of the unit is obtained by acquiring the unit's operating current. h Then, the optimal operating frequency v of the fan is calculated using the following formula. h :

[0027]

[0028] Where: v0 - the operating frequency of the fan under rated operating conditions, 50Hz

[0029] x h - Fitting coefficients related to unit operating load rate under heating conditions

[0030] y h - Heating conditions, fitting coefficients related to the outdoor operating conditions of the unit;

[0031] S3, during summer cooling, monitors the inlet air temperature T of the air-side heat exchanger. c Obtain the operating load rate ζ of the heat pump unit. c Then, the optimal operating frequency v of the fan is calculated using the following formula. c ;

[0032]

[0033] In the formula: x c - Fitting coefficients related to the unit's operating load rate under cooling conditions.

[0034] y c - Cooling operating condition, the fitting coefficient related to the outdoor operating conditions of the unit;

[0035] S4, the efficiency of the permanent magnet direct drive variable frequency fan degrades significantly when the load rate is below 30%, so the lower limit of the fan frequency conversion is set to 15Hz.

[0036] When the theoretical optimal operating frequency of the fan is greater than 50 Hz, the fan is set to operate at the power frequency of 50 Hz.

[0037] When 15Hz≤v≤50Hz, the fan is set to operate at the optimal operating frequency v;

[0038] When v < 15 Hz, some fans are turned off, and the operating frequency of the remaining fans is close to and greater than 15 Hz.

[0039] S5, to avoid frequent frequency changes and start-stop of the fan, uses a given time period (e.g., 5 minutes or other time) as an adjustment cycle.

[0040] In a specific implementation, the method for determining the number and frequency of fans in step S1 is as follows: Select heat pump units of various typical capacity specifications, and use laboratory variable operating condition testing methods to obtain the compressor energy consumption and fan energy consumption of heat pump units under different load rates and different outdoor temperatures, corresponding to different numbers and frequencies of fans in operation. Using these as input boundary conditions, the relationship between the number and frequency of fans in operation and the unit operating load rate and outdoor temperature is derived using heat pump performance analysis software, under the principle of minimizing the overall energy consumption of heat pump unit operation.

[0041] In a specific implementation, in step S4, the number of fans m to be shut down is calculated using the following formula:

[0042]

[0043] Where: n - the total number of fans in the air source heat pump unit, Roundup() - round-up function

[0044] The operating frequency of the remaining wind turbines is calculated using the following formula: nv / (nm).

[0045] Air source heat pump units typically have multiple heat exchange fans, with large-capacity units even having more than 30 fans. Adjusting the number of fans in operation allows for convenient and accurate matching of the required airflow. Therefore, most air source heat pump units on the market currently use fixed-frequency fans. However, for a single fan, adjusting the airflow by frequency conversion results in a cubic relationship between the fan's power consumption and the airflow; while adjusting the number of fans results in a direct proportional relationship between the total power consumption of all fans and the airflow. Therefore, this invention, when the air source heat pump unit is under partial load, uses a synchronous frequency conversion method for all fans to adjust the heat exchange airflow, resulting in a significantly lower total power consumption per fan compared to the method of adjusting the number of fans.

[0046] In addition, the control method of the present invention, by formulating the operation control logic of the number of fans to be turned on and the frequency conversion based on the principle of minimizing the overall energy consumption of the heat pump unit, can significantly reduce the operating energy consumption of the heat pump unit.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] 1. The present invention provides a variable air volume air source heat pump unit with a double-layer heat exchanger. It adopts a double-layer heat exchanger structure and optimizes the arrangement angle of the upper and lower heat exchangers and appropriately increases the width of the exhaust cavity along the exhaust direction. This avoids the "throat" that narrows sharply between the upper and lower heat exchangers, thus ensuring the air volume passing through the lower heat exchanger and achieving the goal of significantly increasing the heating capacity per unit area of ​​the heat pump unit.

[0049] 2. The variable air volume air source heat pump unit with double-layer heat exchanger provided in this embodiment of the invention adopts a structure in which the thickness of the upper heat exchanger is greater than that of the lower heat exchanger, which can balance the air volume and heat exchange capacity of the upper and lower heat exchangers.

[0050] 3. The present invention provides a control method for a variable air volume air source heat pump unit with a double-layer heat exchanger. The fan of the air source heat pump unit adopts a variable frequency fan. Based on the principle of minimizing the overall energy consumption of the heat pump unit, the operation control logic of the number of fans to be turned on and the frequency conversion is formulated, which greatly reduces the operating energy consumption of the heat pump unit. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a front view of the air source heat pump unit provided in Embodiment 1 of the present invention;

[0053] Figure 2 This is a side view of an air source heat pump unit provided in Embodiment 1 of the present invention;

[0054] Figure 3 This is a top view of the air source heat pump unit provided in Embodiment 1 of the present invention;

[0055] Figure 4 This is a schematic diagram of the fan operation control in Embodiment 2 of the present invention;

[0056] Figure 5 This is a front view of an existing air source heat pump unit.

[0057] Figure labels and corresponding component names:

[0058] 1-Compressor and water-side heat exchanger box, 2-Upper first heat exchanger, 3-Upper second heat exchanger, 4-Lower first heat exchanger, 5-Lower second heat exchanger, 6-Exhaust chamber, 7-Inlet chamber, 8-Fan, 9-Air duct, 10-First splicing plate, 11-Second splicing plate, 12-Sound-absorbing and heat-insulating board, 13-Frame. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0060] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures have not been specifically described in order to avoid obscuring the invention.

[0061] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0062] In the description of this invention, the terms "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "high," "low," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention.

[0063] Currently, increasing the height of the air-side heat exchanger in an air-source heat pump unit to increase the heating capacity per unit area is an effective measure to improve the heating capacity of a single heat pump unit.

[0064] There are generally two ways to increase the heat exchanger area by increasing the height. One is to overlap two single-layer heat exchangers, which can double the heat exchanger area without increasing the width dimension. However, this method will create a very narrow channel between the upper and lower heat exchangers, such as... Figure 5As shown in the left figure, this location significantly restricts the airflow through the lower heat exchanger, resulting in a limited increase in heat exchange capacity despite doubling the heat exchange area. Another approach is to extend the V-shaped single-layer heat exchanger directly vertically, such as... Figure 5 As shown in the right figure, this method can significantly increase the heat exchanger area with minimal impact on the heat exchanger's unit area, but it also leads to a substantial increase in the unit's width. Therefore, to solve the above problems, this embodiment of the invention provides a heat pump unit that can both increase the heat output per unit area of ​​the heat pump unit and avoid the appearance of a sharply narrowing "throat" between the upper and lower heat exchangers.

[0065] Example 1

[0066] like Figures 1-3 As shown, this embodiment of the invention provides a variable air volume air source heat pump unit with a double-layer heat exchanger, including a compressor and a water-side heat exchanger box 1 disposed at the lower part and an air-side heat exchanger disposed at the upper part. The air-side heat exchanger includes multiple sets of air-side heat exchanger assemblies arranged sequentially along the length direction. Each set of air-side heat exchanger assemblies includes two air-side heat exchanger assemblies symmetrically arranged along the plane containing the width midline.

[0067] The air-side heat exchanger assembly comprises an upper heat exchanger, a lower heat exchanger, a fan 8, and a guide duct 9;

[0068] The upper heat exchanger includes an upper first heat exchanger 2 and an upper second heat exchanger 3;

[0069] The lower heat exchanger includes a lower first heat exchanger 4 and a lower second heat exchanger 5;

[0070] The upper and lower four heat exchangers of the air-side heat exchanger assembly form an exhaust cavity 6. The upper second heat exchanger 3 and lower second heat exchanger 5 of the left air-side heat exchanger assembly and the upper second heat exchanger 3 and lower second heat exchanger 5 of the right air-side heat exchanger assembly form an air inlet cavity 7.

[0071] With the width of each group of air-side heat exchanger assemblies remaining constant, the width of the exhaust cavity 6 gradually increases from bottom to top, while the width of the air inlet cavity 7 is smaller at the top and larger at the bottom.

[0072] The upper end of the upper second heat exchanger 3 is inclined away from the upper first heat exchanger 2, and the lower end of the lower first heat exchanger 4 is inclined towards the lower second heat exchanger 5; the upper first heat exchanger 2 and the lower second heat exchanger 5 are both arranged vertically.

[0073] This invention adopts a double-layer heat exchanger structure and optimizes the arrangement angle of the upper and lower heat exchangers. By appropriately increasing the width of the exhaust cavity along the exhaust direction, it avoids the sharp narrowing of the "throat" between the upper and lower heat exchangers, thus ensuring the air volume passing through the lower heat exchanger and achieving the goal of significantly increasing the heating capacity per unit area of ​​the heat pump unit.

[0074] Specifically, the upper second heat exchanger 3 and the lower first heat exchanger 4 are arranged at an angle to increase the heat exchange area. The lower second heat exchanger 5 is arranged vertically to increase the cross-sectional area of ​​the air inlet cavity 7, ensuring the air volume in the middle. The upper first heat exchanger 2 is arranged vertically so that the cross-sectional area of ​​the exhaust cavity gradually increases along the exhaust direction, which facilitates balancing the air volume passing through the upper and lower heat exchangers.

[0075] In one specific embodiment, because the upper heat exchanger is closer to the fan, air preferentially passes through it, resulting in a lower airflow to the lower heat exchanger. Considering that the heat exchange capacity and airflow resistance per unit area of ​​the heat exchanger are directly related to the airflow and thickness, but the influence of airflow and thickness on heat exchange capacity and airflow resistance differs, with airflow having a greater impact on heat exchange capacity and thickness having a greater impact on airflow resistance. Therefore, in this invention, the upper heat exchanger is 20% thicker than the lower heat exchanger. This thickened upper heat exchanger design balances the airflow and heat exchange capacity between the upper and lower heat exchangers.

[0076] The fan 8 adopts a permanent magnet direct drive frequency conversion structure, which can maintain high efficiency output at a load rate of 30% to 100%, overcoming the problems of low efficiency and severe motor heat generation when the asynchronous motor is running at low load. It can realize efficient and wide-range frequency conversion regulation of the air source heat pump unit under partial load conditions. The upper end of the air duct 9 has a flow guiding structure, which can prevent exhaust backflow from causing short circuit of the intake air.

[0077] In one specific embodiment, the upper ends of the upper second heat exchangers 3 of the two air-side heat exchanger assemblies are connected by a first splicing plate 10, and the lower ends of the lower second heat exchangers 5 of the two air-side heat exchanger assemblies are connected by a second splicing plate 11. The widths of the first splicing plate 10 and the second splicing plate 11 can be linearly adjusted according to the length of the spliced ​​air-side heat exchanger assemblies to match a suitable intermediate air inlet cavity area, so as to ensure the air intake volume of the air-side heat exchanger assembly located in the middle of the heat pump unit.

[0078] In one specific embodiment, the compressor and water-side heat exchanger box 1 are enclosed by a removable sound-absorbing and heat-insulating board 12 to isolate the unit's operating noise. When the external environment is high and the compressor needs to dissipate heat, the sound-absorbing and heat-insulating board can be removed to partially open the ventilation.

[0079] In one specific embodiment, the air-side heat exchanger assembly is mounted above the compressor and the water-side heat exchanger box 1 via a frame 13.

[0080] Example 2

[0081] like Figure 4 As shown, this embodiment of the invention provides a control method for a variable air volume air source heat pump unit with a double-layer heat exchanger, comprising the following steps:

[0082] (1) Based on the principle of minimizing the overall energy consumption of the compressor and fan of the air source heat pump unit, the total air volume through the heat pump air-side heat exchanger is determined, which is the number and frequency of the fan in operation. Specifically, several typical capacity specifications of heat pump units are selected, and the laboratory variable operating condition test method is used to obtain the compressor energy consumption and fan energy consumption of the heat pump unit under different load rates, different outdoor temperatures, and different numbers and frequencies of fan operation. Using these as input boundary conditions, the heat pump performance analysis software is used to deduce the relationship between the number and frequency of fan operation and the unit operating load rate and outdoor temperature under the principle of minimizing the overall energy consumption of the heat pump unit. In actual operation, the optimal number and frequency of fan operation can be calculated using this relationship.

[0083] (2) During winter heating, the air source heat pump unit monitors the inlet air temperature T of the air-side heat exchanger through its built-in temperature sensor. h The operating load rate ζ of the unit is obtained by reading the operating current of the unit. h The optimal operating frequency v of the fan is then determined by the following formula. h :

[0084]

[0085] Where: v0—the operating frequency of the fan under rated operating conditions, 50Hz

[0086] x h —Fitness coefficients related to unit operating load rate under heating conditions

[0087] y h —Heating operating conditions, the fitting coefficients related to the outdoor operating conditions of the unit;

[0088] (3) When the air source heat pump unit is cooling in summer, the inlet air temperature T of the air-side heat exchanger is monitored. c Read the operating load rate ζ of the heat pump unit c The optimal operating frequency v of the fan is calculated using the following formula. c :

[0089]

[0090] In the formula: x c —Fitness coefficients related to the unit's operating load rate under cooling conditions.

[0091] yc —Coefficients of fit related to the outdoor operating conditions of the unit in cooling mode;

[0092] (4) When the load rate of the permanent magnet direct-drive variable frequency fan is below 30%, a significant energy efficiency degradation will occur. Therefore, the lower limit of the fan frequency is set at 15Hz. When the theoretical optimal operating frequency v of the fan is greater than 50Hz, all fans operate at the power frequency of 50Hz; when 15Hz ≤ v ≤ 50Hz, all fans operate at the optimal operating frequency v; when v < 15Hz, some fans are turned off to ensure that the operating frequency of the remaining active fans is close to and greater than 15Hz. The specific number of fans to be turned off, m, can be calculated using the following formula. The remaining fans operate at a frequency of nv / (nm):

[0093]

[0094] Where: n—the total number of fans in the air source heat pump unit

[0095] Roundup() — The function to round up;

[0096] (5) To avoid frequent frequency changes and start-stop of the fan, a given time period (e.g., 5 minutes or other time) is used as an adjustment cycle.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A variable air volume air source heat pump unit with a double-layer heat exchanger, characterized in that, It includes a compressor and water-side heat exchanger box (1) located at the bottom and an air-side heat exchanger located at the top. The air-side heat exchanger includes multiple sets of air-side heat exchanger assemblies arranged sequentially along the length direction. Each set of air-side heat exchanger assemblies includes two air-side heat exchanger assemblies arranged symmetrically along the plane containing the width midline. The air-side heat exchanger assembly includes an upper heat exchanger and a lower heat exchanger; The upper heat exchanger includes an upper first heat exchanger (2) disposed on the side away from the other air-side heat exchanger assembly and an upper second heat exchanger (3) disposed on the side close to the other air-side heat exchanger assembly. The lower heat exchanger includes a lower first heat exchanger (4) disposed on the side away from the other air-side heat exchanger assembly and a lower second heat exchanger (5) disposed on the side closer to the other air-side heat exchanger assembly. An exhaust chamber (6) is formed between the upper and lower heat exchangers of the air-side heat exchanger assembly, and an air inlet chamber (7) is formed between the upper second heat exchanger (3) and the lower second heat exchanger (5) of the two air-side heat exchanger assemblies in the same group. While ensuring that the width of each group of air-side heat exchanger components remains unchanged, the width of the exhaust cavity (6) gradually increases from bottom to top, and the width of the air inlet cavity (7) is smaller at the top and larger at the bottom.

2. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 1, characterized in that, It also includes a duct (9) set at the top of the exhaust cavity (6), and a fan (8) is installed inside the duct (9).

3. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 1, characterized in that, The upper end of the upper second heat exchanger (3) is inclined away from the upper first heat exchanger (2), and the lower end of the lower first heat exchanger (4) is inclined towards the lower second heat exchanger (5).

4. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 1, characterized in that, The upper first heat exchanger (2) and the lower second heat exchanger (5) are both arranged vertically.

5. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 1, characterized in that, The upper heat exchanger is thicker than the lower heat exchanger.

6. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 2, characterized in that, The fan (8) adopts a permanent magnet direct drive frequency conversion structure, and the upper end of the air duct (9) has a flow guiding structure.

7. A variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 6, characterized in that, The compressor and water-side heat exchanger box (1) are enclosed by a removable sound-absorbing and heat-insulating board (12).

8. A control method for a variable air volume air source heat pump unit with a double-layer heat exchanger as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Based on the principle of minimizing the combined energy consumption of the air source heat pump unit's compressor and fan, determine the total air volume through the air-side heat exchanger, i.e., the number and frequency of the fan in operation. S2, during winter heating, monitors the inlet air temperature T of the air-side heat exchanger. h The operating load rate ζ of the unit is obtained by acquiring the unit's operating current. h Then, the optimal operating frequency v of the fan is calculated using the following formula. h : Where: v0 - the operating frequency of the fan under rated operating conditions, 50Hz x h - Fitting coefficients related to unit operating load rate under heating conditions y h - Heating conditions, fitting coefficients related to the outdoor operating conditions of the unit; S3, during summer cooling, monitors the inlet air temperature T of the air-side heat exchanger. c Obtain the operating load rate ζ of the heat pump unit. c Then, the optimal operating frequency v of the fan is calculated using the following formula. c ; In the formula: x c - Fitting coefficients related to the unit's operating load rate under cooling conditions. y c - Cooling operating condition, the fitting coefficient related to the outdoor operating conditions of the unit; S4, the efficiency of the permanent magnet direct drive variable frequency fan degrades significantly when the load rate is below 30%, so the lower limit of the fan frequency is set to 15Hz; When the theoretical optimal operating frequency of the fan is greater than 50 Hz, the fan is set to operate at the power frequency of 50 Hz. When 15Hz≤v≤50Hz, the fan is set to operate at the optimal operating frequency v; When v < 15 Hz, some fans are turned off, and the operating frequency of the remaining fans is close to and greater than 15 Hz.

9. The control method for the variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 8, characterized in that, In step S1, the method for determining the number and frequency of fans in operation is as follows: Select heat pump units of various typical capacity specifications, and use laboratory variable operating condition test method to obtain the compressor energy consumption and fan energy consumption of heat pump units under different load rates and different outdoor temperatures, corresponding to different number and frequency of fans in operation. Using this as the input boundary condition, use heat pump performance analysis software to deduce the relationship between the number and frequency of fans in operation and the unit operating load rate and outdoor temperature under the principle of minimizing the overall energy consumption of heat pump unit operation.

10. The control method for the variable air volume air source heat pump unit with a double-layer heat exchanger according to claim 8, characterized in that, In step S4, the number of fans m to be shut down is calculated using the following formula: Where: n - the total number of fans in the air source heat pump unit, Roundup() - round-up function The operating frequency of the remaining wind turbines is calculated using the following formula: nv / (nm).

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