Heat exchanger, air conditioner and control method of air conditioner

Abstract

The invention provides a heat exchanger, an air conditioner and a control method thereof, the heat exchanger comprises a front section and a rear section, the front section is located at the upstream of the rear section in the flowing direction of a refrigerant, the pipe diameter of the front section is smaller than that of the rear section, and / or the number of branches of the front section is smaller than that of branches of the rear section; the pipe diameter of the front section and / or the number of the branches can be adjusted according to the superheat degree of the heat exchanger, and / or the pipe diameter of the rear section and / or the number of the branches can be adjusted according to the superheat degree of the heat exchanger. According to the method, the pipe diameter and the flow path can be optimally designed, the heat exchange efficiency of the evaporator is improved, the material cost of the evaporator is saved while the heat exchange capacity of the evaporator is guaranteed, the actual superheat degree can be controlled to be close to the target superheat degree, sufficient heat exchange of the heat exchanger is guaranteed, resistance loss is reduced, and the heat exchange efficiency of the heat exchanger is improved; the energy efficiency of the air-conditioning system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a heat exchanger, an air conditioner and a control method thereof. Background Art

[0002] At present, household air conditioners are widely used, but their manufacture and use will cause a lot of energy loss, and the manufacture of heat exchangers requires a lot of steel. Fin-tube heat exchangers are important components of refrigeration and air-conditioning systems, and their working conditions can directly affect the quality of refrigeration and air-conditioning systems.

[0003] In order to take into account the cooling and heating performance of the air conditioner, the industry usually designs the evaporator system based on the performance requirements of the heating condition. The evaporator size is usually relatively large, and it is easy to cause serious overheating at the heat exchanger outlet, which will not only affect the heat exchange capacity of the evaporator, but also lead to an increase in the cost of the evaporator.

[0004] Combined with the state characteristics of the refrigerant in the evaporator, the refrigerant is a low-temperature, low-pressure gas-liquid two-phase mixture when entering the evaporator. The dryness is relatively low when it first enters the evaporator. As the evaporation process proceeds, the gas phase component continues to increase, the liquid phase component continues to decrease, and the dryness becomes larger and larger until it is completely vaporized and enters the superheating section for superheating. The existing technology usually chooses to divide the refrigerant into several branches when it enters the evaporator. However, due to the low dryness and specific volume of the refrigerant at the inlet, multiple branches will lead to a decrease in the flow rate in the tube and a decrease in the heat exchange coefficient, thereby affecting the heat exchange effect of the refrigerant.

[0005] Since the evaporator in the prior art has unreasonable tube diameter and flow path design, resulting in low heat exchange efficiency of the evaporator and easy heat waste, the present invention studies and designs a heat exchanger, an air conditioner and a control method thereof. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the evaporator in the prior art, such as unreasonable tube diameter and flow path design, which lead to low heat exchange efficiency of the evaporator and easy heat waste, thereby providing a heat exchanger, an air conditioner and a control method thereof.

[0007] In order to solve the above problems, the present invention provides a heat exchanger, comprising:

[0008] A front section and a rear section, along the flow direction of the refrigerant, the front section is located upstream of the rear section, and the pipe diameter of the front section is smaller than the pipe diameter of the rear section, and / or the number of branches of the front section is smaller than the number of branches of the rear section; the pipe diameter size and / or the number of branches of the front section can be adjusted according to the size of the superheat of the heat exchanger, and / or the pipe diameter size and / or the number of branches of the rear section can be adjusted according to the size of the superheat of the heat exchanger.

[0009] In some embodiments,

[0010] If the actual superheat is less than the target superheat, the diameter of the pipe in the front section can be reduced and / or the number of branches in the front section can be reduced, and / or the diameter of the pipe in the rear section can be increased and / or the number of branches in the rear section can be increased;

[0011] If the actual superheat is greater than the target superheat, the pipe diameter of the front section can be increased and / or the number of branches of the front section can be increased, and / or the pipe diameter of the rear section can be decreased and / or the number of branches of the rear section can be decreased.

[0012] The present invention also provides an air conditioner, which includes the aforementioned heat exchanger, a compressor, an internal fan, an external fan and a throttling device.

[0013] The present invention also provides a control method for the air conditioner as described above, comprising:

[0014] Detection step: detect the actual overheat degree ΔT1 of the air conditioner.

[0015] A judgment step, comparing the actual superheat ΔT1 with the target superheat ΔT;

[0016] A control step, when ΔT1≤ΔT, controlling to reduce the pipe diameter of the front section and / or controlling to reduce the number of branches of the front section, and / or controlling to increase the pipe diameter of the rear section and / or controlling to increase the number of branches of the rear section;

[0017] When ΔT1>ΔT, the diameter of the front section is controlled to be enlarged and / or the number of branches of the front section is controlled to be increased, and / or the diameter of the rear section is controlled to be reduced and / or the number of branches of the rear section is controlled to be reduced.

[0018] In some embodiments,

[0019] The control step, before controlling and adjusting the pipe diameter and / or the number of branches of the front section and / or the rear section, also controls and adjusts the frequency of the compressor to change, and / or controls the speed of the fan to change, and / or controls the opening size P of the throttling device to change.

[0020] In some embodiments,

[0021] Control step: when ΔT1<ΔT, control to increase the frequency of the compressor, and / or control to increase the speed R1 of the inner fan, control to increase the speed R2 of the outer fan, and / or control to reduce the opening P of the throttling device; when ΔT1>ΔT, control to reduce the frequency of the compressor, and / or control to reduce the speed R1 of the inner fan, control to reduce the speed R2 of the outer fan, and / or control to increase the opening P of the throttling device; when ΔT1=ΔT, keep the current state unchanged.

[0022] In some embodiments,

[0023] In the control step, the target superheat ΔT is calculated as follows: ΔT = a i F+b i R 外 +c i R 内 +d i P+e i , that is, through the compressor frequency F, the internal fan speed R 内 , External fan speed R 外 and the opening degree P of the throttling device to calculate the target superheat ΔT under this operating condition.

[0024] In some embodiments,

[0025] F is the frequency adjustment amplitude of the compressor, and its value range is 0HZ~5HZ;

[0026] R 外 The speed adjustment amplitude of the outdoor fan is in the range of 0rpm to 100rpm;

[0027] R 内 The speed adjustment amplitude of the indoor fan is in the range of 0rpm to 50rpm;

[0028] P 外 The opening adjustment amplitude of the electronic expansion valve ranges from 0p to 50p;

[0029] The target superheat ΔT ranges from 1°C to 3°C.

[0030] In some embodiments,

[0031] a i , b i 、c i d i 、e i is the fitting coefficient, obtained by fitting during the flow path design process of different models;

[0032] i is the corresponding different temperature intervals and the different coefficients taken, and the value range is 1 to 3.

[0033] In some embodiments,

[0034] According to the difference between the indoor ambient temperature and the air conditioning set temperature △t in The size of a i , b i 、c i d i and e i The value of

[0035] When △t in ∈(-6℃, t1), i=1, ΔT=a1F+b1R 外 +c1R 内 +d1 P+e1;

[0036] When △t in When ∈[t1, t2], i=2, ΔT=a2F+b2R 外 +c2R 内 +d2 P+e2;

[0037] When △t in When ∈(t2, 6℃), i=3, ΔT=a3F+b3R 外 +c3R 内 +d3 P+e3,

[0038] Among them, t1 is -2℃~0℃; t2 is 0℃~2℃.

[0039] A heat exchanger, an air conditioner and a control method thereof provided by the present invention have the following beneficial effects:

[0040] The present invention arranges the heat exchanger to include a front section and a rear section along the refrigerant flow direction, wherein the tube diameter of the front section is smaller than the tube diameter of the rear section, and / or the number of branches of the front section is smaller than the number of branches of the rear section. Thus, the design of "small tube diameter / few branches" can be selected for the flow path of the front section of the evaporator, and the heat exchange effect can be improved by increasing the flow rate. As the gas phase component gradually increases during the evaporation process, the dryness of the refrigerant gradually increases, and the specific volume becomes larger. The present invention selects the design of "large tube diameter / multiple branches" for the flow path of the rear section of the evaporator, and the flow resistance loss of the refrigerant is reduced by reducing the flow rate of the refrigerant. Thus, the design of the tube diameter and the flow path can be optimized, and the heat exchange efficiency of the evaporator can be improved. The waste of heat is reduced, and the material cost of the evaporator is saved while ensuring the heat exchange capacity of the evaporator; further, the present invention can adjust the pipe diameter size and / or the number of branches of the front section according to the superheat of the heat exchanger, and / or the pipe diameter size and / or the number of branches of the rear section according to the superheat of the heat exchanger. The present invention can adjust the pipe diameter and the number of branches according to the superheat of the air conditioner, so as to control the actual superheat near the target superheat, ensure sufficient heat exchange of the heat exchanger, reduce resistance loss, reduce energy waste, improve the heat exchange efficiency of the heat exchanger, and improve the energy efficiency of the air-conditioning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a cross-sectional structural diagram of a first embodiment of a heat exchanger of the present invention (variable tube diameter);

[0042] Figure 2 is a cross-sectional structural diagram of a first embodiment of a heat exchanger of the present invention (variable tube diameter);

[0043] Figure 3 is a cross-sectional structural diagram of a third embodiment of the heat exchanger of the present invention (with a variable number of branches);

[0044] Figure 4 is a cross-sectional structural diagram of a fourth embodiment of the heat exchanger of the present invention (with a variable number of branches);

[0045] Figure 5 is a cross-sectional structural diagram of a fifth embodiment of the heat exchanger of the present invention (with a variable number of branches);

[0046] Figure 6 It is a cross-sectional structural diagram of a sixth embodiment of the heat exchanger of the present invention (with a variable number of branches).

[0047] The reference numerals are:

[0048] 1. The front part; 2. The back part. DETAILED DESCRIPTION

[0049] 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, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. 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.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0051] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0052] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0053] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0054] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0055] like Figure 1-6 As shown, the present invention provides a heat exchanger, which includes:

[0056] The front section 1 and the rear section 2, along the flow direction of the refrigerant, the front section 1 is located upstream of the rear section 2, and the pipe diameter of the front section 1 is smaller than the pipe diameter of the rear section 2, and / or the number of branches of the front section 1 is smaller than the number of branches of the rear section 2; the pipe diameter size and / or the number of branches of the front section 1 can be adjusted according to the size of the superheat of the heat exchanger, and / or the pipe diameter size and / or the number of branches of the rear section 2 can be adjusted according to the size of the superheat of the heat exchanger.

[0057] The present invention arranges the heat exchanger to include a front section and a rear section along the refrigerant flow direction, wherein the tube diameter of the front section is smaller than the tube diameter of the rear section, and / or the number of branches of the front section is smaller than the number of branches of the rear section. Thus, the design of "small tube diameter / few branches" can be selected for the flow path of the front section of the evaporator, and the heat exchange effect can be improved by increasing the flow rate. As the gas phase component gradually increases during the evaporation process, the dryness of the refrigerant gradually increases, and the specific volume becomes larger. The present invention selects the design of "large tube diameter / multiple branches" for the flow path of the rear section of the evaporator, and the flow resistance loss of the refrigerant is reduced by reducing the flow rate of the refrigerant. Thus, the design of the tube diameter and the flow path can be optimized, and the heat exchange efficiency of the evaporator can be improved. The waste of heat is reduced, and the material cost of the evaporator is saved while ensuring the heat exchange capacity of the evaporator; further, the present invention can adjust the pipe diameter size and / or the number of branches of the front section according to the superheat of the heat exchanger, and / or the pipe diameter size and / or the number of branches of the rear section according to the superheat of the heat exchanger. The present invention can adjust the pipe diameter and the number of branches according to the superheat of the air conditioner, so as to control the actual superheat near the target superheat, ensure sufficient heat exchange of the heat exchanger, reduce resistance loss, reduce energy waste, improve the heat exchange efficiency of the heat exchanger, and improve the energy efficiency of the air-conditioning system.

[0058] In some embodiments,

[0059] If the actual superheat is less than the target superheat, the pipe diameter of the front section 1 can be reduced and / or the number of branches of the front section 1 can be reduced, and / or the pipe diameter of the rear section 2 can be increased and / or the number of branches of the rear section 2 can be increased;

[0060] If the actual superheat is greater than the target superheat, the pipe diameter of the front section 1 can be increased and / or the number of branches of the front section 1 can be increased, and / or the pipe diameter of the rear section 2 can be decreased and / or the number of branches of the rear section 2 can be decreased.

[0061] The present invention further increases the number of large-diameter / multi-branch pipes in the rear section of the evaporator by adjusting the pipe diameter size of the front section 1 to be smaller and / or the number of branches of the front section 1 to be reduced when the actual superheat is less than the target superheat, and / or the pipe diameter size of the rear section 2 to be larger and / or the number of branches of the rear section 2 to be increased, so as to reduce the flow rate of the refrigerant to fully exchange heat and control the superheat to be near the target superheat. When the actual superheat is greater than the target superheat, the front section 1 The pipe diameter can be increased and / or the number of branches of the front section 1 can be increased, and / or the pipe diameter of the rear section 2 can be decreased and / or the number of branches of the rear section 2 can be decreased. By increasing the number of small-diameter / few-branch pipes in the front section of the evaporator, it is convenient to increase the refrigerant flow rate to enhance heat exchange, control the superheat near the target superheat, ensure sufficient heat exchange of the heat exchanger, reduce resistance loss, reduce energy waste, improve the heat exchange efficiency of the heat exchanger, and improve the energy efficiency of the air-conditioning system.

[0062] The present invention combines the state characteristics of the refrigerant and the flow and heat exchange characteristics in the evaporator to design the flow path of the air conditioner system, designs the flow path based on a V-type indoor heat exchanger, explores the relationship between the refrigerant flow characteristics and the system flow path design, and proposes a variable flow rate air conditioner and a design method thereof.

[0063] The present invention proposes an air conditioner with a variable flow rate and a control method thereof. Based on the refrigerant state change and heat exchange resistance characteristics of the indoor heat exchanger of the air conditioner, a flow path design with variable pipe diameter (small pipe diameter → large pipe diameter) and variable branches (few branches → multiple branches) is selected. Since the refrigerant is a gas-liquid two-phase mixed state of low temperature and low pressure when entering the evaporator, and has a low dryness and a small specific volume, it is considered to select a "small pipe diameter, few branches" design in the front section of the evaporator flow path, and improve the heat exchange effect by increasing the flow rate; as the evaporation process proceeds, the gas phase component gradually increases, the refrigerant dryness gradually increases, and the specific volume becomes larger, so it is considered to select a "large pipe diameter, multiple branches" design in the rear section of the evaporator flow path, and reduce the flow resistance loss of the refrigerant by reducing the flow rate of the refrigerant. While ensuring the heat exchange capacity of the evaporator, the material cost of the evaporator is also saved.

[0064] The following technical problems have been solved:

[0065] 1. Solve the problem of low heat exchange efficiency and heat waste caused by unreasonable design of evaporator pipe diameter and flow path in the existing technology

[0066] 2. Reduce the cost of the refrigeration system to a certain extent.

[0067] The present invention also provides an air conditioner, which includes the aforementioned heat exchanger, a compressor, an internal fan, an external fan and a throttling device.

[0068] The present invention also provides a control method for the air conditioner as described above, comprising:

[0069] Detection step: detect the actual overheat degree ΔT1 of the air conditioner.

[0070] A judgment step, comparing the actual superheat ΔT1 with the target superheat ΔT;

[0071] A control step, when ΔT1≤ΔT, controlling to reduce the pipe diameter of the front section 1 and / or controlling to reduce the number of branches of the front section 1, and / or controlling to increase the pipe diameter of the rear section 2 and / or controlling to increase the number of branches of the rear section 2;

[0072] When ΔT1>ΔT, the diameter of the front section 1 is controlled to be enlarged and / or the number of branches of the front section 1 is controlled to be increased, and / or the diameter of the rear section 2 is controlled to be reduced and / or the number of branches of the rear section 2 is controlled to be reduced.

[0073] The present invention can increase the number of large-diameter / multi-branch pipes in the rear section of the evaporator by controlling the pipe diameter of the front section 1 to be reduced and / or the number of branches of the front section 1 to be reduced when the actual superheat is less than the target superheat, and / or controlling the pipe diameter of the rear section 2 to be increased and / or the number of branches of the rear section 2 to be increased, so as to reduce the flow rate of the refrigerant to fully exchange heat, and control the superheat to be near the target superheat. When the actual superheat is greater than the target superheat, the front section 1 is controlled to be increased. The diameter of the tube is increased and / or the number of branches of the front section 1 is increased, and / or the diameter of the tube of the rear section 2 is decreased and / or the number of branches of the rear section 2 is decreased. By increasing the number of small-diameter / few-branch tubes in the front section of the evaporator, it is convenient to increase the refrigerant flow rate for enhanced heat exchange, control the superheat near the target superheat, ensure sufficient heat exchange of the heat exchanger, reduce resistance loss, reduce energy waste, improve the heat exchange efficiency of the heat exchanger, and improve the energy efficiency of the air-conditioning system.

[0074] In some embodiments,

[0075] The control step, before controlling and adjusting the pipe diameter and / or the number of branches of the front section 1 and / or the rear section 2, also controls and adjusts the frequency of the compressor to change, and / or controls the speed of the fan to change, and / or controls the opening size P of the throttling device to change.

[0076] The present invention controls and adjusts the frequency of the compressor and / or the speed of the fan and / or the opening P of the throttling device before controlling and adjusting the pipe diameter and / or the number of branches of the front section 1 and / or the rear section 2. It can first control and adjust the compressor frequency, the speed of the fan and the opening of the throttling device to control the actual superheat to reach the vicinity of the target superheat to achieve coarse adjustment, and then further adjust the pipe diameter and / or the number of branches of the front section 1 and / or the rear section 2 to achieve fine adjustment of the superheat, further improve the heat exchange performance of the heat exchanger, further reduce the resistance loss, reduce energy waste, improve the heat exchange efficiency of the heat exchanger, and improve the energy efficiency of the air-conditioning system.

[0077] In some embodiments,

[0078] Control step: when ΔT1<ΔT, control to increase the frequency of the compressor, and / or control to increase the speed R1 of the inner fan, control to increase the speed R2 of the outer fan, and / or control to reduce the opening P of the throttling device; when ΔT1>ΔT, control to reduce the frequency of the compressor, and / or control to reduce the speed R1 of the inner fan, control to reduce the speed R2 of the outer fan, and / or control to increase the opening P of the throttling device; when ΔT1=ΔT, keep the current state unchanged.

[0079] The present invention is based on the superheat control logic of the variable flow rate flow path design:

[0080] Detect the current actual superheat ΔT1 and compare it with the target superheat ΔT:

[0081] 1) When ΔT1≤ΔT, it indicates that the refrigerant heat exchange in the evaporator is insufficient. The first choice is to adjust the load parameters. The compressor frequency F can be increased (increasing the speed of work, improving the efficiency of the system, and making the evaporator heat exchange more sufficient), or increasing the speed of the internal and external fans R1, R2, or reducing the opening P of the electronic expansion valve to allow the refrigerant to fully exchange heat. If the problem still cannot be improved, consider increasing the number of large-diameter / multi-branch pipes in the rear section of the evaporator to reduce the refrigerant flow rate for sufficient heat exchange.

[0082] 2) When ΔT1 = ΔT, it indicates that the current flow path design and its load parameter design are relatively reasonable.

[0083] 3) When ΔT1>ΔT, it indicates that the refrigerant in the evaporator is seriously overheated. The first choice is to adjust the load parameters. The refrigerant flow rate can be increased by reducing the compressor frequency F, or reducing the internal and external fan speeds R1, R2, or increasing the opening of the electronic expansion valve to avoid overheating losses. If the situation still cannot be improved, consider increasing the number of small-diameter / few-branch pipes in the front section of the evaporator to increase the refrigerant flow rate for enhanced heat exchange.

[0084] In some embodiments,

[0085] In the control step, the target superheat ΔT is calculated as follows: ΔT = a i F+b i R 外 +c i R 内 +d i P+e i , that is, through the compressor frequency F, the internal fan speed R 内 , External fan speed R 外 and the opening degree P of the throttling device to calculate the target superheat ΔT under this operating condition.

[0086] The present invention can accurately calculate the target superheat through the above formula, that is, the formula related to the compressor frequency, the rotation speed of the internal and external fans and the opening of the throttling device, thereby realizing accurate calculation of the target superheat.

[0087] In some embodiments,

[0088] F is the frequency adjustment amplitude of the compressor, and its value range is 0HZ~5HZ;

[0089] R 外 The speed adjustment amplitude of the outdoor fan is in the range of 0rpm to 100rpm;

[0090] R 内 The speed adjustment amplitude of the indoor fan is in the range of 0rpm to 50rpm;

[0091] P 外 The opening adjustment amplitude of the electronic expansion valve ranges from 0p to 50p;

[0092] The target superheat ΔT ranges from 1°C to 3°C.

[0093] In some embodiments,

[0094] a i , b i 、c i d i 、e i is the fitting coefficient, obtained by fitting during the flow path design process of different models;

[0095] i is the corresponding different temperature intervals and the different coefficients taken, and the value range is 1 to 3.

[0096] In some embodiments,

[0097] According to the difference between the indoor ambient temperature and the air conditioning set temperature △t in The size of a i , b i 、ci d i and e i The value of

[0098] When △t in ∈(-6℃, t1), i=1, ΔT=a1F+b1R 外 +c1R 内 +d1 P+e1;

[0099] When △t in When ∈[t1, t2], i=2, ΔT=a2F+b2R 外 +c2R 内 +d2 P+e2;

[0100] When △t in When ∈(t2, 6℃), i=3, ΔT=a3F+b3R 外 +c3R 内 +d3 P+e3,

[0101] Among them, t1 is -2℃~0℃; t2 is 0℃~2℃.

[0102] The target superheat ΔT of the present invention can be expressed as:

[0103] ΔT=a i F+b i R 外 +c i R 内 +d i P+e i ;

[0104] The present invention is based on the difference between the indoor ambient temperature and the air conditioning set temperature △t in The size of the corresponding target superheat calculation formula is shown in the following table:

[0105] Table 1

[0106] The difference between the inner ring temperature and the set temperature △tin Target superheat calculation ΔT (-6，t1) <![CDATA[a1F+b1R 外 +c1R 内 +d1 P+e1]]> [t1, t2] <![CDATA[a2F+b2R 外 +c2 R 内 +d2 P+e2]]> (t2，6) <![CDATA[a3F+b3R 外 +c3 R 内 +d3P+e3]]>

[0107] in,

[0108] t1 is used to compare with △t in For comparison of size, generally -2℃~0℃;

[0109] t2 is used to compare with △t in For comparison of size, 0℃~2℃ is generally used;

[0110] The target superheat ΔT during the experimental test has a value range of 1°C to 3°C (because the target superheat ΔT has a range, the coefficients a1\a2, etc. do not limit the range);

[0111] F is the frequency adjustment amplitude of the compressor, and its value range is 0HZ~5HZ;

[0112] Rout is the outdoor fan speed adjustment amplitude, ranging from 0rpm to 100rpm;

[0113] R is the indoor fan speed adjustment amplitude, the value range is 0rpm~50rpm;

[0114] P is the opening adjustment amplitude of the electronic expansion valve, and its value range is 0p~50p;

[0115] ai, bi, ci, di, and ei are fitting coefficients, obtained by fitting during the flow path design process of different models;

[0116] i is the corresponding different temperature intervals and the different coefficients taken, and the value range is 1 to 3.

[0117] The present invention 1. Flow path design of air conditioner system with variable flow rate

[0118] The present invention proposes an air conditioner with a variable flow rate and a control method thereof. Taking the pressure-enthalpy diagram of R32 refrigerant as an example, the refrigerant state changes during the evaporation process, that is, the refrigerant is a low-temperature and low-pressure gas-liquid two-phase mixed state when entering the evaporator. The dryness is relatively small when it just enters the evaporator. As the evaporation process proceeds, the gas phase component continues to increase, the liquid phase component continues to decrease, and the dryness becomes larger and larger until it is completely vaporized and enters the overheating section for overheating.

[0119] The present invention selects the design of "small diameter / few branches" when the dryness and specific volume of the refrigerant entering the front section of the evaporator are small, and improves the heat exchange effect by increasing the flow rate; as the evaporation process progresses, the gas phase components gradually increase, the refrigerant dryness gradually increases, and the specific volume becomes larger, so it is considered to select the design of "large diameter / multiple branches" when the dryness and specific volume of the rear section of the evaporator are large, and reduce the flow resistance loss of the refrigerant by reducing the flow rate of the refrigerant. While ensuring the heat exchange capacity of the evaporator, it also saves the material cost of the evaporator.

[0120] 2. Variable pipe diameter flow path design

[0121] The present invention is based on the refrigerant state change and heat exchange characteristics of the indoor heat exchanger of the air conditioner, and adopts a variable pipe diameter design of small→large flow path. By setting a pipe with a smaller inner diameter at the front section where the refrigerant just enters the evaporator, the refrigerant flow rate can be increased under a constant refrigerant mass flow rate, thereby achieving the effect of enhanced heat exchange; and in the process of the refrigerant evaporation, it gradually changes from a gas-liquid two-phase state to a gaseous state, and the dryness and specific volume gradually increase. Therefore, in the rear section of the evaporator, a pipe with a larger inner diameter is set to reduce the refrigerant flow rate, thereby effectively reducing flow losses and improving heat exchange efficiency.

[0122] like Figure 1-2 When judging whether the indoor heat exchanger is to be set up in sections, variable pipe diameter design will be given priority, mainly to facilitate uniform liquid separation and avoid affecting the performance of the entire machine.

[0123] Take the flow path design of a cabinet evaporator of our company as an example. Figure 1-2 The variable tube diameter design 1 shown in the figure sets the front section of the V-shaped two-fold heat exchanger to a small tube diameter and the rear section to a large tube diameter, wherein the front section uses a Φ5 tube with a smaller tube diameter and the rear section uses a Φ7 tube with a larger tube diameter. Currently, the commonly used tube diameters of heat exchangers are 5mm, 7mm, 9mm or 9.52mm, etc. The variable tube diameter design from small to large here only indicates the relative size of the inner tube diameter.

[0124] Among them, the front section of the heat exchanger refers to the front section in the refrigerant flow direction, such as the variable tube diameter design 2, the front section of the evaporator here refers to the outer side of the two-section heat exchanger, and the rear section of the evaporator refers to the inner side of the two-section heat exchanger.

[0125] In addition, the segmentation form of the heat exchanger is not limited to the V-shaped two-fold cabinet, but also includes various forms such as the hanging three-fold and the cabinet U-shaped segmentation.

[0126] 3. Variable branch flow path design

[0127] The present invention is based on the state change and heat exchange characteristics of the refrigerant in the indoor heat exchanger of the air conditioner, and adopts a variable branch design from few to many flow paths. Since the refrigerant is a gas-liquid two-phase mixed state with low pressure and low temperature when entering the evaporator, the dryness is relatively small when it just enters the evaporator. As the evaporation process proceeds, the gas phase component continues to increase, the liquid phase component continues to decrease, and the dryness becomes larger and larger until it is completely vaporized and enters the superheating section for superheating. If the refrigerant is divided into multiple branches when entering the evaporator, since the refrigerant at the inlet has a low dryness and a small specific volume, multiple branches will reduce the flow rate in the tube, reduce the heat exchange coefficient, and affect the heat exchange effect of the refrigerant. It is beneficial to heat transfer to have no branches or fewer branches at the evaporator inlet. When the dryness gradually increases, the gaseous refrigerant becomes more, the specific volume becomes larger, the refrigerant volume increases, and the flow rate also increases. In order to reduce the flow resistance of the refrigerant, multiple branches should be designed to reduce the flow rate.

[0128] When judging whether the indoor heat exchanger is an integral type (for segmented setting), variable branch design will be given priority. In addition to considering the impact of uniform liquid separation, attention should also be paid to the heat transfer effect between flow paths with different pipe diameters.

[0129] Take the U-shaped evaporator flow path design of the cabinet as an example. Figure 3-6As shown, flow path 1, flow path 2, flow path 3, and flow path 4 are all variable branch flow path designs from few to many, among which flow path 1 places the few branch flow path at the lower end of the heat exchanger in the gravity direction, while flow path 2, flow path 3, and flow path 4 place the few branch flow path at the upper end of the heat exchanger in the gravity direction; in addition, flow path 1 and flow path 2 are both variable branch flow path designs from 2 to 4, while flow path 3 and flow path 4 are variable branch flow path designs from 3 to 4 and 2 to 6, respectively.

[0130] The variable branch flow design of "few → more" here refers only to the number of branches of the diversion, that is, it is necessary to make fewer branches in the front section of the flow direction of the refrigerant entering the evaporator, and make more branches in the rear section of the flow direction of the refrigerant in the evaporator. The specific number of branches and the location of the few branches / multiple branches at the upper / lower end of the heat exchanger need to be determined according to the actual size of the heat exchanger and the performance of the whole machine.

[0131] 4. Optimization control logic of the flow path design of the variable flow rate air conditioner of the present invention

[0132] In order to take into account the cooling and heating performance of the air conditioner, the industry usually designs the evaporator system based on the performance requirements of the heating condition, without personalized design based on the refrigerant state changes and heat exchange characteristics. Usually, the evaporator size is relatively large, and it is easy to cause serious overheating at the heat exchanger outlet, which not only affects the evaporator's heat exchange capacity, but also increases the evaporator cost. This patent designs variable pipe diameters and variable branches according to the changes in the refrigerant operating state in the evaporator to adjust the refrigerant flow rate in the evaporator as the refrigerant state changes.

[0133] Based on the above variable flow rate flow path design method, the corresponding internal and external fan speeds, compressor frequency, and electronic expansion valve opening should also be adaptively controlled accordingly. In the actual evaporator pipeline experimental test, the rationality of the current flow path design is judged by the relationship between the actual superheat ΔT1 and the target superheat ΔT.

[0134] (1) The target superheat ΔT can be expressed as:

[0135] ΔT=a i F+b i R 外 +c i R 内 +d i P+e i ;

[0136] According to the difference between the indoor ambient temperature and the air conditioning set temperature during the experiment, △t in The size of corresponds to the target superheat calculation formula, as shown in Table 1 above.

[0137] in,

[0138] t1 is used to compare with △t in For comparison of size, generally -2℃~0℃;

[0139] t2 is used to compare with △t in For comparison of size, 0℃~2℃ is generally used;

[0140] The target superheat ΔT during the experimental test has a value range of 1°C to 3°C (because the target superheat ΔT has a range, the coefficients a1\a2, etc. do not limit the range);

[0141] F is the frequency adjustment amplitude of the compressor, and its value range is 0HZ~5HZ;

[0142] Rout is the outdoor fan speed adjustment amplitude, ranging from 0rpm to 100rpm;

[0143] R is the indoor fan speed adjustment amplitude, the value range is 0rpm~50rpm;

[0144] P is the opening adjustment amplitude of the electronic expansion valve, and its value range is 0p~50p;

[0145] a i , b i 、c i d i 、e i is the fitting coefficient, obtained by fitting during the flow path design process of different models;

[0146] i is the corresponding different temperature intervals and the different coefficients taken, and the value range is 1 to 3.

[0147] (2) Superheat control logic based on variable flow rate flow path design

[0148] Detect the current actual superheat ΔT1 and compare it with the target superheat ΔT:

[0149] 1) When ΔT1≤ΔT, it indicates that the refrigerant heat exchange in the evaporator is insufficient. The first choice is to adjust the load parameters. The compressor frequency F can be increased (increasing the speed of work, improving the efficiency of the system, and making the evaporator heat exchange more sufficient), or increasing the speed of the internal and external fans R1, R2, or reducing the opening P of the electronic expansion valve to allow the refrigerant to fully exchange heat. If the problem still cannot be improved, consider increasing the number of large-diameter / multi-branch pipes in the rear section of the evaporator to reduce the refrigerant flow rate for sufficient heat exchange.

[0150] 2) When ΔT1 = ΔT, it indicates that the current flow path design and its load parameter design are relatively reasonable.

[0151] 3) When ΔT1>ΔT, it indicates that the refrigerant in the evaporator is seriously overheated. The first choice is to adjust the load parameters. The refrigerant flow rate can be increased by reducing the compressor frequency F, or reducing the internal and external fan speeds R1, R2, or increasing the opening of the electronic expansion valve to avoid overheating losses. If the situation still cannot be improved, consider increasing the number of small-diameter / few-branch pipes in the front section of the evaporator to increase the refrigerant flow rate for enhanced heat exchange.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A heat exchanger, characterized in that: include: The front section (1) and the rear section (2) are such that, along the flow direction of the refrigerant, the front section (1) is located upstream of the rear section (2), and the pipe diameter of the front section (1) is smaller than the pipe diameter of the rear section (2), and / or the number of branches of the front section (1) is smaller than the number of branches of the rear section (2); the pipe diameter size and / or the number of branches of the front section (1) can be adjusted according to the degree of superheat of the heat exchanger, and / or the pipe diameter size and / or the number of branches of the rear section (2) can be adjusted according to the degree of superheat of the heat exchanger.

2. The heat exchanger according to claim 1, characterized in that: If the actual superheat is less than the target superheat, the pipe diameter of the front section (1) can be reduced and / or the number of branches of the front section (1) can be reduced, and / or the pipe diameter of the rear section (2) can be increased and / or the number of branches of the rear section (2) can be increased; If the actual superheat is greater than the target superheat, the pipe diameter of the front section (1) can be increased and / or the number of branches of the front section (1) can be increased, and / or the pipe diameter of the rear section (2) can be decreased and / or the number of branches of the rear section (2) can be decreased.

3. An air conditioner, characterized in that: The heat exchanger comprises the heat exchanger according to any one of claims 1 to 2, and further comprises a compressor, an internal fan, an external fan and a throttling device.

4. A method for controlling an air conditioner as claimed in claim 3, characterized in that: include: Detection step: detect the actual overheat degree ΔT1 of the air conditioner. A judgment step, comparing the actual superheat ΔT1 with the target superheat ΔT; A control step, when ΔT1≤ΔT, controlling to reduce the pipe diameter of the front section (1) and / or controlling to reduce the number of branches of the front section (1), and / or controlling to increase the pipe diameter of the rear section (2) and / or controlling to increase the number of branches of the rear section (2); When ΔT1>ΔT, the diameter of the pipe of the front section (1) is controlled to be increased and / or the number of branches of the front section (1) is controlled to be increased, and / or the diameter of the pipe of the rear section (2) is controlled to be decreased and / or the number of branches of the rear section (2) is controlled to be reduced.

5. The control method according to claim 4, characterized in that: The control step, before controlling and adjusting the pipe diameter and / or the number of branches of the front section (1) and / or the rear section (2), also controls and adjusts the frequency of the compressor to change, and / or controls the speed of the fan to change, and / or controls the opening size P of the throttling device to change.

6. The control method according to claim 5, characterized in that: Control steps: when ΔT1<ΔT, control to increase the compressor frequency, and / or control to increase the speed R1 of the inner fan, control to increase the speed R2 of the outer fan, and / or control to reduce the opening P of the throttling device; when ΔT1>ΔT, control to reduce the compressor frequency, and / or control to reduce the speed R1 of the inner fan, control to reduce the speed R2 of the outer fan, and / or control to increase the opening P of the throttling device; when ΔT1=ΔT, keep the current state unchanged.

7. The control method according to claim 5 or 6, characterized in that: In the control step, the target superheat ΔT is calculated as follows: ΔT = a i F+b i R 外 +c i R 内 +d i P+e i , that is, through the compressor frequency F, the internal fan speed R 内 , External fan speed R 外 and the opening degree P of the throttling device to calculate the target superheat ΔT under this operating condition.

8. The control method according to claim 7, characterized in that: F is the frequency adjustment amplitude of the compressor, and its value range is 0HZ~5HZ; R 外 The speed adjustment amplitude of the outdoor fan is in the range of 0rpm to 100rpm; R 内 The speed adjustment amplitude of the indoor fan is in the range of 0rpm to 50rpm; P 外 The opening adjustment amplitude of the electronic expansion valve ranges from 0p to 50p; The target superheat ΔT ranges from 1°C to 3°C.

9. The control method according to claim 7 or 8, characterized in that: a i , b i 、c i ,d i 、e i is the fitting coefficient, obtained by fitting during the flow path design process of different models; i is the corresponding different temperature intervals and the different coefficients taken, and the value range is 1 to 3.

10. The control method according to claim 9, characterized in that: According to the difference between the indoor ambient temperature and the air conditioning set temperature △t in The size of a i , b i 、c i ,d i and e i The value of When △t in ∈(-6℃, t1), i=1, ΔT=a1F+b1R 外 +c1R 内 +d1 P+e1; When △t in When ∈[t1, t2], i=2, ΔT=a2F+b2R 外 +c2R 内 +d2 P+e2; To △t in When ∈(t2, 6℃), i=3, ΔT=a3F+b3R 外 +c3R 内 +d3 P+e3, Among them, t1 is -2℃~0℃; t2 is 0℃~2℃.

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