A heat pump unit

Abstract

The present application relates to a kind of heat pump unit, using the method of refrigerant counter heat pump cycle to defrost outdoor heat exchanger, and based on this design a kind of defrosting control method, by obtaining the continuous running time of compressor, heating cumulative running time and ambient temperature jointly to judge to start defrosting, and using the discharge temperature, condensation temperature obtained to adjust defrosting opening degree, and to the transition stage before exiting defrosting and turns heating mode using water temperature and back gas temperature control electronic expansion valve opening degree, and then control the frequency of compressor.The method can effectively judge the frost degree, avoid the problem that defrosting is started for a long time;The frequency of electronic expansion valve before the heating of the defrosting end is designed to control, effectively solve the problem of oil return during defrosting, ensure the reliable operation of unit.

Description

Technical Field

[0001] This invention relates to the field of heat pumps, and more particularly to a heat pump unit. Background Technology

[0002] Heat pump units are highly efficient energy-saving devices. However, when operating in outdoor environments with excessively low temperatures and high relative humidity, their outdoor heat exchangers are particularly prone to frosting, sometimes to the point of becoming unusable. This leads to a continuous decrease in the heating efficiency of the heat pump unit, reducing its overall energy efficiency. Therefore, it is necessary to set up defrost control to defrost the frosted outdoor heat exchanger.

[0003] Currently, heat pump units mainly use a refrigerant reverse heat pump cycle to defrost the outdoor heat exchanger. When the heat pump unit detects that the outdoor coil temperature has dropped to the defrost set temperature, the defrost program is activated, switching the four-way valve to allow high-temperature refrigerant to enter the outdoor heat exchanger and release heat to melt the frost on the outer surface of the outdoor heat exchanger. When the heat pump unit is in a low ambient temperature (below -10℃), problems such as incomplete defrosting, prolonged frost buildup before defrosting is initiated, high-pressure alarms during defrosting, and defrost liquid slugging are prone to occur. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a heat pump unit that, through an improved defrosting control method, effectively avoids problems such as incomplete defrosting, prolonged defrosting time, high-pressure defrosting alarms, and defrosting liquid slugging that occur when the heat pump unit is operating at low ambient temperatures (below -10℃).

[0005] A heat pump unit includes a compressor, a four-way valve, an evaporator, an electronic expansion valve, and a condenser connected sequentially via a refrigerant circulation pipeline, as well as several temperature sensors and several pressure sensors, and a controller electrically and / or communicatively connected to the compressor, the four-way valve, the electronic expansion valve, the temperature sensors, and the pressure sensors. The controller controls the defrosting of the heat pump unit in the following manner:

[0006] S10 acquires the compressor's continuous running time, the compressor's cumulative heating running time, and the ambient temperature. If the compressor's continuous running time is greater than the preset minimum heating time, and the compressor's cumulative heating running time is greater than the preset defrost interval time, and the ambient temperature meets the temperature control start conditions, then a defrost start signal is output.

[0007] S20 enters defrosting operation according to the defrosting start signal of the heat pump unit, and obtains the exhaust temperature, condensing temperature and preset opening adjustment temperature difference threshold in real time. It also determines the defrosting opening of the electronic expansion valve according to the temperature difference between the exhaust temperature and the condensing temperature and the preset opening adjustment temperature difference threshold.

[0008] S30 acquires the defrosting operation time, coil temperature, or outlet water temperature in real time, and determines whether the defrosting operation time, coil temperature, or outlet water temperature meets the defrosting exit condition. If it does, it outputs an exit defrosting signal.

[0009] S40 acquires the inlet water temperature and return gas temperature in real time during the transition control before the heat pump unit enters heating mode based on the defrosting signal exit, and adjusts the opening degree of the electronic expansion valve during the transition phase according to the inlet water temperature and return gas temperature.

[0010] Compared with existing technologies, the heat pump unit of this invention uses a refrigerant reverse heat pump cycle to defrost the outdoor heat exchanger. Specifically, it determines the start of defrosting by acquiring the compressor's continuous running time, cumulative heating running time, and ambient temperature. This effectively judges the degree of frost and avoids the problem of long frost time before defrosting is initiated. Furthermore, during the transition phase before exiting defrosting and switching to heating mode, the opening of the electronic expansion valve is controlled by the inlet water temperature and return gas temperature, thereby controlling the compressor's frequency increase. This effectively solves the problem of oil shortage and liquid return during defrosting and ensures reliable unit operation.

[0011] Furthermore, the specific conditions for activating the temperature control are as follows:

[0012] The ambient temperature is compared with a preset ambient temperature start-up threshold:

[0013] If the ambient temperature is greater than or equal to the ambient temperature start threshold, the coil temperature is further obtained and compared with the preset coil temperature start threshold. If the coil temperature is less than or equal to the coil temperature start threshold and the situation lasts for more than 1 minute, a defrost start signal is output; otherwise, no defrost start signal is output.

[0014] If the ambient temperature is lower than the ambient temperature start threshold, the first temperature difference between the ambient temperature and the coil temperature is further calculated, and the first temperature difference is compared with the preset start temperature difference threshold. If the first temperature difference is greater than or equal to the start temperature difference threshold, and the situation lasts for more than 1 minute, a defrost start signal is output; otherwise, a defrost start signal is not output.

[0015] Furthermore, the specific conditions for activating the temperature control are as follows:

[0016] The ambient temperature is compared with a preset first ambient temperature start-up threshold:

[0017] If the ambient temperature is greater than the preset first ambient temperature start threshold, no defrosting start signal will be output.

[0018] If the ambient temperature is less than or equal to the first ambient temperature start-up threshold, then the ambient temperature is further compared with the preset second ambient temperature start-up threshold:

[0019] If the ambient temperature is greater than the second ambient temperature start threshold, no defrosting start signal will be output;

[0020] If the ambient temperature is less than or equal to the second ambient temperature start-up threshold, and this condition persists for more than 1 minute, then the compressor's cumulative heating operation time will be further compared with the preset cumulative heating operation time limit:

[0021] If the cumulative heating time is greater than or equal to the cumulative heating time limit, a defrost start signal will be output; otherwise, a defrost start signal will not be output.

[0022] The ambient temperature mentioned is the ambient temperature monitored 10 minutes after the compressor started.

[0023] Furthermore, step S40 adjusts the opening degree of the electronic expansion valve using the following method:

[0024] S41, based on the defrost exit signal, controls the four-way valve to switch from cooling connection mode to heating connection mode, then obtains the inlet water temperature and compares the inlet water temperature with the preset inlet water temperature adjustment threshold T. IW-TV Comparison:

[0025] If the inlet water temperature is lower than the inlet water temperature adjustment threshold, then proceed to step S42;

[0026] If the inlet water temperature is greater than or equal to the inlet water temperature adjustment threshold, then proceed to step S43;

[0027] During the first time period, S42 controls the opening of the electronic expansion valve to 90% of its pre-defrost opening; during the second time period, it acquires the return gas temperature, calculates the return gas superheat and the target return gas superheat, and calculates and controls the opening of the electronic expansion valve as follows:

[0028] When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 5℃,

[0029] When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 3℃ and less than or equal to 5℃,

[0030] When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 0℃ and less than or equal to 3℃,

[0031] In the above formula, K represents the opening degree of the electronic expansion valve, and ΔT RG Indicates the degree of superheat in the return gas. Indicates the target return gas superheat, and I represents the control parameter of the electronic expansion valve;

[0032] S43 During the first time period, the controller controls the opening of the electronic expansion valve to the initial opening determined by the ambient temperature and the inlet water temperature when the heat pump unit is started; during the second time period, the return gas temperature is acquired and the return gas superheat and the target return gas superheat are calculated, and the opening of the electronic expansion valve is calculated and controlled in the manner shown in step S42.

[0033] Furthermore, the target return gas superheat is calculated as follows:

[0034]

[0035] In the formula, The target return gas superheat is represented by T, which represents the preset parameter for calculating the target return gas superheat, and its value is preferably 10; t represents the time during which the return gas temperature is acquired in real time during the second time period.

[0036] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a heat pump unit under defrosting control according to an embodiment of the present invention;

[0038] Figure 2 This is a flowchart of a defrosting control method for a heat pump unit according to an embodiment of the present invention;

[0039] Figure 3 This is a flowchart illustrating the start-up defrosting judgment process for a heat pump unit according to an embodiment of the present invention;

[0040] Figure 4 This is a flowchart illustrating the start-up defrosting judgment process for a heat pump unit according to another embodiment of the present invention. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention.

[0042] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; and the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0043] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only for distinction and not to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0044] To address the problems of incomplete defrosting, untimely defrosting, high-pressure defrosting reports, liquid slugging, and false defrosting that arise when using external coil temperature to determine the start and end of the defrosting procedure in low ambient temperatures (below -10℃) for heat pump units, this invention proposes a heat pump unit that employs an improved frosting degree judgment system for reliable and precise defrosting control. Specifically, by analyzing compressor running time, ambient temperature, and coil temperature, the degree of frosting on the evaporator is determined, thereby determining the defrosting time. This ensures that the heat pump unit defrosts promptly and thoroughly. Furthermore, the defrosting opening is adjusted using exhaust temperature and condensing temperature. During the transition phase before exiting defrosting and switching to heating mode, the opening of the electronic expansion valve is controlled by inlet water temperature and return gas temperature, thereby controlling the compressor's frequency increase. This effectively solves the problem of insufficient oil return during defrosting, ensuring reliable unit operation.

[0045] For specific implementation details, please refer to [link / reference]. Figure 1 The heat pump unit proposed in this invention includes a compressor 10, a four-way valve 20, a condenser 30, an electronic expansion valve 40, an evaporator 50, multiple temperature sensors (not shown), multiple pressure sensors (not shown), a controller (not shown), a fan (not shown), and other auxiliary pipes. The compressor 10, four-way valve 20, condenser 30, electronic expansion valve 40, and evaporator 50 are sequentially connected in a refrigerant pipeline; the controller is electrically or communicatively connected to the compressor 10, four-way valve 20, electronic expansion valve 40, multiple temperature sensors, multiple pressure sensors, and the fan. Specifically, when the heat pump unit defrosts, the exhaust port A of the compressor 10, the inlet D of the four-way valve 20, the first working port E of the four-way valve 20, the evaporator 50, the electronic expansion valve 40, the condenser 30, the second working port C of the four-way valve 20, the return port S of the four-way valve 20, and the return port B of the compressor 10 are connected in sequence to form a refrigerant circulation pipeline. This allows the high-temperature and high-pressure gaseous refrigerant generated by the compressor 10 to flow through the evaporator 50, releasing heat to the evaporator 50 and heating and defrosting the frost on its outer surface.

[0046] The plurality of temperature sensors includes at least a first temperature sensor (not shown), a second temperature sensor (not shown), a third temperature sensor (not shown), a fourth temperature sensor (not shown), a fifth temperature sensor (not shown), and a sixth temperature sensor (not shown); wherein, the placement of the first temperature sensor is not limited in this application, as long as its placement allows it to transmit the ambient temperature T. E The signal is transmitted to the controller; the second temperature sensor is installed in the evaporator 50, and it measures the coil temperature T of the evaporator 50. P The signal is transmitted to the controller; the third temperature sensor is located at the inlet of the condenser 30, and it measures the condensation temperature T of the gaseous refrigerant flowing into the condenser 30. C The signal is transmitted to the controller; the fourth sensor is located at the outlet of the evaporator and measures the return gas temperature T. RG The signal is transmitted to the controller; the fifth sensor is located at the outlet of the condenser, and it measures the outlet water temperature T. OW The signal is transmitted to the controller; the sixth sensor is located at the water inlet of the condenser, and it measures the inlet water temperature T. IW The signal is transmitted to the controller.

[0047] The plurality of pressure sensors includes at least a first pressure sensor (not shown) and a second pressure sensor (not shown). The first pressure sensor is located at the exhaust port A of the compressor 10, and measures the exhaust pressure P of the compressor 10. Exhaust The signal is transmitted to the controller, which converts the acquired exhaust port pressure into exhaust temperature T. Exhaust The second pressure sensor is installed at the return port B of the compressor 10, and it measures the return pressure P of the compressor 10. R The information is transmitted to the controller.

[0048] The controller receives temperature signals from each temperature sensor, pressure signals from each pressure sensor, and operating frequency and time signals from the compressor 10; and obtains the minimum heating time set by the heat pump unit. Defrosting interval t DF Ambient temperature start-up threshold T E-TV and / or the first ambient temperature start-up threshold Second ambient temperature start-up threshold Coil temperature start-up threshold T P-TV Activate the temperature difference threshold ΔT TV Heating cumulative operating time limit Opening adjustment temperature difference threshold Longest defrosting time and / or coil temperature exit threshold T P-ED First defrosting exit monitoring time t1-ED And / or defrost outlet water temperature T OW-ED Second defrost exit monitoring time t 2-ED Inlet water temperature regulation threshold T IW-TV .

[0049] The controller sends defrosting start or defrosting end signals to the compressor 10 and the four-way valve 20 via the defrosting start and defrosting end judgment programs stored thereon, controlling the valve switching of the four-way valve 20; and sends an adjustment opening signal to the electronic expansion valve 40 via the defrosting opening degree control program stored thereon, controlling the opening degree adjustment of the electronic expansion valve 40.

[0050] Please see Figure 2 Specifically, the controller controls the defrosting operation of the heat pump unit by controlling the opening of the electronic expansion valve, including the following steps.

[0051] (I) Defrost Activation Detection

[0052] S10 acquires the compressor's continuous running time, the compressor's cumulative heating running time, and the ambient temperature. If the compressor's continuous running time is greater than the preset minimum heating time, the compressor's cumulative heating running time is greater than the preset defrost interval time, and the ambient temperature meets the temperature control start conditions, then a defrost start signal is output.

[0053] Please see Figure 3 This step includes the following sub-steps.

[0054] S11 obtains the continuous running time t of the compressor. c and the continuous running time t c With the preset minimum heating time Comparison:

[0055] If the continuous running time t c Less than or equal to minimum heating time Then no defrost start signal will be output;

[0056] If the continuous running time t c Greater than the minimum heating time Then proceed to step S12.

[0057] The minimum heating time When a heat pump unit is operating in heating mode, the minimum time during which the heat pump unit operates in heating mode is defined as the period between the end of one defrost cycle and the start of the next defrost cycle. The preferred time is 40 to 45 minutes, which can be adjusted according to the operation of the heat pump unit and the climate characteristics of the application scenario.

[0058] S12 further obtains the compressor's cumulative heating operation time. The cumulative heating operation time The preset defrost interval t DF Comparison:

[0059] If the cumulative heating operation time Less than or equal to the defrosting interval t DF If so, no defrost start signal will be output;

[0060] If the cumulative heating operation time Greater than the defrost interval t DF Then proceed to step S13.

[0061] The defrosting interval refers to the period from the end of one defrosting control to the start of the next defrosting control. The defrosting interval is preferably 50 to 60 minutes and can be adjusted according to the operation of the heat pump unit and the climate characteristics of the application scenario.

[0062] Furthermore, when the heat pump unit is first powered on and starts operating in heating mode, the defrosting interval t1 for the first defrosting is... DF The preferred time is 8-10 minutes.

[0063] S13 further obtains the ambient temperature T E and coil temperature T P And determine the ambient temperature T E With the preset ambient temperature start-up threshold T E-TV The coil temperature T P With the preset coil temperature start-up threshold T P-TV The ambient temperature T E With coil temperature T P The first temperature difference value and the preset start-up temperature difference threshold ΔT TV If the relationship meets the defrosting start condition, a defrosting control signal is output.

[0064] This step includes the following sub-steps.

[0065] S131 obtains the ambient temperature T E The ambient temperature T E With the preset ambient temperature start-up threshold T E-SD Comparison:

[0066] If the ambient temperature T E Greater than or equal to the ambient temperature start-up threshold T E-SD Then, the coil temperature T is further obtained. P The temperature T of the coil P With the preset coil temperature start-up threshold T P-SD Comparison:

[0067] Such as coil temperature T P Less than or equal to the coil temperature start-up threshold T P-SD If the above situation lasts for more than 1 minute, a defrosting start signal will be output; otherwise, no defrosting start signal will be output.

[0068] If the ambient temperature T E Less than the ambient temperature start-up threshold T E-SD Then proceed to step S132.

[0069] The preset ambient temperature start-up threshold T E-SD The preferred temperature range is 3℃ to 5℃, with a coil temperature start-up threshold T. P-SD The preferred temperature range is -3℃ to -1℃. The above start-up threshold can be adjusted according to the operation of the heat pump unit and the climate characteristics of the application scenario.

[0070] S132 further calculates the ambient temperature T E With coil temperature T P The first temperature difference value ΔT1 is then compared with the preset start-up temperature difference threshold ΔT. TV Comparison:

[0071] If the first temperature difference value ΔT1 is greater than or equal to the starting temperature difference threshold ΔT TV If the above situation lasts for more than 1 minute, a defrosting start signal will be output; otherwise, a defrosting start signal will not be output.

[0072] If the first temperature difference value ΔT1 is less than the starting temperature difference threshold ΔT TV If not, the defrost start signal will not be output.

[0073] The first temperature difference ΔT1 satisfies ΔT1=T E -T P The preset start-up temperature difference threshold ΔT TV The optimal temperature is 5℃ to 7℃, but this can be adjusted based on the operating conditions of the heat pump unit and the climate characteristics of the application scenario.

[0074] In practical implementation, based on the ambient temperature T E The temperature range in question is adjusted using temperature compensation to adjust the starting temperature difference threshold ΔT. TV The corrected starting temperature difference threshold ΔT is obtained by performing the correction. T ′ V As shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] Please see Figure 4 In other embodiments, step S13 can be replaced by S`13.

[0079] S`13 further obtains the compressor start-up time period t. start After the ambient temperature and the cumulative heating operation time of the compressor And determine the ambient temperature With the preset ambient temperature start-up threshold T E-TV The cumulative heating operation time Compared with the preset cumulative heating operation time limit If the relationship between the two conditions is met, the defrosting start signal is output.

[0080] S`131 obtains the compressor start-up time period t. start After the ambient temperature and the ambient temperature With the preset first ambient temperature start-up threshold Comparison:

[0081] If the ambient temperature Greater than the preset first ambient temperature start-up threshold Then no defrost start signal will be output;

[0082] If the ambient temperature Less than or equal to the first ambient temperature start-up threshold Then further compare the ambient temperature With the preset second ambient temperature start-up threshold

[0083] Such as ambient temperature Greater than the second ambient temperature start-up threshold Then no defrost start signal will be output;

[0084] Such as ambient temperature Less than or equal to the second ambient temperature start-up threshold If the situation continues for more than 1 minute, then step S`132 will be executed.

[0085] The time period t start Preferably, it is 8 to 12 minutes. The preset first ambient temperature start-up threshold... Preferably, the temperature is 12℃ to 15℃; the preset second ambient temperature start-up threshold The optimal temperature is 5℃ to 7℃. This can be adjusted based on the operating conditions of the heat pump unit and the climate characteristics of the application scenario.

[0086] S`132 further obtains the compressor's cumulative heating operation time. The cumulative heating operation time Compared with the preset cumulative heating operation time limit Comparison:

[0087] If the cumulative heating operation time Greater than or equal to the cumulative heating operation time limit Then output a defrosting start signal;

[0088] In other cases, no defrosting start signal will be output.

[0089] The preset cumulative heating operation time limit The preferred time is 170 to 190 minutes. These parameters can be adjusted according to the operation of the heat pump unit and the climate characteristics of the application scenario.

[0090] In other embodiments, steps S13 and S`13 can be judged simultaneously. If either condition is met, defrosting control can be started.

[0091] This invention does not limit the controller to first determining the continuous operating time t of the compressor. c With the preset minimum heating time The comparative judgment should be based on the cumulative heating time of the compressor. The preset defrost interval t DF The comparison judgment is still the temperature comparison judgment shown in steps S13 and / or S`13 above, as long as the logic is set to satisfy: the continuous running time t of the compressor c Greater than the minimum heating time And the cumulative heating operation time of the compressor Greater than the defrost interval t DF Furthermore, the ambient temperature meets the temperature control start-up conditions. Once all three conditions are met, a defrosting start signal is output.

[0092] (II) Defrosting Control

[0093] S20, upon receiving the defrosting start signal, acquires the exhaust temperature, condensing temperature, and preset opening adjustment temperature difference threshold in real time after the heat pump unit enters defrosting operation. Based on the temperature difference between the exhaust temperature and the condensing temperature and the preset opening adjustment temperature difference threshold, S20 determines the defrosting opening of the electronic expansion valve.

[0094] According to the defrosting start signal, the controller controls the four-way valve 20 to switch from heating connection mode to cooling connection mode, and controls the opening of the electronic expansion valve 40 to adjust to the initial defrosting opening K1.

[0095] The initial defrosting opening K1 is preferably 300.

[0096] S22 obtains the exhaust temperature T Exhaust Condensation temperature T C And calculate the exhaust temperature T Exhaust With condensation temperature T C The second temperature difference value ΔT2 is then compared with the preset opening adjustment temperature difference threshold. Comparison:

[0097] If the second temperature difference value ΔT2 is greater than or equal to the opening adjustment temperature difference threshold The opening degree of the electronic expansion valve 40 is then maintained at the initial defrosting opening degree K1;

[0098] If the second temperature difference value ΔT2 is less than the opening adjustment temperature difference threshold Then the opening degree of the electronic expansion valve 40 is adjusted to the defrost opening degree K2.

[0099] The second temperature difference ΔT2 satisfies ΔT2=T Exhaust -T C The preset opening degree adjustment temperature difference threshold The optimal temperature range is 9℃ to 11℃, which can be adjusted based on the operating conditions of the heat pump unit and the climate characteristics of the application scenario. The defrosting opening degree K2 is preferably 100.

[0100] Furthermore, to protect the compressor, the compressor's discharge port pressure P needs to be monitored in real time during the defrosting process. high and return air pressure P low Therefore, the defrosting control process also includes the following steps.

[0101] S23 obtains the exhaust port pressure P high and return air pressure P low and the preset differential pressure threshold ΔP TV And calculate the exhaust port pressure P. high With return air pressure P low The pressure difference ΔP is calculated, and the pressure difference ΔP is compared with the pressure difference threshold ΔP. TV Comparison:

[0102] If the pressure difference ΔP is greater than or equal to the pressure difference threshold ΔP TV If so, start the fan and run it at a low speed;

[0103] If the pressure difference ΔP is less than the pressure difference threshold ΔP TV If not, the fan will not be started.

[0104] The pressure difference threshold ΔP TV The preferred pressure is 2.5 to 2.7 MPa.

[0105] (III) Exiting the defrosting judgment

[0106] S30 obtains defrost time t Defrosting And the defrosting time t Defrosting With the preset longest defrosting time Comparison:

[0107] If the defrosting time t Defrosting Less than the longest defrost time Then proceed to step S20;

[0108] If the defrosting time t Defrosting The longest defrosting time is greater than or equal to Then output an exit defrost signal.

[0109] The longest defrosting time The preferred time is 10 to 12 minutes.

[0110] In other embodiments, step S30 may be replaced by S`30.

[0111] S`30 obtains the coil temperature T P and the temperature T of the coil P With the preset coil temperature exit threshold T P-ED Comparison:

[0112] If the coil temperature T P Exit threshold T when the coil temperature is less than the coil temperature P-ED Then proceed to step S20;

[0113] If the coil temperature T P Exit threshold T when the coil temperature is greater than or equal to P-ED And the duration of the aforementioned situation is greater than or equal to the preset first defrost exit monitoring time t. 1-ED If the defrosting is completed, a defrosting exit signal will be output; otherwise, step S20 will be executed.

[0114] In practical implementation, the coil temperature exit threshold T P-ED and defrost exit monitoring time t ED The settings are shown in Table 2.

[0115] Table 2

[0116] Serial Number <![CDATA[Coil temperature exit threshold T P-ED (°C)]]> <![CDATA[First defrost exit monitoring time t ED (seconds)]]> 1 15～16 6～8 2 17～18 4～6 3 19～20 2～4

[0117] In other embodiments, step S30 may be replaced by S``30.

[0118] S``30 obtains the outlet water temperature T OW and the outlet water temperature T OW With the preset defrost outlet water temperature T OW -ED comparison:

[0119] If the outlet water temperature TOW ≥Defrost outlet water temperature T OW-ED Then proceed to step S20;

[0120] If the outlet water temperature T OW Less than the defrost outlet water temperature T OW-ED And the duration of the aforementioned situation is greater than or equal to the second defrost exit monitoring time t. 2-ED If the defrosting is completed, a defrosting exit signal will be output; otherwise, step S20 will be executed.

[0121] The defrost outlet water temperature T OW-ED The preferred temperature is 14℃~16℃; the second defrosting exit monitoring time t 2-ED The preferred time is 10 to 12 seconds.

[0122] (iv) Transition control before exiting defrosting and switching to heating mode

[0123] Based on the defrost exit signal, S40 initiates a transitional control phase before heating begins, and acquires the inlet water temperature T in real time. IW and return gas temperature T RG The opening degree of the electronic expansion valve during the transition phase is adjusted according to the inlet water temperature and the return air temperature.

[0124] This step includes the following sub-steps.

[0125] Based on the defrost exit signal, S41 controls the four-way valve 20 to switch from cooling connection mode to heating connection mode, and then obtains the inlet water temperature T. IW and the inlet water temperature T IW With the preset inlet water temperature adjustment threshold T IW-TV Comparison:

[0126] If the inlet water temperature T IW Less than the inlet water temperature regulation threshold T IW-TV Then proceed to step S42;

[0127] If the inlet water temperature T IW Greater than or equal to the inlet water temperature regulation threshold T IW-TV Then proceed to step S43.

[0128] The inlet water temperature adjustment threshold T IW-TV The preferred temperature is 44℃~46℃.

[0129] S42 controls the opening degree of the electronic expansion valve 40 to be the pre-defrost opening degree K during the first time period. PD 90%; during the second time period, the return gas temperature T was obtained. RG And calculate the return gas superheat ΔT RG Target return gas superheat The opening degree K of the electronic expansion valve 40 is calculated and controlled as follows, where I represents the control parameter of the electronic expansion valve 40:

[0130] When the return gas superheat ΔT RG With target return gas superheat When the absolute value of the difference is greater than 5℃,

[0131] When the return gas superheat ΔT RG With target return gas superheat When the absolute value of the difference is greater than 3℃ and less than or equal to 5℃,

[0132] When the return gas superheat ΔT RG With target return gas superheat When the absolute value of the difference is greater than 0℃ and less than or equal to 3℃,

[0133] The first time period refers to 0 to 60 seconds after the defrosting ends; the second time period refers to 0 to 220 seconds after the first time period ends.

[0134] The target return gas superheat Calculate as follows:

[0135]

[0136] Where T represents a preset parameter for calculating the target return gas superheat, and its value is preferably 10; t represents the return gas temperature T obtained in real time during the second time period. RG The time range is 0 to 220.

[0137] S43 controls the opening degree of the electronic expansion valve 40 during the first time period to be determined by the ambient temperature T when the heat pump unit is started. E and inlet water temperature T IW The initial opening degree K0 is determined; during the second time period, the return gas temperature T is obtained. RG And calculate the return gas superheat ΔT RG Target return gas superheat The opening degree K of the electronic expansion valve 40 is calculated and controlled in accordance with the method shown in step S42.

[0138] The heat pump unit of this invention uses the compressor's continuous running time, cumulative heating running time, and ambient temperature together to determine the start-up defrosting function. This effectively judges the degree of frost formation and avoids the problem of starting defrosting only after a long frost formation period. The frequency-increase opening control of the electronic expansion valve before heating ends after defrosting effectively solves the problem of oil shortage and liquid return during defrosting, ensuring reliable operation of the unit.

[0139] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A heat pump unit, comprising a compressor, a four-way valve, an evaporator, an electronic expansion valve, and a condenser connected sequentially via a refrigerant circulation pipeline, and a plurality of temperature sensors and a plurality of pressure sensors, and a controller electrically and / or communicatively connected to the compressor, the four-way valve, the electronic expansion valve, the temperature sensors, and the pressure sensors, characterized in that, The controller controls the defrosting of the heat pump unit in the following ways: S10 acquires the compressor's continuous running time, the compressor's cumulative heating running time, and the ambient temperature. If the compressor's continuous running time is greater than the preset minimum heating time, and the compressor's cumulative heating running time is greater than the preset defrost interval time, and the ambient temperature meets the temperature control start conditions, then outputs a defrost start signal. S20 The heat pump unit enters defrosting operation according to the defrosting start signal, and acquires the exhaust temperature, condensing temperature, and preset opening adjustment temperature difference threshold in real time. It then determines the defrosting opening of the electronic expansion valve based on the temperature difference between the exhaust temperature and the condensing temperature and the preset opening adjustment temperature difference threshold. Specifically: S21 According to the defrost start signal, the controller controls the four-way valve port to switch from heating connection mode to cooling connection mode, and adjusts the opening of the electronic expansion valve to the initial defrost opening. S22 acquires the exhaust temperature and condensation temperature, calculates the second temperature difference between the exhaust temperature and the condensation temperature, and compares the second temperature difference with a preset opening adjustment temperature difference threshold: If the second temperature difference value is greater than or equal to the opening adjustment temperature difference threshold, the opening of the electronic expansion valve is maintained at the initial defrosting opening. If the second temperature difference value is less than the opening adjustment temperature difference threshold, the opening of the electronic expansion valve is adjusted to the defrost opening. S30 acquires the defrosting operation time, coil temperature, or outlet water temperature in real time, and determines whether the defrosting operation time, coil temperature, or outlet water temperature meets the defrosting exit condition. If it does, it outputs an exit defrosting signal. S40, based on the defrost exit signal, performs transition control before the heat pump unit enters heating mode, acquires the inlet water temperature and return gas temperature in real time, and adjusts the opening of the electronic expansion valve during the transition phase according to the inlet water temperature and return gas temperature.

2. The heat pump unit according to claim 1, characterized in that, The specific conditions for activating the temperature control are as follows: The ambient temperature is compared with a preset ambient temperature start-up threshold: If the ambient temperature is greater than or equal to the ambient temperature start threshold, the coil temperature is further obtained and compared with the preset coil temperature start threshold. If the coil temperature is less than or equal to the coil temperature start threshold and this situation lasts for more than 1 minute, a defrost start signal is output; otherwise, no defrost start signal is output. If the ambient temperature is lower than the ambient temperature start threshold, the first temperature difference between the ambient temperature and the coil temperature is further calculated, and the first temperature difference is compared with the preset start temperature difference threshold. If the first temperature difference is greater than or equal to the start temperature difference threshold, and this situation lasts for more than 1 minute, a defrost start signal is output; otherwise, a defrost start signal is not output.

3. The heat pump unit according to claim 1, characterized in that, The specific conditions for activating the temperature control are as follows: The ambient temperature is compared with a preset first ambient temperature start-up threshold: If the ambient temperature is greater than the preset first ambient temperature start threshold, no defrosting start signal will be output. If the ambient temperature is less than or equal to the first ambient temperature start-up threshold, then the ambient temperature is further compared with the preset second ambient temperature start-up threshold: If the ambient temperature is greater than the second ambient temperature start threshold, no defrosting start signal will be output; If the ambient temperature is less than or equal to the second ambient temperature start-up threshold, and this condition persists for more than 1 minute, then the compressor's cumulative heating operation time will be further compared with the preset cumulative heating operation time limit: If the cumulative heating time is greater than or equal to the cumulative heating time limit, a defrost start signal will be output; otherwise, a defrost start signal will not be output. The ambient temperature mentioned is the ambient temperature monitored 10 minutes after the compressor started.

4. The heat pump unit according to claim 1, characterized in that, In step S30, the defrosting time is acquired in real time, and the defrosting exit determination is made using the following method: The defrosting time is compared with the preset longest defrosting time: If the defrosting time is less than the maximum defrosting time, proceed to step S20; If the defrosting time is greater than or equal to the maximum defrosting time, then output an exit defrosting signal.

5. The heat pump unit according to claim 1, characterized in that, In step S30, the coil temperature is acquired in real time, and the defrosting exit judgment is determined using the following method: The coil temperature is compared with a preset coil temperature exit threshold: If the coil temperature is lower than the coil temperature exit threshold, then proceed to step S20. If the coil temperature is greater than or equal to the coil temperature exit threshold, and the duration of this condition is greater than or equal to the preset first defrost exit monitoring time, then an exit defrost signal is output; otherwise, step S20 is executed.

6. The heat pump unit according to claim 1, characterized in that, In step S30, the outlet water temperature is acquired in real time, and the defrosting exit determination is made using the following method: The outlet water temperature is compared with the preset defrost outlet water temperature: If the outlet water temperature is greater than or equal to the defrost outlet water temperature, proceed to step S20; If the outlet water temperature is lower than the defrost outlet water temperature, and the duration of this condition is greater than or equal to the preset second defrost exit monitoring time, then an exit defrost signal is output; otherwise, step S20 is executed.

7. The heat pump unit according to any one of claims 1-6, characterized in that, Step S40 adjusts the opening of the electronic expansion valve using the following method: S41 Based on the defrost exit signal, the controller controls the four-way valve to switch from cooling connection mode to heating connection mode, then obtains the inlet water temperature and compares the inlet water temperature with a preset inlet water temperature adjustment threshold: If the inlet water temperature is lower than the inlet water temperature adjustment threshold, then proceed to step S42; If the inlet water temperature is greater than or equal to the inlet water temperature adjustment threshold, then proceed to step S43; S42 During the first time period, the controller controls the opening of the electronic expansion valve to 90% of the pre-defrost opening; during the second time period, the return gas temperature is acquired, and the return gas superheat and target return gas superheat are calculated, and the opening of the electronic expansion valve is calculated and controlled in the following manner: When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 5℃, ; When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 3℃ and less than or equal to 5℃, ; When the absolute value of the difference between the return gas superheat and the target return gas superheat is greater than 0℃ and less than or equal to 3℃, ; In the above formula, Indicates the opening degree of the electronic expansion valve. Indicates the degree of superheat in the return gas. Indicates the target return gas superheat. Indicates the control parameters of the electronic expansion valve; S43 During the first time period, the controller controls the opening degree of the electronic expansion valve to the initial opening degree determined by the ambient temperature and the inlet water temperature when the heat pump unit is started. During the second time period, the return gas temperature is obtained and the return gas superheat and target return gas superheat are calculated. The opening degree of the control electronic expansion valve is calculated in the manner shown in step S42.

8. The heat pump unit according to claim 7, characterized in that, The first time period refers to 0 to 60 seconds after the defrosting ends; the second time period refers to 0 to 220 seconds after the first time period ends.

9. The heat pump unit according to claim 8, characterized in that, The target return gas superheat is calculated as follows: In the formula, Indicates the target return gas superheat. This represents the preset parameter for calculating the target return gas superheat, with a value of 10. This indicates the time during which the return air temperature is acquired in real time during the second time period.

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