Air source heat pump defrosting control method suitable for different climate areas

Abstract

An air source heat pump defrosting control method suitable for different climate zones belongs to air source heat pump defrosting control methods, and adopts the specific scheme as follows: when an air source heat pump is applied to different climate zones, the temperature difference between outdoor air and the surface of an outdoor coil pipe is continuously monitored during frostless stable operation of a unit; and matching with a frostless temperature difference threshold value of the air source heat pump at the outdoor temperature corresponding to each climate zone, reversely deducing the climate zone where the air source heat pump is located, and further performing defrosting control by adopting a defrosting starting temperature difference control line of the climate zone. According to the defrosting control method, the climate area where the air source heat pump is located can be automatically recognized, and the reasonable defrosting starting temperature difference control line is selected, so that the defrosting accuracy of the air source heat pump can be greatly improved, the heating performance coefficient of the air source heat pump when the air source heat pump is applied to different climate areas is improved, the heating energy consumption of a building and the mistaken defrosting frequency are reduced, and the heating efficiency of the building is improved. And the interference of defrosting on the indoor thermal comfort of the building is reduced.

Description

Technical Field

[0001] The invention belongs to an air source heat pump defrosting control method, and in particular relates to an air source heat pump defrosting control method suitable for different climate zones. Background Art

[0002] Due to its good energy-saving effect, air source heat pumps have been widely used in building heating. However, under low temperature and high humidity conditions, air source heat pumps often encounter frosting problems. The main method to solve the frosting problem is defrosting. The current defrost control method is mainly designed based on the temperature difference between the outdoor air and the outdoor coil surface. When the air source heat pump is heating, as long as the temperature difference between the outdoor air and the outdoor coil surface reaches the set value, the defrost operation will be started. When designing the defrost control method, the manufacturer did not consider the impact of climate zones on frosting characteristics. As a result, when an air source heat pump is operated in different climate zones, the set value of the temperature difference between the outdoor air and the outdoor coil surface temperature when starting the defrost operation is the same. However, when the same air source heat pump unit is used in different climate zones, even at the same outdoor temperature, there are still large differences in the operating status, and the frosting rate varies significantly. For example, when the same air source heat pump is used in Harbin, Beijing, and Shanghai, because Harbin has the lowest outdoor design temperature for heating and the smallest heating area, at the same outdoor temperature, the compressor speed is the lowest and the unit frosting rate is the slowest; on the contrary, when heating in Shanghai, the unit frosting rate is the fastest. The difference in frosting rate leads to different defrosting start-up conditions for air source heat pumps. Therefore, the current defrost control method has the problem of poor applicability and cannot be applied to different climate zones. There is an urgent need for an air source heat pump defrost control method that is suitable for different climate zones. Summary of the Invention

[0003] In order to solve the problems existing in the background technology, the present invention provides an air source heat pump defrost control method suitable for different climate zones. In the control system of the air source heat pump, defrost starting temperature difference control lines suitable for different climate zones such as severe cold, cold, hot summer and cold winter are respectively set. When the air source heat pump is applied to different climate zones, the temperature difference between the outdoor air and the outdoor coil surface is continuously monitored when the unit is in frost-free and stable operation, and matched with the corresponding starting defrost temperature difference at different outdoor temperatures in each climate zone, the climate zone where the air source heat pump is located is inferred, and the defrost starting temperature difference control line of the climate zone is used for defrost control. Since the defrost control method can automatically identify the climate zone where the air source heat pump is located and select a reasonable defrost starting temperature difference control line, it can greatly improve the accuracy of air source heat pump defrosting, improve the heating performance coefficient of the air source heat pump when it is applied in different climate zones, reduce the building heating energy consumption and the frequency of false defrosting, and reduce the interference of defrosting on the indoor thermal comfort of the building.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A defrost control method for air source heat pumps applicable to different climate zones is disclosed. When the air source heat pump leaves the factory, defrost start temperature difference control lines applicable to different climate zones are set, and the defrost start temperature difference control line for one climate zone is selected as the basis for initial defrost determination. During actual heating, the climate zone in which the air source heat pump is actually used is determined based on operating data, and the corresponding defrost start temperature difference control line is selected and iteratively updated. The specific steps are as follows:

[0006] Step 1: During the actual application of the air source heat pump, the outdoor air temperature t1, the outdoor coil surface temperature t2 and the presence of frost are monitored every hour. The i-th monitoring result is recorded as t 1,i and t 2,i , calculate the outdoor air temperature t in real time 1,i and the outdoor coil surface temperature t 2,i The difference Δt i , use the initial defrost judgment basis to determine whether the air source heat pump unit is frosted when the data is collected. If it is frosted, the i value remains unchanged and the step is repeated; if it is not frosted, t 1,i and Δt i Save and proceed to step 2;

[0007] Step 2: When i≤n, increase the value of i by 1 and return to step 1, otherwise go to step 3;

[0008] Step 3: Δt based on different outdoor temperatures i Frost-free temperature difference threshold Δt at the outdoor temperature in different climate zones compared to air source heat pumps i,j , calculate the sum of the absolute values ​​of the differences ΔT j , and then according to ΔT j The minimum value of is used to infer the closest climate zone where the air source heat pump is located;

[0009] Step 4: Identify the closest climate zone as the climate zone where the air source heat pump is located, and select the defrost start temperature difference control line of the air source heat pump in the climate zone as the new defrost judgment basis, so that the air source heat pump can accurately defrost in different climate zones.

[0010] Furthermore, the defrost start temperature difference control line of the climate zone selected in step 1 is dynamically updated and automatically calibrated regularly.

[0011] Furthermore, the defrost start temperature difference control line of each climate zone is obtained by the following method: when developing the air source heat pump, a typical city in the hot summer and cold winter climate zone is selected, and the air source heat pump defrosting experiment is carried out by creating the load of the air source heat pump at different outdoor temperatures in the climate zone in the enthalpy difference laboratory. Based on the optimal defrost control point theory, the optimal defrost temperature difference at different temperatures is obtained, and the defrost start temperature difference control line of the hot summer and cold winter climate zone is obtained by fitting the optimal defrost temperature difference at different outdoor temperatures; the same method is used to obtain the defrost start temperature difference control line of the cold and extremely cold climate zones.

[0012] Furthermore, the frost-free temperature difference threshold Δt i,j It is obtained by the following method: When developing air source heat pumps, typical cities in different climate zones are selected. By creating the load of air source heat pumps at different outdoor temperatures in different climate zones in the enthalpy difference laboratory, frost-free heating experiments are carried out. The value is calculated by calculating the difference between the outdoor air temperature and the surface temperature of the outdoor heat exchanger.

[0013] Furthermore, the sum of the absolute values ​​of the differences ΔT j The calculation formula is:

[0014]

[0015] Where, j refers to the jth climate zone; Δt i,j is the frost-free temperature difference threshold at the same outdoor temperature in climate zone j;

[0016] ΔT j The smaller the value, the more Δt i The frost-free temperature difference threshold Δt of the air source heat pump in this climate zone i,j The closer they are, the higher the accuracy of defrost control using the defrost start temperature difference control line in that climate zone.

[0017] Furthermore, the defrost start temperature difference Δt changes with the outdoor temperature and has a maximum value. When the outdoor temperature is higher or lower than the outdoor temperature t3 corresponding to the maximum value of Δt, the defrost start temperature difference Δt decreases.

[0018] Furthermore, the outdoor temperature t3 corresponding to the maximum value of Δt varies in different climate zones, and the overall rule is: the lower the outdoor design temperature for heating is, the lower the outdoor temperature t3 corresponding to the maximum value of Δt is.

[0019] Furthermore, different climate zones include severe cold climate zones, cold climate zones, and hot summer and cold winter climate zones.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] When the air source heat pump unit of the present invention is used in a certain area, the climate zone in which the unit is located is automatically determined by the method described in the present invention, and the basis for defrosting determination is automatically adjusted, thereby reducing the frequency of false defrosting of the air source heat pump by more than 90% and improving the defrosting accuracy by more than 80%.

[0022] Reducing the frequency of false defrosts can improve the performance coefficient of air source heat pumps under "no-frost defrost" conditions by more than 35%. Compared with the currently widely used constant temperature difference-time defrost control method, the annual operating power consumption in Beijing is reduced by more than 14%;

[0023] This defrost control method can greatly improve the thermal comfort of indoor rooms. When the air source heat pump is in operation throughout the heating season, the thermal comfort time can reach more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the control method of the present invention; wherein, t 1,i —The outdoor air temperature monitored for the i-th time; t 2,i —The outdoor coil surface temperature monitored for the i-th time; Δt i —The temperature difference between the outdoor air and the outdoor coil surface monitored for the i-th time; i—the number of data monitoring, which can be 1, 2, 3, 4, etc.; n—the number of samples required for data analysis; j—climate zone code, 1 refers to extremely cold areas, 2 refers to cold areas, 3 refers to areas with hot summers and cold winters, etc.; ΔT j —Δt at different outdoor temperatures i The frost-free temperature difference threshold Δt of the air source heat pump at the outdoor temperature in each climate zone i,j The sum of the absolute values ​​of the differences in a certain climate zone. The smaller the value in a certain climate zone, the closer the application area is to that climate zone.

[0025] Figure 2 It is the defrost start-up temperature difference control line used by the air source heat pump in different climate zones during the experiment;

[0026] Figure 3 It is the carrier of this control method, namely the principle diagram of the air source heat pump system; among them, 1 is the compressor, 2 is the condenser, 3 is the expansion valve, and 4 is the evaporator. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The flow chart of the control method of the present invention is as follows: Figure 1As shown, the carrier of the control method is as follows Figure 3 As shown, it is a conventional air source heat pump, the exhaust port of the compressor 1 is connected to the inlet of the condenser 2, the outlet of the condenser 2 is connected to the inlet of the electronic expansion valve 3, the outlet of the electronic expansion valve 3 is connected to the inlet of the evaporator 4, and the outlet of the evaporator 4 is connected to the intake port of the compressor 1.

[0029] Example 1:

[0030] A defrosting control method for an air source heat pump suitable for different climate zones comprises the following steps:

[0031] (1) Before the air source heat pump leaves the factory, a typical city in the extremely cold, cold, and hot summer and cold winter climate zones is selected to test the heating capacity of the unit at the outdoor design temperature of the heating in the city, and the heating area in the three cities is calculated based on the building thermal index. Then, based on the heating area of ​​the three cities, the building heat load at different outdoor temperatures is calculated. The heat load of the air source heat pump at different outdoor temperatures in different cities is created in the enthalpy difference laboratory. Based on the optimal defrost control point theory, the optimal defrost temperature difference at different temperatures is obtained. Through data processing, the defrost start temperature difference control lines of the air source heat pump in the three climate zones are obtained. The results are shown in the attached figure. Figure 2 As shown. When leaving the factory, the attached Figure 2 The defrost start temperature difference control line in medium and cold areas formulates the original defrost control method.

[0032] (2) When the air source heat pump starts to be used in a certain area, the outdoor air temperature t1, the outdoor coil surface temperature t2 and the presence of frost are monitored every hour. The i-th monitoring result is recorded as t 1,i and t 2,i , calculate the outdoor air temperature t in real time 1,i and the outdoor coil surface temperature t 2,i The difference Δt i The initial defrost judgment basis is used to determine whether the air source heat pump unit is frosted when the data is collected. If it is frosted, the i value remains unchanged and the step is repeated; if it is not frosted, the t 1,i and Δt i Save and go to step 2.

[0033] (3) If i≤120, increase the value of i by 1 and return to repeat step (2); otherwise, go to step (4).

[0034] (4) Using Δt at different outdoor temperatures i Frost-free temperature difference threshold Δt at the outdoor temperature in different climate zones compared to air source heat pumps i,j , calculate the sum of the absolute values ​​of the differences ΔT j , the calculation formula is as follows:

[0035]

[0036] Where j refers to the j climate zone, Δt i,j is the frost-free temperature difference threshold at the same outdoor temperature in climate zone j.

[0037] ΔT j The climate zone corresponding to the minimum value is the climate zone closest to the area where the air source heat pump is located.

[0038] (5) The closest climate zone is identified as the climate zone where the air source heat pump is located, and the defrost start temperature difference control line of the air source heat pump in the climate zone is selected as the new defrost judgment basis, so that the air source heat pump can accurately defrost in different climate zones.

[0039] (6) Dynamically optimize the defrost control method and revise it every 20 days according to the above steps.

[0040] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A defrost control method for air source heat pumps suitable for different climate zones, characterized by: When the air source heat pump leaves the factory, the defrost start temperature difference control line is set for different climate zones, and the defrost start temperature difference control line of one climate zone is selected as the basis for initial defrost determination. In actual heating, the climate zone in which the air source heat pump is actually used is determined based on the operating data, and the corresponding defrost start temperature difference control line is selected and iteratively updated. The specific steps are as follows: Step 1: During the actual application of the air source heat pump, the outdoor air temperature t1, the outdoor coil surface temperature t2 and the presence of frost are monitored every hour. The i-th monitoring result is recorded as t 1,i and t 2,i , calculate the outdoor air temperature t in real time 1,i and the outdoor coil surface temperature t 2,i The difference Δt i , use the initial defrost judgment basis to determine whether the air source heat pump unit is frosted when the data is collected. If it is frosted, the i value remains unchanged and the step is repeated; if it is not frosted, t 1,i and Δt i Save and proceed to step 2; Step 2: When i≤n, increase the value of i by 1 and return to step 1, otherwise go to step 3; Step 3: Δt based on different outdoor temperatures i Frost-free temperature difference threshold Δt at the outdoor temperature in different climate zones compared to air source heat pumps i,j , calculate the sum of the absolute values ​​of the differences ΔT j , and then according to ΔT j The minimum value of is used to infer the closest climate zone where the air source heat pump is located; Step 4: Identify the closest climate zone as the climate zone where the air source heat pump is located, and select the defrost start temperature difference control line of the air source heat pump in the climate zone as the new defrost judgment basis, so that the air source heat pump can accurately defrost in different climate zones.

2. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: Dynamically update the defrost start temperature difference control line of the climate zone selected in step 1 and perform automatic calibration regularly.

3. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: The defrost start temperature difference control line of each climate zone is obtained by the following method: when developing air source heat pumps, typical cities in the hot summer and cold winter climate zone are selected, and the air source heat pump defrosting experiment is carried out by creating the load of the air source heat pump at different outdoor temperatures in the climate zone in the enthalpy difference laboratory. Based on the optimal defrost control point theory, the optimal defrost temperature difference at different temperatures is obtained, and the defrost start temperature difference control line of the hot summer and cold winter climate zone is obtained by fitting the optimal defrost temperature difference at different outdoor temperatures; the same method is used to obtain the defrost start temperature difference control line of the cold and extremely cold climate zones.

4. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: Frost-free temperature difference threshold Δt i,j It is obtained by the following method: When developing air source heat pumps, typical cities in different climate zones are selected. By creating the load of air source heat pumps at different outdoor temperatures in different climate zones in the enthalpy difference laboratory, frost-free heating experiments are carried out. The value is calculated by calculating the difference between the outdoor air temperature and the surface temperature of the outdoor heat exchanger.

5. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: The sum of the absolute values ​​of the differences ΔT j The calculation formula is: Where, j refers to the jth climate zone; Δt i,j is the frost-free temperature difference threshold at the same outdoor temperature in climate zone j; ΔT j The smaller the value, the more Δt i The frost-free temperature difference threshold Δt of the air source heat pump in this climate zone i,j The closer they are, the higher the accuracy of defrost control using the defrost start temperature difference control line in that climate zone.

6. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: The defrost start temperature difference Δt changes with the outdoor temperature and has a maximum value. When the outdoor temperature is higher or lower than the outdoor temperature t3 corresponding to the maximum value of Δt, the defrost start temperature difference Δt decreases.

7. The air source heat pump defrosting control method applicable to different climate zones according to claim 6, characterized in that: The outdoor temperature t3 corresponding to the maximum value of Δt varies in different climate zones. The overall rule is: the lower the outdoor design temperature for heating is, the lower the outdoor temperature t3 corresponding to the maximum value of Δt is.

8. The air source heat pump defrosting control method applicable to different climate zones according to claim 1, characterized in that: Different climate zones include severe cold climate zones, cold climate zones, and hot summer and cold winter climate zones.

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