Oil return control method of heat pump

Abstract

An oil return control method of a heat pump comprises the following steps that firstly, the heat pump is powered on, and the second step is executed; 2, normal operation is carried out, and the step 3 is carried out; 3, the value sigma Zi is assigned to be equal to 0, sigma Zi is the total oil return accumulation time, i is a natural number, and the step 4 is executed; fourthly, a central controller of the heat pump obtains the current operation frequency U, the current operation time T0 corresponding to the current operation frequency U, the current environment temperature K and the current pressure ratio M of the heat pump in time, then the fifth step, the twelfth step and the twenty-fourth step are executed at the same time, and the current pressure ratio M is the ratio of the current condensation pressure to the current evaporation pressure; 5, the central controller judges whether U is larger than F1 or not, if yes, the step 9 is executed, and if not, the step 6 is executed. The oil return requirement of the heat pump system is met, frequent oil return is avoided, fluctuation during operation is reduced, the working efficiency of the heat pump is improved, and the energy efficiency of the heat pump is also improved.

Description

Technical Field

[0001] The invention relates to a heat pump, in particular to an oil return control method of a heat pump. Background Art

[0002] At present, the usual practice for oil return protection in air source heat pumps or household air conditioners is: when the operating frequency of the compressor is lower than a certain set frequency and the operating time exceeds the set value, the compressor frequency is controlled to operate at a certain set oil return operating frequency. For example: when the operating frequency of the compressor is lower than 40Hz and runs continuously for more than 120 minutes, the compressor operating frequency is required to switch to the oil return operating frequency of 60Hz for 3 minutes.

[0003] The problem with this common practice is that if the current operating frequency before oil return is about 20 Hz, and the oil return operating frequency during oil return is set to 60 Hz, then due to the large span of the operating frequencies before and after oil return, the operating parameters of the heat pump system will fluctuate greatly.

[0004] Another problem is that the purpose of oil return protection is to prevent the compressor from running out of oil. However, this common practice does not take into account when the compressor will run out of oil. As a result, the compressor often returns oil frequently even when it is not running out of oil, resulting in low working efficiency.

[0005] Chinese patent document number CN 104764167A disclosed on July 8, 2015 a method for controlling oil return of a variable frequency air conditioner compressor, wherein the variable frequency air conditioner includes an auxiliary heating device with adjustable heat supply, and when the variable frequency air conditioner compressor needs to increase the frequency to an oil return frequency f2 for oil return operation, the variable frequency air conditioner increases a matching auxiliary heat source according to the difference △f=f2-f1 between the oil return frequency f2 and the current frequency f1 to increase the ambient temperature, so as to offset the output capacity increased by increasing the frequency during the oil return operation of the compressor. The oil return control method includes the following steps: S2, when the variable frequency air conditioner compressor is in oil return operation, the compressor is adjusted from the current frequency f1 to the oil return frequency f2, and the matching auxiliary heat source is increased according to the difference △f between the oil return frequency f2 and the current frequency f1; S3, judging whether the variable frequency air conditioner meets the frequency reduction limit condition, if so, executing step S5, otherwise executing step S4; S4, detecting the oil return time, when the oil return time reaches the preset oil return time t2, exiting the oil return operation and returning to the running state before oil return; S5, oil return ends, returning to the running state before oil return. After actual use, the effect of this oil return control method for variable frequency air conditioner compressor is not ideal and needs to be improved. Summary of the invention

[0006] The object of the present invention is to provide an oil return control method for a heat pump with high energy efficiency, so as to overcome the shortcomings of the prior art.

[0007] A heat pump oil return control method designed for this purpose is characterized by comprising the following steps:

[0008] Step 1: Power on the heat pump and proceed to step 2;

[0009] Step 2: Normal operation, go to step 3;

[0010] Step 3, assign ∑Zi=0, where ∑Zi is the total oil return accumulation time, i is a natural number, and proceed to step 4;

[0011] Step 4: The central controller of the heat pump timely obtains the current operating frequency U of the heat pump, the current operating time T0 corresponding to the current operating frequency U, the current ambient temperature K, and the current pressure ratio M, and then respectively enters step 5, step 12, and step 24 at the same time, wherein the current pressure ratio M is the ratio of the current condensing pressure to the current evaporating pressure;

[0012] Step 5, the central controller determines whether U>F1 is established. If it is established, it goes to step 9, otherwise it goes to step 6, where F1 is the first set operating frequency, and the value range of F1 is 55-65Hz;

[0013] Step 6, the central controller determines whether F1≥U>F2 is established. If it is established, it goes to step 10, otherwise it goes to step 7, where F2 is the second set operating frequency, and the value range of F2 is 40~50Hz;

[0014] Step 7, the central controller determines whether F2≥U>F3 is established. If it is established, it goes to step 11, otherwise it goes to step 8, where F3 is the third set operating frequency, and the value range of F3 is 25~35Hz;

[0015] Step 8, T1i=C*T0, T1i is the frequency equivalent time, C is the third constant, and the value range of C is 1.8-2.5, and then proceed to step 17;

[0016] Step 9, T1i=0, go to step 17;

[0017] Step 10, T1i=A*T0, A is the first constant, and the value range of A is 0.5-0.8, and then proceed to step 17;

[0018] Step 11, T1i=B*T0, B is the second constant, and the value range of B is 1 to 1.5, and then proceed to step 17;

[0019] Step 12, the central controller determines whether K>P1 is established. If it is established, it goes to step 20, otherwise it goes to step 13, where P1 is the first set ambient temperature, and the value range of P1 is 7-17°C;

[0020] Step 13, the central controller determines whether P1≥K>P2 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 14, where P2 is the second set ambient temperature, and the value range of P2 is -6 to 6°C;

[0021] Step 14, the central controller determines whether P2≥K>P3 is established. If it is established, it proceeds to step 22, otherwise it proceeds to step 15, wherein P3 is the third set ambient temperature, and the value range of P3 is -15°C to -5°C;

[0022] Step 15, the central controller determines whether P3≥K>P4 is established. If it is established, it proceeds to step 23, otherwise it proceeds to step 16, wherein P4 is the fourth set ambient temperature, and the value range of P4 is -24°C to -14°C;

[0023] Step 16, T2i=D*T0, T2i is the ambient temperature equivalent time, D is the fourth constant, and the value range of D is 2.5-3, and then proceed to step 17;

[0024] Step 17, Zi = T1i + T2i + T3i, Zi is the current oil return cumulative time, T3i is the pressure ratio equivalent time, and then proceed to step 18;

[0025] Step 18, the central controller determines whether ∑Zi≥TM is established. If it is established, it goes to step 19, otherwise it goes to step 4, where TM is the oil return judgment time, and the value range of TM is 360 to 450 minutes;

[0026] Step 19, oil return control, the central controller controls the compressor to operate at an oil return frequency of 55-65Hz, an electronic expansion valve opening of 200-300 steps, and an oil return operation time of 1-5 minutes, and then enters step 2;

[0027] Step 20, T2i=0, go to step 17;

[0028] Step 21, T2i=A*T0, go to step 17;

[0029] Step 22, T2i=B*T0, go to step 17;

[0030] Step 23, T2i=C*T0, go to step 17;

[0031] Step 24, the central controller determines whether M>S1 is established. If it is established, it goes to step 28, otherwise it goes to step 25, where S1 is the first set compression ratio, and the value range of S1 is 7 to 9;

[0032] Step 25, the central controller determines whether S1≥M>S2 is established. If it is established, it proceeds to step 29, otherwise it proceeds to step 26, where S2 is the second set compression ratio, and the value range of S2 is 4 to 6;

[0033] Step 26, the central controller determines whether S2≥M>S3 is established. If it is established, it proceeds to step 30, otherwise it proceeds to step 27, where S3 is the third set compression ratio, and the value range of S3 is 1 to 3;

[0034] Step 27, T3i=C*T0, go to step 17;

[0035] Step 28, T3i=0, go to step 17;

[0036] Step 29, T3i=A*T0, go to step 17;

[0037] Step 30, T3i=B*T0, proceed to step 17.

[0038] The present invention adopts the above-mentioned technical scheme, comprehensively considers the ambient temperature, compressor operating frequency and pressure ratio, divides the current oil return cumulative time Zi into frequency equivalent time T1i, ambient temperature equivalent time T2i and pressure ratio equivalent time T3i, and accurately controls the specific time of oil return, thereby not only meeting the oil return needs of the heat pump system, but also avoiding frequent oil return, reducing fluctuations during operation, improving the working efficiency of the heat pump, and improving its energy efficiency.

[0039] In summary, the present invention has the characteristic of high energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 FIG. 4 is a control flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] See also Figure 1 , a heat pump oil return control method, characterized in that it includes the following steps:

[0043] Step 1: Power on the heat pump and proceed to step 2;

[0044] Step 2: Normal operation, go to step 3;

[0045] Step 3, assign ∑Zi=0, where ∑Zi is the total oil return accumulation time, i is a natural number, and proceed to step 4;

[0046] Step 4: The central controller of the heat pump timely obtains the current operating frequency U of the heat pump, the current operating time T0 corresponding to the current operating frequency U, the current ambient temperature K, and the current pressure ratio M, and then respectively enters step 5, step 12, and step 24 at the same time, wherein the current pressure ratio M is the ratio of the current condensing pressure to the current evaporating pressure;

[0047] Step 5, the central controller determines whether U>F1 is established. If it is established, it goes to step 9, otherwise it goes to step 6, where F1 is the first set operating frequency, and the value range of F1 is 55-65Hz;

[0048] Step 6, the central controller determines whether F1≥U>F2 is established. If it is established, it goes to step 10, otherwise it goes to step 7, where F2 is the second set operating frequency, and the value range of F2 is 40~50Hz;

[0049] Step 7, the central controller determines whether F2≥U>F3 is established. If it is established, it goes to step 11, otherwise it goes to step 8, where F3 is the third set operating frequency, and the value range of F3 is 25~35Hz;

[0050] Step 8, T1i=C*T0, T1i is the frequency equivalent time, C is the third constant, and the value range of C is 1.8-2.5, and then proceed to step 17;

[0051] Step 9, T1i=0, go to step 17;

[0052] Step 10, T1i=A*T0, A is the first constant, and the value range of A is 0.5-0.8, and then proceed to step 17;

[0053] Step 11, T1i=B*T0, B is the second constant, and the value range of B is 1 to 1.5, and then proceed to step 17;

[0054] Step 12, the central controller determines whether K>P1 is established. If it is established, it goes to step 20, otherwise it goes to step 13, where P1 is the first set ambient temperature, and the value range of P1 is 7-17°C;

[0055] Step 13, the central controller determines whether P1≥K>P2 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 14, where P2 is the second set ambient temperature, and the value range of P2 is -6 to 6°C;

[0056] Step 14, the central controller determines whether P2≥K>P3 is established. If it is established, it proceeds to step 22, otherwise it proceeds to step 15, wherein P3 is the third set ambient temperature, and the value range of P3 is -15°C to -5°C;

[0057] Step 15, the central controller determines whether P3≥K>P4 is established. If it is established, it proceeds to step 23, otherwise it proceeds to step 16, wherein P4 is the fourth set ambient temperature, and the value range of P4 is -24°C to -14°C;

[0058] Step 16, T2i=D*T0, T2i is the ambient temperature equivalent time, D is the fourth constant, and the value range of D is 2.5-3, and then proceed to step 17;

[0059] Step 17, Zi = T1i + T2i + T3i, Zi is the current oil return cumulative time, T3i is the pressure ratio equivalent time, and then proceed to step 18;

[0060] Step 18, the central controller determines whether ∑Zi≥TM is established. If it is established, it goes to step 19, otherwise it goes to step 4, where TM is the oil return judgment time, and the value range of TM is 360 to 450 minutes;

[0061] Step 19, oil return control, the central controller controls the compressor to operate at an oil return frequency of 55-65Hz, an electronic expansion valve opening of 200-300 steps, and an oil return operation time of 1-5 minutes, and then enters step 2;

[0062] Step 20, T2i=0, go to step 17;

[0063] Step 21, T2i=A*T0, go to step 17;

[0064] Step 22, T2i=B*T0, go to step 17;

[0065] Step 23, T2i=C*T0, go to step 17;

[0066] Step 24, the central controller determines whether M>S1 is established. If it is established, it goes to step 28, otherwise it goes to step 25, where S1 is the first set compression ratio, and the value range of S1 is 7 to 9;

[0067] Step 25, the central controller determines whether S1≥M>S2 is established. If it is established, it proceeds to step 29, otherwise it proceeds to step 26, where S2 is the second set compression ratio, and the value range of S2 is 4 to 6;

[0068] Step 26, the central controller determines whether S2≥M>S3 is established. If it is established, it proceeds to step 30, otherwise it proceeds to step 27, where S3 is the third set compression ratio, and the value range of S3 is 1 to 3;

[0069] Step 27, T3i=C*T0, go to step 17;

[0070] Step 28, T3i=0, go to step 17;

[0071] Step 29, T3i=A*T0, go to step 17;

[0072] Step 30, T3i=B*T0, proceed to step 17.

[0073] The current oil return cumulative time Zi in the present invention is the sum of the frequency equivalent time T1i, the ambient temperature equivalent time T2i and the pressure ratio equivalent time T3i. When the heat pump is started, the frequency equivalent time T1i, the ambient temperature equivalent time T2i and the pressure ratio equivalent time T3i are accumulated from 0 respectively. When the total oil return cumulative time ∑Zi≥the oil return judgment time TM, the central controller controls to execute an oil return action, and the frequency equivalent time T1i, the ambient temperature equivalent time T2i and the pressure ratio equivalent time T3i are accumulated from 0 respectively, and the cycle repeats.

[0074] The frequency equivalent time T1i in the present invention is accumulated at different time rates according to different current operating frequencies; the ambient temperature equivalent time T2i is accumulated at different time rates according to different current ambient temperatures; and the pressure ratio equivalent time T3i is accumulated at different time rates according to different current pressure ratios.

[0075] During calculation, the frequency equivalent time T1i, ambient temperature equivalent time T2i and pressure ratio equivalent time T3i are calculated simultaneously. When the total oil return cumulative time ∑Zi≥oil return judgment time TM, the oil return control logic is entered.

[0076] In this embodiment, the oil return control logic is that the central controller controls the compressor to operate at an oil return frequency of 55-65 Hz, an electronic expansion valve opening of 200-300 steps, and an oil return operation time of 1-5 minutes. Preferably, the oil return operation time is 2-3 minutes.

[0077] Application Examples

[0078] Preset F1=60Hz, F2=45Hz, F3=30Hz, P1=10℃, P2=0℃, P3=-10℃, P4=-20℃, S1=8, S2=5, S3=3, A=0.7, B=1.2, C=2, D=2.8, TM=360 minutes.

[0079] After the heat pump was turned on, it has run for a total of 60 minutes so far, including 20 minutes at the current operating frequency of 35Hz and 40 minutes at the current operating frequency of 15Hz; 10 minutes at the current ambient temperature of 15℃ and 50 minutes at the current ambient temperature of -15℃; 25 minutes at 6 times the current pressure ratio and 35 minutes at 4 times the current pressure ratio.

[0080] Since ∑Zi=Z1+Z2, Z1=T11+T21+T31, Z2=T12+T22+T32;

[0081] Therefore, ∑Zi=T11+T12+T21+T22+T31+T32;

[0082] Frequency equivalent time T11+T12=20*B+40*C=20*1.2+40*2=24+80=104 minutes;

[0083] Ambient temperature equivalent time T21+T22=10*0+5*C=0+5*2=100 minutes;

[0084] Pressure ratio equivalent time T31+T32=25*A+35*B=25*0.7+35*1.2=17.5+42=59.5 minutes;

[0085] Therefore, ∑Zi=104+100+59.5=263.5 minutes<TM=360 minutes, and oil return is not required at present.

[0086] When the heat pump returns oil once, accumulation starts again from 0.

[0087] After the present invention adopts the above technical solution, it can operate efficiently and will not enter the misunderstanding of oil return when the ambient temperature is above 2°C and the pressure ratio is lower than 10. It not only improves energy efficiency, but also greatly improves user experience.

[0088] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0089] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A heat pump oil return control method, characterized in that The following steps are involved: Step 1: Power on the heat pump and proceed to step 2; Step 2: Normal operation, go to step 3; Step 3, assign ∑Zi=0, where ∑Zi is the total oil return accumulation time, i is a natural number, and proceed to step 4; Step 4: The central controller of the heat pump timely obtains the current operating frequency U of the heat pump, the current operating time T0 corresponding to the current operating frequency U, the current ambient temperature K, and the current pressure ratio M, and then respectively enters step 5, step 12, and step 24 at the same time, wherein the current pressure ratio M is the ratio of the current condensing pressure to the current evaporating pressure; Step 5, the central controller determines whether U>F1 is established. If it is established, it goes to step 9, otherwise it goes to step 6, where F1 is the first set operating frequency, and the value range of F1 is 55-65Hz; Step 6, the central controller determines whether F1≥U>F2 is established. If it is established, it goes to step 10, otherwise it goes to step 7, where F2 is the second set operating frequency, and the value range of F2 is 40~50Hz; Step 7, the central controller determines whether F2≥U>F3 is established. If it is established, it goes to step 11, otherwise it goes to step 8, where F3 is the third set operating frequency, and the value range of F3 is 25~35Hz; Step 8, T1i=C*T0, T1i is the frequency equivalent time, C is the third constant, and the value range of C is 1.8-2.5, and then proceed to step 17; Step 9, T1i=0, go to step 17; Step 10, T1i=A*T0, A is the first constant, and the value range of A is 0.5-0.8, and then proceed to step 17; Step 11, T1i=B*T0, B is the second constant, and the value range of B is 1 to 1.5, and then proceed to step 17; Step 12, the central controller determines whether K>P1 is established. If it is established, it goes to step 20, otherwise it goes to step 13, where P1 is the first set ambient temperature, and the value range of P1 is 7-17°C; Step 13, the central controller determines whether P1≥K>P2 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 14, where P2 is the second set ambient temperature, and the value range of P2 is -6 to 6°C; Step 14, the central controller determines whether P2≥K>P3 is established. If it is established, it proceeds to step 22, otherwise it proceeds to step 15, wherein P3 is the third set ambient temperature, and the value range of P3 is -15°C to -5°C; Step 15, the central controller determines whether P3≥K>P4 is established. If it is established, it proceeds to step 23, otherwise it proceeds to step 16, wherein P4 is the fourth set ambient temperature, and the value range of P4 is -24°C to -14°C; Step 16, T2i=D*T0, T2i is the ambient temperature equivalent time, D is the fourth constant, and the value range of D is 2.5-3, and then proceed to step 17; Step 17, Zi = T1i + T2i + T3i, Zi is the current oil return cumulative time, T3i is the pressure ratio equivalent time, and then proceed to step 18; Step 18, the central controller determines whether ∑Zi≥TM is established. If it is established, it goes to step 19, otherwise it goes to step 4, where TM is the oil return judgment time, and the value range of TM is 360 to 450 minutes; Step 19, oil return control, the central controller controls the compressor to operate at an oil return frequency of 55-65Hz, an electronic expansion valve opening of 200-300 steps, and an oil return operation time of 1-5 minutes, and then enters step 2; Step 20, T2i=0, go to step 17; Step 21, T2i=A*T0, go to step 17; Step 22, T2i=B*T0, go to step 17; Step 23, T2i=C*T0, go to step 17; Step 24, the central controller determines whether M>S1 is established. If it is established, it goes to step 28, otherwise it goes to step 25, where S1 is the first set compression ratio, and the value range of S1 is 7 to 9; Step 25, the central controller determines whether S1≥M>S2 is established. If it is established, it proceeds to step 29, otherwise it proceeds to step 26, where S2 is the second set compression ratio, and the value range of S2 is 4 to 6; Step 26, the central controller determines whether S2≥M>S3 is established. If it is established, it proceeds to step 30, otherwise it proceeds to step 27, where S3 is the third set compression ratio, and the value range of S3 is 1 to 3; Step 27, T3i=C*T0, go to step 17; Step 28, T3i=0, go to step 17; Step 29, T3i=A*T0, go to step 17; Step 30, T3i=B*T0, proceed to step 17.

Images