Method for judging frosting of air source heat pump unit

Abstract

The invention discloses a method for judging frosting of an air source heat pump unit, and belongs to the technical field of air source heat pump units. The method specifically comprises the following steps of S1, frosting data measurement, S2, frosting curve fitting, specifically, a frosting database is sent to a function fitting tool, and a coil pipe temperature function and a return air temperature function are obtained through calculation through data fitting; s3, frosting judgment is conducted, when the air source heat pump unit obtains the coil pipe actual collection temperature and the return air actual collection temperature in real time, the current environment temperature is synchronously obtained, and then the environment temperature is sent to a coil pipe temperature function and a return air temperature function; respectively outputting a coil pipe calculation temperature and a return air calculation temperature through a coil pipe temperature function and a return air temperature function; according to the method for judging frosting of the air source heat pump unit, whether frosting exists or not is comprehensively judged in the mode that the environment temperature, the return air temperature and the coil pipe temperature are combined, and the accuracy of frosting judgment can be improved.

Description

Technical Field

[0001] The present invention specifically relates to a method for determining frosting of an air source heat pump unit, and belongs to the technical field of air source heat pump units. Background Art

[0002] Air source heat pump units are also called air-cooled heat pump units. Traditional air source systems are very prone to frost. After frost, the compressor is usually switched to change the evaporator to the condenser, and the refrigerant condenses and releases heat to complete defrosting. It takes a long time for the system to complete a switch. For this reason, China Patent Authorization Announcement No.: CN110793239B discloses a large-scale air source heat pump frost determination and online defrosting system and method. By measuring the air temperature of the inlet and outlet ambient air heat exchanger and the antifreeze temperature of the inlet and outlet ambient air heat exchanger, the temperature difference between the two is calculated and compared with the system set temperature difference to determine the degree of frost on the ambient air heat exchanger and whether to perform defrosting operation. In addition, the city When judging frost in heating of the air source heat pump unit on site, defrost starts when the ambient temperature - coil temperature > set difference. False defrost is prone to occur because the coil temperature sensor is installed on the lowest or one of the multiple liquid pipes of the fin heat exchanger. Under special circumstances, defrost water may remain in this pipe and freeze or be covered with heavy snow, resulting in inaccurate coil temperature. In addition, during welding, if the liquid pipe is blocked, causing inaccurate temperature, and the temperature sensor is detached or falls off during transportation, this line of the coil temperature sensor cannot fully reflect the frost condition of the entire fin heat exchanger, causing the unit to defrost frequently or not at all, resulting in a poor user experience for customers. Summary of the invention

[0003] To solve the above problems, the present invention proposes a method for determining frosting of an air source heat pump unit, which comprehensively determines whether frosting occurs by combining ambient temperature, return air temperature and coil temperature, thereby improving the accuracy of frosting determination.

[0004] The method for determining frosting of an air source heat pump unit of the present invention is as follows: S1. Determination of frosting data: establish an experimental chamber outside the air source heat pump unit and control the temperature of the experimental chamber. The temperature of the experimental chamber is used as the ambient temperature. At the same time, the return air temperature and the coil temperature of the air source heat pump unit are monitored; the ambient temperature, return air temperature and coil temperature of the finned heat exchanger of the air source heat pump unit when frosting occurs are obtained; and a frosting database is obtained; S2, frosting curve fitting, the frosting database is sent to the function fitting tool, and the fitting function is calculated through data fitting; specifically, the ambient temperature in the frost database is taken as input, and the coil temperature is taken as the result, so as to output the coil temperature function; then the ambient temperature in the frost database is taken as input, and the return air temperature is taken as the result, so as to output the return air temperature function; S3, frost judgment, when the air source heat pump unit obtains the actual coil temperature and the return air temperature in real time, it obtains the current ambient temperature synchronously, and then sends the ambient temperature to the coil temperature function and the return air temperature function; the coil calculated temperature and the return air calculated temperature are output through the coil temperature function and the return air temperature function respectively; then, frost judgment is made, when the actual coil temperature is equal to or lower than the coil calculated temperature, or the actual return air temperature is equal to or lower than the return air calculated temperature, the defrost instruction is output.

[0005] Furthermore, the actual coil temperature and the actual return air temperature are subtracted and an absolute value is calculated. When the absolute value reaches a set threshold, a defrost pipeline 2 fault signal is output. When the defrost pipeline 2 fault signal is received, it is obtained that the return air temperature or the coil temperature of the air source heat pump unit is abnormal. At this time, the early warning function is turned on to remind the user to check, and the defrost judgment is made according to the lower temperature between the actual coil temperature and the actual return air temperature.

[0006] Furthermore, the set threshold is ≥8; when the unit operates normally, when the absolute value of the difference between the return air temperature and the coil temperature is ≥8, a defrost pipeline 2 fault signal is output.

[0007] Furthermore, the coil temperature function is specifically as follows: (1) Ta>6℃, and Te = -3+first defrost compensation coefficient; (2) -5℃<Ta≤6℃ and Te =[K1*(12×Ta-112)] / 16+first defrost compensation coefficient; (3) -10℃<Ta≤-5℃ and Te=[K2*(16×Ta-55) / 16]+second defrost compensation coefficient; (4) -10℃≥Ta and Te=[K3*(16×Ta-95) / 20]+second defrost compensation coefficient; Wherein, Ta is the ambient temperature, Te is the calculated coil temperature, K1 is the first temperature coefficient, K1=1.02, K2 is the second temperature coefficient, K2=1.2, K3 is the third temperature coefficient, K3=1.1; the first defrost compensation coefficient and the second defrost compensation coefficient are both 3°C; When the fin heat exchanger is frosted, it is often accompanied by a relatively low return air temperature. The reason is that the fin heat exchanger is covered with frost, resulting in insufficient heat exchange area. Therefore, frosting and return air temperature are associated; the return air temperature function is as follows: Ta≥2℃, Tc=-6℃; 0℃<Ta≤-20℃, Tc=Ta*K3+first return air compensation coefficient; -20℃<Ta≤-35℃, Tc=-1.2*Ta+second return air compensation coefficient; Among them, Ta is the ambient temperature, Tc is the return air calculation temperature; the first return air compensation coefficient is -1°C; the second return air compensation coefficient is -2°C; K3 is the third temperature coefficient, K3=3+(0+Ta)*0.1.

[0008] Furthermore, the frosting database is obtained as follows: an initial temperature value is set, then, the power of the air source heat pump unit is controlled, and the return air temperature and the coil temperature of the fin-type heat exchanger when frosting is observed to obtain a set of frosting data, then, the temperature is lowered in sequence based on the initial temperature value, and the above process test is performed each time the temperature is lowered to obtain a set of frosting data, and the step value is reduced by 1°C; finally, the frosting database is obtained.

[0009] Compared with the prior art, the method for determining frosting of an air source heat pump unit of the present invention relies on the combination of ambient temperature, compressor return air temperature and coil temperature on the air source heat pump unit to comprehensively determine whether the air source heat pump unit is frosted. It can form a backup when the coil temperature or the return air temperature fails in certain special circumstances. At the same time, it can verify each other to determine whether the unit is frosted, improve the stability of the determination of the unit's defrost, and achieve a more scientific and accurate determination of frosting of the air source heat pump; thereby solving the problem of frequent or no defrosting of the air source heat pump unit due to temperature monitoring errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The present invention is a schematic diagram of the working process of the method for determining frosting of an air source heat pump unit.

[0011] Figure 2 This is a schematic diagram of the installation structure of the first temperature sensor of the present invention.

[0012] Figure 3 It is a schematic diagram of the installation structure of the second temperature sensor of the present invention.

[0013] Figure numerals: 1. finned heat exchanger, 2. defrost pipeline, 3. first temperature sensor, 4. compressor, 5. gas-liquid separator, 6. second temperature sensor. DETAILED DESCRIPTION

[0014] like Figures 1 to 3 The method for determining frosting of an air source heat pump unit shown is as follows: S1, frosting data determination, establish an experimental chamber outside the air source heat pump unit, and control the temperature of the experimental chamber, the temperature of the experimental chamber is used as the ambient temperature, and at the same time, monitor the return air temperature of the air source heat pump unit and the coil temperature of the air source heat pump unit; obtain the ambient temperature, return air temperature and coil temperature of the finned heat exchanger 1 of the air source heat pump unit when frosting; the coil temperature is obtained by the first temperature sensor 3 on the defrost pipeline 2; the return air temperature is obtained by the second temperature sensor 6 on the pipeline between the compressor 4 and the gas-liquid separator 5; obtain the frosting database; S2, frosting curve fitting, the frosting database is sent to the function fitting tool, and the fitting function is calculated through data fitting; specifically, the ambient temperature in the frost database is taken as input, and the coil temperature is taken as the result, so as to output the coil temperature function; then the ambient temperature in the frost database is taken as input, and the return air temperature is taken as the result, so as to output the return air temperature function; S3, frost judgment, when the air source heat pump unit obtains the actual coil temperature and the return air temperature in real time, it obtains the current ambient temperature synchronously, and then sends the ambient temperature to the coil temperature function and the return air temperature function; the coil calculated temperature and the return air calculated temperature are output through the coil temperature function and the return air temperature function respectively; then, frost judgment is made, when the actual coil temperature is equal to or lower than the coil calculated temperature, or the actual return air temperature is equal to or lower than the return air calculated temperature, the defrost instruction is output.

[0015] The absolute value of the actual coil temperature and the actual return air temperature is calculated by taking the difference. When the absolute value reaches the set threshold, the defrost pipeline 2 fault signal is output. When the defrost pipeline 2 fault signal is received, it is obtained that the return air temperature or the coil temperature of the air source heat pump unit is abnormal. At this time, the early warning function is turned on to remind the user to check, and the defrost judgment is made according to the lower temperature between the actual coil temperature and the return air temperature.

[0016] The set threshold is ≥8; when the unit is operating normally, when the absolute value of the difference between the return air temperature and the coil temperature is ≥8, a defrost pipeline 2 fault signal is output.

[0017] The coil temperature function is as follows: (1) Ta>6℃, and Te = -3+first defrost compensation coefficient; (2) -5℃<Ta≤6℃ and Te =[K1*(12×Ta-112) / 16] + first defrost compensation coefficient; (3) -10℃<Ta≤-5℃ and Te=[K2*(16×Ta-55)] / 16+second defrost compensation coefficient; (4) -10℃≥Ta and Te=[K3*(16×Ta-95) / 20]+second defrost compensation coefficient; Wherein, Ta is the ambient temperature, Te is the calculated coil temperature, K1 is the first temperature coefficient, K1=1.02, K2 is the second temperature coefficient, K2=1.2, K3 is the third temperature coefficient, K3=1.1; the first defrost compensation coefficient and the second defrost compensation coefficient are both 3°C; When the fin heat exchanger 1 is frosted, the return air temperature is often relatively low because the fin heat exchanger 1 is covered with frost, resulting in insufficient heat exchange area. Therefore, frosting and return air temperature are associated; the return air temperature function is specifically as follows: Ta≥2℃, Tc=-6℃; 0℃<Ta≤-20℃, Tc=Ta*K3+first return air compensation coefficient; -20℃<Ta≤-35℃, Tc=-1.2*Ta+second return air compensation coefficient; Among them, Ta is the ambient temperature, Tc is the return air calculation temperature; the first return air compensation coefficient is -1°C; the second return air compensation coefficient is -2°C; K3 is the third temperature coefficient, K3=3+(0+Ta)*0.1.

[0018] The frosting database is obtained as follows: an initial temperature value is set, then the power of the air source heat pump unit is controlled, and the return air temperature and the coil temperature of the finned heat exchanger 1 when frosting is observed to obtain a set of frosting data, then, the temperature is lowered in sequence based on the initial temperature value, and the above process test is performed each time the temperature is lowered to obtain a set of frosting data, and the step value is reduced by 1°C; finally, the frosting database is obtained.

[0019] Example: The method for determining frosting of the air source heat pump unit of the present invention is specifically as follows: When the air source heat pump unit is running for heating, the ambient temperature Ta=-6℃; coil temperature -7℃; return air temperature -16℃ are obtained through the temperature sensor of the air source heat pump unit; First, obtain the calculated temperature of the coil, which is calculated through the coil temperature function as follows: Since Ta = -6°C, we can know that the calculation formula corresponding to the coil temperature function is: That is, -10<Ta≤-5, Te=[K2*(16×Ta-55) / 16] + second defrost compensation coefficient; among them, K2=1.2, Ta=-6℃, and the calculated coil temperature Te=[1.2*(16×-6-55) / 16]+3=-8.32℃; when the actual coil temperature is lower than -8.32℃, defrost begins; since the actual coil temperature is -7℃, the actual temperature has not reached -8.32℃ at this time, and the defrost temperature condition is not met at this time.

[0020] Then calculate the return air temperature, which is calculated by the return air temperature function as follows: Since Ta = -6°C, we can know that the calculation formula corresponding to the return air temperature function is: 0<Ta≤-20, Tc=Ta*K3+first return air compensation coefficient; first calculate K3, K3= K3=3+(0+Ta)*0.1; that is, K3=3+(-6)*0.1=2.4; Next, the calculated return air temperature Tc=-6*2.4+(-1)=-14.4+(-1)=-15.4℃ is obtained; when the actual return air temperature is lower than -15.4℃, defrosting begins; since the actual return air temperature is -16℃, at this time, the actual temperature is lower than the calculated return air temperature; when the defrost temperature is reached, the air source heat pump unit outputs a defrost command.

[0021] In addition, when the air source heat pump unit is running for heating, the coil temperature is -7℃ and the return air temperature is -16℃. At this time, the coil temperature is obviously higher, and the difference between the coil temperature and the return air temperature is greater than or equal to 8℃, and the return air temperature has reached the defrosting standard, so after a delay of 5 minutes, the unit starts to defrost. At the same time, a fault command is issued. Due to the high coil temperature, the fault prompt is "the temperature sensor at the coil is faulty". After receiving the fault command, an on-site inspection is carried out, and after subsequent inspection, it is found that the coil temperature has fallen off and failed.

[0022] The above embodiments are only preferred implementations of the present invention, so any equivalent changes or modifications made according to the structures, features and principles described in the scope of application of the present invention are included in the scope of application of the present invention.

Claims

1. A method for determining frosting of an air source heat pump unit, characterized in that: The method is specifically as follows: S1. Determination of frosting data: establish an experimental chamber outside the air source heat pump unit and control the temperature of the experimental chamber. The temperature of the experimental chamber is used as the ambient temperature. At the same time, the return air temperature and the coil temperature of the air source heat pump unit are monitored; the ambient temperature, return air temperature and coil temperature of the finned heat exchanger of the air source heat pump unit when frosting occurs are obtained; and a frosting database is obtained; S2, frosting curve fitting, the frosting database is sent to the function fitting tool, and the fitting function is calculated through data fitting; specifically, the ambient temperature in the frost database is taken as input, and the coil temperature is taken as the result, so as to output the coil temperature function; then the ambient temperature in the frost database is taken as input, and the return air temperature is taken as the result, so as to output the return air temperature function; S3, frost judgment, when the air source heat pump unit obtains the actual coil temperature and the return air temperature in real time, it obtains the current ambient temperature synchronously, and then sends the ambient temperature to the coil temperature function and the return air temperature function; the coil calculated temperature and the return air calculated temperature are output through the coil temperature function and the return air temperature function respectively; then, frost judgment is made, when the actual coil temperature is equal to or lower than the coil calculated temperature, or the actual return air temperature is equal to or lower than the return air calculated temperature, the defrost instruction is output.

2. The method for determining frosting of an air source heat pump unit according to claim 1, characterized in that: The actual temperature of the coil and the actual temperature of the return air are subtracted and then the absolute value is calculated. When the absolute value reaches a set threshold, a defrost pipeline 2 fault signal is output.

3. The method for determining frosting of an air source heat pump unit according to claim 2, characterized in that: The set threshold is ≥8.

4. The method for determining frosting of an air source heat pump unit according to claim 2, characterized in that: The coil temperature function is as follows: (1) Ta>6℃, and Te = -3+first defrost compensation coefficient; (2) -5℃<Ta≤6℃ and Te =[K1*(12×Ta-112) / 16]+first defrost compensation coefficient; (3) -10℃<Ta≤-5℃ and Te=[K2*(16×Ta-55) / 16]+second defrost compensation coefficient; (4) -10℃≥Ta and Te=[K3*(16×Ta-95) / 20]+second defrost compensation coefficient; Wherein, Ta is the ambient temperature, Te is the calculated coil temperature, K1 is the first temperature coefficient, K1=1.02, K2 is the second temperature coefficient, K2=1.2, K3 is the third temperature coefficient, K3=1.1; the first defrost compensation coefficient and the second defrost compensation coefficient are both 3°C; The return air temperature function is as follows: Ta≥2℃, Tc=-6℃; 0℃<Ta≤-20℃, Tc=Ta*K3+first return air compensation coefficient; -20℃<Ta≤-35℃, Tc=-1.2*Ta+second return air compensation coefficient; Among them, Ta is the ambient temperature, Tc is the return air calculation temperature; the first return air compensation coefficient is -1°C; the second return air compensation coefficient is -2°C; K3 is the third temperature coefficient, K3=3+(0+Ta)*0.

1.

5. The method for determining frosting of an air source heat pump unit according to claim 1, characterized in that: The frosting database is obtained as follows: an initial temperature value is set, then the power of the air source heat pump unit is controlled, and the return air temperature and the coil temperature of the finned heat exchanger when frosting is observed to obtain a set of frosting data, then the temperature is lowered in sequence based on the initial temperature value, and the above process test is performed each time the temperature is lowered to obtain a set of frosting data, and the step value is reduced by 1°C; finally, the frosting database is obtained.

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