Detection method for outdoor defrosting of heat pump unit

Abstract

The invention discloses a detection method for outdoor defrosting of a heat pump unit, and belongs to the technical field of control methods. An initial distance L1 between an ultrasonic ranging unit and the surface of an outdoor fin heat exchanger of the heat pump unit is detected and obtained based on the ultrasonic ranging unit pre-fixed to a designated position on the periphery of the outdoor fin heat exchanger of the heat pump unit, and outdoor environment humidity H is obtained based on a preset humidity detection unit; after the heat pump unit runs for rated time, detecting and acquiring a dynamic distance L2 between the heat pump unit and the surface of an outdoor fin heat exchanger of the heat pump unit based on an ultrasonic ranging unit; calculating a distance difference value L between the initial distance L1 and the dynamic distance L2 based on the initial distance L1 and the dynamic distance L2; and correspondingly adjusting the time interval T0 when the heat pump unit is switched to the defrosting mode next time according to the environment humidity H and the distance difference value L. Based on the detection method, efficient and stable operation of the heat pump unit is achieved, the influence of defrosting on user experience is reduced, and the method is more stable and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of control methods, and in particular to a detection method for outdoor defrosting of a heat pump unit. Background Art

[0002] In the field of heat pumps, heat pump units are prone to frost when operating outdoors in winter, especially when frost / ice forms on the outdoor fin heat exchanger. If defrosting is not performed in time, the heat exchanger will reduce the performance of the heat pump and reduce energy efficiency. In extreme cases, the compressor may even fail. Therefore, it is of great significance to defrost the heat pump unit in a timely manner.

[0003] The existing defrost detection method generally detects the difference between the fin heat exchanger temperature and the ambient temperature during heating to judge and control the defrost switch. This method requires the temperature sensor used to detect the temperature of the fin heat exchanger to be installed on the outdoor fin heat exchanger. However, in actual application, when the outdoor fin heat exchanger is frosted / frozen, the temperature sensor will also cover the frost or ice layer, which is easy to detect inaccurate temperature and other misjudgments, resulting in the unit not defrosting or frequently defrosting, affecting the normal operation of the unit. Secondly, this type of detection method is mainly used for short-term detection and judgment. Once an abnormal temperature is detected, it will switch to defrost mode without a transition stage, which often leads to frequent switching to defrost, causing large temperature fluctuations at the indoor end, greatly affecting the user experience. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an efficient, stable, accurate and reliable method for detecting outdoor defrosting of a heat pump unit.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a method for detecting outdoor defrosting of a heat pump unit, comprising the following steps: Step S1. The heat pump unit operates in defrost mode; Step S2. After the rated defrost mode is finished, an ultrasonic distance measuring unit pre-fixed at a designated position on the periphery of the outdoor fin heat exchanger of the heat pump unit is used to detect and obtain an initial distance L1 between the ultrasonic distance measuring unit and the surface of the outdoor fin heat exchanger of the heat pump unit, and an outdoor ambient humidity H is obtained based on a preset humidity detection unit; Step S3. The heat pump unit switches to the normal mode, and after running for a rated time, the dynamic distance L2 between the heat pump unit and the surface of the outdoor fin heat exchanger of the heat pump unit is obtained based on the ultrasonic distance measuring unit detection; Step S4. Calculate the distance difference △L between the initial distance L1 and the dynamic distance L2; Step S5. According to the ambient humidity H and the distance difference ΔL, the time interval T0 for the heat pump unit to switch to the defrost mode next time is correspondingly adjusted, wherein the ambient humidity H and / or the distance difference ΔL are inversely proportional to the time interval T0.

[0006] Furthermore, it also includes three ultrasonic ranging units which are vertically aligned and respectively aimed at the upper position, middle position and lower position of the outdoor fin heat exchanger, wherein the ultrasonic ranging unit located at the middle position detects and obtains the horizontal distance between it and the surface of the outdoor fin heat exchanger as the initial distance L1; the two ultrasonic ranging units located at the upper position and the lower position detect and obtain the average value of the horizontal distance between each of them and the surface of the outdoor fin heat exchanger as the dynamic distance L2.

[0007] Further, the humidity value is divided into a first humidity interval, a second humidity interval, a third humidity interval and a fourth humidity interval of [0%, 40%], (40%, 60%], (60%, 80%], (80%, 100%], and the distance value is divided into a first distance interval, a second distance interval and a third distance interval of [0], (0, 0.5], (0.5, +∞], wherein any level of humidity interval and any level of distance interval are mapped to a corresponding time interval T0; the corresponding time interval T0 is determined according to the humidity interval corresponding to the ambient humidity H and the distance interval corresponding to the distance difference △L.

[0008] Further, in step S4, the operating frequency P of the compressor of the heat pump unit before entering the next defrosting mode is adjusted accordingly based on the distance difference ΔL, wherein the distance difference ΔL is inversely proportional to the operating frequency P of the compressor.

[0009] Further, in step S4, the fan speed S of the heat pump unit before entering the next defrost mode is adjusted accordingly based on the distance difference ΔL, wherein the distance difference ΔL is proportional to the fan speed S.

[0010] Furthermore, the rated duration in step S3 is 45 minutes.

[0011] The present invention adopts the above-mentioned scheme, and its beneficial effect lies in: by mapping the detected ambient humidity H and distance difference △L with the corresponding humidity interval and distance interval, the corresponding time interval T0 is determined, so that the heat pump unit can operate in normal mode for the time interval T0, and then switch to the defrost mode for defrosting, thereby realizing efficient and stable operation of the heat pump unit, reducing the impact of defrosting on user experience, and being more stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Flowchart of the detection method for outdoor defrosting of heat pump units.

[0013] Figure 2 This is a schematic diagram of the structure of the ultrasonic ranging unit in the heat pump unit.

[0014] Among them, 1-ultrasonic ranging unit, 2-outdoor fin heat exchanger. DETAILED DESCRIPTION

[0015] In order to facilitate the understanding of the present invention, the present invention is described more fully below with reference to the accompanying drawings. The accompanying drawings provide preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0016] See attached Figure 1-2 As shown, in this embodiment, a method for detecting outdoor defrosting of a heat pump unit is applicable to a heat pump unit operating in an outdoor low temperature environment, thereby solving the problem of frosting of the outdoor fin heat exchanger 2 of the heat pump unit. Specifically, the following steps are included: Step S1: The heat pump unit operates in defrost mode.

[0017] Step S2. After the defrost mode ends, the ultrasonic ranging unit 1 pre-fixed at a designated position outside the outdoor fin heat exchanger 2 of the heat pump unit detects and obtains the initial distance L1 between it and the surface of the outdoor fin heat exchanger 2 of the heat pump unit, and the outdoor environmental humidity H is obtained based on the preset humidity detection unit.

[0018] In step S2, after the defrost mode ends, the surface of the outdoor fin heat exchanger 2 of the heat pump unit should be in a frost-free / ice-free state. At this time, the initial distance L1 detected and obtained by the ultrasonic ranging unit 1 is equivalent to the maximum distance between the ultrasonic ranging unit 1 and the surface of the outdoor fin heat exchanger 2. If frost / ice occurs on the surface of the outdoor fin heat exchanger 2, it is equivalent to reducing the distance between the ultrasonic ranging unit 1 and the surface of the outdoor fin heat exchanger 2.

[0019] Step S3: the heat pump unit switches to the normal mode, and after running for a rated time, the ultrasonic distance measuring unit 1 detects and obtains the dynamic distance L2 between it and the surface of the outdoor fin heat exchanger 2 of the heat pump unit.

[0020] In step S3, the heat pump unit operates in normal mode in a low temperature environment or a high humidity environment, and frost / icing problems are likely to occur on the surface of the outdoor fin heat exchanger 2. Therefore, based on the frost / icing conditions of the rated operating time of the heat pump unit, a shorter time period is used to predict the future frost / icing conditions and make adaptive adjustments in advance to avoid affecting the normal operation of the heat pump unit and avoiding frequent switching of defrost modes, which affects the user experience. Specifically, the dynamic distance L2 detected and obtained by the ultrasonic ranging unit 1 indirectly reflects the frost / icing conditions of the outdoor fin heat exchanger 2.

[0021] Step S4: Calculate the distance difference ΔL between the initial distance L1 and the dynamic distance L2 based on the initial distance L1 and the dynamic distance L2.

[0022] In step S4, the calculated distance difference △L directly reflects the frost / ice condition of the outdoor fin heat exchanger 2, that is, the thicker the frost / ice condition of the outdoor fin heat exchanger 2, the larger the distance difference △L; conversely, if the outdoor fin heat exchanger 2 is in a frost-free / ice-free state, the distance difference △L is 0.

[0023] Step S5. According to the ambient humidity H and the distance difference ΔL, the time interval T0 for the heat pump unit to switch to the defrost mode next time is correspondingly adjusted, wherein the ambient humidity H and / or the distance difference ΔL are inversely proportional to the time interval T0.

[0024] In step S5, the time interval T0 of the next defrost mode is adjusted accordingly based on the ambient humidity H and the distance difference ΔL, so as to ensure the duration of the heat pump unit running in normal mode as much as possible and reduce the impact of defrosting on the user's physical sensation.

[0025] In this embodiment, an ultrasonic ranging unit 1 is used as a detection means for detecting the initial distance L1 and the dynamic distance L2. This method is special and effectively solves the problems of large errors and misjudgments in the traditional temperature measurement and judgment using temperature sensors and optical ranging sensors. The main reason is that the outdoor fin heat exchanger 2 of the heat pump unit is in the outdoor environment. When frost / ice accumulates on the surface, it either directly covers the temperature sensor or affects the judgment of the optical ranging sensor, and cannot be used as an effective judgment basis, causing the heat pump unit to be unable to switch or frequently switch to the defrost mode, thereby affecting the normal operation of the heat pump unit.

[0026] In the present embodiment, three ultrasonic ranging units 1 are also included, which are vertically aligned and respectively aimed at the upper position, middle position and lower position of the outdoor fin heat exchanger 2, wherein the ultrasonic ranging unit 1 located at the middle position detects and obtains the horizontal distance between it and the surface of the outdoor fin heat exchanger 2 as the initial distance L1; the two ultrasonic ranging units 1 located at the upper position and the lower position detect and obtain the average value of the horizontal distance between each of them and the surface of the outdoor fin heat exchanger 2 as the dynamic distance L2. Specifically, when frost / ice forms on the surface of the outdoor fin heat exchanger 2, the frost / ice is not evenly distributed on the surface, but is mainly concentrated at the refrigerant inlet or refrigerant outlet of the outdoor fin heat exchanger 2 (corresponding to the upper position and the lower position of the outdoor fin heat exchanger 2). When frost / ice forms at one of the upper position or the lower position of the outdoor fin heat exchanger 2, the other positions have not yet been frosted. Therefore, the average value of the horizontal distances monitored by the two ultrasonic ranging units 1 at the upper position and the lower position is used as the dynamic distance L2, which can more accurately predict and determine the future frost / ice conditions of the outdoor fin heat exchanger 2.

[0027] For ease of understanding, the following explanation is made based on the initial distance L1 and the dynamic distance L2 in combination with specific frosting / icing conditions.

[0028] Case 1: When the detection obtains that the initial distance L1 and the dynamic distance L2 are equal, it means that the outdoor fin heat exchanger 2 has not yet been frosted / iced, and it is predicted that the risk of frosting / icing during the subsequent normal operation is small, and normal operation can be performed, and the time interval T0 is relatively longer.

[0029] Case 2: When the detection obtains that the distance difference △L between the initial distance L1 and the dynamic distance L2 is between the rated distance range, it means that although a small amount of frost / icing has occurred on the outdoor fin heat exchanger 2, and it is predicted that the risk of frost / icing during the subsequent normal operation is medium, although the formed frost / ice layer has a certain impact on the performance of the heat pump unit, it can still operate in normal mode relatively stably, and the operation time of the normal mode can be extended as much as possible, and the time interval T0 is relatively medium.

[0030] Case 3: When the detection obtains that the distance difference △L between the initial distance L1 and the dynamic distance L2 is greater than the rated distance range, it means that although a large amount of frost / icing has occurred on the outdoor fin heat exchanger 2, and it is predicted that the risk of frost / icing during the subsequent normal operation is high, the formed frost / ice layer not only has a certain impact on the performance of the heat pump unit, but also has an impact on the normal operation mode. It is necessary to switch to the defrost mode as soon as possible, and the time interval T0 is relatively shorter.

[0031] In this embodiment, in step S4, the compressor operating frequency P of the heat pump unit is adjusted accordingly before entering the next defrost mode based on the distance difference △L, wherein the distance difference △L is inversely proportional to the compressor operating frequency P. This method of adjusting the compressor operating frequency P is mainly used to delay the frosting / icing rate of the outdoor fin heat exchanger 2. For ease of understanding, the following is a further explanation in combination with the above three situations: For situation one, the risk of frosting / icing is small, and the compressor operating frequency P runs at 100%; for situation two, the risk of frosting / icing is medium, and the compressor operating frequency P runs at 80% to appropriately slow down the frosting; for situation three, the risk of frosting / icing is high, and the compressor operating frequency P runs at 60% to slow down the frosting as much as possible.

[0032] In this embodiment, in step S4, the fan speed S of the heat pump unit is adjusted accordingly before entering the next defrost mode based on the distance difference △L, wherein the distance difference △L is proportional to the fan speed S. This method of adjusting the fan speed S is mainly used to delay the frost / icing rate of the outdoor fin heat exchanger 2. For ease of understanding, the following is a further explanation in combination with the above three situations: for situation one, the risk of frost / icing is small, and the fan speed S runs at 100%; for situation two, the risk of frost / icing is medium, and the fan speed S runs at 120%, and the air circulation rate is appropriately accelerated to increase the heat exchange rate; for situation three, the risk of frost / icing is high, and the fan speed S runs at 140%, which greatly accelerates the air circulation rate to increase the heat exchange rate, especially to prevent moisture in the air from staying in the outdoor fin heat exchanger 2.

[0033] In summary, the adjustment of the compressor operating frequency P and / or the fan speed S is intended to slow down the frost / freeze rate of the outdoor fin heat exchanger 2, thereby ensuring that the heat pump unit can maintain normal mode operation as much as possible when there is a risk of frost / freeze, thereby ensuring the user experience.

[0034] In this embodiment, the rated time in step S3 is preferably 45 minutes. Those skilled in the art may adjust the rated time according to actual working conditions, and no specific limitation is made here.

[0035] In this embodiment, the first humidity interval, the second humidity interval, the third humidity interval and the fourth humidity interval are divided into [0%, 40%], (40%, 60%], (60%, 80%], (80%, 100%] according to the humidity value, and the first distance interval, the second distance interval and the third distance interval are divided into [0], (0, 0.5], (0.5, +∞] according to the distance value, wherein any level of humidity interval and any level of distance interval are mapped to a corresponding time interval T0; the corresponding time interval T0 is determined according to the humidity interval corresponding to the ambient humidity H and the distance interval corresponding to the distance difference △L.

[0036] Specifically, according to the mapping relationship between each humidity interval and each distance interval, the corresponding time interval T0 is confirmed. If the ambient humidity H and / or the distance difference △L are larger, the time interval T0 is shorter. Therefore, the corresponding time interval T0 is determined by mapping the detected ambient humidity H and the distance difference △L with the corresponding humidity interval and distance interval, so that the heat pump unit can run in the normal mode at the time interval T0 and then switch to the defrost mode for defrosting.

[0037] To summarize, after the heat pump unit has been running in normal mode for a rated period of time, the ultrasonic ranging unit 1 detects and obtains the dynamic distance L2, and combines the initial distance L1 detected just at the end of defrosting to calculate and confirm the distance difference △L to reflect the risk of frost / icing, which is more convenient for making accurate predictions and adjustments to the time interval T0, especially to solve the problems of inaccurate traditional defrost detection methods and frequent defrost switching that affects the experience.

[0038] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any technician familiar with the art who, without departing from the scope of the technical solution of the present invention, makes more possible changes and modifications to the technical solution of the present invention using the technical content disclosed above, or modifications are all equivalent embodiments of the present invention. Therefore, any equivalent and equivalent changes made according to the ideas of the present invention without departing from the content of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting outdoor defrosting of a heat pump unit, characterized in that: The following steps are included: Step S1. The heat pump unit operates in defrost mode; Step S2. After the rated defrost mode is finished, an ultrasonic distance measuring unit pre-fixed at a designated position on the periphery of the outdoor fin heat exchanger of the heat pump unit is used to detect and obtain an initial distance L1 between the ultrasonic distance measuring unit and the surface of the outdoor fin heat exchanger of the heat pump unit, and an outdoor ambient humidity H is obtained based on a preset humidity detection unit; Step S3. The heat pump unit switches to the normal mode, and after running for a rated time, the dynamic distance L2 between the heat pump unit and the surface of the outdoor fin heat exchanger of the heat pump unit is obtained based on the ultrasonic distance measuring unit detection; Step S4. Calculate the distance difference △L between the initial distance L1 and the dynamic distance L2; Step S5. According to the ambient humidity H and the distance difference ΔL, the time interval T0 for the heat pump unit to switch to the defrost mode next time is correspondingly adjusted, wherein the ambient humidity H and / or the distance difference ΔL are inversely proportional to the time interval T0.

2. A method for detecting outdoor defrosting of a heat pump unit according to claim 1, characterized in that: It also includes three ultrasonic ranging units which are vertically aligned and respectively aimed at the upper, middle and lower positions of the outdoor fin heat exchanger, wherein the ultrasonic ranging unit located at the middle position detects and obtains the horizontal distance between it and the surface of the outdoor fin heat exchanger as the initial distance L1; the two ultrasonic ranging units located at the upper and lower positions detect and obtain the average value of the horizontal distances between each of them and the surface of the outdoor fin heat exchanger as the dynamic distance L2.

3. A method for detecting outdoor defrosting of a heat pump unit according to claim 1, characterized in that: According to the humidity value, there are the first humidity interval, the second humidity interval, the third humidity interval and the fourth humidity interval of [0%, 40%], (40%, 60%], (60%, 80%], (80%, 100%]; according to the distance value, there are the first distance interval, the second distance interval and the third distance interval of [0], (0, 0.5], (0.5, +∞]; any level of humidity interval and any level of distance interval are mapped to a corresponding time interval T0; the corresponding time interval T0 is determined according to the humidity interval corresponding to the ambient humidity H and the distance interval corresponding to the distance difference △L.

4. A method for detecting outdoor defrosting of a heat pump unit according to claim 1, characterized in that: In step S4, the operating frequency P of the compressor of the heat pump unit is adjusted accordingly before entering the next defrosting mode based on the distance difference ΔL, wherein the distance difference ΔL is inversely proportional to the operating frequency P of the compressor.

5. A method for detecting outdoor defrosting of a heat pump unit according to claim 3, characterized in that: In step S4, the fan speed S of the heat pump unit is adjusted accordingly before entering the next defrost mode based on the distance difference ΔL, wherein the distance difference ΔL is proportional to the fan speed S.

6. A method for detecting outdoor defrosting of a heat pump unit according to claim 3, characterized in that: The set time in step S3 is 45 minutes.

Images