Noise reduction improvement design method of twin-screw compressor and noise reduction improvement method of refrigeration equipment

Abstract

The application discloses a noise reduction improvement design method of a double-rotor compressor and a noise reduction improvement method of a refrigeration equipment, the double-rotor compressor comprising a first rotor and a second rotor which are engaged with each other, the first rotor having a tooth number z1 and a design rotating speed n1 r / min, the second rotor having a tooth number z2 and a design rotating speed n2 r / min, and the noise reduction improvement design method comprising the following step a: improving the design of the double-rotor compressor so that the tooth number and the rotating speed of the first rotor and the second rotor satisfy a relationship n > (21300 / z), wherein when n is n1, z is z1, and when n is n2, z is z2.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of noise reduction of refrigeration equipment, and particularly relates to a noise reduction improvement design method of a double-rotor compressor and a noise reduction improvement method of refrigeration equipment. BACKGROUND

[0002] Refrigeration equipment such as air conditioners and refrigerators are widely used, and are mostly equipped with double-rotor compressors such as double-screw compressors for refrigeration cycles. The double-rotor compressor generates noise when in operation, and the noise generation sources are complex, including aerodynamic noise generated by compressor suction and exhaust and electromagnetic noise generated by motor rotation. Different types of noise also appear to be coupled to make the noise more chaotic, and reducing the noise of the compressor during operation is an important work direction. The inventors have found that in the prior art, methods such as mufflers, baffles, and shock absorbers are mostly used to reduce noise, which can reduce the noise of the compressor to a certain extent, but the reduction effect is not ideal. SUMMARY

[0003] The present application relates to the field of noise reduction of refrigeration equipment, and particularly relates to a noise reduction improvement design method of a double-rotor compressor and a noise reduction improvement method of refrigeration equipment.

[0004] The present application discloses a noise reduction improvement design method of a double-rotor compressor, the double-rotor compressor comprising a first rotor and a second rotor that are intermeshed, the first rotor having a tooth number z1 and a design speed n1 r / min, the second rotor having a tooth number z2 and a design speed n2 r / min, the noise reduction improvement design method comprising: step a, improving the design of the double-rotor compressor to make the tooth number and the speed of the first rotor and the second rotor satisfy the relationship n > (21300 / z), wherein when n is n1, z is z1, and when n is n2, z is z2.

[0005] In some embodiments, the method comprises: when the design speed and the tooth number of the first rotor of the double-rotor compressor satisfy the relationship n1 < (21300 / z1), testing the noise of the double-rotor compressor, wherein when the ratio of the noise intensity of the double-rotor compressor in the medium-high frequency band to the noise limit value is less than a first threshold value, the step a comprises: step b, improving the design of the first rotor by increasing the design speed n1 of the first rotor to make the design speed and the tooth number of the first rotor satisfy the relationship n1 > (21300 / z1).

[0006] In some embodiments, the step a comprises: testing the noise of the double rotor compressor, wherein when the ratio of the noise intensity of the double rotor compressor in the middle-high frequency band to the noise limit value is greater than a first threshold value, the step a comprises: step c1, improving the design of the double rotor compressor by increasing the number of teeth of the first rotor so that the designed rotation speed and the number of teeth of the first rotor satisfy the relationship n1>(21300 / z1).

[0007] In some embodiments, the step a further comprises: after step c1, the step a further comprises step c2, testing the noise of the double rotor compressor, and if the ratio of the noise intensity of the double rotor compressor in the middle-high frequency band to the noise limit value is greater than a first threshold value, further improving the design of the double rotor compressor by reducing the designed rotation speed of the first rotor, and continuing to test the noise of the improved double rotor compressor to make the ratio of the noise intensity of the double rotor compressor in the middle-high frequency band to the noise limit value lower than the first threshold value.

[0008] In some embodiments, the step c2 further comprises: when the designed rotation speed and the number of teeth of the first rotor cannot continue to satisfy the relationship n1>(21300 / z1) by continuously reducing the designed rotation speed of the first rotor, first using the improved design of increasing the number of teeth of the first rotor, and then continuing to improve the design of the double rotor compressor by reducing the designed rotation speed of the first rotor, and continuing to test the noise of the improved double rotor compressor to make the ratio of the noise intensity of the double rotor compressor in the middle-high frequency band to the noise limit value lower than the first threshold value.

[0009] In some embodiments, the first threshold value is 15db.

[0010] In some embodiments, n1 is 1200r / min-3600r / min.

[0011] In some embodiments, z1 is 4-12.

[0012] In some embodiments, the double rotor compressor is a double screw compressor.

[0013] The second aspect of the present application discloses a noise reduction improvement method of a refrigeration equipment, comprising the noise reduction improvement method of the double rotor compressor according to any one of the claims.

[0014] Based on the double rotor compressor noise reduction improvement design method provided by the application, by improving the design of the double rotor compressor to make the tooth number and rotation speed of the first rotor and the second rotor satisfy the relationship n>(21300 / z), the aerodynamic noise of the double rotor compressor can be changed from low frequency noise with poor noise reduction effect by using silencers, baffles, shock absorbers and other methods to medium and high frequency noise with better noise reduction effect by using silencers, baffles, shock absorbers and other methods, so that the noise of the double rotor compressor during operation can be effectively improved.

[0015] Other features and advantages of the present application will become apparent from the following detailed description of illustrative embodiments thereof, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings described herein are intended to provide further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0017] Figure 1 Structure schematic diagram of the double rotor compressor of the embodiment of the present application;

[0018] Figure 2 Design range schematic diagram of the male rotor of the screw compressor of the double rotor compressor of another embodiment of the present application;

[0019] Figure 3 Noise test result schematic diagram of the double rotor compressor of another embodiment of the present application;

[0020] Figure 4 Noise test result schematic diagram of the double rotor compressor of another embodiment of the present application;

[0021] Figure 5 Noise test result schematic diagram of the double rotor compressor of another embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] The foregoing is considered as illustrative only of the principles of the application. Other variations and modifications can be made to the above-described embodiments consistent with the principles of the present application. Accordingly, the patent is not intended to limit the application to the embodiments set forth herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. It is to be understood that the phrases "in one embodiment" or "implementing the application" as used herein do not necessarily refer to the same embodiment, but differently implemented embodiments of the application can be implemented. No language indicates a dependent claim to subject matter recited in another dependent claim, except for a phrase according to "some embodiments" appended hereto indicating that the phrase can span subject matter of a dependent claim or claims to an independent claim or claims. Various specific features of the application are shown in parts in several claims, which can also manifest themselves in combinations of mentioned claims. Each claim can be combined with another without changing the general nature of the subject matter recited in that claim or additional claims.

[0024] In the description of the application, it is necessary to understand that the use of the words "first", "second" and the like words to define parts, only for the convenience of the corresponding parts to be distinguished, as no further declaration, the above words have no special meaning, therefore can not be understood as limiting the scope of the present application.

[0025] In the description of the application, it should be noted that unless otherwise specifically stated and limited, the terms "mounting", "connected", "connection" should be broadly understood, for example, can be fixedly connected, can also be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] For the convenience of description, spatial relative terms such as "above", "upper", "top", "up", etc. can be used herein to describe the spatial relationship of one device or feature to another device or feature as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "above" the other device or structure will be positioned "below" or "below" the other device or structure. Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative description used herein is interpreted accordingly.

[0027] As Figure 1As shown, the double rotor compressor 100 of the embodiment comprises a first rotor 1 and a second rotor 2 which are engaged with each other, the first rotor 1 has a number of teeth z1 and a design rotating speed n1 r / min, the second rotor 2 has a number of teeth z2 and a design rotating speed n2 r / min. The design rotating speed is usually the rated rotating speed, since the first rotor 1 and the second rotor 2 are engaged with each other, one of which is the driving one and the other is the driven one, the rotating speed and the number of teeth of the first rotor 1 and the second rotor 2 satisfy the relationship n2 / n1=z1 / z2.

[0028] The following table is the frequency band table divided by 1 / 3 octave from 1 to 20000 Hz:

[0029] Table 1 Frequency band table

[0030]

[0031] The inventor found that the conventional methods of noise eliminator, baffle, shock absorber and the like are usually used to reduce the noise of the compressor in the current technology, which has obvious effect on the noise of the middle and high frequency band greater than 355 Hz, but for the noise of the low frequency band lower than 355 Hz, that is, in the frequency band with the theoretical center frequency not higher than 315 Hz, since its penetration is strong and the decreasing speed is slow, the above conventional reduction method is difficult to eliminate the noise of the low frequency band. The noise generated by the double rotor compressor includes various sources, among which the electromagnetic noise is mainly the middle and high frequency noise greater than 355 Hz, and the conventional noise elimination method has good effect, while the frequency of the pneumatic noise generated by the suction and exhaust of the double rotor compressor is mainly the rotor suction and exhaust fundamental frequency, and the pneumatic noise generated by many compressors in the currently used double rotor compressor is the noise of the low frequency band lower than 355 Hz, and the reduction effect of the conventional noise elimination method is not ideal. Therefore, in order to improve the noise reduction effect of the pneumatic noise which is difficult to eliminate, the noise reduction improvement design method of the double rotor compressor 100 of the embodiment comprises the following steps: a. The double rotor compressor 100 is improved and designed so that the number of teeth and the rotating speed of the first rotor 1 and the second rotor 2 satisfy the relationship n>(21300 / z), wherein when n is n1, z is z1, and when n is n2, z is z2. When the rotor rotating speed and the number of teeth of the first rotor 1 or the second rotor 2 of the double rotor compressor 100 are improved and designed to satisfy the above relationship, that is, to satisfy nz / 60>355, that is, the suction and exhaust fundamental frequency of the double rotor compressor is improved and designed from the low frequency band to the middle and high frequency band, so that the suction and exhaust noise of the double rotor compressor is improved and designed from the low frequency band which is difficult to eliminate to the middle and high frequency band which is easier to eliminate, and the noise reduction effect can be obviously improved.

[0032] The noise reduction improvement design method of the twin-rotor compressor 100 in this embodiment improves the design of the twin-rotor compressor 100 so that the number of teeth and the speed of the first rotor 1 and the second rotor 2 satisfy the relationship n>(21300 / z). This can change the aerodynamic noise of the twin-rotor compressor 100 from low-frequency noise that is not well silenced by methods such as silencers, baffles, and shock absorbers to mid-to-high-frequency noise that is well silenced by methods such as silencers, baffles, and shock absorbers. This can effectively improve the noise of the twin-rotor compressor 100 during operation.

[0033] In some embodiments, the noise reduction improvement design method includes: when the relationship between the design speed and number of teeth of the first rotor 1 of the dual-rotor compressor 100 is n1 < (21300 / z1), according to the relationship between the speed and number of teeth of the first rotor 1 and the second rotor 2, the relationship between the design speed and number of teeth of the second rotor 2 is n2 < (21300 / z2). In this case, it is necessary to increase the fundamental frequency of the suction and exhaust noise of the dual-rotor compressor. First, the noise of the dual-rotor compressor 100 is tested. According to the test results, when the ratio of the noise intensity of the dual-rotor compressor 100 in the mid-to-high frequency band to the noise limit value is less than a first threshold, step a includes: step b, by increasing the design speed n1 of the first rotor 1 through an improved design method, so that the design speed and number of teeth of the first rotor 1 satisfy the relationship n1 > (21300 / z1). The noise limit value is the noise compliance requirement for the dual-rotor compressor. The noise compliance requirements for the dual-rotor compressor in each frequency band can be determined according to working environment requirements or enterprise standards, etc. Figures 3 to 5 In the illustrated embodiment, the light-colored curve represents the noise test value curve, and the dark-colored curve represents the noise limit value curve. The first threshold is the upper limit of the ratio of noise intensity to the noise limit value when the noise test value can be reduced to below the noise limit value through noise reduction treatment by methods such as silencers, baffles, and shock absorbers. When the ratio of the noise intensity measured in the mid-to-high frequency range to the noise limit value is less than the first threshold, it indicates that the noise in the mid-to-high frequency range of the twin-rotor compressor can be reduced to within the noise limit value through methods such as silencers, baffles, and vibration dampers. When the ratio of the noise intensity measured in the mid-to-high frequency range to the noise limit value is greater than the first threshold, it indicates that the noise in the mid-to-high frequency range of the twin-rotor compressor is difficult to reduce to within the noise limit value through methods such as silencers, baffles, and vibration dampers. Since increasing the rotor's design speed will increase the vibration amplitude, i.e., vibration intensity, of the twin-rotor compressor's noise in the mid-to-high frequency range, it will also increase the compressor's intake and exhaust efficiency. Therefore, when the ratio of the noise intensity measured in the mid-to-high frequency range to the noise limit value is less than the first threshold, the noise reduction improvement method in this embodiment is to increase the rotor's speed to raise the fundamental frequency of the twin-rotor compressor's intake and exhaust to the mid-to-high frequency range, which helps to improve the intake and exhaust efficiency of the twin-rotor compressor and improve the compressor's working efficiency.

[0034] In some embodiments, the step a comprises: when the relationship between the design speed and the number of teeth of the first rotor 1 of the double rotor compressor 100 is n1<(21300 / z1), testing the noise of the double rotor compressor 100, wherein when the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value is greater than the first threshold value, the step a comprises: a step c1, improving the design of the double rotor compressor 100 by increasing the number of teeth of the first rotor 1 so that the relationship between the design speed and the number of teeth of the first rotor 1 is n1>(21300 / z1). When the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value is greater than the first threshold value, it means that the noise of the double rotor compressor in the middle and high frequency band is difficult to be reduced to the noise limit value by the methods such as silencer, baffle, shock absorber, etc. In this case, the noise reduction improvement method of the present embodiment is to increase the number of teeth of the rotor to improve the suction and exhaust fundamental frequency of the double rotor compressor to the middle and high frequency band.

[0035] In some embodiments, the step a further comprises: after the step c1, a step c2, testing the noise of the double rotor compressor 100, and if the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value is greater than the first threshold value, further improving the design of the double rotor compressor 100 by reducing the design speed of the first rotor 1, and continuing to test the noise of the double rotor compressor 100 after the improvement of the design to make the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value be lower than the first threshold value. After the suction and exhaust fundamental frequency of the double rotor compressor is improved to the middle and high frequency band by increasing the number of teeth of the rotor, if the ratio of the noise intensity in the middle and high frequency band to the noise limit value is greater than the first threshold value, the design speed of the rotor needs to be further reduced to reduce the ratio of the noise intensity in the high frequency band to the noise limit value until the design speed of the rotor is reduced to make the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value be lower than the first threshold value.

[0036] In some embodiments, during the process of reducing the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value by reducing the design speed of the rotor, it is necessary to always ensure that the relationship between the design speed and the number of teeth of the first rotor 1 continues to satisfy the relationship n1>(21300 / z1). Therefore, the step c2 further comprises: when the continued reduction of the design speed of the first rotor 1 cannot make the relationship between the design speed and the number of teeth of the first rotor 1 continue to satisfy the relationship n1>(21300 / z1), first using the improved design method of increasing the number of teeth of the first rotor 1, and then continuing to improve the design of the double rotor compressor 100 by reducing the design speed of the first rotor 1, and continuing to test the noise of the double rotor compressor 100 after the improvement of the design to make the ratio of the noise intensity in the middle and high frequency band of the double rotor compressor 100 to the noise limit value be lower than the first threshold value.

[0037] In some embodiments, the first threshold value is 15db.

[0038] In some embodiments, n1 is 1200r / min~3600r / min.

[0039] In some embodiments, z1 is 4~12.

[0040] In some embodiments, the double rotor compressor 100 is a double screw compressor. The two rotors of the double screw compressor include a male rotor for driving and a female rotor driven by the male rotor.

[0041] In some embodiments, a noise reduction improvement method for a refrigeration device is also disclosed, including any of the above noise reduction improvement methods for the double rotor compressor 100. The refrigeration device includes an air conditioner and a refrigerator.

[0042] The following is a specific embodiment to illustrate the present application.

[0043] The design speed of the male rotor of a double screw compressor for a certain refrigeration device is designed to be 1200r / min~3600r / min, and the number of teeth of the male rotor is designed to be 4~12 teeth. Therefore, when designing the design speed n1 and the number of teeth z1 of the male rotor of the double screw compressor to be improved in noise reduction, it is necessary to satisfy z1>(21300 / n1). According to the above three conditions, the design range of the male rotor of the screw compressor is obtained as shown in the hatched part. Figure 2

[0044] A double screw compressor of an existing product is a 5 / 6 tooth male-female rotor structure, the number of teeth of the male rotor is 5, and the speed is 3000r / min. After testing, the distribution of the noise of the working product in each frequency band and the noise limit value curve are as shown in Figure 3 Figure 3 The product has a large noise vibration amplitude near 250Hz, which belongs to low frequency noise, and the suction and exhaust base frequency of the product is calculated to be 250Hz, which is less than 355Hz, belonging to the low frequency noise range that is difficult to eliminate. The suction and exhaust base frequency of the product needs to be improved. To this end, the design speed or the number of teeth of the male rotor of the product can be improved. Since Figure 3 ​​The vibration amplitude of the noise test value of the double-rotor compressor at the middle and high frequency bands is greater than the vibration amplitude of the noise limit value by a first threshold 15db at some frequencies, so that the suction and exhaust base frequency cannot be increased by increasing the rotation speed, and can only be increased by increasing the number of teeth. Therefore, the number of teeth of the male rotor of the double-screw compressor is first increased to 8, and the rotation speed is 3000r / min, so that the double-screw compressor becomes an 8 / 8 male-female rotor structure. After testing, the noise distribution and the noise limit curve of the 8-tooth double-screw compressor are as shown in Figure 4 As shown, the suction and exhaust base frequency of the double-screw compressor is 400Hz, which is greater than 355Hz, but the noise of the double-screw compressor at the middle and high frequency bands still exceeds the noise limit value by a large margin, exceeding the first threshold. To this end, an attempt is made to reduce the design rotation speed of the male rotor, but since the suction and exhaust base frequency of the double-screw compressor is 400Hz, which is close to 355Hz, in order to avoid reducing the suction and exhaust base frequency to below 355Hz by only reducing the design rotation speed, the number of teeth of the male rotor is first increased, and then the design of the double-screw compressor is improved by further reducing the design rotation speed of the male rotor. To this end, the male rotor is first improved to 12 teeth at 1800r / min, and the rotor of the double-screw compressor is improved to a 12 / 12 male-female rotor structure, and the noise of the improved double-screw compressor is continuously tested, and the test results are as shown in Figure 5 As shown, the suction and exhaust base frequency of the double-screw compressor is 360Hz, which is greater than 350Hz, and the ratio of the noise intensity in the middle and high frequency bands to the noise limit value is lower than the first threshold, meeting the noise reduction requirement.

[0045] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application.

Claims

1. A method of noise reduction improvement design of a dual rotor compressor, characterized in that, The double rotor compressor comprises a first rotor and a second rotor which are engaged with each other, the first rotor has a number of teeth z1 and a design rotating speed n1 r / min, the second rotor has a number of teeth z2 and a design rotating speed n2 r / min, and the noise reduction improvement design method comprises the following steps: a, improving the design of the double rotor compressor so that the number of teeth and the rotating speed of the first rotor and the second rotor satisfy the relationship n> (21300 / z), wherein when n is n1, z is z1, and when n is n2, z is z2; When the design rotating speed and the number of teeth of the first rotor of the double rotor compressor satisfy the relationship n1< (21300 / z1), the noise of the double rotor compressor is tested, wherein when the ratio of the noise intensity of the double rotor compressor in the medium-high frequency band to the noise limit value is less than a first threshold value, the step a comprises the following step b: improving the design of the first rotor by increasing the design rotating speed n1 of the first rotor so that the design rotating speed and the number of teeth of the first rotor satisfy the relationship n1> (21300 / z1); or when the design rotating speed and the number of teeth of the first rotor of the double rotor compressor satisfy the relationship n1< (21300 / z1), the noise of the double rotor compressor is tested, wherein when the ratio of the noise intensity of the double rotor compressor in the medium-high frequency band to the noise limit value is greater than the first threshold value, the step a comprises the following step c1: improving the design of the first rotor by increasing the number of teeth of the first rotor so that the design rotating speed and the number of teeth of the first rotor satisfy the relationship n1> (21300 / z1); wherein the first threshold value is the upper limit value of the ratio of the noise intensity to the noise limit value when the noise test value can be reduced below the noise limit value by the method of silencer, baffle or shock absorber.

2. The method of noise reduction improvement design of a twin-rotor compressor as set forth in claim 1, characterized in that, When the ratio of the noise intensity of the double rotor compressor in the medium-high frequency band to the noise limit value is greater than the first threshold value, the step a comprises the following step c1: improving the design of the first rotor by increasing the number of teeth of the first rotor so that the design rotating speed and the number of teeth of the first rotor satisfy the relationship n1> (21300 / z1); the step a further comprises the following step c2: after step c1, the noise of the double rotor compressor is tested, and if the ratio of the noise intensity of the double rotor compressor in the medium-high frequency band to the noise limit value is greater than the first threshold value, the double rotor compressor is further improved in design by reducing the design rotating speed of the first rotor, and the noise of the improved double rotor compressor is continuously tested so that the ratio of the noise intensity of the double rotor compressor in the medium-high frequency band to the noise limit value is lower than the first threshold value.

3. The method of claim 2, wherein the step of modifying the design of the dual-rotor compressor to reduce noise is performed by modifying the design of the dual-rotor compressor to reduce noise by reducing the amplitude of the second harmonic of the rotational speed of the second rotor. The step c2 further comprises: when the first rotor's design rotating speed cannot be continuously reduced to make the first rotor's design rotating speed and the number of teeth continuously satisfy the relationship n1> (21300 / z1), first using an improved design method of increasing the number of teeth of the first rotor, and then continuously improving the design of the double rotor compressor by reducing the design rotating speed of the first rotor, and continuously testing the noise of the improved double rotor compressor to make the ratio of the noise intensity of the double rotor compressor in the middle and high frequency band to the noise limit value lower than the first threshold value.

4. The method of noise reduction improvement design of a twin-rotor compressor according to any one of claims 1 to 3, characterized in that, The first threshold value is 15db.

5. The method of noise reduction improvement design of a twin-rotor compressor according to any one of claims 1 to 3, characterized in that, n1 is 1200 ~ 3600.

6. The method of noise reduction improvement design of a dual rotor compressor as set forth in claim 4, characterized in that, z1 is 4 ~ 12.

7. The method of noise reduction improvement design of a twin-rotor compressor according to any one of claims 1 to 3, characterized in that, The double rotor compressor is a double screw compressor.

8. A method of noise reduction improvement of a refrigeration appliance, characterized in that, A noise reduction improved design method comprising the double rotor compressor of any one of claims 1 to 7.

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