How to control the noise of air-cooled heat pump?

Air source heat pump unit has the advantages of energy saving and environmental protection, which is widely used in the field of heating The main engine of this kind of air central heating equipment has a feature that the power of the main engine and the circulating pump is very large, and the resulting noise problem can not be ignored Noise source analysis of heat pump unit noise is also known as heat pump vibration noise, heat pump sound vibration, heat pump unit noise, heat pump unit structure noise, which belongs to the physical nature of the noise Generally speaking, the noise of the heat pump unit is the irregular, intermittent and continuous random noise produced by the heat pump unit during operation The noise level is about 70 to 90 dB (a) The noise sources of the heat pump unit mainly include: the axial-flow fan at the upper part of the heat pump; the compressor at the lower part of the heat pump; and its supporting water supply pump According to the different ways of noise transmission, we usually adopt vibration isolation, muffler, sound insulation and other ways to deal with the noise of heat pump unit Heat pump unit belongs to low-frequency noise The characteristics of low-frequency noise are slow attenuation, long sound wave and strong penetration ability (its diffraction wave can easily bypass obstacles), so low-frequency noise is not easy to deal with From the structure analysis of heat pump, the noise source is compressor and exhaust fan The compressor and exhaust fan produce noise, and the steel structure of the heat pump produces micro vibration and structural vibration noise due to the operation of the equipment, but the former is the main noise (1) there is a certain difference between the measured noise level of the large heat pump and the noise index or sample provided by the seller, and the measured noise should exceed 3 ~ 10dB The sound level noise of general heat pump a is 79-82db, and some heat pumps are over 90dB If several heat pumps are installed near the residential building or on the top of the office building, the noise of the heat pump will inevitably have a greater impact on the surrounding environment (2) the noise of large-scale heat pump is open The noise mainly radiates from both sides and top of the heat pump, and the area of radiated noise is large For example, the number of exhaust fans on the top is large, and there are nearly 100 fans, with a total area of more than 12 ㎡ and the area on both sides of more than 10 square meters The noise spreads out from such a large area (echo source propagation), with a large influence range and slow attenuation There is no attenuation on the noise basis within 3M on both sides of the heat pump, and the attenuation rate within the length of the heat pump is 3dB (3) the noise frequency characteristic of heat pump is generally neutral low frequency, the main noise frequency is 63 ~ 500Hz, the distance attenuation of low frequency noise is slow, the influence range is wide, and it is not easy to eliminate (4) because the bottom of the general heat pump often does not have a fully enclosed chassis, only the steel structure frame, the compressor is supported on the frame, so the noise also spreads from the bottom down If the heat pump is installed on the roof, the downward noise is blocked by the floor to form a reflection If it is installed on the structural plane with gaps or holes, the noise will spread out from the gaps or holes Noise control measures of heat pump unit how to make sound insulation and noise reduction of pump unit? The pump unit is generally located on the roof of the building, and its noise mainly includes the following aspects: the air noise generated by the operation of the pump unit motor, the vibration of the pump unit compressor, the vibration of the building foundation and the work of the pump unit, so as to stimulate the resonance of the pipeline Therefore, to thoroughly solve the problem of heat pump noise, we should start from three aspects: air noise, equipment vibration and pipeline vibration 1 The air noise treatment and sound insulation are relatively easy in the aspect of noise control of the pump unit The air noise generated by the pump unit is generally no more than 85dB (a), and there is at least one floor space between the pump unit and the owner's room Generally, the air sound insulation of 120mm cast-in-place concrete is greater than 52dB, which is quite beneficial to isolate the air sound of the pump unit But now the country has strict requirements for the indoor acoustic environment, so if the distance between the pump unit and the owner is one floor, special treatment should be taken for the sound insulation The common methods include adding sound insulation cover, sound insulation ceiling, indoor sound absorption, etc 2 Generally, the vibration isolator is selected for the system vibration isolation of the pump set If the vibration of the pump set is relatively strong, the floating floor is preferred, because the floating floor has better vibration reduction effect and wider frequency band 3 Rubber soft connection is added (replaced) to the pipes connected with the pump unit for vibration isolation treatment Generally, the length of the soft connection is short and the elasticity is poor, resulting in the overall vibration isolation effect is not ideal, and the vibration isolation effect will be significantly increased after replacement The soft connection is suitable to select professional vibration isolation products with good vibration isolation performance, long length and corrosion resistance 4 The connection between the pipe support and the ground is hard link, which leads to the transmission of the vibration of the pipe to the building structure The vibration reduction treatment under the support can better prevent the transmission of the vibration energy to the building structure 5 In general, pipes and walls are hard connected when they pass through walls A considerable part of the vibration energy of pipes is transmitted to the building structure Therefore, the pipes and walls should be separated to prevent the energy transmission 6 The vibration and noise of the pipeline with damping and sound insulation binding is relatively high, and the air noise of vibration will also affect the residents Therefore, the comprehensive damping and sound insulation binding shall be carried out for the pipeline to reduce the vibration of the pipeline on the one hand, and on the other hand, it can also play a role in isolating the air noise It can be seen that the noise control of the pump unit is a professional and systematic reconstruction project The design and treatment of vibration and acoustics should be done from the sound source, transmission and the user receiving end, so as to reduce the impact of the noise of the heat pump unit on the owner Conclusion: with regard to the field measurement and noise treatment of air-cooled heat pump noise, at that time, the super high-rise apartment was designed to use air-cooled heat pump and placed on the roof of the tower After Zui, due to the failure of vibration and noise treatment, the renovation was carried out and the vibration treatment was completed, but the noise transmission was still not solved, which seriously affected the quality of the apartment and brought a certain impact on the apartment sales.