Research ArticleResearch on Noise Reduction Scheme of Heat Pump Unit ina Square

Xueyong Zhang 123 Yuanyuan Hu13 Shengyuan Geng2 Qianyong Hu1

and Huanbao Wang13

1School of Mathematics and Physics Institute of Acoustics Anhui Jianzhu University Hefei 230601 China2Anhui Province Key Laboratory of Intelligent Building amp Building Energy Saving Hefei 230022 China3Key Laboratory of Architectural Acoustic Environment of Anhui Higher Education Institutes Hefei 230601 China

Correspondence should be addressed to Xueyong Zhang xyzhang_aua126com

Received 30 October 2019 Revised 16 December 2019 Accepted 7 January 2020 Published 9 March 2020

Guest Editor Shaohui Wang

Copyright copy 2020 Xueyong Zhang et al is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Heat pump unit is a host device located in the central air-conditioning terminal providing cold and hot water Heat pump unit hasthe advantages of energy saving environmental protection easy maintenance and so on It is adopted to solve the problems ofrefrigeration and heating in ventilation and air conditioning from many engineering projects in China When the equipment isturned on however the high noise generated by the heat pump unit has a very negative impact on the life and work of thesurrounding residentserefore noise reduction is needed to improve the environment quality In this paper the noise of the air-cooled heat pump unit of the square area in Shanghai was detected the noise source was analyzed and the corresponding noisereduction schemewas proposed After the completion of the scheme measurements indicate that A-weighted sound pressure levelis less than or equal to 60 dB (A) during the day and less than or equal to 50 dB (A) at night whichmeets the relevant national noiselimit emission standards and conforms to the second-class quality standard of the acoustic environment

1 Introduction

Statistics released by Chinarsquos ministry of ecology and en-vironment protection show that by February 2019 thehotline 12369 had received noise pollution accounted for 32percent of reports Noise has gradually become one of thebiggest public hazards in recent years [1ndash5] Among themthe impact of the heat pump unit on the surrounding en-vironment is a universal environmental pollution problemthat the city faces and needs to be solved [6 7] Effectivecontrol noise is therefore very urgent and necessary

e air-cooled heat pump unit is widely used in theprojects with its advantages such as dual functions ofcooling and heating simple operation convenient man-agement and maintenance [8 9] In order to reduce thenoise of the heat pump unit and thus providing a morecomfortable living environment for people a reasonableimplementation scheme should be adopted in severalprojects In this paper the acoustic environment of the heat

pump unit of the square in Shanghai is taken as the mainresearch area First the sound environment is tested enaccording to the noise evaluation standards in China[10ndash12] a reasonable implementation scheme is developedand given to solve the noise disturbance of heat pump unitsin the square

2 Methods

21 Project Overview e air-cooled heat pump unitequipment (model AEH1080E unit weight 6900 kg ratedrefrigerationheat 180179 kw China) has a total of fourunits and a supporting water pump which are located in theiron fence area beside the road in a squaree main body ofthe equipment is 2300mm away from the other sideenclosing wall and the height of the wall is 1900mm eground between the wall and the main part of the equipmentis mainly paved with equipment pipelines e heat pumpunit has 40 fans at the top the chassis is not fully closed and

HindawiJournal of ChemistryVolume 2020 Article ID 1237034 6 pageshttpsdoiorg10115520201237034

the compressor is all supported on the steel frame e heatpump unit is surrounded by high-rise residential buildingsonly 8m from the nearest west side residence as shown inFigure 1

e units operate 24 hours without stopping When theequipment is in operation the sound pressure level is highWhen the noise generated by the heat pump unit exceed theemission limit of the corresponding area stipulated in thenational standard ldquoacoustic environment quality standardrdquo(GB-3096 China) effective measures should be taken im-mediately to reduce the noise

22 Noise Sources From the analysis of the overall structureof the heat pump unit the noise radiated by the equipmentduring operation can be divided into two parts When theheat pump unit is running its steel structure will have aslight vibration and this vibration will produce noise theother is generated by the compressor and the exhaust fan ofthe heat pump unit e latter may be the main part of thenoise of the heat pump unit

According to the field investigation the noise areaemitted by the heat pump unit is very large Because the twosides and the top of the unit emit noise outwards the noise ofthe heat pump unit is open In addition the compressor issupported fully on the steel frame and the noise of the heatpump unit also spreads down from the bottom

23 Acoustic Measurements In order to evaluate theacoustic quality of the square and to solve the noise dis-turbance of heat pump units acoustic measurements werecarried out A hand-held analyzer type 2250 (Bruel amp KjaeligrSound amp Vibration Measurement AS Naeligrum Denmark)was used in this study is sound level meter was calibratedbefore measurement e noise measured values werecharacterized by equivalent continuous A sound pressurelevel (see equations (1) and (2) e time recording char-acteristic of the instrument was ldquoslowrdquo response 100 valueswere read continuously e interval of reading the in-stantaneous value of the measuring point was 5 seconds Inorder to improve the precision several cares were takensuch as good weather conditions e measurement timeplace and temperature were accurately recorded In thiscurrent study the temperature measured was 20 to 26 de-grees Celsius and the weather was clear In addition themicrophone diaphragm of the sound level meter should beclean during measurement In order to reduce the influenceof wind on noise measurement results when the wind speedis greater than 3ms the microphone should be timelycovered with a windshield when the wind speed is greaterthan 5ms the measurement should be stopped immedi-ately During measurement the microphone should be faraway from other reflective surfaces and the vertical distancefrom the ground should be greater than 12m Finally safetyshould be observed during measurement to avoidobstructing the passage of vehicles and pedestrians

When the four heat pump units are all working the noiseof the unit itself and the interior of the west residentialbuilding is measured at eleven orsquoclock in the day time e

measurement points and test data are shown in Tables 1 and2 respectively

24 0eoretical Model of Sound Source Attenuation eattenuation of point sound source can be given by thefollowing equation

LA(r) LA r0( 1113857 minus 20 logr

r01113888 1113889 minus ΔL (1)

where LA(r) is A-weighted sound pressure level (SPL (A)) atr distance from the sound source in units of dB (A) LA(r0)

is the A-weighted sound pressure level at the point r0 andr0 1m from the sound source in units of dB (A) ΔL is theamount of attenuation caused by various factors includingshielding air absorption and ground effect and the unitis dB (A)

In the current study noise sources are varied Accordingto the superposition theorem of sound sources the equiv-alent sound pressure level at any point in the sound field canbe given by the following equation

LeqA 10 log1N

1113944

N

i110 LAi10( )⎛⎝ ⎞⎠ (2)

where LeqA is the equivalent A sound pressure level in dB(A) LAi is the ith A sound pressure level in dB (A) N is thetotal number of sources

25 Noise Reduction Measures For noise reduction of theair-cooled heat pump unit we mainly design a closed noisereduction structure that is steel structure beams and col-umns are designed on the periphery of the heat pump unitand the sound insulation plate is used to seal the air-cooledheat pump unit on three sides forming a large soundinsulation space At the same time the muffler is installed inthe inlet and outlet of the heat pump unit to avoid secondarynoise pollution

In order to prevent the vibration of the heat pump unitand the pump from being transmitted to other placesthrough the pipeline we installed the vibration absorptionand vibration isolation devices at the base of the heat pumpunit and the inlet and outlet water pipes respectively andinstalled the vibration absorption support at the mainpipeline

3 Results and Discussion

31 Sound Pressure Level Before noise modification themeasurement data of sound pressure level of the noise fromheat pump units are shown in Table 1 and the measure-ments of equivalent sound pressure level in the west resi-dential building with windows closed are shown in Table 2

In Table 1 it can be found that the noise generated by theair-cooled heat pump unit during operation is about 80 dB(A) and the maximum noise value reaches 92 dB (A) ehuge noise generated by the heat pump unit causes noisepollution to the adjacent floors and affects the lives of theresidents

2 Journal of Chemistry

As can be seen in Table 2 the noise generated by the heatpump unit presents a mid-low frequency characteristicBecause the low-frequency noise has strong penetrationwide frequency band slow distance attenuation and wideinfluence range the fifth and sixth floors are the areas mostaffected by the noise e equivalent sound pressure levelsare 497 dB (A) and 509 dB (A) respectively To create acomfortable living environment noise must be controlled

32 Overall Noise Reduction Scheme Generally there arethree ways to consider for noise reduction of the heat pumpunit first sound source management Because the unit is noteasy to reform sound source management has operationaldisadvantages and it is difficult to achieve second the noisetransmission way to control such as sound insulation noisereduction and vibration reduction methods for noise control

and third on the receiver side the noise-sensitive people shouldwear earmuffs and other labor protectionmeasures to indirectlyprevent and control noise [13 14] In the current study thesecond noise reduction method is adopted

Considering that the noise mainly comes from thecompressor and the exhaust fan during the operation of theheat pump unit the exhaust air of the heat pump unit andthe running water pump we use the overall sound insulationcover design for the heat pump unit that is the heat pumpunit area is closed and isolated In order to facilitate theventilation and heat dissipation of the equipment we set upan inlet and outlet air channel on the sound insulation coverand further apply a muffler in the inlet and outlet air channelfor noise elimination e schematic diagram of the soundshield for the heat pump unit is shown in Figure 2 It shouldbe mentioned here that in order to improve the soundinsulation effect of the sound enclosure sealing materials are

(a) (b)

Figure 1 e air-cooled heat pump unit before noise reduction treatment (a) left photograph (b) right schematic diagram

Table 1 Sound pressure levels of the noise from heat pump units before noise modification

Serialnumber Noise source Measuring point Sound pressure level (dB)

(A)1 Heat pump unit Next to the unit 892 Heat pump unit outlet Beside air outlet 923 Water pump Near the water pump 84

4 Heat pump unit and waterpump In front of the residential building on the south side 74

5 Heat pump unit and waterpump In front of the west side residential building 72

6 Heat pump unit outlet West side residential building 4-5 floors outside thewindow 77

7 Heat pump unit outlet South side residential building 4-5 floors outside thewindow 75

Table 2 Sound pressure levels in the west residential building with windows closed before noise modification

Measuring point Time (s) Leq T (dB) (A)Frequency (Hz)

125 250 500 1k 2k 4k 8k8F room 831 37 463 562 523 388 319 356 238 1938F room 822 45 463 545 516 408 384 362 24 1987F room 731 51 491 574 547 436 417 402 273 2157F room 722 33 489 584 559 417 353 355 291 2396F room 622 30 509 497 482 392 369 36 273 2255F room 522 30 497 473 46 378 419 394 295 228

Journal of Chemistry 3

used between the sound enclosure modules In particularwhen installing the sound insulation cover rubber dampingpad should be installed between the module and the groundto prevent rigid sound transmission

As for the air inlet design due to the limited space in theregion a vertical direct-insert muffler with a size of 1500mmlowast1000mm is adopted for the air inlet on the south side and thenorth side of the unit which is installed at a tilt of 15deg as shownin Figure 2 In this way the labyrinth channel is formed to

ensure that the heat pump unit can enter the air and achieve thebest noise reduction effect Considering the top air exhaustmuffler we use half bending muffler insert and use professionalsound-absorbing wall to block the equipment exhaust outlet Inthis way after the exhaust area of each equipment is separatedby the sound-absorbing wall the exhaust air of the heat pumpunit will form an independent space e lower part of theindependent space is the slow flow area of exhaust air which ismainly used for static pressure and rectification of the exhaust

Air inlet

South

Exhaust outlet

(a)

NorthAir inlet

Exhaust outlet

(b)

Figure 2 e schematic diagram of the sound shield for the heat pump unit

Water pipe

Steel frame

Spring shock absorber

Rubber pad

(a)

Water pump

So connection So connection

Spring shockabsorber

(b)

Figure 3 e schematic diagram of vibration isolation of the water pipe and the water pump

80

90

Before improvement (day)Aer improvement (day)Aer improvement (night)

30

40

50

60

70

SPL

dB (A

)

0

10

20

In front of theresidential building on

the south side

In front of the westside residential

building

West sideresidential building4-5 floors outside

the window

South sideresidential building4-5 floors outside

the window

Figure 4 Sound pressure levels of the noise outside the window of the building before and after improvement

4 Journal of Chemistry

air e upper part is the muffler channel composed of two-sidedmetal perforated plate filled with environmentally friendlysound-absorbing cotton which has dual functions of resistancemuffler and reactivemuffler For themuffling of the top exhaustair we adopt the half-folded muffler insert which has beenproved to be effective in multifrequency and wide-band muf-fling e upper and lower parts constitute the exhaust mufflerof the heat pump unit (noise attenuation 24dB (A)) which caneffectively control the influence of exhaust noise on the sur-rounding environment

As shown in Figure 3 in order to prevent the noisefrom being transmitted to other places through the pipevibration we install the vibration absorption and vibrationisolation devices on the base of the heat pump unit and theinlet and outlet water pipes respectively To overcome thevibration of the heat pump unit the concrete approach isto add a steel frame base on its side and then to install aspring shock absorber with deformation of 50mm underthe steel frame base Meanwhile 25mm spring shockabsorber is installed in the ground riser of the heat pumpunit e spring shock absorbers are all provided with8mm thick shock absorbent rubber pads To reduce thevibration of the water pump a spring shock absorbershould be added on the side of the base of the steel frameSoft connection is installed on both ends of the inlet andthe outlet and the concentricity should be adjusted[15 16] Current practice shows that these methods arevery effective in reducing noise transmission

Before and after improvement sound pressure levels ofthe noise outside the window of the building are shown inFigure 4 e noise interference generated by sound su-perposition outside the window of the affected building is nomore than 60 dB (A) during day time and no more than50 dB (A) at night In the west residential building the soundpressure levels after closing the window are shown in

Figure 5 It can be found that the sound pressure level is lessthan or equal to 35 dB (A) after noise improvement

4 Conclusions

enoise of the air-cooled heat pump unit of a square area inShanghai was detected the source of the noise was analyzedand the corresponding noise reduction scheme was pro-posed Noise reduction construction was carried out with thescheme e scheme is simple in construction and nice indesign After the completion of the scheme the heat pumpunit has smooth ventilation and heat dissipation and runsnormally Measurements indicate that the designed schemesmeet the relevant national noise limit emission standardswhich conform to the second-class quality standard ofacoustic environment (SPL (A) le60 dB (A) during the dayand le50 dB (A) at night) in China In addition on thepremise of ensuring the noise reduction effect the schemecan be well integrated with the environment and has a goodlandscape effect

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

All authors declare no conflicts of interest regarding thecontent and implications of this manuscript

Acknowledgments

is work was sponsored by the Open Foundation of AnhuiProvince Key Laboratory of Intelligent Building amp BuildingEnergy Saving (no IBBE2018KX04) and the National

0

10

20

30

40

50

60

8F room831

8F room822

7F room731

7F room722

6F room622

5F room522

Leq

T dB

(A)

Before improvementAer improvement

Figure 5 Sound pressure levels in the west residential building with windows closed before and after improvement

Journal of Chemistry 5

Natural Science Foundation of China (no 61471003) eauthors are grateful for the supports of Z-X He for hercontributions to the study

References

[1] Y De Kluizenaar S A Janssen F J Van LentheH M E Miedema and J P Mackenbach ldquoLong-term roadtraffic noise exposure is associated with an increase inmorning tirednessrdquo 0e Journal of the Acoustical Society ofAmerica vol 126 no 2 pp 626ndash633 2009

[2] G Licitra L Fredianelli D Petri and M A Vigotti ldquoAn-noyance evaluation due to overall railway noise and vibrationin Pisa urban areasrdquo Science of 0e Total Environmentvol 568 pp 1315ndash1325 2016

[3] G Bluhm and C Eriksson ldquoCardiovascular effects of envi-ronmental noise research in Swedenrdquo Noise and Healthvol 13 no 52 pp 212ndash216 2011

[4] T N Le L V Straatman J Lea and B Westerberg ldquoCurrentinsights in noise-induced hearing loss a literature review ofthe underlying mechanism pathophysiology asymmetry andmanagement optionsrdquo Journal of OtolaryngologymdashHead ampNeck Surgery vol 46 no 1 p 41 2017

[5] P Lercher G W Evans and M Meis ldquoAmbient noise andcognitive processes among primary school childrenrdquo Envi-ronment and Behavior vol 35 no 6 pp 725ndash735 2003

[6] C Bai Z Han HWei X Ju X Meng and Q Fu ldquoSimulationstudy on performance of a dual-source hybrid heat pump unitwith alternative refrigerantsrdquo Energy and Built Environmentvol 1 no 1 pp 1ndash10 2020

[7] M Dongellini and G L Morini ldquoOn-off cycling losses ofreversible air-to-water heat pump systems as a function of theunit power modulation capacityrdquo Energy Conversion andManagement vol 196 no 15 pp 966ndash978 2019

[8] S Li G Gong and J Peng ldquoDynamic coupling methodbetween air-source heat pumps and buildings in Chinarsquos hot-summercold-winter zonerdquo Applied Energy vol 254 no 15Article ID 113664 2019

[9] Y Cai D-D Zhang D Liu F-Y Zhao and H-QWang ldquoAirsource thermoelectric heat pump for simultaneous cold airdelivery and hot water supply full modeling and performanceevaluationrdquo Renewable Energy vol 130 pp 968ndash981 2019

[10] GB 22337 Noise Emission from Social Life China Environ-mental Science Press Beijing China 2008

[11] GBT 50121 Evaluation Standard for Sound Insulation ofBuildings China Building Industry Press Beijing China 2005

[12] GBJ 50118 Code for Sound Insulation Design of Civil Build-ings China Building Industry Press Beijing China 2010

[13] O Gustafsson C Haglund Stignor and J-O DalenbackldquoHeat exchanger design aspects related to noise in heat pumpapplicationsrdquo Applied 0ermal Engineering vol 93 no 25pp 742ndash749 2016

[14] O Gustafsson H Hellgren C H Stignor M AxellK Larsson and C Teuillieres ldquoFlat tube heat exchan-gersmdashdirect and indirect noise levels in heat pump applica-tionsrdquo Applied 0ermal Engineering vol 66 no 1-2pp 104ndash112 2014

[15] D Yano S Ishikawa K Tanaka and S Kijimoto ldquoVibrationanalysis of viscoelastic damping material attached to a cy-lindrical pipe by added mass and added dampingrdquo Journal ofSound and Vibration vol 454 no 18 pp 14ndash31 2019

[16] K Bi and H Hao ldquoUsing pipe-in-pipe systems for subseapipeline vibration controlrdquo Engineering Structures vol 109no 15 pp 75ndash84 2016

6 Journal of Chemistry

As can be seen in Table 2 the noise generated by the heatpump unit presents a mid-low frequency characteristicBecause the low-frequency noise has strong penetrationwide frequency band slow distance attenuation and wideinfluence range the fifth and sixth floors are the areas mostaffected by the noise e equivalent sound pressure levelsare 497 dB (A) and 509 dB (A) respectively To create acomfortable living environment noise must be controlled

32 Overall Noise Reduction Scheme Generally there arethree ways to consider for noise reduction of the heat pumpunit first sound source management Because the unit is noteasy to reform sound source management has operationaldisadvantages and it is difficult to achieve second the noisetransmission way to control such as sound insulation noisereduction and vibration reduction methods for noise control

and third on the receiver side the noise-sensitive people shouldwear earmuffs and other labor protectionmeasures to indirectlyprevent and control noise [13 14] In the current study thesecond noise reduction method is adopted

Considering that the noise mainly comes from thecompressor and the exhaust fan during the operation of theheat pump unit the exhaust air of the heat pump unit andthe running water pump we use the overall sound insulationcover design for the heat pump unit that is the heat pumpunit area is closed and isolated In order to facilitate theventilation and heat dissipation of the equipment we set upan inlet and outlet air channel on the sound insulation coverand further apply a muffler in the inlet and outlet air channelfor noise elimination e schematic diagram of the soundshield for the heat pump unit is shown in Figure 2 It shouldbe mentioned here that in order to improve the soundinsulation effect of the sound enclosure sealing materials are

(a) (b)

Figure 1 e air-cooled heat pump unit before noise reduction treatment (a) left photograph (b) right schematic diagram

Table 1 Sound pressure levels of the noise from heat pump units before noise modification

Serialnumber Noise source Measuring point Sound pressure level (dB)

(A)1 Heat pump unit Next to the unit 892 Heat pump unit outlet Beside air outlet 923 Water pump Near the water pump 84

4 Heat pump unit and waterpump In front of the residential building on the south side 74

5 Heat pump unit and waterpump In front of the west side residential building 72

6 Heat pump unit outlet West side residential building 4-5 floors outside thewindow 77

7 Heat pump unit outlet South side residential building 4-5 floors outside thewindow 75

Table 2 Sound pressure levels in the west residential building with windows closed before noise modification

Measuring point Time (s) Leq T (dB) (A)Frequency (Hz)

125 250 500 1k 2k 4k 8k8F room 831 37 463 562 523 388 319 356 238 1938F room 822 45 463 545 516 408 384 362 24 1987F room 731 51 491 574 547 436 417 402 273 2157F room 722 33 489 584 559 417 353 355 291 2396F room 622 30 509 497 482 392 369 36 273 2255F room 522 30 497 473 46 378 419 394 295 228

Journal of Chemistry 3

used between the sound enclosure modules In particularwhen installing the sound insulation cover rubber dampingpad should be installed between the module and the groundto prevent rigid sound transmission

As for the air inlet design due to the limited space in theregion a vertical direct-insert muffler with a size of 1500mmlowast1000mm is adopted for the air inlet on the south side and thenorth side of the unit which is installed at a tilt of 15deg as shownin Figure 2 In this way the labyrinth channel is formed to

ensure that the heat pump unit can enter the air and achieve thebest noise reduction effect Considering the top air exhaustmuffler we use half bending muffler insert and use professionalsound-absorbing wall to block the equipment exhaust outlet Inthis way after the exhaust area of each equipment is separatedby the sound-absorbing wall the exhaust air of the heat pumpunit will form an independent space e lower part of theindependent space is the slow flow area of exhaust air which ismainly used for static pressure and rectification of the exhaust

Air inlet

South

Exhaust outlet

(a)

NorthAir inlet

Exhaust outlet

(b)

Figure 2 e schematic diagram of the sound shield for the heat pump unit

Water pipe

Steel frame

Spring shock absorber

Rubber pad

(a)

Water pump

So connection So connection

Spring shockabsorber

(b)

Figure 3 e schematic diagram of vibration isolation of the water pipe and the water pump

80

90

Before improvement (day)Aer improvement (day)Aer improvement (night)

30

40

50

60

70

SPL

dB (A

)

0

10

20

In front of theresidential building on

the south side

In front of the westside residential

building

West sideresidential building4-5 floors outside

the window

South sideresidential building4-5 floors outside

the window

Figure 4 Sound pressure levels of the noise outside the window of the building before and after improvement

4 Journal of Chemistry

air e upper part is the muffler channel composed of two-sidedmetal perforated plate filled with environmentally friendlysound-absorbing cotton which has dual functions of resistancemuffler and reactivemuffler For themuffling of the top exhaustair we adopt the half-folded muffler insert which has beenproved to be effective in multifrequency and wide-band muf-fling e upper and lower parts constitute the exhaust mufflerof the heat pump unit (noise attenuation 24dB (A)) which caneffectively control the influence of exhaust noise on the sur-rounding environment

As shown in Figure 3 in order to prevent the noisefrom being transmitted to other places through the pipevibration we install the vibration absorption and vibrationisolation devices on the base of the heat pump unit and theinlet and outlet water pipes respectively To overcome thevibration of the heat pump unit the concrete approach isto add a steel frame base on its side and then to install aspring shock absorber with deformation of 50mm underthe steel frame base Meanwhile 25mm spring shockabsorber is installed in the ground riser of the heat pumpunit e spring shock absorbers are all provided with8mm thick shock absorbent rubber pads To reduce thevibration of the water pump a spring shock absorbershould be added on the side of the base of the steel frameSoft connection is installed on both ends of the inlet andthe outlet and the concentricity should be adjusted[15 16] Current practice shows that these methods arevery effective in reducing noise transmission

Before and after improvement sound pressure levels ofthe noise outside the window of the building are shown inFigure 4 e noise interference generated by sound su-perposition outside the window of the affected building is nomore than 60 dB (A) during day time and no more than50 dB (A) at night In the west residential building the soundpressure levels after closing the window are shown in

Figure 5 It can be found that the sound pressure level is lessthan or equal to 35 dB (A) after noise improvement

4 Conclusions

enoise of the air-cooled heat pump unit of a square area inShanghai was detected the source of the noise was analyzedand the corresponding noise reduction scheme was pro-posed Noise reduction construction was carried out with thescheme e scheme is simple in construction and nice indesign After the completion of the scheme the heat pumpunit has smooth ventilation and heat dissipation and runsnormally Measurements indicate that the designed schemesmeet the relevant national noise limit emission standardswhich conform to the second-class quality standard ofacoustic environment (SPL (A) le60 dB (A) during the dayand le50 dB (A) at night) in China In addition on thepremise of ensuring the noise reduction effect the schemecan be well integrated with the environment and has a goodlandscape effect

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

All authors declare no conflicts of interest regarding thecontent and implications of this manuscript

Acknowledgments

is work was sponsored by the Open Foundation of AnhuiProvince Key Laboratory of Intelligent Building amp BuildingEnergy Saving (no IBBE2018KX04) and the National

0

10

20

30

40

50

60

8F room831

8F room822

7F room731

7F room722

6F room622

5F room522

Leq

T dB

(A)

Before improvementAer improvement

Figure 5 Sound pressure levels in the west residential building with windows closed before and after improvement

Journal of Chemistry 5

Natural Science Foundation of China (no 61471003) eauthors are grateful for the supports of Z-X He for hercontributions to the study

References

[1] Y De Kluizenaar S A Janssen F J Van LentheH M E Miedema and J P Mackenbach ldquoLong-term roadtraffic noise exposure is associated with an increase inmorning tirednessrdquo 0e Journal of the Acoustical Society ofAmerica vol 126 no 2 pp 626ndash633 2009

[2] G Licitra L Fredianelli D Petri and M A Vigotti ldquoAn-noyance evaluation due to overall railway noise and vibrationin Pisa urban areasrdquo Science of 0e Total Environmentvol 568 pp 1315ndash1325 2016

[3] G Bluhm and C Eriksson ldquoCardiovascular effects of envi-ronmental noise research in Swedenrdquo Noise and Healthvol 13 no 52 pp 212ndash216 2011

[4] T N Le L V Straatman J Lea and B Westerberg ldquoCurrentinsights in noise-induced hearing loss a literature review ofthe underlying mechanism pathophysiology asymmetry andmanagement optionsrdquo Journal of OtolaryngologymdashHead ampNeck Surgery vol 46 no 1 p 41 2017

[5] P Lercher G W Evans and M Meis ldquoAmbient noise andcognitive processes among primary school childrenrdquo Envi-ronment and Behavior vol 35 no 6 pp 725ndash735 2003

[6] C Bai Z Han HWei X Ju X Meng and Q Fu ldquoSimulationstudy on performance of a dual-source hybrid heat pump unitwith alternative refrigerantsrdquo Energy and Built Environmentvol 1 no 1 pp 1ndash10 2020

[7] M Dongellini and G L Morini ldquoOn-off cycling losses ofreversible air-to-water heat pump systems as a function of theunit power modulation capacityrdquo Energy Conversion andManagement vol 196 no 15 pp 966ndash978 2019

[8] S Li G Gong and J Peng ldquoDynamic coupling methodbetween air-source heat pumps and buildings in Chinarsquos hot-summercold-winter zonerdquo Applied Energy vol 254 no 15Article ID 113664 2019

[9] Y Cai D-D Zhang D Liu F-Y Zhao and H-QWang ldquoAirsource thermoelectric heat pump for simultaneous cold airdelivery and hot water supply full modeling and performanceevaluationrdquo Renewable Energy vol 130 pp 968ndash981 2019

[10] GB 22337 Noise Emission from Social Life China Environ-mental Science Press Beijing China 2008

[11] GBT 50121 Evaluation Standard for Sound Insulation ofBuildings China Building Industry Press Beijing China 2005

[12] GBJ 50118 Code for Sound Insulation Design of Civil Build-ings China Building Industry Press Beijing China 2010

[13] O Gustafsson C Haglund Stignor and J-O DalenbackldquoHeat exchanger design aspects related to noise in heat pumpapplicationsrdquo Applied 0ermal Engineering vol 93 no 25pp 742ndash749 2016

[14] O Gustafsson H Hellgren C H Stignor M AxellK Larsson and C Teuillieres ldquoFlat tube heat exchan-gersmdashdirect and indirect noise levels in heat pump applica-tionsrdquo Applied 0ermal Engineering vol 66 no 1-2pp 104ndash112 2014

[15] D Yano S Ishikawa K Tanaka and S Kijimoto ldquoVibrationanalysis of viscoelastic damping material attached to a cy-lindrical pipe by added mass and added dampingrdquo Journal ofSound and Vibration vol 454 no 18 pp 14ndash31 2019

[16] K Bi and H Hao ldquoUsing pipe-in-pipe systems for subseapipeline vibration controlrdquo Engineering Structures vol 109no 15 pp 75ndash84 2016

6 Journal of Chemistry

used between the sound enclosure modules In particularwhen installing the sound insulation cover rubber dampingpad should be installed between the module and the groundto prevent rigid sound transmission

As for the air inlet design due to the limited space in theregion a vertical direct-insert muffler with a size of 1500mmlowast1000mm is adopted for the air inlet on the south side and thenorth side of the unit which is installed at a tilt of 15deg as shownin Figure 2 In this way the labyrinth channel is formed to

ensure that the heat pump unit can enter the air and achieve thebest noise reduction effect Considering the top air exhaustmuffler we use half bending muffler insert and use professionalsound-absorbing wall to block the equipment exhaust outlet Inthis way after the exhaust area of each equipment is separatedby the sound-absorbing wall the exhaust air of the heat pumpunit will form an independent space e lower part of theindependent space is the slow flow area of exhaust air which ismainly used for static pressure and rectification of the exhaust

Air inlet

South

Exhaust outlet

(a)

NorthAir inlet

Exhaust outlet

(b)

Figure 2 e schematic diagram of the sound shield for the heat pump unit

Water pipe

Steel frame

Spring shock absorber

Rubber pad

(a)

Water pump

So connection So connection

Spring shockabsorber

(b)

Figure 3 e schematic diagram of vibration isolation of the water pipe and the water pump

80

90

Before improvement (day)Aer improvement (day)Aer improvement (night)

30

40

50

60

70

SPL

dB (A

)

0

10

20

In front of theresidential building on

the south side

In front of the westside residential

building

West sideresidential building4-5 floors outside

the window

South sideresidential building4-5 floors outside

the window

Figure 4 Sound pressure levels of the noise outside the window of the building before and after improvement

4 Journal of Chemistry

air e upper part is the muffler channel composed of two-sidedmetal perforated plate filled with environmentally friendlysound-absorbing cotton which has dual functions of resistancemuffler and reactivemuffler For themuffling of the top exhaustair we adopt the half-folded muffler insert which has beenproved to be effective in multifrequency and wide-band muf-fling e upper and lower parts constitute the exhaust mufflerof the heat pump unit (noise attenuation 24dB (A)) which caneffectively control the influence of exhaust noise on the sur-rounding environment

As shown in Figure 3 in order to prevent the noisefrom being transmitted to other places through the pipevibration we install the vibration absorption and vibrationisolation devices on the base of the heat pump unit and theinlet and outlet water pipes respectively To overcome thevibration of the heat pump unit the concrete approach isto add a steel frame base on its side and then to install aspring shock absorber with deformation of 50mm underthe steel frame base Meanwhile 25mm spring shockabsorber is installed in the ground riser of the heat pumpunit e spring shock absorbers are all provided with8mm thick shock absorbent rubber pads To reduce thevibration of the water pump a spring shock absorbershould be added on the side of the base of the steel frameSoft connection is installed on both ends of the inlet andthe outlet and the concentricity should be adjusted[15 16] Current practice shows that these methods arevery effective in reducing noise transmission

Before and after improvement sound pressure levels ofthe noise outside the window of the building are shown inFigure 4 e noise interference generated by sound su-perposition outside the window of the affected building is nomore than 60 dB (A) during day time and no more than50 dB (A) at night In the west residential building the soundpressure levels after closing the window are shown in

Figure 5 It can be found that the sound pressure level is lessthan or equal to 35 dB (A) after noise improvement

4 Conclusions

enoise of the air-cooled heat pump unit of a square area inShanghai was detected the source of the noise was analyzedand the corresponding noise reduction scheme was pro-posed Noise reduction construction was carried out with thescheme e scheme is simple in construction and nice indesign After the completion of the scheme the heat pumpunit has smooth ventilation and heat dissipation and runsnormally Measurements indicate that the designed schemesmeet the relevant national noise limit emission standardswhich conform to the second-class quality standard ofacoustic environment (SPL (A) le60 dB (A) during the dayand le50 dB (A) at night) in China In addition on thepremise of ensuring the noise reduction effect the schemecan be well integrated with the environment and has a goodlandscape effect

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

All authors declare no conflicts of interest regarding thecontent and implications of this manuscript

Acknowledgments

is work was sponsored by the Open Foundation of AnhuiProvince Key Laboratory of Intelligent Building amp BuildingEnergy Saving (no IBBE2018KX04) and the National

0

10

20

30

40

50

60

8F room831

8F room822

7F room731

7F room722

6F room622

5F room522

Leq

T dB

(A)

Before improvementAer improvement

Figure 5 Sound pressure levels in the west residential building with windows closed before and after improvement

Journal of Chemistry 5

Natural Science Foundation of China (no 61471003) eauthors are grateful for the supports of Z-X He for hercontributions to the study

References

[1] Y De Kluizenaar S A Janssen F J Van LentheH M E Miedema and J P Mackenbach ldquoLong-term roadtraffic noise exposure is associated with an increase inmorning tirednessrdquo 0e Journal of the Acoustical Society ofAmerica vol 126 no 2 pp 626ndash633 2009

[2] G Licitra L Fredianelli D Petri and M A Vigotti ldquoAn-noyance evaluation due to overall railway noise and vibrationin Pisa urban areasrdquo Science of 0e Total Environmentvol 568 pp 1315ndash1325 2016

[3] G Bluhm and C Eriksson ldquoCardiovascular effects of envi-ronmental noise research in Swedenrdquo Noise and Healthvol 13 no 52 pp 212ndash216 2011

[4] T N Le L V Straatman J Lea and B Westerberg ldquoCurrentinsights in noise-induced hearing loss a literature review ofthe underlying mechanism pathophysiology asymmetry andmanagement optionsrdquo Journal of OtolaryngologymdashHead ampNeck Surgery vol 46 no 1 p 41 2017

[5] P Lercher G W Evans and M Meis ldquoAmbient noise andcognitive processes among primary school childrenrdquo Envi-ronment and Behavior vol 35 no 6 pp 725ndash735 2003

[6] C Bai Z Han HWei X Ju X Meng and Q Fu ldquoSimulationstudy on performance of a dual-source hybrid heat pump unitwith alternative refrigerantsrdquo Energy and Built Environmentvol 1 no 1 pp 1ndash10 2020

[7] M Dongellini and G L Morini ldquoOn-off cycling losses ofreversible air-to-water heat pump systems as a function of theunit power modulation capacityrdquo Energy Conversion andManagement vol 196 no 15 pp 966ndash978 2019

[8] S Li G Gong and J Peng ldquoDynamic coupling methodbetween air-source heat pumps and buildings in Chinarsquos hot-summercold-winter zonerdquo Applied Energy vol 254 no 15Article ID 113664 2019

[9] Y Cai D-D Zhang D Liu F-Y Zhao and H-QWang ldquoAirsource thermoelectric heat pump for simultaneous cold airdelivery and hot water supply full modeling and performanceevaluationrdquo Renewable Energy vol 130 pp 968ndash981 2019

[10] GB 22337 Noise Emission from Social Life China Environ-mental Science Press Beijing China 2008

[11] GBT 50121 Evaluation Standard for Sound Insulation ofBuildings China Building Industry Press Beijing China 2005

[12] GBJ 50118 Code for Sound Insulation Design of Civil Build-ings China Building Industry Press Beijing China 2010

[13] O Gustafsson C Haglund Stignor and J-O DalenbackldquoHeat exchanger design aspects related to noise in heat pumpapplicationsrdquo Applied 0ermal Engineering vol 93 no 25pp 742ndash749 2016

[14] O Gustafsson H Hellgren C H Stignor M AxellK Larsson and C Teuillieres ldquoFlat tube heat exchan-gersmdashdirect and indirect noise levels in heat pump applica-tionsrdquo Applied 0ermal Engineering vol 66 no 1-2pp 104ndash112 2014

[15] D Yano S Ishikawa K Tanaka and S Kijimoto ldquoVibrationanalysis of viscoelastic damping material attached to a cy-lindrical pipe by added mass and added dampingrdquo Journal ofSound and Vibration vol 454 no 18 pp 14ndash31 2019

[16] K Bi and H Hao ldquoUsing pipe-in-pipe systems for subseapipeline vibration controlrdquo Engineering Structures vol 109no 15 pp 75ndash84 2016

6 Journal of Chemistry

air e upper part is the muffler channel composed of two-sidedmetal perforated plate filled with environmentally friendlysound-absorbing cotton which has dual functions of resistancemuffler and reactivemuffler For themuffling of the top exhaustair we adopt the half-folded muffler insert which has beenproved to be effective in multifrequency and wide-band muf-fling e upper and lower parts constitute the exhaust mufflerof the heat pump unit (noise attenuation 24dB (A)) which caneffectively control the influence of exhaust noise on the sur-rounding environment

As shown in Figure 3 in order to prevent the noisefrom being transmitted to other places through the pipevibration we install the vibration absorption and vibrationisolation devices on the base of the heat pump unit and theinlet and outlet water pipes respectively To overcome thevibration of the heat pump unit the concrete approach isto add a steel frame base on its side and then to install aspring shock absorber with deformation of 50mm underthe steel frame base Meanwhile 25mm spring shockabsorber is installed in the ground riser of the heat pumpunit e spring shock absorbers are all provided with8mm thick shock absorbent rubber pads To reduce thevibration of the water pump a spring shock absorbershould be added on the side of the base of the steel frameSoft connection is installed on both ends of the inlet andthe outlet and the concentricity should be adjusted[15 16] Current practice shows that these methods arevery effective in reducing noise transmission

Before and after improvement sound pressure levels ofthe noise outside the window of the building are shown inFigure 4 e noise interference generated by sound su-perposition outside the window of the affected building is nomore than 60 dB (A) during day time and no more than50 dB (A) at night In the west residential building the soundpressure levels after closing the window are shown in

Figure 5 It can be found that the sound pressure level is lessthan or equal to 35 dB (A) after noise improvement

4 Conclusions

enoise of the air-cooled heat pump unit of a square area inShanghai was detected the source of the noise was analyzedand the corresponding noise reduction scheme was pro-posed Noise reduction construction was carried out with thescheme e scheme is simple in construction and nice indesign After the completion of the scheme the heat pumpunit has smooth ventilation and heat dissipation and runsnormally Measurements indicate that the designed schemesmeet the relevant national noise limit emission standardswhich conform to the second-class quality standard ofacoustic environment (SPL (A) le60 dB (A) during the dayand le50 dB (A) at night) in China In addition on thepremise of ensuring the noise reduction effect the schemecan be well integrated with the environment and has a goodlandscape effect

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

All authors declare no conflicts of interest regarding thecontent and implications of this manuscript

Acknowledgments

is work was sponsored by the Open Foundation of AnhuiProvince Key Laboratory of Intelligent Building amp BuildingEnergy Saving (no IBBE2018KX04) and the National

0

10

20

30

40

50

60

8F room831

8F room822

7F room731

7F room722

6F room622

5F room522

Leq

T dB

(A)

Before improvementAer improvement

Figure 5 Sound pressure levels in the west residential building with windows closed before and after improvement

Journal of Chemistry 5

Natural Science Foundation of China (no 61471003) eauthors are grateful for the supports of Z-X He for hercontributions to the study

References

[1] Y De Kluizenaar S A Janssen F J Van LentheH M E Miedema and J P Mackenbach ldquoLong-term roadtraffic noise exposure is associated with an increase inmorning tirednessrdquo 0e Journal of the Acoustical Society ofAmerica vol 126 no 2 pp 626ndash633 2009

[2] G Licitra L Fredianelli D Petri and M A Vigotti ldquoAn-noyance evaluation due to overall railway noise and vibrationin Pisa urban areasrdquo Science of 0e Total Environmentvol 568 pp 1315ndash1325 2016

[3] G Bluhm and C Eriksson ldquoCardiovascular effects of envi-ronmental noise research in Swedenrdquo Noise and Healthvol 13 no 52 pp 212ndash216 2011

[4] T N Le L V Straatman J Lea and B Westerberg ldquoCurrentinsights in noise-induced hearing loss a literature review ofthe underlying mechanism pathophysiology asymmetry andmanagement optionsrdquo Journal of OtolaryngologymdashHead ampNeck Surgery vol 46 no 1 p 41 2017

[5] P Lercher G W Evans and M Meis ldquoAmbient noise andcognitive processes among primary school childrenrdquo Envi-ronment and Behavior vol 35 no 6 pp 725ndash735 2003

[6] C Bai Z Han HWei X Ju X Meng and Q Fu ldquoSimulationstudy on performance of a dual-source hybrid heat pump unitwith alternative refrigerantsrdquo Energy and Built Environmentvol 1 no 1 pp 1ndash10 2020

[7] M Dongellini and G L Morini ldquoOn-off cycling losses ofreversible air-to-water heat pump systems as a function of theunit power modulation capacityrdquo Energy Conversion andManagement vol 196 no 15 pp 966ndash978 2019

[8] S Li G Gong and J Peng ldquoDynamic coupling methodbetween air-source heat pumps and buildings in Chinarsquos hot-summercold-winter zonerdquo Applied Energy vol 254 no 15Article ID 113664 2019

[9] Y Cai D-D Zhang D Liu F-Y Zhao and H-QWang ldquoAirsource thermoelectric heat pump for simultaneous cold airdelivery and hot water supply full modeling and performanceevaluationrdquo Renewable Energy vol 130 pp 968ndash981 2019

[10] GB 22337 Noise Emission from Social Life China Environ-mental Science Press Beijing China 2008

[11] GBT 50121 Evaluation Standard for Sound Insulation ofBuildings China Building Industry Press Beijing China 2005

[12] GBJ 50118 Code for Sound Insulation Design of Civil Build-ings China Building Industry Press Beijing China 2010

[13] O Gustafsson C Haglund Stignor and J-O DalenbackldquoHeat exchanger design aspects related to noise in heat pumpapplicationsrdquo Applied 0ermal Engineering vol 93 no 25pp 742ndash749 2016

[14] O Gustafsson H Hellgren C H Stignor M AxellK Larsson and C Teuillieres ldquoFlat tube heat exchan-gersmdashdirect and indirect noise levels in heat pump applica-tionsrdquo Applied 0ermal Engineering vol 66 no 1-2pp 104ndash112 2014

[15] D Yano S Ishikawa K Tanaka and S Kijimoto ldquoVibrationanalysis of viscoelastic damping material attached to a cy-lindrical pipe by added mass and added dampingrdquo Journal ofSound and Vibration vol 454 no 18 pp 14ndash31 2019

[16] K Bi and H Hao ldquoUsing pipe-in-pipe systems for subseapipeline vibration controlrdquo Engineering Structures vol 109no 15 pp 75ndash84 2016

6 Journal of Chemistry

Natural Science Foundation of China (no 61471003) eauthors are grateful for the supports of Z-X He for hercontributions to the study

References

[1] Y De Kluizenaar S A Janssen F J Van LentheH M E Miedema and J P Mackenbach ldquoLong-term roadtraffic noise exposure is associated with an increase inmorning tirednessrdquo 0e Journal of the Acoustical Society ofAmerica vol 126 no 2 pp 626ndash633 2009

[2] G Licitra L Fredianelli D Petri and M A Vigotti ldquoAn-noyance evaluation due to overall railway noise and vibrationin Pisa urban areasrdquo Science of 0e Total Environmentvol 568 pp 1315ndash1325 2016

[3] G Bluhm and C Eriksson ldquoCardiovascular effects of envi-ronmental noise research in Swedenrdquo Noise and Healthvol 13 no 52 pp 212ndash216 2011

[4] T N Le L V Straatman J Lea and B Westerberg ldquoCurrentinsights in noise-induced hearing loss a literature review ofthe underlying mechanism pathophysiology asymmetry andmanagement optionsrdquo Journal of OtolaryngologymdashHead ampNeck Surgery vol 46 no 1 p 41 2017

[5] P Lercher G W Evans and M Meis ldquoAmbient noise andcognitive processes among primary school childrenrdquo Envi-ronment and Behavior vol 35 no 6 pp 725ndash735 2003

[6] C Bai Z Han HWei X Ju X Meng and Q Fu ldquoSimulationstudy on performance of a dual-source hybrid heat pump unitwith alternative refrigerantsrdquo Energy and Built Environmentvol 1 no 1 pp 1ndash10 2020

[7] M Dongellini and G L Morini ldquoOn-off cycling losses ofreversible air-to-water heat pump systems as a function of theunit power modulation capacityrdquo Energy Conversion andManagement vol 196 no 15 pp 966ndash978 2019

[8] S Li G Gong and J Peng ldquoDynamic coupling methodbetween air-source heat pumps and buildings in Chinarsquos hot-summercold-winter zonerdquo Applied Energy vol 254 no 15Article ID 113664 2019

[9] Y Cai D-D Zhang D Liu F-Y Zhao and H-QWang ldquoAirsource thermoelectric heat pump for simultaneous cold airdelivery and hot water supply full modeling and performanceevaluationrdquo Renewable Energy vol 130 pp 968ndash981 2019

[10] GB 22337 Noise Emission from Social Life China Environ-mental Science Press Beijing China 2008

[11] GBT 50121 Evaluation Standard for Sound Insulation ofBuildings China Building Industry Press Beijing China 2005

[12] GBJ 50118 Code for Sound Insulation Design of Civil Build-ings China Building Industry Press Beijing China 2010

[13] O Gustafsson C Haglund Stignor and J-O DalenbackldquoHeat exchanger design aspects related to noise in heat pumpapplicationsrdquo Applied 0ermal Engineering vol 93 no 25pp 742ndash749 2016

[14] O Gustafsson H Hellgren C H Stignor M AxellK Larsson and C Teuillieres ldquoFlat tube heat exchan-gersmdashdirect and indirect noise levels in heat pump applica-tionsrdquo Applied 0ermal Engineering vol 66 no 1-2pp 104ndash112 2014

[15] D Yano S Ishikawa K Tanaka and S Kijimoto ldquoVibrationanalysis of viscoelastic damping material attached to a cy-lindrical pipe by added mass and added dampingrdquo Journal ofSound and Vibration vol 454 no 18 pp 14ndash31 2019

[16] K Bi and H Hao ldquoUsing pipe-in-pipe systems for subseapipeline vibration controlrdquo Engineering Structures vol 109no 15 pp 75ndash84 2016

6 Journal of Chemistry