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亚热带香港的中央空调系统节能的中性温度的影响

Effect of neutral temperature on energy saving of centralized air-conditioning systems in subtropical Hong Kong

K.F.Fong *,T.T.Chow,C.Li,Z.Lin,L.S.Chan

Division of Building Science and Technology,College of Science and Engineering,City University of Hong Kong,Tat Chee Avenue,Kowloon Tong,Kowloon,Hong Kong SAR,China

a r t i c l e i n f o

Article history:

Received 7December 2009Accepted 15March 2010

Available online 25March 2010Keywords:Energy saving Comfort air speed Neutral temperature Thermal comfort Air-conditioning

a b s t r a c t

Higher room temperature can still let the occupants have a neutral thermal sensation if higher air speed is provided.With a suitable scheme of neutral temperature and comfort air speed,reduction of energy consumption of the central chiller plant may surpass the additional energy requirement of the air side equipment,then both energy saving and thermal comfort can be achieved for the entire air-conditioning system.To evaluate this,the energy consumptions of a centralized air-conditioning system using the common air side alternatives were studied for the subtropical Hong Kong.The alternatives are variable air volume (VAV)system,constant air volume (CAV)system and fan coil (FC)system.Each of them was associated to a central chiller plant to serve a high-rise of ?ce building.The studying range of the room air temperature was from 23 C to 30 C.It is found that the VAV and FC systems can provide both thermal comfort and energy saving for higher room temperature,but CAV system is not feasible when the room air temperature is above 27 C.If the indoor air speed threshold is considered,the neutral temperature can be brought up to 26.5 C,and the energy saving potentials of VAV and FC systems would be 12.9%and 9.3%respectively.

1.Introduction

It seems not easy to have a balance between thermal comfort and energy saving for buildings with centralized air-conditioning https://www.wendangku.net/doc/6c13963907.html,fortable indoor room temperature should not be high as perceived by general occupants.The government has advocated the “Energy Conservation Charter ”for promoting energy saving of air-conditioning system in Hong Kong,the key guideline is to raise the room temperature to 25.5 C for the participating organizations [1].But a study has found that the neutral temperature is 23.6 C in the air-conditioned of ?ce environment in the subtropical Hong Kong [2].Hwang et al.[3]conducted a ?eld study to understand the priority between thermal comfort and energy saving in hot humid regions.It is found that thermal comfort is more important and it should be ensured ?rst,energy saving is just the second.This implies that people may prefer thermal comfort rather than energy saving if these two requirements cannot be compromised.Dounis and Caraiscos [4]proposed an advanced control system to provide both energy and comfort management.The thermal comfort was

maintained by the conventional PMV model,which has been queried about its representativeness in different cultures and climatic regions [5,6].

To balance thermal comfort and energy performance,Yamtraipt et al.[7]conducted thermal comfort ?eld studies to evaluate the neutral temperature by considering additional factors of acclima-tization and education level of building occupants.The proposed higher room temperature settings would be used to promote local energy saving in air-conditioning systems.Atthajariyakul and Lertsatittanakorn [8]proposed to install small fans before the building occupants so that the neutral temperature can be possibly elevated to 28 C and energy consumption of air-conditioning systems can be reduced.Toftum et al.[9]studied the occupant performance in buildings with and without mechanical cooling,and thermal sensation was used as an input to the estimation of occupant performance.It is found that the occupant performance is only slightly lower without mechanical cooling,showing that the effect of air speed can compensate the increase of room tempera-ture and provide an acceptable comfort level.

It is true that higher room temperature can let the occupants have the neutral thermal sensation if higher air speed is provided.In fact apart from the air temperature,there are ?ve more classical factors of thermal comfort,including the air speed,relative

*Corresponding author.Tel.:t852********;fax:t852********.E-mail address:bssquare@https://www.wendangku.net/doc/6c13963907.html,.hk (K.F.

Fong).Contents lists available at ScienceDirect

Applied Thermal Engineering

journal ho mepage:www.elsevier.co m/lo

cate/apthermeng

Applied Thermal Engineering 30(2010)1659e 1665

humidity,mean radiant temperature,clothing insulation and activity level of occupants.However,Givoni et al.[10]conducted a series of thermal comfort studies and found that relative humidity has a minimal effect to neutral comfort of the people living in the hot humid regions,including Japan,Singapore,Thailand and Indonesia.In a certain functional area,the clothing insulation and activity level of different occupants would be similar.If the mean radiant temperature is supposed to be close to the air temperature,particularly in an indoor environment,then the air speed can be a factor that affects the thermal comfort of occupants.Therefore it is necessary to study about using an effective scheme of comfort air speed to achieve both thermal comfort and energy saving of the air-conditioning system.

Hong Kong is a metropolis in subtropical climate region,full of high-rise buildings.For the local of ?ce buildings,it is common to design a multiple chiller plant for supplying chilled water to the air side equipment,which is installed around in different ?oors or zones.In the air side design,variable air volume (VAV)system,constant air volume (CAV)system and fan coil (FC)system are the

common alternatives for performance and economic consider-ations.Fig.1shows the schematic diagram of the VAV,CAV and FC systems associated with a central chiller plant.From the viewpoint of energy consumption,the difference of the VAV,CAV and FC systems is their equipment involved.In the VAV or CAV system,energy consumption is mainly originated from the supply air fan of the air handling unit.In the FC system,it is also related to the supply air fans,which are installed in the small fan coil units scattered around the air-conditioned spaces.

In the VAV system,the supply air ?ow rate is variable and decreased according to the part-load conditions,so the energy consumption of the supply air fans would be reduced.If the supply air ?ow reaches the minimum threshold,the chilled water ?ow rate entering the cooling coil would be reduced so that the room temperature can be maintained.In the CAV or FC system,the ?ow rate hence the energy consumption of the supply air fans is generally constant.So during the part-load conditions,reduction of chilled water ?ow rate entering the coil would be directly applied.This subsequently reduces the energy consumption of the chillers,as well as the associated pumps and cooling towers.The coef ?cient of performance (COP)of the chiller plant would then be enhanced,but it depends on the type of air side design.Therefore the energy consumption of these three alternatives of air side design,as well as that of the entire air-conditioning system,would be different due to higher room air temperature and supply air ?ow rate.Generally there is energy saving in the chiller plant by applying higher room temperature associated with higher supply ?ow rate based on comfort air speed.However,higher supply air ?ow rate would lead to higher energy consumption of the air side equipment accord-ingly.Owing to this dilemma,it is worth studying whether there is energy saving potential of the centralized air-conditioning system from a holistic viewpoint.

Water Pump

Unit Unit Fig.1.Schematic diagram of typical centralized air-conditioning system for high-rise buildings,comprising a central chiller plant and air side system (abbreviation:CHW:chilled water supply and return;OA:outdoor air;RA:return air;SA:supply air).

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In this paper,Section2presents the comfort air speed as determined from a thermal comfort survey for Hong Kong people, and how the supply air?ow rate of a centralized air-conditioning system is related to the scheme of comfort air speed.Section3 evaluates the year-round performances of the VAV,CAV and FC systems for different room temperatures through building energy simulation.The results are also benchmarked with the conven-tional air side design.Recommendations are then provided for both design and operation purposes.Section4is the conclusion.

2.Supply air requirement of centralized air-conditioning systems at different neutral temperatures

2.1.Scheme of comfort air speed from the thermal comfort survey

ASHRAE[11]covers the effect of air speed required to offset the

increased temperature that applies to a lightly clothed person in sedentary activity.However the acclimatization effect to the people living in the subtropical and tropical regions has not been consid-ered.As a result,an indoor thermal comfort survey was conducted by the authors for developing a scheme of comfort air speeds at different neutral temperatures in the subtropical Hong Kong.In the survey,203Hong Kong people aged between19and50were involved.The subjects all wore local typical summer clothing in sedentary position.The thermal comfort survey was carried out in an environmental chamber with control of temperature,air speed and humidity for each subject under test.In general,the subjects provided the feedback of thermal sensation according to the ASH-RAE7-point scale,which usesà3,à2,à1,0,t1,t2andt3to represent the thermal sensation of cold,cool,slightly cool,neutral, slightly warm,warm and hot[11].The details of the thermal comfort survey have been reported and discussed in[12].With reference to the results of regression analysis,the comfort air speeds for different room temperatures are summarized in Table1. Generally,the comfort air speed is increased with the neutral temperature from23 C to30 C.

2.2.Correlation of supply air requirement and comfort air speed

According to the thermal comfort survey,the supply air was provided by a500mm?100mm supply air grille which was1m apart from the subject in an environmental chamber.Based on such experimental setup,the indoor air?ow was study carried out by the computational?uid dynamics(CFD)program Fluent6.3[13]. Gambit2.4.6was used for geometry modeling and mesh genera-tion,and Fluent6.3.26is the solver for the indoor air?ow simu-lation.The RNG k e3turbulence model is adopted,which is reliable for a number of indoor air?ow studies[14e16].The entire CFD model was validated by the measurement pro?les of temperature and air speed at the levels of0.1m,0.6m,1.1m and1.7m of the subjects in the environmental chamber.By using the validated model,the required air?ow rates for different comfort air speeds were determined and plotted in Fig.2.It is found that the supply air ?ow rate per person is linearly related to the comfort air speed.This information would be applied to determine the required supply air ?ow rate of the VAV,CAV and FC systems,hence their energy consumption and the effect to the central chiller plant can be evaluated.

3.Performance evaluation of air-conditioning systems at different room temperatures

3.1.Simulation of centralized air-conditioning system serving typical of?ce building

In order to understand the effect of supply air?ow on the performance of the air side systems at different neutral tempera-tures,a building energy model was built to simulate the centralized air-conditioning system serving a typical high-rise of?ce building in Hong Kong.The schematic diagram of the energy simulation model is same as the one in Fig.1.The energy consumption of the entire air-conditioning system was considered in a holistic way.

Table1

Comfort air speeds for different room air temperatures for sedentary occupants (1.0met and0.55clo).

Room air temperature( C)Comfort air speed(m/s)

23<0.42

24<0.42

250.42

260.90

27 1.37

28 1.85

29 2.34

2.82

Fig.2.Correlation of supply air?ow rate and comfort air speed.

Table2

Design information of the of?ce building and centralized air-conditioning system. Parameter Value

Building con?guration and envelope

Number of storeys30

Floor-to-?oor height(m) 3.6

Total usable?oor area(m2)47,386

U-value of fenestration(W/m2/K) 6.93

U-value of roof(W/m2/K)0.39

U-value of opaque wall(W/m2/K) 3.3

Indoor conditions

Occupant density(m2/person)8

Outdoor air(litre/s/person)8

Lighting power density(W/m2)17

Equipment power density(W/m2)25

Operating schedule08:00e20:00

Air-conditioning system

Cooling capacity of chiller(kW)2400

Number of chiller2

Chilled water supply temperature( C)7

COP of chiller 4.6

Pump pressure(kPa)179

Combined impeller e motor ef?ciency of pump60%

Minimum supply air temperature( C)12.8

Fan pressure(Pa)VAV:500;

CAV:350;FC:50 Combined impeller e motor e drive

ef?ciency of fan

40%

Economizer Included

(except FC system)

K.F.Fong et al./Applied Thermal Engineering30(2010)1659e16651661

Therefore the robust building energy simulation program Ener-gyPlus version 2.2[17]was used.In this study,EnergyPlus was used for annual energy evaluation and cooling load simulation of a typical of ?ce building.The building cooling load was ?rstly determined through the required thermal control setpoints,working conditions of the air side and water side components.Then the year-round energy consumption of the entire centralized air-conditioning system,including the central chiller plant and air side,could be evaluated.The design information of a typical of ?ce building is summarized in Table 2,which is based on the engi-neering practice of Hong Kong [18].The building is usually designed with slightly positive pressure indoors,so no in ?ltration is taken into consideration for cooling load calculation.

3.2.Results and discussions

3.2.1.Effect of room temperature on building cooling energy

The year-round building cooling energy of the 30-storey of ?ce building was determined by EnergyPlus.The result of cooling energy for room temperature of 24 C was veri ?ed by that deter-mined according to the local design practice [18].From the building energy simulation,it is found that the building cooling energy decreases approximately linearly when the room air temperature increases from 23 C to 30 C,as shown in Fig.3.It is about 4%of cooling energy drop per each increment of room temperature.The annual cooling energy pro ?les for room air temperatures from 23 C to 30 C are presented in Fig.4.Generally they follow the variation of subtropical climatic conditions in Hong Kong,with August the highest and February the lowest,which are the peak summer and winter respectively.

3.2.2.Effect of room temperature on year-round energy consumption

In the building energy simulation,the minimum supply air temperature was set at 12.8 C based on the chilled water supply temperature of 7 C.It was to prevent the supply air ?ow rate hence the comfort air speed insuf ?cient or unreasonably low.For the room air temperature from 23 C to 26 C,the supply air ?ow rates were set at this minimum supply air temperature.For the room temperature from 27 C to 30 C,the required ?ow rates were determined in Fig.2through the comfort air speeds of the corre-sponding room temperatures.Table 3summarizes the settings of supply air ?ow rates and temperatures for different room temper-atures in this building energy simulation.

Fig.5presents the energy results of the centralized air-condi-tioning systems using VAV,CAV or FC for different room air temperatures,as divided by the usable ?oor area.These results are broadly divided into three areas:

energy consumption of water side equipment (i.e.the central chiller plant,including the two chillers,associated chilled water pumps,condenser water pumps and cooling towers); energy consumption of air side equipment (i.e.the supply air fans of VAV,CAV or FC system);and

total energy consumption of the entire air-conditioning system (https://www.wendangku.net/doc/6c13963907.html,bination of water side and air side).

The energy consumptions of the air side of the three air-conditioning systems have a similar trend,they generally decrease from 23 C to 26 C,and then increase to 30 C.However the increasing trend of the air side of the CAV system is quite remark-able,as shown in Fig.5(b).The energy consumptions of the water side of the VAV and FC systems fall along with the increase of the room temperature,as shown in Fig.5(a)and (c),but that of the CAV system increases from 26 C to 30 C in Fig.5(b).In the studying range of room air temperature,the proportion of energy consumption of the air side to the total of the VAV,CAV and FC systems is 12%,27%and 7%in average respectively.Therefore the effect of the air side on the CAV system would have a noticeable in ?uence to the total.In the CAV system,since a higher supply air ?ow is required in order to maintain the comfort air speed to the occupants for higher room temperature,so the energy consump-tion of the air side equipment would be raised due to its nature of constant supply air ?ow rate.In addition,the performance of the central chiller plant is also affected due to higher demand of supply air ?ow of the CAV system,since the corresponding fan heat gain would be increased and causing additional cooling requirement.Therefore the water side energy consumption of the CAV system is slightly increased from the room temperature of 26 C.In the VAV and FC systems,since their air side energy proportions are not as high as that of CAV system,so their trends of the total energy consumption are still decreasing along the room temperature.Fig.6summarizes the total year-round energy consumptions of the VAV,CAV and FC systems.For the room temperature from 23 C to 26 C,it is found that the total energy consumption of the

VAV

Fig.3.Year-round cooling energy vs.room air

temperature.

Fig.4.Annual pro ?les of cooling energy for room air temperatures from 23 C to 30 C.

Table 3

Settings of supply air ?ow rate and supply air temperature.Room air

temperature ( C)Supply air ?ow rate (kg/s/person)Supply air

temperature ( C)230.11012.8240.09912.8250.08912.8260.08112.8270.09416.48280.11819.73290.14222.2430

0.166

24.31

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system is the least,the CAV system is the second,and the FC system is the largest.For the VAV and FC systems,it is found that the annual energy consumption is decreased according to the increase of room air temperature from23 C to30 C,but it is not exactly linear.The energy consumption of the entire air-conditioning system using VAV is about40%less than that using FC system.The CAV system is more energy-ef?cient than the FC system only in

a limited range,with around10%saving for room temperature from

23 C to26 C.However,the CAV system has larger energy consumption for room temperature exceeding27.3 C.As mentioned before,the air side energy consumption of the CAV system is changed from decreasing to remarkably increasing at higher room air temperature.

3.2.3.Effect of room temperature on COP

The comparative study of the VAV,CAV and FC systems can also be extended to the COP.From a year-round perspective,the COP can be de?ned in that of the water side COP avg,w and that of the entire air-conditioning system COP avg,w&a in Eqs.(1)and(2)respectively.COP avg;w?

P8760

i?1

Q i

j?1

W w;j

(1)

where,COP avg,w:yearly averaged COP of the water side system,Q: cooling load(kJ/h),W w:power input of water side equipment, including chillers,chilled water pumps,condenser water pumps and cooling towers(kJ/h).

COP avg;wa?

P8760

i?1

Q i

j?1

W w;jtW a;j

(2)

where,COP avg,w&a:yearly averaged COP of the entire centralized air-conditioning system,W a:power input of air side equipment(kJ/h).

Fig.7shows the pro?les of COP avg,w of the VAV,CAV and FC systems for the room air temperatures from23 C to30 C.The VAV system is able to continuously let the COP avg,w soar from3.35 for room air temperature of23 C to4.27for30 C,with27%up. The FC system seems maintaining the COP avg,w fairly constant about1.99,with very little increase from26 C to29 C.Since the drop of water side energy consumption of FC system along

the Fig.5.Energy consumptions of the centralized air-conditioning systems using VAV,CAV or FC for different room air temperatures.(a)VAV system.(b)CAV system.(c)FC

system. Fig.6.Total energy consumptions of the three HVAC systems at different room air

temperatures.Fig.7.Yearly averaged COP of the water side system for different room air temperatures.

K.F.Fong et al./Applied Thermal Engineering30(2010)1659e16651663

increase of room temperature was not as signi ?cant as that of VAV system,as found in Fig.5(c),so its COP avg,w becomes relatively ?at.The CAV system,however,has a drop of COP avg,w from 2.81for room temperature of 23 C to 2.15for 30 C,with 23%decrease.This is because the water side energy consumption of CAV system increases from 26 C and onwards,as found in Fig.5(b),that leads to its COP avg,w decreasing.

Fig.8presents the changes of COP avg,w&a of the VAV,CAV and FC systems along the room air temperatures from 23 C to 30 C.Their changing patterns are similar to those in Fig.7.However,the CAV system has a signi ?cant drop of COP avg,w&a after 26 C due to the pull-up of energy consumption from the air side equipment.In the CAV system,COP avg,w&a is running down from 2.09for room air temperature of 23 C to 1.41for 30 C,with 33%drop.

Consequently,application of the scheme of comfort air speed is favourable to the COP of the entire air-conditioning system using VAV.On the contrary,both the air side and central chiller plant for CAV system would have descending COP for room temperature above 26 C.In the FC system,the COP is fairly constant throughout the range of room air temperature under study.

3.2.

4.Benchmarking with air side design using conventional supply air temperature

In order to have a complete understanding of the effect of the comfort air speed to the energy consumption of the VAV,CAV and FC systems,each type is benchmarked with its conventional design,in which the supply air temperature is kept at a ?xed setting.In this study,this temperature is 12.8 C.Fig.9presents the comparison results.Among the three air side systems,the VAV system can have energy saving potential for the room air temperature above 26 C as shown in Fig.9(a).On the contrary,the FC system has slightly more energy demand than the conventional design above 26 C due to higher supply air ?ow rate,but it is only 3.7%more even the room temperature at 30 C,as shown in Fig.9(c).The CAV system has clearly higher energy consumption than the conventional design above 26 C as presented in Fig.9(b).For the room temperature of 30 C,50%more energy is needed.Again,this shows that the CAV system is not suitable to apply the scheme of comfort air speed from the energy perspective.

3.3.Recommendations

In order to achieve both the thermal comfort and energy ef ?-ciency,the centralized air-conditioning using the VAV system is the most suitable one among the three air side systems based on the scheme of comfort air speed.The FC system is also likely to provide both the thermal comfort and energy ef ?ciency,although the FC system has slightly higher energy demand than the conventional design for room air temperature above 26 C.The CAV system based on the scheme of comfort air speed is not suitable from the energy viewpoint,although it can maintain thermal comfort for higher room temperature.Consequently,both the VAV and FC systems can achieve both energy saving and thermal comfort through the scheme of comfort air speed for higher neutral temperature,although the year-round energy consumption of the FC system is higher than the VAV system by about 40kWh/m 2for the neutral temperature from 25 C to 30 C,as shown in Fig.6

Fig.8.Yearly averaged COP of the entire centralized air-conditioning system for different room air temperatures.(a)VAV system.(b)CAV system.(c)FC

system.

Fig.9.Benchmarking with air side design using conventional supply air temperature.(a)VAV system.(b)CAV system.(c)FC system.

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The typical room temperature of of?ce buildings is24 C as found by Federspiel[19]through a statistical analysis of survey,and it is also a design practice in Hong Kong.If the thermal comfort is maintained at a higher neutral temperature through higher comfort air speed,the energy saving potential can be determined for the VAV and FC systems against this typical room temperature. Table4shows that the energy saving potentials of both the VAV and FC systems are getting more attractive when the neutral temper-ature increases.Indeed a too high air speed is not recommended to prevent?ying papers in a working environment.By considering a drop of supply air speed about0.4m/s between the occupant and the work desk,and the air speed reaching the work desk would not exceed the common threshold of0.8m/s[11],it implies the allowable supply air speed at the occupant can be1.2m/s.Such air speed leads to the neutral temperature to be26.5 C from Table4. Therefore the VAV and FC systems would have an energy saving of 12.9%and9.3%respectively.In fact,with more reliance on the information technology in modern of?ce environment,it is getting more feasible to maintain the thermal comfort at higher room temperature through higher comfort air speed.However,it does not mean that mechanical cooling is obsolete and can be replaced by mechanical ventilation in the hot humid regions.The role of air-conditioning is still indispensable,since it is needed for handling latent load and dehumidi?cation.

It is worthwhile to note that the scheme of comfort air speed can be applied to the VAV system even if it has the nature of variable supply air?ow rate.It is particularly feasible if the cooling load is mainly contributed from the internal heat gains,such as the occu-pants and the associated electric appliances.During the part-load conditions,the reduction of the total supply air?ow would mainly follow the drop of the number of occupants.If an occupant is present and served by an individual VAV box,the supply air?ow rate and the required comfort air speed can be maintained,otherwise the VAV box can be closed to reduce the total supply air?ow.With this arrangement,the VAV system can achieve both the merits of energy saving and thermal comfort at a higher room temperature.

4.Conclusion

With a higher but acceptable comfort air speed,it is feasible to have a win e win situation of thermal comfort and energy ef?-ciency by elevating the room air temperature in an of?ce envi-ronment for the subtropical Hong Kong.Through the thermal comfort survey,a scheme of comfort air speed at different neutral temperatures has been developed for the Hong Kong people.In this study,it is found that higher comfort air speed can be implemented only by the VAV and FC systems,not CAV system, among the common air side alternatives of centralized air-conditioning system.If the year-round energy consumption of the air-conditioning system for room temperature of24 C is used as a baseline,the VAV system can have the energy saving potential from5.0%for room temperature of25 C to33.2%for30 C.The FC system would also have the energy saving potential from3.7%for 25 C to19.5%for30 C.By considering the limit of indoor air speed,the neutral temperature can be brought up to26.5 C,and the VAV and FC systems would have the energy saving potential at 12.9%and9.3%respectively.However,the CAV system cannot apply the scheme of comfort air speed for higher room temper-ature,since its energy consumption of air side equipment would be signi?cantly increased for room temperature above27 C.In fact,the proposed scheme of comfort air speed is not only applied to the design of new systems,but also to the operation of existing air-conditioning systems where appropriate.Better design and energy management can be therefore achieved for both energy saving and thermal comfort.

Acknowledgement

This work described in this paper is fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.CityU112906). References

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Table4

Energy saving potential of VAV and FC systems based on the scheme of comfort air speed.

Neutral temperature( C)Comfort air

speed(m/s)

Year-round energy saving

VAV system FC system

24<0.42Baseline Baseline

250.42 5.0% 3.7%

260.909.8%7.5%

27 1.3715.9%11.0%

28 1.8521.6%14.3%

29 2.3427.1%17.5%

30 2.8233.2%19.5%

K.F.Fong et al./Applied Thermal Engineering30(2010)1659e16651665

中央空调节能方案说明

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明中央空调清洗可节约能耗和运行的费用超过 3、中央空调化学清洗现状堪忧（1）中央空调用户的清洗和节能意识淡薄对大多数中央空调用户来说，化学清洗只是为满足空调制冷需要的无奈之举，很少有用户是从节能降耗的角度来看待化学清洗。（2）中央空调化学清洗技术落后、清洗队伍的数量和素质普遍都较低传统化学清洗是一项专业性特强的技术。往往一个小的疏忽可能会造成严重的安全事故或巨大的经济损失。上千万元的制冷设备在化学清洗时报废的报道屡见不鲜，这是使得中央空调用户望而却步的原因之一。（3）政府管理和引导不够现在政府往往只提倡提高中央空调使用时的室内温度，却不知通过对中央空调化学清洗的有效管理对于节能降耗的意义更加重大。

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空调温度控制系统

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中央空调节能控制设计方案

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中央空调系统的节能措施摘要：中央空调是宾馆、商场、办公大楼和工厂不可缺少的设施，它既能给人们带来温馨舒适的环境，但也需要支付昂贵的电费，故对中央空调加节能装置是降运行成本和增加效益的一条捷径。关键字：中央空调，节能，楼宇自动化，变频控制，蓄能建筑节能是在满足居住舒适性要求的前提下，在建筑中使用隔热保温的新型墙体材料和高能效比的采暖空调设备，达到节约能源、减少能耗、提高能源利用效率之目的。在我国建筑物的能耗约占全国能耗的1/3，中央空调系统的能耗占了我国建筑物能耗的60％，这是一个非常惊人的数字。而中央空调机组是以满足使用场所的最大冷热量来进行设计的，而在实际应用中绝大多数用户在使用时，冷热负荷是变化的，一般与最大设计供冷热量存在着很大的差异，系统各部分90%以上运行是在非满载额定状态的。对于中央空调系统节能而言，一方面是要从系统本身的设计上,考虑整体的能耗，另一方面，在使用和维护过程中,要尽量按要求进行管理,这样既可延长系统的使用寿命，也可减少不必要的物资、能源浪费。那么中央空调是如何实现最大化节能，除了它本身外，风机盘管、风机、水泵、压缩机等中央空调设备都要求最大化节能，可采用如下措施实现节能。 1、采用楼宇自动化系统：在智能建筑中通常采用楼宇设备自控系统，对中央空调系统末端的新风机、回风机、变风量风机、风机盘管等装置进行状态监视和使用的“精细化”控制，以实现节能的目的。其通过控制器，将检测的相关量值进行运算，实现对上述设备的控制，达到一定的节能效果。这种对空调末端设备的控制可节能10％左右。楼宇设备自控系统实现了对空调末端设备的节能自动控制，并为动态变流量空调节能控制系统的运行创造了更为良好的外部条件。 2、采用变频控制系统：应用交流变频技术通过对中央空调的末端空调风机、冷却塔风机、冷冻水/冷却水水泵、压缩机电机转速进行控制调节，从而使空调各子系统风量、水流量等负荷工况参数按负荷情况得到自动调节，不但能改善系统的调节品质，改善空调的舒适性，达到节约大量电能，降低设备运行噪声，延长设备使用寿命，减轻设备维护工作量及费用的理想运行效果。通过变频控制调节，中央空调系统的水、风系统耗电水平可降低30%-50%，主机系统可节电30%以上，总体系统节电可达40%左右。中央空调变频节能控制器投资价值高，用户用于该产品的全部投资，可在很短的时间内通过减少能耗支出予以回收。因此中央空调用户应用变频节能控制系统不仅有着良好的直接经济收益，还能达到节约能源消耗、有利于环境保护的社会效益。 3、采用蓄能空调技术：蓄能空调技术就是利用夜间电网低谷时的电力来制冷或制热，把冷量或热能储存起来，在白天电力高峰用电紧张时释放冷量或热能，满足建筑物空调冷源或热水需要。蓄冷中央空调简单地讲就是在常规中央空调增加了一套蓄冷装置，如：蓄冰槽、蓄冰桶等。蓄冰空调主要利用分时电价政策，在夜间用电低谷期，采用电制冷机制冷，将制得冷量以冰的形式储存起来。在白天空调负荷高峰期，将冷量释放，便可达到少开中央空调主机甚至不开主机的目标。采用蓄能空调技术可以减少制冷主机的装机容量和功率，可减少30%-50%；利用低谷廉价电力，节省大量的运行费用，可节省40%左右。能源是人类生存和社会发展必需的物质基础，节约能源是人类共同的使命。

中央空调温度控制系统

过程控制课程设计报告 ——中央空调温度控制系统一、课程设计目的 1、熟悉并掌握组态王软件的基本使用； 2、通过组态王软件的使用，进一步掌握了解过程控制理论基础知识； 3、培养自主查找资料、收索信息的能力； 4、培养实践动手能力与合作精神。二、选题背景随着计算机技术、信息技术、控制理论的快速发展，人们对生活质量和工作环境的要求也不断增长，智能建筑应运而生。中央空调是智能建筑的重要组成部分，中央空调的能耗占整个建筑能耗的50%~70％，因此中央空调系统的监控是楼宇自动化系统研究的重点。在民航业中，中央空调系统是航站楼内最为重要的系统之一，其系统的性能直接影响到旅客的感受。三、设计任务由于中央空调系统非常复杂，本设计选取温度作为主要被控对象，使用组态王设计温度监控画面，能实现被控环境的温度设定并实时监控温度的变化趋势，控制器采用PID控制算法，可以在监控界面上对PID参数进行整定，实现稳态误差小于5%。四、详细设计 1、监控界面说明监控界面主要由三部分组成：系统组成部分、PID调节部分和显示部分，如图1所示。系统组成部分位于画面左上侧，由被控环境、温度传感器、A/D模块、控制器、D/A模块、变频器、风机和管道组成。温度传感器检测被控环境的温度，经过A/D模块传送至控制器，与温度设定值比较，输出控制值，经D/A模块传送至变频器，控制风机的转速。值0-10对应管道流速，0为不流动，10为最快，运行时点击“系统运行”按钮，管道出现流动效果。 PID调节部分位于画面右侧，包括PID控件、环境温度设定显示按钮和PID参数输入按钮。利用系统PID控件内置的PID实现温度的控制，点击相应的按钮可输入值。显示部分位于画面左下侧和右上侧，包括实时温度曲线、历史温度曲线、报警窗口和实时报表。实时温度曲线显示温度的调节变化过程。

中央空调节能自控管理系统

中央空调节能自控管理系统一、背景长期以来，随着中央空调在公共建筑中的普及应用，所产生的“高能耗”带来的负担也日益加剧。据统计，建筑能耗约占全社会总能耗的，其中最大的能耗就是由中央空调系统产生的。这与国家所倡导的美丽中国、节能低碳、绿色环保等趋势显得格格不入。以一座每天总耗电量高达数千度的商务大楼为例，其中有接近40%到50%的电量是被中央空调系统消耗掉的。因此，如何实现中央空调的节能控制成为摆在我们面前的一个重要问题。二、现状目前市场上做空调节能自控的厂家多为机房自控，将末端与机房连接起来的只有郑州春泉暖通节能设备有限公司。郑州春泉是“当量能量计费方法”的奠基人，空调末端的数据可实时采集，瘵末端需要的能量传递到机房中心，改变了从“送多少用多少”或是“送不出去了再不送”到“用多少送多少”的局面，有效地解决了能源的浪费问题。三、原理郑州春泉节能股份有限公司自主研发的“中央空调节能自控管理系统”就是针对传统中央空调系统运行中存在大量能耗问题而研发的高科技产品，由中央空调末端能耗监控系统和能源中心集中监控系统两个子系统组成，利用中央空调末端能耗检测系统的实时数据和能源中心设备的运行特性，采用负荷随动的专利技术，在确保中央空调系统安全和舒适的前提下，同步调节中央空调主机能量输出，实现运行能效最大化，降低系统能耗。四、技术中央空调节能自控管理系统采用了“实时监测”、“负荷随动”等优势技术，使用现场编辑和就地数字化方法，使产品在实际应用中安装方便，使用简单，最终达到节能环保、减少使用成本和延长中央空调系统使用寿命的效果。其中采用的实时监测系统能进行全天候自动检测，实现高度实时的状态监测、能耗分析及故障报警等功能。而“负荷随动”技术则是一种以中央空调系统为模型对

空调机温度控制系统

单片机课程（设计）（设计目）题：空调机温度控制系统学院：明德学院专业：机械设计制造及其自动化班级：机电12151 学号：学生姓名：指导教师：

2015年6月贵州大学单片机课程（设计）诚信责任书本人郑重声明：本人所呈交的课程设计，是在指导老师的指导下独立进行研究所完成。在文本设计中凡引用他人已经发表或未发表的成果、数据、观点等，均已明确注明出处。特此声明。课程（设计）作者签名：日期：

空调机温度控制系统摘要新世纪里，人们生活质量不断提高，同时也对高科技电子产业提出了更高的要求，为了使人们生活更人性化、智能化。我设计了这一个基于单片机的空调温度控制系统，人们只有生活在一定的温度环境内才能长期感觉舒服，才能保证不中暑不受冻，所以对室内温度要求要高。对于不同地区空调要求不同，有的需要升温，有的需要降温。一般都要维持在22~26°C。目前，虽然我国大量生产空调制冷产品，但由于我国人口众多，需求量过盛，在我国的北方地区，还有好多家庭还没有安装有效地室内温控系统。温度不能很好的控制在一定的范围内，夏天室内温度过高，冬天温度过低，这些均对人们正常生活带来不利的影响，温度、湿度均达不到人们的要求。以前温度控制主要利用机械通风设备进行室内、外空气的交换来达到降低室内温度，实现室内温度适宜人们生活。以前通风设备的开启和关停，均是由人手动控制的，即由人们定时查看室内外的温度、湿度情况，按要求开关通风设备，这样人们的劳动强度大，可靠性差，而且消耗人们体力，劳累成本过高。为此，需要有一种符合机械温控要求的低成本的控制器，在温差和湿度超过用户设定值范围时，启动制冷通风设备，否则自动关闭制冷通风设备。鉴于目前大多数制冷设备现在状况，我设计了一款基于MCS51单片机空调温度控制系统。

中央空调节能自控系统改造方案设计

1.1空调自控系统改造方案 1.1.1控制设备范围一套制冷系统中的制冷机组、冷冻水循环泵、冷却水循环泵、冷却塔、相关阀门、膨胀水箱、软化水箱等。 1.1.2空调自控系统 1.1. 2.1.监测功能信息采集优化 A通过冷机通讯接口读取（包括但不限于）以下参数：冷水机组运行状态、故障报警状态冷冻水供/回水温度、冷却水供/回水温度冷冻水温度设定值运行时间、压缩机运行电流百分比、压缩机运行小时数、压缩机启动次数、蒸发温度、冷凝温度、蒸发压力、冷凝压力。 B冷冻水系统冷冻水泵运行状态、故障报警、手/自动模式反馈(DI) 冷冻水补水泵运行状态、故障报警、手/自动模式反馈(DI) 冷冻水供回水管温度、水流量反馈(AI) 冷冻水泵进口、出口分支管压力(AI) 冷冻水供回水环网压力、冷冻水供回水环网间压差反馈(AI) 冷冻水泵变频器频率反馈(AI) 最不利末端供回水压差

C冷却水系统冷却水泵、冷却塔风机运行状态、故障报警、手/自动模式反馈(DI) 冷却水供回水管温度、环网水流量反馈(AI) 冷却水泵进口、出口分支管压力反馈(AI) 冷却水泵、冷却塔风机变频器频率反馈(AI) 冷却水补水泵运行状态、故障报警、手/自动模式反馈(DI) D电动蝶阀压差旁通阀开度反馈（AI）免费供冷管路上切换电动蝶阀开关状态反馈（DI）E液位监控膨胀水箱超高、超低水位监测(DI) 软化水补水箱高、低水位监测（DI） F其他参数室外干球温度、相对湿度（AI）计算室外湿球温度、焓值免费供冷系统水泵运行、故障、手/自动状态（DI）免费供冷板换进出口压力监测（AI） 1.1. 2.2.控制功能 1、冷水机组启/停控制、出水温度设定（通过冷机通讯接口控制） 2、冷冻水系统：冷冻水泵启/停控制(DO)及反馈

中央空调温控器操作说明

现在很多小伙伴家里在装修的时候，都安装了中央空调，随之配套的还有中央空调的温控器，很多小伙伴还不知道温控器怎么操作，下面就一起来看看温控器的操作说明吧。中央空调温控器分爲电子式和机器式两种，按显示不同分爲液晶显示和调理式。中央空调温控器是经过顺序编辑，用顺序来控制并向执行器收回各种信号，从而到达控制空调风机盘管以及电动二通阀的目的。机器式机器盘管温控器使用于商业、工业及民用修建物。可对采暖、冷气的中央空调末端风机盘管、水阀停止控制。使所控场所环境温度恒定爲设定温度范围内。温度设定拔盘指针应设定爲所需恒定温度地位。拔动开关功用辨别爲:电源开关(开ON—关OFF);运转形式开关(暖气HEAT—冷气COOL)，FAN风速开关(低速L—中速M—高速H)。可控制设备：三档风机盘管风速，三线电动阀，二线电动阀，也可接电磁阀、开关型风阀或三线型风阀。外型尺寸。

操作办法 1、开关机：把拨动开关拨动到ON地位，温控器开机；把开关拨动到OFF 地位，温控器关机。 2、打工形式设定：把拨动开关拨动到COOL地位，温控器设定爲制冷形式；把拨动开关拨动到HEAF地位，温控器设定爲制热形式。 3、温度设定：机器式温控器，采用旋钮式设定温度，把红点对着面板标明的温度数据即可。 4、风速设定：把开关拨动到LOW地位；温控器设定爲高档风速；把开关拨动到WED地位，温控器设定爲中档风速；把开关拨动到High地位，温控器设定爲高档风速。快益修以家电、家居生活为主营业务方向，提供小家电、热水器、空调、燃气灶、油烟机、冰箱、洗衣机、电视、开锁换锁、管道疏通、化粪池清理、家具维修、房屋维修、水电维修、家电拆装等保养维修服务。

空调温度控制系统流程图

网上找到以下两种空调的自动控制方案。比较简单的一种是如下图所示的单回路的闭环控制系统，传感器采用温度传感器，调节器采用pid控制，执行器指电机，调节阀指的是出风口的阀门开度。另一种比较复杂的是如下所示的串级控制，分主回路和副回路，当室温偏离设定值时，调节器输出偏差指令信号，控制调节阀开大或关小，改变进入空气热交换器的蒸汽量或热水量，从而改变送风温度，达到控制室温的目的。飞机飞行自动控制系统例子 1、高度控制系统控制飞机在某一恒定高度上飞行的系统。它以飞机俯仰角控制系统为内回路，因此除包括与自动驾驶仪俯仰通道中相同的元、部件（如俯仰角敏感元件、计算机、舵回路等）外，还包括产生高度差（当前高度与期望高度的差值ΔH）信号和升降速度(夑)信号的敏感元件。专用的高度修正器或大气数据计算机能输出高度差和升降速度信号。高度控制系统有两种工作状态：一种是自动保持飞机在当时的高度上飞行，简称定高状态；另一种是自动改变飞行高度直到人工预先选定的高度，再保持定高飞行，简称预选高度状态。当驾驶员拨动预选高度旋钮调到预选高度刻度时，飞机自动进入爬高（或下滑）状态。在飞机趋近预选高度后，自动保持在预选的高度上作平直飞行。 2、速度控制系统通过升降舵或升降舵加油门来自动控制空速或马赫数的系统。通过升降舵调节的系统与高度控制系统相似，也以自动驾驶仪俯仰通道作为内回路。在保持定速状态下，空速差(ΔV)等于当时空速(V)与系统投入该状态瞬间空速(V0)之差。在预选空速状态下，空速差等于当时空速与预选空速(Vg)之差。为提高控制速度的精度，须引入空速差的积分信号。在保持飞机

姿态或飞行高度不变的条件下，空速也可由油门自动控制。将空速差和空速变化率(妭)信号引入油门控制器来改变发动机油门的大小。如不满足上述条件，改变油门大小只能使飞机升高或降低，而速度不变。为防止随机阵风引起空速频繁变化以致对发动机过分频繁调节，一般将空速差和空速变化率信号经过阵风滤波器（通常为低通滤波器）进行滤波。为了改善飞机速度控制的质量，常采用比例加积分再加微分的控制方式。

中央空调节能方案

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基于PLC的变频中央空调温度控制系统的毕业设计说明

唐山学院毕业设计设计题目：基于PLC的变频中央空调温度控制系统设计系别：智能与信息工程学院班级：姓名：指导教师：田丽欣 2016年6月 1 日

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空调温度控制系统

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中央空调系统节能改造方案

中央空调系统水泵变频节能改造方案一、概述中央空调系统在现代企业及生活环境改善方面极为普遍，而且某此生活环境或生产工序中是属必须的，即所谓人造环境，不仅是温度的要求，还有湿度、洁净度等。至所以要中央空调系统，目的是提高产品质量，提高人的舒适度，集中供冷供热效率高，便管理，节省投资等原因，为此几乎企业、高层商厦、商务大楼、会场、剧场、办公室、图书馆、宾馆、商场、超市、酒店、娱乐场、体育馆等中大型建筑上都采用中央空调的，它是现代大型建筑物不可缺少的配套设施之一，电能的消耗非常之大，是用电大户，几乎占了用电量50%以上，日常开支费用很大。由于中央空调系统都是按最大负载并增加一定余量设计，而实际上在一年中，满负载下运行最多只有十多天，甚至十多个小时，几乎绝大部分时间负载都在70%以下运行。通常中央空调系统中冷冻主机的负荷能随季节气温变化自动调节负载，而与冷冻主机相匹配的冷冻泵、冷却泵却不能自动调节负载，几乎长期在100%负载下运行，造成了能量的极大浪费，也恶化了中央空调的运行环境和运行质量。随着变频技术的日益成熟，利用变频器、PLC、数模转换模块、温度传感器、温度模块等器件的有机结合，构成温差闭环自动控制系统，自动调节水泵的输出流量；采用变频调速技术不仅能使商场室温维持在所期望的状态，让人感到舒适满意，可使整个系统工作状态平缓稳定，更重要的是其节能效果高达30%以上，能带来很好的经济效益。二、水泵节能改造的必要性中央空调是大厦里的耗电大户，每年的电费中空调耗电占60% 左右，因此中央空调的节能改造显得尤为重要。由于设计时，中央空调系统必须按天气最热、负荷最大时设计，并且留 10-20% 设计余量，然而实际上绝大部分时间空调是不会运行在满负荷状态下，存在较大的富余，所以节能的潜力就较大，其中，冷冻主机可以根据负载变化随之加载或减载，冷冻水泵和冷却水泵却不能随负载变化作出相应调节，存在很大的浪费。水泵系统的流量与压差是靠阀门和旁通调节来完成，因此，不可避免地存在较大截流损失和大流量、高压力、低温差的现象，不仅大量浪费电能，而且还造成中央空调最末端达不到合理效果的情况。为了解决这些问题需使水泵随着负载的变化调节水流量并关闭旁通。再因水泵采用的是Y- △起动方式，电机的起动电流均为其额定电流的3 ～4倍，一台90KW的电动机其起动电流将达到500A ，在如此大的电流冲击下，接触器、电机的使用寿命大大下降，同时，起动时的机械冲击和停泵时水垂现象，容易对机械散件、轴承、阀门、管道等造成破坏，从而增加维修工作量和备品、备件费用。采用变频器控制能根据冷冻水泵和冷却水泵负载变化随之调整水泵电机的转速，在满足中央空调系统正常工作的情况下使冷冻水泵和冷却水泵作出相应调节，以达到节能目的。水泵电机转速下降，电机从电网吸收的电能就会大大减少。其减少的功耗△ P=P0 〔 1-(N1/N0)3 〕（ 1 ）式

基于PLC的中央空调温度控制系统设计

摘要中央空调已经广泛应用于商用与民用建筑中，用于保持整栋建筑温度恒定。传统的设计中，无论季节、昼夜和用户负荷的怎样变化，各电机都长期固定在工频状态下全速运行，所以会造成极大的的能源浪费。本设计采用变频器、PLC、温度传感器等器件的有机结合，构成温差闭环自动控制系统，自动调节水泵的输出流量达到节能目的。该系统采用西门子的S7—200PLC作为主控制单元，利用传统PID控制算法，通过西门子MM440变频器控制水泵运转速度，保证系统根据实际负荷的情况调整流量，实现恒温控制，从而最大程度的解决能源浪费问题。本设计通过采用基于USS 协议的RS-485总线通讯的网络，通过西门子TD200文本显示器实现人机界面的设计，使用MCGS工控组态软件，对系统进行理论分析。通过分析该设计，验证了该设计的可靠性，可以解决中央空调的能源浪费问题。关键词：中央空调，PLC，PID，变频器

ABSTRACT The central air conditioning has been widely used in commercial and civil buildings, which are used to maintain constant temperature of the building. In traditional design, regardless of the season, day and night, and how the user load changes, the motor is fixed to run at full speed for a long time in the condition of power frequency. It will cause great waste of energy. This design is developed based on the combination of frequency converter, PLC, temperature sensor. It makes up a temperature difference closed-loop automatic control system and automatically adjust the output flow of pump to achieve energy saving. The system adopts the Siemens S7-200 PLC as the main control unit, using the traditional PID to control algorithm, using Siemens MM440 inverter to control of pump speed, to guarantee system adjust load flow according to actual situation. All of these will bring out constant temperature control, so as to solve the problem of energy waste to a great extent. This design use RS - 485 bus communication networks which is based on USS protocol and using the Siemens TD200 to realize the human-computer interface design, and using the software made from MCGS, to carries on the theoretical analysis to the system. Verified the reliability of the design, the design can solve the problem of central air conditioning energy waste through the analysis of the design. KEY WORDS: The central air conditioning, PLC, PID, frequency converter