THE ADAPTABILITY OF EVAPORATIVE VENTILATION AND AIR-CONDITIONING TECHNOLOGY IN CHINA AND THE COUNTRIES ALONG THE BELT AND ROAD INITIATIVE

THE ADAPTABILITY OF EVAPORATIVE VENTILATION AND AIR-CONDITIONING TECHNOLOGY IN CHINA AND THE COUNTRIES ALONG THE BELT AND ROAD INITIATIVE ——CHINA (Sh...
Author: Alexina Parks
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THE ADAPTABILITY OF EVAPORATIVE VENTILATION AND AIR-CONDITIONING TECHNOLOGY IN CHINA AND THE COUNTRIES ALONG THE BELT AND ROAD INITIATIVE

——CHINA (Shaanxi Province) In 2013, The Chinese General Secretary, Xi Jinping put forward the strategy of "The Belt and Road Initiative", which is the abbreviation of the Silk Road Economic Belt and the 21st Century Maritime Silk. There are 64 countries involved in (43 countries from Asia, 16 countries from Central and Eastern Europe, 4 from Commonwealth of Independent States and 1 from Africa). "The Belt and Road Initiative" is not only the dominant strategy to guide the future development of China, but also to strengthen exchanges and cooperation with other countries in the world. Under the guidance of this strategy, evaporative ventilation and air-conditioning technology, a form of air conditioning which is very suitable for the climate conditions and economic situation along the Belt and Road Initiative, will serve more countries and regions and become the leading air-conditioning mode of these countries. James Bond pointed out: "Although evaporative coolers cannot be used in all countries, they are generally underutilized in places where they can be used successfully. This is unfortunate for the potential users and the global environment." Northwest China, an important part of the Silk Road Economic Belt, is abundant for the "dry air energy". It is the most suitable application areas for evaporative ventilation and air-conditioning technology and should be promoted. The driving force of evaporative ventilation and air-conditioning technology is the dry bulb temperature and wet bulb temperature difference. It uses the latent heat when water evaporates to absorb heat from air. It is a technology that is efficient and environmental friendly. Meanwhile, evaporative ventilation and air-conditioning technology can not only cool and humidify the fresh air, but also purify the air (evaporative ventilation and air-conditioning technology can effectively filter the particulate matter of 5μm or above and adsorb the soluble harmful gas), improving the air quality. Finally, evaporative ventilation and air-conditioning technology also has good humidifying function, adjusting the indoor air’s humidity, especially suitable for dry areas in Northwest China. In the background of "the Belt and Road Initiative", Shaanxi as the starting point of the ancient Silk Road once again stands at a new starting point of "the Silk Road Economic Belt". Located in the northwest, the unique advantage of "dry air energy" provides Shaanxi conditions and opportunities for the application of evaporative ventilation and air-conditioning technology. The climate of Shaanxi province varies greatly from north to south with arid and semi-arid climate as shown in Figure 1. Due to the impact of the monsoon, Shaanxi has four distinct seasons with hot summer and cold winter. The average temperature of hottest month-July in the northern Shaanxi is 21~25℃, Guanzhong is 23~27℃, southern Shaanxi is 1

24~27.5℃. The distribution of the annual precipitation is less in the south than that in the north. The storm begins in April and ends in November, and mainly happens in July and August as shown in Figure 2. From the climatic conditions and the distribution of precipitation in Shaanxi Province, it can be seen that evaporative ventilation and air-conditioning technology has a good applicability in northern the central Shaanxi. The multi-stage evaporative ventilation and air-conditioning technology can be used to meet the comfort requirements. Even in the southern Shaanxi, evaporative cooling can also be used as a precooler to reduce the energy consumption of mechanical refrigeration. The above is a brief introduction to the adaptability of evaporative ventilation and air-conditioning technology in Shaanxi. A detailed analysis is carried out. As the driving potential is the difference between the dry bulb temperature and the wet bulb temperature. Reasonable calculation parameters can only be used to accurately determine the applicability of evaporative ventilation and air-conditioning technology. However, there is no uniform outdoor air calculation parameter for evaporative ventilation and air-conditioning technology. Designers usually use the summer outdoor air-conditioning calculation-dry bulb temperature and wet bulb temperature in Design Code for Heating Ventilation and Air Conditioning of Civil Buildings, but this calculation does not exist at the same hour. Actually, it is more reasonable to use the instantaneous design parameters which are recommended in 2009 ASHRAE Handbook-Fundamentals. The summer outdoor design parameters in Shaanxi are modified using the hourly meteorological parameters (typical meteorological Year in China Building Thermal Environmental Analysis Specific Meteorological Data Set) with the statistical method of ASHRAE as shown in Table 1. Using the revised outdoor design parameters, the operation mode and effect are analyzed.

Figure 3

The dry bulb temperature and wet bulb temperature in Shaanxi

Figure 4 The design partitions of evaporative ventilation and air-conditioning in psychometric chart

As can be seen from Figure 3, the dry and wet bulb temperature difference is about 10℃ in Shaanxi Province. Thus, the driving potential is present in these regions, and the application conditions of the evaporative ventilation and air-conditioning technology are possible. Meanwhile, the wet bulb temperature of typical cities in Shaanxi Province is in the range of 16 ℃~23℃, which belongs to the high applicable area of evaporative ventilation and air-conditioning technology. Consequently, evaporative ventilation and air-conditioning technology in Shaanxi Province has good prospects. In the following, the specific operation mode and the outlet temperature 2

of evaporative ventilation and air-conditioning technology in Shaanxi Province are analyzed in details. According to the Design Code for Heating Ventilation and Air Conditioning of Civil Buildings (GB50736-2012), the indoor state point N selects dry-bulb temperature of 26℃ and relative humidity of 60%; the supply air temperature difference is 8℃, and then the ideal state point of air supply O (dew-point temperature L) selects dry-bulb temperature of 18℃ and relative humidity of 95%. And then the specific operating modes of the typical cities in Shaanxi Province are divided according to the partition map which is determined by the indoor state point N and the ideal state point of air supply O (Figure 4). See table 1 for details: Table 1 The specific operation mode and the outlet temperature of evaporative ventilation and air-conditioning technology in Shaanxi Province

City

The Ideal State Point O Outdoor State Point W(Cooling1%) (18℃, 95%)

Indoor State Point

Outlet

Outlet

The Specific

Temperature

Temperature

Operation Mode

IEC+DEC

2IEC+DEC

/℃

/℃

N (26℃, 60%)

DB

WB

SE

HR

SE

HR

WB

SE

HR

WB

/℃

/℃

KJ/kg

g/kg

KJ/kg

g/kg

/℃

KJ/kg

g/kg

/℃

Dingbian

30.2

16.7

52.1

8.4

54.8

14.5

17.5

64.2

14.9

20

DEC

Yulin

31.1

18.8

57.8

10.3

53.4

13.9

17.5

62.7

14.3

20.1

IEC+DEC

17.3

Suide

33.3

21

65.2

12.3

52.8

13.7

17.5

62.2

14.1

20.1

2 IEC+DEC

19.7

17.9

Baoji

33.3

21.5

64.8

12.2

51

13

17.5

60.3

13.4

20.2

EC+MR

20.2

18.5

Xi’an

34.4

23.1

70.5

13.9

50.7

12.8

17.5

59.9

13.2

20.2

EC+MR

22.5

19.0

Yan’an

40.9

34.2

26.1

87.4

20.6

53

13.7

17.5

62.3

14.1

EC+MR

25.9

24.9

Note:DB—Dry-Bulb Temperature;WB—Wet Bulb Temperature;SE—Specific Enthalpy;HR—Humidity Ratio;DEC—Direct Evaporative Air Condition; IEC—Indirect Evaporative Air Condition;MR—Mechanical Refrigeration.

From the above analysis, it can be seen that evaporative ventilation and air-conditioning technology has good prospects in Shaanxi Province. Case studies are carried out in the following sections to show that evaporative ventilation and air-conditioning technology has been successfully used in Shaanxi Province. 1. A Communication Room in Xi'an The communications room is located in Xi'an, Chang'an industrial park; two-storeyed structure, and the construction area is about 440m2. The equipment in the engine room is TD communications network equipment and the fatigue test machine is carried out in this room. The engine room is planned to place 110 DC cabinets, 25 AC cabinets, 16 equipment racks, and the communication equipments to be tested is placed on the shelf. Communications equipment room arrangement is shown in Figure 5.

Figure5 Communication equipment room equipment layout

3

(One) Optimization scheme of air conditioning unit According to the requirements of the indoor environment in the electronic information room as well as the business-to-energy saving requests, the indoor temperature for evaporative cooling technology is kept at 28±2℃, the indoor air relative humidity is 45%±15%. Xi'an is a moderate humidity area so that the communication CRAC system runs the whole year. It is a large load of the air conditioning system. As a result, two evaporative cooling air handling units are applied. The supply and exhaust pipe is the same as the original air-conditioning system. The air volume is 42000 m3/h for the original modular air conditioning units, and thus the indirect evaporative coolers of the same air volume is setting in front of the unit and the humidifier in the original air handling units is changed into more efficient direct evaporative cooler. The optimization program has the following characteristics: 1. Tube indirect evaporative cooler has a high wet cooling capacity and in the transitional season, it is able to reduce the temperature of the outdoor air. 2. Original wet membrane humidifier is replaced by a direct evaporative cooling section, and the air can be cooled for the enthalpy and the temperature drop is larger than before. 3. Water spray humidifier uses the direct form while the optimized direct evaporation cooling adopts circulating water. It saves water. 4. The cooling effect is obvious for tube indirect evaporative cooler in Xi'an during the summer and tube indirect evaporative cooler can be processed as a pre-cooling section to save energy. The optimized structure unit is shown in Figure 6 and the physical map is shown in Figure 7.

Figure 6 Schematic diagram of the original air

Figure 7 After evaporative cooling technology to

handling units optimization scheme

optimize unit physical map

(Two) The effect of energy-saving Xi'an is a moderate humidity area and the cooling efficiency of direct evaporative and indirect evaporation cooling section is tested. Taking indirect stage efficiency of 65%, direct stage efficiency of 90%, the outlet temperature of the tube indirect and direct evaporative cooling units in Xi'an can be calculated. And the hourly meteorological parameters are extracted from China Building Thermal Environmental Analysis Specific Meteorological Data Set. There are total 8760 sets of a year. The operation mode and outlet temperature for the tube indirect and direct evaporative cooling units is carried out and the outlet temperature is 0-14 ℃ as shown in Figure 8.

4

Figure 8 Tube indirect and direct evaporative cooling mode of operation of the air temperature statistics

As can be seen from Figure 8, the outlet temperature is in the range of 0-14 ℃ mainly in March, April, May, October, November, and December. In January and February, the outdoor air temperature in Xi'an is below 0℃ and the direct evaporative cooling section opens when the room temperature is below 0 ℃. The tube indirect and direct evaporative cooling units can ensure the supply air temperature between 0~14℃ for 3400h and 55420kWh annual consumption. The power consumption is 234600kW/h for mechanical refrigeration systems. The tube indirect and direct evaporative cooling units power consumption accounts for 23.6% of the original mechanical refrigeration systems. According to Xi'an industrial electricity prices (1yuan/kW/h), the annual electricity bill of evaporative cooling ventilation and air conditioning system is about 55,000RMB while the annual electricity bill of mechanical refrigeration and air conditioning systems is around 235,000RMB. In one year, the use of the tube indirect and direct evaporative cooling units can save money for enterprises is 180,000RMB, and the carbon dioxide emissions are reduced about 163 tons. 2. A Frequency Conversion Room in Yulin The frequency conversion room is located in Yulin, Shenmu, Shaanxi Province. The air volume is 52000m3/h. The unit structure is indirect-direct two evaporative cooling air conditioning units placed on the roof .The primary and secondary air of the tube indirect evaporative cooling section all use the outdoor ambient air; and 8-station exhaust fans are used as exhaust indoor air. Figures 9 to 12 is a pictorial diagram of the unit, the structure diagram, the unit roof structure diagram arrangement plan and frequency room equipment and duct layout, respectively.

Figures 9 The pictorial diagram with evaporative cooling

Figures10 The structure diagram with

in the Frequency room

evaporative cooling air conditioning units

5

Figures11 The unit roof structure diagram arrangement plan

Figures12 Frequency room equipment and duct layout

Test runs of direct evaporating section are reported in Table 2: Table 2 Direct evaporative cooling section to run a separate data analysis Air inlet size(mm×mm)

2300×2400

Wind(m3/h)

44215

45Hz

DB(℃)

WB(℃)

DP(℃)

RH(%)

SE(KJ/kg)

HR(g/kg)

Outdoor state point

28.4

21.0

17.9

53.5

66.6

14.8

Directly after the parameter

21.9

21.1

20.5

92.4

66.5

17.5

segment Outlet parameters

22.8

21.3

20.6

88.4

67.9

17.7

Indoor state point Unit temperature drop(℃) Direct segment wet bulb efficiency

27.3

21.5

19.1

61.3

68.3

19.1

6.5 η=87.7 %

Note:DP—Dew point temperature.

The period of the test is 12:10-13:40, running unit 1, using 45Hz fixed frequency and operating 4 exhaust fans. The test runs of indirect and direct evaporative cooling sections are given in Table 3. Table 3

45Hz

Indirect - direct evaporative cooling section run data analysis

Air inlet size(mm×mm) Wind(m3/h) DB/℃ WB/℃

2300×2400 56386 SEKJ/kg

HRg/kg

DP/℃

RH%

Outdoor state point

29.5

20.7

16.9

48.5

66.4

14.3

Directly after the

25.8

19.9

17.3

59.9

62.4

14.2

parameter segment Outlet parameters

20.7

19.9

19.5

93.5

62.5

16.4

Indoor state point

21.6

20.1

19.4

88.1

63.3

16.3

Secondary air outlet

27.9

25.4

24.5

82.3

85.4

22.4

point state drop Unit temperature

8.8

Tubular(℃) segment wet

η=41.8 %

bulb efficiency Tubular segment dew

η=29.4%

pointsegment efficiency Direct wet

η=87.6 %

bulb efficiency

NOTE: The test air flow rate of primary air to secondary air and the amount of air

The period of the test is 14:30-16:00, running unit 1, using 45Hz fixed frequency operation and operating 4 exhaust fans. When running direct evaporative cooling section, the average outdoor dry bulb temperature is 28.4℃, the average relative humidity is 53.5% and the wet bulb temperature is 21.0℃. After the direct evaporative cooling section, the average temperature is 21.9℃, the average relative humidity is 92.4% and the average efficiency is 87.7%; the average indoor temperature in the frequency room is 27.3℃, relative humidity is 61.3%, meeting the requirements. When running indirect-direct evaporative cooling section, the average outdoor dry bulb temperature is 29.5℃, 6

the average relative humidity is 48.5% and the wet bulb temperature is 20.7℃; after direct evaporative cooling section, the average temperature is 20.7℃ and the average relative humidity is 93.5%; the average indoor temperature in the frequency room is 25.5℃, the relative humidity is 64.5% and the indoor temperature and humidity can meet the requirements. Opening the indirect and direct function is able to adjust the room temperature and the relative humidity is ensured. Through the above examples, we can see that the project of evaporative ventilation and air-conditioning technology in Shaanxi works well. The typical projects using evaporative air conditioning in Shaanxi are shown in table 4. Table4 Using evaporative ventilation and air-conditioning technology system typically works in Shaanxi Province Location Yulin

Application

Form

A power inverter room

Tube indirect - direct two-stage evaporative air conditioning units

A thermo electron corporation An office building

Two-stage evaporative air handling units Evaporative cooling and mechanical refrigeration complex high-temperature chiller

A glass production plant

Evaporative air conditioners combining with task air supply

A communication room

Evaporative cooling combined with mechanical refrigeration technology

A factory test plant

Three-stage tube indirect +direct evaporative air conditioning units

An assembly plant

Three-stage tube indirect and direct evaporative air conditioning units

A cotton mill air station

Xi'an

Xianyang

High-pressure jet-tube direct evaporative

air conditioning system

A textile mill compressed air station

High pressure jet-tube indirect evaporative air conditioning system

A catering company processing plant

Evaporative air-conditioners (new wind blowing on a direct-current)

An Internet cafe

Evaporative air-conditioners (unilateral side air)

A terrace restaurant in catering company

Evaporative air-conditioners (underfloor air)

A hot pot restaurant

Evaporative air-conditioners (Fresh Air DC-type air supply)

A shopping mall

Evaporative cooling energy-saving clean air conditioning units

A barber shop

Mechanical refrigeration combine with evaporative air conditions

An office building

Dry fan coil + evaporative fresh air handling units system

An office building in high-tech Area(a)

Evaporative cooling+ mechanical refrigeration semi-central air conditioning system

An office building in high-tech Area (b)

Radiant +displacement ventilation mode

World horticulture expo park

Spray cooling system

An office(a)

Evaporative air-conditioners (Fresh Air DC-type air supply)

An office(b)

Evaporative air-conditioners (new wind blowing DC side)

An office(c)

New composite dew point indirect evaporative cooler

An office(c)

Evaporative air-conditioners (new wind blowing DC side)

A students’ dormitory

Evaporative air-conditioners (new wind blowing DC side)

A pharmacy

Evaporative air-conditioners (underfloor air supply)

A traffic booth

Evaporative air-conditioners ( task air supply)

A production company foundry

Indirect riser - target nozzle evaporative cooling air conditioning units

An equipment company

Evaporative cooling chiller

Baoji

A swimming pool

Indirect - direct evaporative cooling and mechanical refrigeration joint air handling units

A power plant

Surface type air condensing steam system

Weinan

An ecological restaurant

Wet curtain - fan cooling system

A flower greenhouse in Fuping

Wet curtain - fan cooling system

7

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