Technical characteristics and application promotio

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Technical characteristics and application promotion of digital central air conditioning system

Abstract: digital variable multi connected central air conditioning system is a new generation of modular multi connected system, which belongs to advanced air conditioning technology. Digital vortex technology can make the compressor operate in the range of 10% to 100% capacity, and realize stepless regulation in the whole range. The energy consumption is lower than the comprehensive energy consumption of variable frequency compressor, and there is no electromagnetic interference. The unit is highly intensive, There is no need to set up a machine room and no water. The simplicity and flexibility of its installation and maintenance make it more able to meet the needs of the air conditioning market. It is a technology worthy of promotion. This paper focuses on the characteristics and practical application of this technology

key words: digital air conditioning digital vortex pulse regulation cooling capacity attenuation electromagnetic interference

1 technical characteristics of digital central air conditioning system

digital (variable multi connection) central air conditioning system is composed of outdoor units of variable capacity vortex compressor with digital width pulse regulation control technology and multiple indoor units that can be controlled independently, referred to as DVM, which is a new generation of modular multi connection system, which is an advanced technology of air conditioning, The simplicity and flexibility of its installation and maintenance make it more able to meet the needs of the air conditioning market. The maximum pipe length of the unit is 100 meters, and the height difference can reach 50 meters. Because the unit is highly intensive and does not need to set up a machine room, it saves effective space for users. Compared with water-cooled units, there is no water system, which is both water-saving and convenient to maintain. The new digital central air-conditioning system can provide a wide range of air-conditioning methods for offices, apartments, shopping malls, hotels, hospitals, schools, factory workshops and other venues, as well as computer rooms, laboratories and other buildings of all sizes

the deformation of the width material completely disappears, but the overall profitability of the pulse regulated digital vortex is still low. The rotary compressor technology (PWM) can automatically adjust the cooling and heating capacity according to the load, so as to effectively reduce the operating cost. The essence of this technology is that the compressor itself has the characteristics of "axial flexibility". When the fixed scroll plate moves upward, the compressor's massless flow passes through. At this time, the compressor's capacity is zero and does not work on the refrigerant, that is, the "unloading state"; When the fixed scroll plate returns to its original position, it is the state when the ordinary scroll compressor is running. All the refrigerant passes through the compressor, and the compressor does work on the refrigerant. At this time, the compressor capacity is 100%, which is called "load state". The digital scroll compressor realizes the micro movement of the scroll plate (axial movement of 0.6 ~ 1mm) through the action and time of the precisely controlled PWM valve, so as to constantly change the lifting and meshing of the fixed scroll plate, that is, to change the cycle time of "load" and "unloading" to realize the adjustment of variable capacity. The external solenoid valve controls the "lifting" and "recovery" of the scroll plate through system signals according to the requirements of system capacity, Make the compressor automatically adjust the ratio of on-off time, realize "" output, reflect the digital function, and effectively reduce the operation cost

the transformation loss of digital scroll compressor from "load state" to "unloading state" is only 10%, which is lower than the comprehensive energy loss of variable frequency compressor. Moreover, digital scroll technology can make the compressor operate in the range of 10% to 100% capacity, realizing stepless regulation in the whole range, making the energy regulation range wider. In addition, the digital air conditioner also has the following characteristics: it can be flexibly combined according to the actual energy needs; The whole combined system adopts distributed control, and each unit adopts an independent refrigeration system, which can automatically adjust the load in different seasons and temperatures to ensure the operation in an energy-saving state; The stepless capacity output provided by digital vortex air conditioner ensures the control accuracy of room temperature at ± 0.5 ℃, which enables users to work in the most comfortable air conditioning environment. The room temperature of other types of air conditioners is controlled at ℃, which is very different from the comfort of the use environment of digital air conditioners. The digital scroll compressor operates at a single speed, so it will not produce additional noise and vibration, and will not cause adverse effects on the surrounding environment. The noise of indoor unit is very low, which is far lower than the national indoor noise standard; When the digital scroll compressor is running, the load unloading of the scroll plate is a simple mechanical movement, which does not produce high-order harmonics and electromagnetic interference; Digital vortex does not need oil separator or oil return circulation system. It uses the gas flow rate to fully flow the lubricating oil to the compressor, and will not burn the compressor due to poor oil return

2 technical comparison and analysis chart

Figure 1 Relationship between PWM valve and load

Figure 2 Comparison of refrigeration and heating performance/efficiency

Figure 3 Comparison of refrigeration capacity Figure 4 Comparison of power consumption

comparison of operating costs is shown in Table 1, and the consumption of energy consumption ratio is shown in Table 2. Operation cost comparison table 1



water cooler

VAV variable air volume system

energy consumption

44.2kw × 0.8

(Variable Compressor)

43kw × 1.0

52.5kw × 1.0

monthly consumption

12906 kW

15695 kW

19162 kW

half year consumption (6 months)

77436 kW

94170 kW

114972 kW

1-year consumption




3-year consumption




5-year consumption




comparison results


121% ↑

148% ↑

note: the test conditions of the above data are as follows: the building area is 750 ㎡, the load is 7740kw, and the winter and summer are operated for three months respectively

calculation table of energy consumption ratio 2

control area

test conditions



load rate

performance w

Power W

energy consumption ratio

load rate

performance w

Power W

energy consumption ratio

P> 25%
















































15 857









































note: the test conditions of the above data are as follows: the load is 77400kw

A:DB26.7/WB19.4℃ , DB35/WB23.9℃; B:DB26.7/WB19.4℃ , DB27.8/WB18.3℃。

Figure 5 (cold/warm) schematic diagram of outdoor unit system

3 Application Research of digital air conditioning

in South Korea, hundreds of buildings, especially high-rise buildings, have adopted this air conditioning method, and the market development is promising. The author once visited South Korea to investigate the use of this series of air conditioners. In a 22 story apartment and office building in Seoul, all use DVM air conditioning systems, and are equipped with total heat exchangers for fresh air replacement. The area of the apartment ranges from 180 to 400 square meters. Each apartment is equipped with 6 outdoor units, 1 to 2 units, which are placed on a semi enclosed balcony specially designed for the unit. The balcony is equipped with openable floor blinds, and the unit is equipped with a special air duct, The flow direction of the condensed air of the outdoor unit is conducive to the heat dissipation of the unit, and there is no air short circuit and turbulence. The upper part of the balcony is equipped with a total heat exchanger, which is connected with the indoor exhaust outlet with an air duct to solve the problem of indoor fresh air exchange. Depending on the size, height and load of the room, the air-conditioning indoor unit is installed with a ceiling embedded indoor unit with multi-directional airflow and a ceiling embedded indoor unit with unidirectional airflow respectively; The room further reduces the low height of the raw material input room, and the installation of ceiling suspended or wall mounted; Some places are equipped with cabinet indoor units, and some large spaces are also equipped with air duct indoor units. In office buildings, due to the large space, most of them are equipped with a large number of air duct indoor units, which are arranged according to the distribution of rooms. The indoor units bear the main indoor air conditioning load, and are equipped with high static pressure air duct indoor units, which are used as fresh air units, and the indoor units only bear the fresh air load. Due to the heavy load of office buildings, in order to save energy, several total heat exchangers are also installed for air replacement to ensure that the indoor air environment meets the health requirements

it is worth mentioning that although the DVM units used in many buildings with DVM air-conditioning systems are heat pump units that can be cooled and heated, all the buildings seen are equipped with water coils of low-temperature hot water floor heating systems or heating cables for heating in winter. Few buildings have only a single air conditioning system. Asked the local engineering and technical personnel about the reason, or unclear, or said that the local heating is very cheap, or there are regulations, etc., the result is unknown

in Jiangnan area of China, air conditioning is mainly used for cooling in summer. Due to the relatively high outdoor air temperature in winter in the south, low temperature operation will not occur even for heating. Therefore, many users have adopted this air conditioning system, and its development prospect is also very optimistic. However, it is different in the vast northern region of China. Due to the low outdoor temperature in winter, winter heating is required. Although from the technical parameters of the product samples, the air conditioner can start heating normally at minus 15 ℃, and even work below minus 20 ℃. At this time, the problem of efficiency decline should be considered, but whether in South Korea or China, In fact, the real use of this air-conditioning system for winter heating is still lack of extensive application examples. According to the data provided by the manufacturer's technical data, when starting at low temperature, the output of the unit will decay by 20% - 25%, so it is necessary to increase the power configuration of the machine and increase the initial investment, which will directly affect the promotion of this air conditioning mode

4 application examples

taking the actual engineering design done by the author as an example, this is a two-story comprehensive office building located in the northern city, an antique building, with one floor underground, one floor above the ground, and an office on the ground. One part of the underground is used as an employee dormitory, and the other part is used as an office building. The total area of the building is 1400 ㎡. Due to the prevalence of SARS, Party A requires that there should be sufficient fresh air ventilation in the rooms above and below the ground. All rooms are equipped with exhaust ducts and pressure testing machines. How to effectively protect and maintain: exhaust fans. The heating load of the building in winter is 130kW, and the air conditioning load in summer is 138 kW (both including fresh air load). Due to the strict environmental protection requirements in the area where the building is located, coal-fired boilers cannot be used, and there is no natural gas source, so only electric energy can be used. The original design scheme is electric boiler heating and air conditioning system, which cannot be implemented because the location of boiler room and air conditioning room cannot be provided. After that, digital cooling and heating air conditioners were used. In the design process, five rvmh100gamo outdoor units are selected at the initial stage, with a theoretical refrigerating capacity of 140kW and a theoretical heating capacity of 157 kW. The indoor units are equipped with 50% - 100% of the capacity of the outdoor units, and a total of 38 air duct built-in low static pressure indoor units are equipped for room air conditioning; smallpox

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