Abstract: This paper analyzes the characteristics of air-cooled heat pump household central air conditioning, application conditions and design should pay attention to the problem; analysis of green building and home central air conditioning. It is pointed out that the household central air conditioning system has the advantages of energy saving, reliable operation and flexible application. It is suitable for some buildings, such as multi - rooms, villas, offices and entertainment venues.
Keywords: home air conditioning ultra-micro central air-conditioning air-cooled heat pump
1. Household Air-conditioners and Green Buildings In recent years, with the substantial improvement of people's living standards, the per-capita living space in Shanghai has been continuously increasing from 4m2 to 10m2 and the quality of life of the people has greatly improved. The demand for residential property soared and no longer satisfied with 60 ~ 70m2 continued to grow into a similar category of two-bedroom, but to 90 ~ 250m2 continued to grow to multi-bedroom, small villas in the direction of development in residential green environment, cultural atmosphere, Room design, functional requirements and interior decoration have reached the standard of well-off conditions, air conditioning has become home, office buildings, entertainment and electrical appliances necessary for the application of air conditioning put forward higher requirements. According to the statistics, by the year 2000, the number of air-conditioners owned by every 100 residents in Shanghai has reached about 90%, and many families have already achieved one multi-machine or one-room-one machine so that the air-conditioning ownership in Shanghai has exceeded that of some developed countries. Not only that, real estate developers also timely put forward the "green building" of the new concept. The so-called "green building" is the building of "Resource-efficient resources (ResourceEfficientBuildings)". Reduce "the use of building materials, various resources and non-renewable energy sources;" Renewable "which utilizes renewable energy and materials;" Recycle "which uses recycled materials and" reclaimed water "to set up waste recycling systems; Reuse ", re-use of old materials 4" R "building. To sum up, "green building" is a kind of sustainable building that makes comprehensive use of resources, energy saving, environmental protection, closeness and return to nature and health. Since "green building" gives special attention to indoor environment quality, it requires clean, fresh and safe standards for many physical and chemical factors in environmental physical and indoor air quality such as sound, light and heat. It is clear that all buildings Single use of split air conditioners can not meet the requirements of environmental protection. Home split air conditioner there are some disadvantages:
1) Currently the market supply of air conditioning machine performance coefficient COP is relatively low, only between 2.7 ~ 3. Household air conditioners are the most energy-intensive appliances in the average home. In Shanghai, for example, there are 4.0 million households in Shanghai, and the number of air-conditioners should not be less than 3.6 million units, which consumes a lot of power. If the COP value is reduced by 0.1, the total power consumption is increased by 3.4%.
2) As the split air conditioner air can only circulate in the room, there is no fresh air supply, resulting in difficult to ensure the indoor air quality, increased indoor CO2 air pollution. In addition, the air conditioner's filtration efficiency is not high. In particular, respirable dust with a particle diameter of less than 10 μm hardly works. As a result, cross-infection of air-conditioning syndrome and certain diseases is easily caused, adversely affecting human health.
3) For the outdoor buildings of the old-fashioned buildings and split-type air-conditioners, the outdoor installation machines generally hang on the wall facades, which destroys the walls and hinders the view. Condensate is discharged everywhere, and the noise and exhaust of the outdoor unit also pollute the environment. A large number of outdoor unit suspension also exist hidden threats.
Based on the above analysis, it is imperative to develop a small household central air-conditioning system for some large-scale, multi-family residential buildings with one room and one machine and a single multi-machine model that has violated the requirements of green building.
2, the characteristics of home central air conditioning system Home central air conditioning system is a new concept of ultra-micro central air conditioning. Residential buildings, villas, offices, restaurants and entertainment venues that require a dedicated central air-conditioning system for residential use are relatively suitable for relatively independent (the area of ​​use is continuously increased from 90 m2 to 50 m2, and the average growth rate is 10 000 m2) . The design uses air - water heat pump type household central adjustment system, its advantages are:
1) The whole or the whole building Central air conditioning has a host to drive multiple end devices, summer cooling, winter heating. The unit can be automatically adjusted according to changes in load, saving 20% ​​energy than ordinary split air conditioners at full load conditions.
2) The unit can be installed in the balcony roof and the courtyard, without another engine room, without damaging the wall facades, flexible and convenient.
3) Comprehensive utilization of resources, the use of cooling heat can be used to supply hot water.
4) Set energy-saving fresh air system, to send fresh air indoors, improve indoor air quality, provide a comfortable and healthy living environment.
5) As the system is dedicated to every household, there is no charge for residential air conditioners. Avoided due to different billing methods and the use of contradictions arising from, is conducive to property management.
3, air-cooled heat pump home central air conditioning system design Air-cooled heat pump home central air conditioning is the outdoor air as a "heat source", through mechanical work, the output heat to solve the central air conditioning hot and cold water supply, adjust the indoor air temperature. The so-called "heat pump", which can absorb heat in low-temperature environment, and its position can be increased, the heat output to the high-temperature environment of the device machinery, can be called "heat pump." The advantage is no water, you can omit the cooling tower, water pump cooling water circulation system, energy saving, water saving can also reduce the total investment.
Air-cooled heat pump home air conditioning system conditions for the application:
①winter outdoor air conditioning calculation temperature should be above -10 ℃, unit evaporation temperature <-8 ℃, continuous operation time <110h. ② winter air temperature is low, that is, the annual defrosting time 500 ~ 1000h, defatted per kg of dry air 7 ~ 20kg. The middle and lower reaches of the Yangtze River this area more appropriate conditions. Heat pump air-conditioning system shown in Figure 1. Air-cooled heat pump home central air-conditioning system host is air-cooled cold (hot) water unit, the configuration system shown in Figure 2.
The general use of the area in the room 100 ~ 120m2, the unit power 3kW host, with an increase of 20 ~ 30m2 increase of 0.75kW, you can initially determine the unit selected power, the cooling capacity of 10.8 ~ 19.5kW, thermal capacity of 11.5 ~ 21.3kW , The piping conditions shown in Figure 3.
Air-cooled heat pump air conditioning system design is the key must be the best balance point temperature (ie air-cooled heat pump heat transfer is equal to the outdoor heat consumption of buildings calculated value) to choose the heat pump. Whether to add an auxiliary heat source depends on the outdoor temperature in winter. If the outdoor temperature is below the equilibrium point, add an auxiliary heat source. Auxiliary heat sources generally use electric heaters. The cooling conditions for the ambient temperature 35 ℃, backwater temperature 12 ℃, water temperature 7 ℃; heating conditions for the ambient temperature 7 ℃, return water temperature 40 ℃, water temperature 45 ℃.
Second, the key to the design is defrosting and defrosting. Frost now commonly used method is to add an auxiliary outdoor heat exchanger; commonly used defrost method is to use electronic expansion valve to convert the working condition with hot air recoil. As defrosting inevitably lead to increased energy consumption and hot water temperature fluctuations, it is necessary to arrange defrosting cycle.
In addition, the design must also consider the installation location and noise control unit. General aircrew installation position to smooth, wind speed control at 3 ~ 4m / s, exhaust unobstructed, especially the top of the outlet should not have a barrier, otherwise it will cause exhaust air flow short circuit, thermal protection and downtime.
4 Conclusion In the above analysis of the air-cooled heat pump household central air conditioning system features, applications and design should pay attention to the problem. Compared with other types of air-conditioning systems, the air-cooled heat pump air conditioning system has a slightly lower thermal efficiency, but due to its unique split structure and convenient combination, the unit can adjust itself according to the load changes, especially under part load operating conditions. Significant energy-saving features, with cold, warm, bath water supply function, suitable for small and medium-sized buildings and general home use, should be more promotion and use.
references
[1] war Qin Wen. Villa building air conditioning design. HVAC, 1 998, 2 0 (4)
[2] Bu Xiaohua. Refrigeration and air conditioning technology quiz. Beijing: Metallurgical Industry Press, 2000
[3] Han Wei, Chen Zhichun. Study on the Performance of Air-Water Heat Pump System. Refrigeration, 2 0 0 0, 1 9 (3)
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