14 common cold and heat sources and the principles and introduction of air conditioning systems, increase knowledge!

14 common cold and heat sources and the principles and introduction of air conditioning systems, increase knowledge!

1. Conventional electric refrigeration and air-conditioning system

　　 At present, more air-conditioning forms are used. After more than a century of development, there are various forms of refrigeration hosts, which have the advantages of high refrigeration efficiency. It has the following characteristics.

　　1. Advantages:

　　① The system is simple and occupies a little smaller area than other forms;

　　② High efficiency, COP (refrigeration efficiency) is generally greater than 5.3;

　　③ The equipment investment is less than other systems.

　　 2. Shortcomings:

　　① The number and capacity of water chillers are relatively large, and the number and capacity of other electrical equipment have also increased correspondingly, increasing the workload of maintenance and repair.

　　② The total power load is large, which increases the transformer power distribution capacity and power distribution facility fees.

　　③ The electricity used is peak electricity, and the peak-to-valley electricity price policy is not enjoyed, and the operating cost is high.

　　④ The air conditioner cannot be used during the power cut. In the summer of 2003/2004, the operation of air-conditioning mainframes was halved, which caused most central air-conditioners to fail to achieve the effect.

　　⑤ The operation mode is not flexible. During transition seasons, holidays or breaks, individual areas need to be operated for cooling. The main engine needs to be operated, forming a large horse-drawn cart, which wastes the configuration capacity of the unit and increases the operating cost.

　　⑥ For large-scale district cooling systems, it is difficult to achieve better cooling (the temperature of the water supply cannot be lowered), the pipeline network investment is large, the transmission energy consumption is high, and the air conditioning quality is poor.

　　 2. Ice storage air conditioning system

　　Ice storage air conditioner is based on the conventional water-cooled chiller system to reduce the capacity of the refrigeration unit, increase the ice storage device, and use the low and low-priced electricity period at night to store the cold in the form of ice, and release it when it needs to be cooled during the day. This technology began to be used in the United States in the 1930s, and was developed vigorously in the energy crisis of the 1970s. Judging from the development of more developed countries and regions such as the United States, Japan, South Korea, and Taiwan, ice storage has become the development direction of central air conditioning. For example, in South Korea, buildings over 2,000 square meters must use ice storage or gas air conditioning, while buildings over 5,000 square meters in Japan should consider ice storage air-conditioning systems. Many countries have adopted incentive measures to promote this technology. For example, South Korea transfers 1kW peak power, a one-time award of 2,000 US dollars, and the United States a one-time award of 500 US dollars.

　　 China has also increased the promotion of energy storage technology. The State Planning Commission and the Economic and Trade Commission issued the "Administrative Measures for Energy Conservation", requiring all units to promote energy storage technology and gradually increase the peak-to-valley electricity price gap. The air-conditioning systems using energy storage technology have increased significantly across the country. In October 2001, the Shanghai Science and Technology City of 100 thousand square meters, the new campus of Zijingang of Zhejiang University, and the 5 million square meters of Guangzhou University City used ice. Cold storage air conditioning system.

　　 Ice storage central air conditioners represent the advanced level of central air conditioners in the world today, heralding the development direction of central air conditioners, and have the following characteristics.

　　1. Advantages:

　　① Reduce the capacity of the chiller (reduce the one-time investment of the host), reduce the total electricity load, and reduce the transformer power distribution capacity and power distribution facility costs.

　　② The refrigeration host has high refrigeration efficiency (COP greater than 5.3), and at the same time, it uses the peak-to-valley charge price difference to greatly reduce the annual operating cost of the air conditioner, which can save more than 35% of the operating cost (compared with the heat pump and lithium bromide air conditioner, it can save more than 40%).

　　③ Reduce the power distribution capacity of the building, save the investment in transformation and distribution, and save about 30% (the power distribution investment of the air conditioner); avoid the high reliability cost of the double line and save the investment.

　　④ It is flexible to use. In some areas, the air conditioner can be provided by melting ice without turning on the main engine, which has obvious energy saving effect.

　　⑤ It can melt ice and provide cooling for small loads (such as individual offices only) without turning on the host.

　　⑥ In the transitional season, the ice can be melted for quantitative cooling without the need to turn on the main engine, there will be no large horse-drawn carts, the operation is more reasonable, and the cost savings are obvious.

　　⑦ It has an emergency function to improve the reliability of the air conditioning system. It can show its advantages even more when the power is cut off: as long as it has the power to drive the water pump (such as the generator to generate electricity and reduce the power supply), the ice can be melted for cooling, and the air conditioner will not be unavailable (summer 2003/2004 The air-conditioning host halved operation, causing most central air-conditioning to fail to achieve the effect, only the effect of ice-storage air-conditioning was not affected).

　　⑧ The cooling temperature is low and stable, and the air conditioning effect is good, which improves the comfort and taste of the building.

　　⑨ With low-temperature cold source, the cooling speed is fast, and the start-up time is short before going to work. The longer the start-up time before going to work, the more the air conditioner will be ineffective and the greater the unnecessary waste.

　　⑩ As a driving energy source, it is clean, environmentally friendly, stable, simple and reliable, and the peak-to-valley power price difference is bound to be more favorable in the near future (peripheral provinces have already had substantial discounts last year, and foreign peak-to-valley differences are even greater).

　　For large-scale multi-building area cooling, low-temperature water supply can be used to reduce water energy consumption and reduce pipeline network investment; at the same time, compared with the form of a cooling station for each building, it can save investment, reduce management costs, and reduce machine room area. (For example, Guangzhou University City 5 million square meters, Zhejiang University Zijingang New Campus 130,000 square meters, Hangzhou Business School 100,000 square meters, Hangzhou Civic Center 580,000 square meters, etc.).

It can provide low-temperature cold water for the terminal and reduce the investment at the terminal; strengthen the dehumidification capacity and greatly improve the comfort of the air conditioner; if the low-temperature air supply system is adopted, it can save the energy consumption of the fan at the terminal, improve the quality of the air conditioner, and reduce the size and investment of the air duct .

　　 The air-conditioning system has a high degree of intelligence, which can realize the fully automatic operation of the system, and has the BAS interface with the building. It is currently the most advanced air-conditioning system in the world.

　　 2. Shortcomings:

　　① If the host and cold storage devices are all arranged in the refrigeration machine room, the ice storage device needs to take up a certain amount of space (solution: it can be buried under the green belt, arranged under the car ramp and other useless spaces).

　　②The equipment room investment is slightly higher than that of conventional water-cooled electric refrigeration and lithium bromide unit systems.

　　③ Ice storage can only be used for cooling in summer and requires a heating system (heating network can be used for heat exchange and heating, and the capacity of the heating network is much lower than the lithium bromide unit needs, only about 50% of the capacity).

　　 3. Water source heat pump air conditioning system

　　1) Renewable energy utilization technology

　　Water source heat pump is a heating and air conditioning system that uses solar energy stored in the earth's water body as a source of cold and heat to convert energy. The water bodies that can be used include groundwater or rivers, rivers and lakes on the surface, and the ocean. The surface soil and water body is not only a huge heat collector, collecting 47% of solar radiation energy, 500 times more than the energy used by humans every year (the underground water body indirectly receives solar radiation energy through the soil), but also a With a huge dynamic energy balance system, the soil and water on the surface naturally maintain a relative balance of energy acceptance and emission. This makes it possible to use the nearly infinite or ground energy stored in it. Therefore, the water source heat pump uses a technology of clean renewable energy.

　　2) Easy to measure and charge

　　The air-conditioning electricity load is at the user's location, so it is convenient to meter and charge the air-conditioning. This is beneficial for users to rationally use the air-conditioning system, save the energy consumption of the air-conditioning system, and allocate air-conditioning operation management in a fair, just and open manner.

　　3) Safe and reliable operation

The air conditioning system of 　　 water source heat pump unit can basically ensure that the air conditioning system is turned on according to the needs of users throughout the year, especially in the spring and autumn air conditioning transition seasons, which is equivalent to a four-pipe air conditioning system. Generally, the supply and return water temperature of the water source heat pump is relatively stable throughout the year, and its fluctuation range is much smaller than that of the air temperature. The water body is used as the cold source of the air conditioner in summer and the heat source of the air conditioner in winter. The relatively constant water temperature makes the operation of the heat pump unit more reliable and stable, and also ensures the efficiency and economy of the system. There are no difficult problems such as winter defrosting of air source heat pumps.

　　4) High efficiency and energy saving

　　 water source heat pump unit can use the ambient water temperature in winter is 12-22 ℃, the water temperature is higher than the ambient air temperature, so the evaporation temperature of the heat pump cycle is increased, and the energy efficiency ratio is also improved. In summer, the water temperature is 18~35℃, and the water temperature is lower than the ambient temperature, so the cooling condensing temperature is lowered and the unit efficiency is improved.

　　5) Flexible application

In some buildings, especially in the transition season, some areas need cooling and some areas need heating. The water source heat pump can provide cooling and heating at the same time, which can realize the transfer and balance of cold and heat in the building, so that the system uses less energy. .

Water-ground source air-conditioning has been widely recognized for its excellent energy-saving and environmental protection characteristics. In 2006, the Ministry of Science and Technology of China took building energy conservation as a scientific and technological support project of the "Eleventh Five-Year Plan". The sixth topic is the application technology of water and ground source heat pumps. "The comprehensive promotion of the application of energy saving and environmental protection technology has been one of the important topics of the conference. In just a few years, the development of water-to-ground source heat pump central air-conditioning in large and medium-sized cities is in full swing, especially in economically developed areas such as Beijing, Shandong, and the Yangtze River Delta. It has become a symbol of energy-saving and environmentally-friendly high-end air-conditioning systems. At present, it is rapidly developing into the central and western regions, and demonstration projects of water and ground source air-conditioning have been established in various places. The government is also actively encouraging enterprises and institutions to choose water and ground source heat pump air conditioners.

　　 At present, climate warming is a serious threat to the sustainable development of mankind, and tackling climate change has become a major challenge facing q*. In addition to natural factors, the causes of climate change are closely related to human activities, especially the use of fossil fuels and the degree of carbon dioxide emissions.

　　Energy saving will inevitably become a necessary indicator to measure the quality of future buildings. The concept of "low carbon emission" is receiving widespread attention from academic research institutions in the environmental protection industry.

　　 The central air-conditioning system is a device that consumes the largest amount of electricity in a building, and the need for energy saving and emission reduction should be the brunt of it. According to the "China Energy Conservation Technology Policy Outline", the development of geothermal source, water source, air source heat pump technology and sewage source heat pump technology, under normal circumstances should not use direct electric heating. Advocate cold storage, heat storage air-conditioning and heating, and try to make use of low grid load. The State Council document (Guo Fa (2008) No. 03) recommends the use of water source heat pump and ice storage technology for energy saving technology.

　　 4. Electric heat storage air conditioning system

　　Electric heat storage air conditioner uses low-cost low-cost electric boilers at night to produce heat. The heat produced is stored in the heat storage device in the form of hot water, and the stored heat is released during the day to provide heat to the end of the air conditioner.

　　The electric heat storage air conditioner has a stable heating capacity and has the following characteristics:

　　①Using energy storage technology to shift peaks and fill valleys, balance the grid load, improve the utilization of power generation equipment in power plants, reduce the operating costs of power plants and power grids, and save power plant and power grid infrastructure investment.

　　②Using the peak-to-valley charge price difference, greatly reducing the annual operating cost of air-conditioning.

　　③Flexible use. Air conditioning in some offices during transition seasons, holidays or after get off work can be provided quantitatively by heat storage, no need to start the group, energy saving effect is obvious, and operating costs are greatly reduced.

　　④It has an emergency function to improve the reliability of the air conditioning system.

　　⑤High degree of automation, it can be unattended, real-time tracking according to the change of air conditioning, how much cooling capacity is needed, there will be no big horse-drawn carts, energy saving is obvious.

　　 5. Air-cooled heat pump air conditioning system

　　 Air-cooled heat pump is a form of air conditioning that relies on outdoor air to cool. Its cooling and heating performance is closely related to the outdoor ambient temperature. It has the following characteristics:

　　① Integrated cooling and heating, no need for additional heat source.

　　② When the impact on the appearance of the building and the vibration of the unit is not considered, the unit can be placed on the roof without a special air-conditioning room. It is more suitable in a small area without a refrigerated machine room.

　　③ Air cooling, no cooling tower is required.

　　④ Relying on air cooling, the cooling and heating performance is closely related to the outdoor ambient temperature, resulting in unstable performance. When the outdoor temperature is high in summer and the cooling capacity is large, its cooling capacity becomes worse; when the outdoor temperature is low in winter and the heating capacity is large, its heating capacity becomes worse. In winter, specific defrosting measures are required, which affects the heating effect; the heating temperature is low, so that the indoor temperature cannot meet the requirements in cold weather.

　　⑤ Relying on air cooling, the cooling efficiency is low (nominal COP is lower than 3.2, actual operation is generally about 2.5), and the operating cost is high.

⑥ Because the unit is placed outdoors and cooled by wind, the condenser is covered with dust for a long time, which greatly affects the heat exchange efficiency, the operating efficiency of the unit decreases, and the cooling capacity also drops sharply. Generally, its cooling capacity needs to be reassessed after 3 years. , Carry out corresponding treatment, sometimes even need to add a unit.

　　⑦ The influence of the environment on the system needs to be considered when the unit is selected, and the configuration needs to be increased, and the investment is increased. The investment is z* high among several air conditioning forms.

　　⑧ Low efficiency and large total electricity load, increasing the transformer power distribution capacity of the conventional air-conditioning system itself, high power distribution facilities, and more electricity subsidies and power construction fees.

　　⑨ Because the unit is placed outdoors, it is difficult to operate, manage, and maintain. The unit is easily damaged and the maintenance workload is heavy.

　　⑩ In the transitional season, when the demand for cooling or heat is reduced, its cooling or heating capacity has reached a high level of z*. Large horse-drawn carts form waste and increase operating costs.

　　VI. Lithium Bromide Air Conditioning System

　　 Lithium bromide unit uses heat energy as the energy source of the unit. Through the absorption and release between lithium bromide and water, water is used as a refrigerant to circulate to achieve the purpose of refrigeration. According to the method of providing heating energy, lithium bromide units are divided into direct-fired type (oil, gas or natural gas), steam type (heating network steam or preparing boiler to provide steam) and hot water type (heating network hot water or self-heating). Prepare boiler to provide hot water).

　　 Since water is used as the refrigerant and lithium bromide is used as the absorbent, the characteristics of the refrigeration host are completely different from other air conditioners. Its advantages are as follows:

　　① The energy of the system is mainly heat energy, so the power distribution capacity is small (about 1/3 of the conventional electric refrigeration, 1/2 of the ice storage system), and the operation power consumption is small. (But it still can’t run during a power outage. The use of self-provided generators can only guarantee part of the water pumps. The entire system cannot provide cooling. It cannot be used like an ice storage system. Half of the units cannot achieve the air conditioning effect, and ice storage can ensure the air conditioning effect).

　　② It is more feasible to use in the occasions where waste heat is generated, such as steel mills, textile mills, etc. The application of lithium bromide units in developed countries in Europe and the United States is in the occasions where waste heat is generated.

　　③ (Direct-fired type) integrated cooling and heating, no additional heating equipment is required (it is a gas boiler for heating, but the thermal efficiency is lower than that of a separate gas boiler).

　　④ The machine room covers an area slightly smaller than ice storage.

　　 Deficiencies:

　　① Due to the characteristics of the lithium bromide unit, the cooling capacity is attenuated (annual attenuation is about 3% to 8%), so the capacity of the lithium bromide unit is designed with a margin of 15%.

②The outlet water temperature of the refrigeration host is high, the actual operation is higher than 8℃, the air conditioning effect is poor, the cooling speed is slow, and the start-up time before work is long, which reduces the taste of the building; at the same time, due to the high water supply temperature, the capacity of the terminal equipment must be increased to achieve The effect of reducing the indoor temperature increases the investment.