What is the difference between an air source heat pump and a heating and cooling air conditioner

What is the difference between an air source heat pump and a heating and cooling air conditioner

According to statistics, in 2017, a total of 5.78 million households were converted from coal to electricity and gas, and 3.94 million households were completed in 28 cities in Beijing-Tianjin-Hebei and surrounding areas. It is expected that in 2018, the northern region is expected to complete 4 million "coal-to-electricity" and "coal-to-gas" households, and accelerate the elimination of small boilers of 10 tons or less.

　　 It is foreseeable that for a long period of time in the future, the coal-to-clean energy market will be vast and the potential for coal-to-electricity conversion is unlimited. So what is the difference between air source heat pump and air conditioning, why air energy heat pump heating has gradually become the mainstream clean heating mode?

　　 working principle difference

Air source heat pump: the electric power drives the compressor to compress the low-temperature refrigerant into high-temperature refrigerant. The high-temperature refrigerant exchanges heat with water through the hot water heat exchanger. The high-temperature refrigerant after the heat exchange is depressurized by the expansion valve and absorbed in the air through the evaporator The refrigerant after absorbing heat is sucked in by the compressor, continuously absorbing heat from the air, and releasing heat on the side of the hot water heat exchanger to heat the cold water. The heat absorbed by the water is the sum of the heat produced by the compressor and the heat absorbed by the air by the refrigerant.

Air conditioner: The electric drive compressor works to compress the low-temperature refrigerant into high-temperature refrigerant. The high-temperature refrigerant is radiated by the evaporator. The air-conditioning host fan discharges the heat to the outside. The heat-dissipated high-temperature refrigerant is decompressed by the expansion valve and absorbed by the indoor unit evaporator of the air conditioner. The heat in the air reduces the indoor temperature, and the refrigerant after absorbing the heat is sucked in by the compressor. In this way, the heat is continuously discharged from the room to the outdoor air, and the heat is absorbed from the room to achieve the purpose of reducing the indoor temperature.

　　 Differences in heating methods

　　 Air source heat pump: The air energy heat pump itself is just a device that provides hot water. It supplies heat, and then cooperates with other heating terminals to achieve heating, such as radiators, fan coils, air-energy floor heaters, floor heating pipes, etc., can be used as the heating terminals, and different heating methods can be selected according to different residences.

　　 Air conditioner: Whether it is a cabinet-type air conditioner or a wall-mounted air conditioner, it can only use active hot air to achieve heating.

　　Part differences

　　 Air source heat pump: heat pump dedicated compressor, antifreeze high-efficiency tank condenser, outdoor fin heat exchanger with hydrophilic membrane, system high pressure protection and control.

　　 Air conditioner: air conditioner compressor, fin condenser or plate condenser, outdoor fin heat exchanger without hydrophilic film

　　 Among these parts, the difference in compressors is the biggest difference between air source heat pumps and air conditioners, because different compressors determine the product's use effect and the use of different regions. Air-conditioning compressors are used for air-conditioning. Take R22 as an example. The maximum operating pressure does not exceed 2MPa, the compressor ratio is less than 7, and the maximum exhaust temperature does not exceed 90℃. However, the air source heat pump must use a heat pump compressor. Take R22 as an example, the maximum The operating pressure reaches 3MPa, the compressor ratio reaches 12 or even higher to 20, and the maximum exhaust temperature reaches 110°C. The difference in these parameters requires an order of magnitude improvement in the processing accuracy, bearing strength, and motor temperature resistance of the heat pump compressor compared to the air conditioning compressor.

Differences in heat transfer mechanism

　　 Air source heat pump: Although the heat transfer is achieved through refrigerant, in the final heat exchange stage, the heat pump uses water to exchange heat, and the air conditioner uses refrigerant as the medium from beginning to end. One is the water cycle and the other is the fluorine cycle. In the water cycle, even if the heat pump is shut down, the water flow will always stay in the indoor pipe and continue to emit temperature. This is equivalent to adding a buffer process of heat. Moreover, if a fan coil or an air-energy floor heater is used as the end, the hot air is obtained from the hot water at the end, so the overall humidity is more in line with human physiological habits and will not cause "air conditioning diseases" such as dry mouth and tongue.

　　 Air conditioner: Air conditioner adopts "fluorine cycle" to realize heat conduction. The air outlet of the air conditioner discharges a large amount of hot air, and the purpose of heating is indeed achieved, but this kind of aggressive active thermal convection scheme will greatly increase the amount of water evaporation on the human skin surface, resulting in dry air, dry mouth and poor comfort.

　　Differences in operating mode

　　 The operation mode of air source heat pump and air conditioner has the following differences:

　　First: Although the air source heat pump is energized throughout the day, when the heating is completed, the unit will stop working and automatically keep warm. Household appliances generally work no more than 2 hours a day, so air source heat pumps save electricity than air conditioners, and can better protect the compressor and extend its service life.

　　Second: Air conditioners are used frequently in summer, especially in northern areas, but air source heat pumps integrate hot water, heating, and cooling, and run longer in winter. Especially in winter, the demand for hot water is large, so the air source heat pump needs a longer time to run to raise the water temperature, and the compressor needs more time to run, so the compressor basically runs in the area with higher refrigerant. . Operating temperature is one of the main factors that affect the life of the compressor. Under the same operating time, the overall load of the compressor in the air source heat pump is higher than that of the compressor in the air conditioner.

　　Use environment difference

　　 Air conditioners and air source heat pumps can be used under different ambient temperatures. When the air conditioner is heating, the maximum ambient temperature is 21℃. According to the national standard, the best use environment is 21℃ to -7℃. But the air source heat pump is different. For the water heater, it is also used in spring and autumn. According to the national standard of the air source heat pump, its use range is 43°C to -20°C. Because the ambient temperature range of the air source heat pump is wider, the specifications and selection of the parts it uses are more demanding than the air conditioner.

　　 In addition, due to different use environments and purposes, air source heat pumps require higher temperature and pressure. The maximum air outlet temperature of the air conditioner is also 50°C, and the condensing pressure is 1.8-2MPa at this time. The air source heat pump requires 60°C or even 65°C, at which time the condensing pressure reaches 2.5-2.8MPa. The pressure difference of 30-40%, coupled with the low temperature environment, especially at -20℃, the evaporation pressure is also very low, 0.2～0.15MPa, the water temperature still has to be heated to more than 50℃, or 60℃ or even 65℃, At this time, the condensing pressure is still 2.7～2.8MPa, and the compression ratio is far greater than 15, which is greater than the compression ratio range of the air-conditioning compressor.

　　The difference of system defrost

　　 Generally speaking, the greater the difference between the temperature of the refrigerant and the outdoor temperature, the more severe the frost. The air source heat pump itself transfers heat by a small temperature difference, while the air conditioner uses a large temperature difference. Air source heat pumps focus on heating in winter. They absorb heat in a low temperature environment. In winter, the temperature is minus ten or twenty degrees, and the temperature of the refrigerant is also minus twenty or thirty degrees, with a temperature difference of only ten degrees; air conditioning focuses on refrigeration. The highest temperature in summer is 45°C, while the compressor discharge temperature reaches 80 to 90°C, or even 100°C, with a temperature difference of 40 to 50°C.

　　 Therefore, under the same circumstances, the heat exchange area of ​​the air source heat pump is much larger than that of the air conditioner, which is why the air source heat pump is larger than the air conditioner.

According to the conventional control logic, the defrosting time of the air conditioner is generally about 10 minutes, while the defrosting time of the air source heat pump heating unit is usually a control logic for one place, such as Qingdao in Shandong and Qinhuangdao in Hebei, defrosting takes longer than in Shanxi. Frequently. Professional air source heat pump manufacturers generally have one control logic for each latitude, and they are adjusted according to local climate conditions.

The advanced stage of defrosting is "defrost with frost, no defrost without frost, more defrost with more frost, less defrost with less frost". This is based on the premise of a complete pressure and temperature control system. At present, there are only some high-end machines. Only available because of the high cost. Whether it is from the control logic and the area of ​​the evaporator, or from the difference between the refrigerant and the outdoor temperature, the defrosting performance of the air source heat pump is far better than that of the air conditioner, and the possibility of frosting is less, so the whole can provide The effective heat is greater than that of an air conditioner.

　　 Implementation of national standard differences

　　 Air source heat pump: Mainly include domestic hot water, commercial hot water, domestic heating, commercial heating and other standards. With heating capacity and coefficient of performance as measurement indicators, cooling and heating machines must also assess cooling capacity and energy efficiency ratio.

　　 Air-conditioning: Mainly including domestic air-conditioning, multi-line, air-cooled chillers and other standards, with cooling capacity and energy efficiency ratio as the measurement index