What exactly is EVI? Why use EVI ultra-low temperature air source heat pump in northern China ?"Coal-to-electricity" has been going on in northern China, and air-source heat pumps have become a hot topic of discussion among all households. Because the main battlefield of "coal to electricity" is mainly in the north, the Inner Mongolia and the three northeastern provinces in northern China are also known for low winter temperatures. With the implementation of the coal-to-electricity policy, the EVI ultra-low temperature air-source heat pump has gradually replaced the "leading position" of coal-fired heating in northern China due to its energy-saving, environmentally friendly, and efficient heating characteristics. In the face of the low temperature environment in northern China in winter, why can ultra-low temperature air source heat pumps still show good heating effects and operate efficiently?
The restriction of ultra-low temperature environment on the operation of air source heat pump
A diagram of an air source heat pump system. The two major heat exchange components are the fin heat exchanger (liquid refrigerant absorbs heat from the air and evaporates into gas) and the tube heat exchanger (the refrigerant releases heat for heating).
The compressor plays a role of "heat transfer". The electronic expansion valve throttling makes the refrigerant pressure drop and enters the evaporator cycle again.
Once this system is placed in an environment with a temperature below -15°C, the ultra-low temperature air cannot release enough heat to satisfy the evaporation process of the liquid refrigerant in the evaporator. Insufficient evaporation makes the amount of low-temperature and low-pressure gaseous refrigerant entering the compressor insufficient, causing the compressor's exhaust temperature to be high, and it is easy to report a high-temperature exhaust failure.
On the other hand, the operating temperature of the lubricating oil inside the compressor is limited. Long-term exposure to a high temperature environment will cause the lubricating oil to deteriorate and lose its lubrication effect, limiting the life of the compressor.
Even if these problems are aside, the heat absorbed by the evaporator from the air is not enough, so the condenser side cannot release enough heat for heating, resulting in extremely poor heating effect for users.
We often hear a word-EVI. So what exactly is EVI? In fact, EVI is "air jet enthalpy", and everyone is familiar with the term "air jet enthalpy". Basically, we know that using this technology enables ultra-low temperature air to run efficiently below -15°C to meet the heating needs of users.
The EVI ultra-low temperature air source heat pump loaded with the “jet-enhancing enthalpy” compressor can perform “quasi-secondary compression” of the low-temperature heat in the air, so that the air-source heat pump compressor’s displacement will increase. The system will be stable and the heating efficiency will be improved.
The working principle of air jet enthalpy in the fluorine circuit
An enthalpy-increasing plate exchange and an enthalpy-increasing electronic expansion valve are added behind the casing, and the cycle of the fluorine circuit system has changed slightly.
After the heat exchange through the condenser (tube), a part of the medium-temperature and high-pressure liquid refrigerant has the same energy as conventional air, and returns to the evaporator after throttling and pressure reduction. Although the heat absorbed at ultra-low temperature is insufficient, it is only in the system Part of the refrigerant exchanges heat, so the evaporation effect can be guaranteed.
The other part of the refrigerant enters the enthalpy plate exchange after throttling and depressurization, absorbing part of the heat and returning to the compressor. The use of this method increases the return air volume of the compressor (the volume of low-temperature and low-pressure gaseous refrigerant), and avoids the hidden danger of the compressor reporting high exhaust temperature. Moreover, part of the refrigerant obtains heat from the enthalpy-increasing plate exchange, thereby ensuring the heating effect on the use side.
Therefore, the application of jet enthalpy technology can ensure the efficient heating of EVI ultra-low temperature air source heat pump units in ultra-low temperature environments.