EVI technology – what is it?

The Impact of Temperature on the Power of Heat Pumps.

Understanding the dependence of power and efficiency of heat pumps on the temperature of the primary heat source (air, ground, water, rock, etc.) is a key factor in optimizing their operation. In ground/water heat pump systems, a stable temperature of the primary source during the heating season ensures reliable efficiency and performance.

However, air heat pumps (air/water and similar) directly depend on the ambient environment. The efficiency and power of these systems decrease with a drop in outdoor temperature, as does the temperature of the heat carrier, which is related to the properties of Freon and the Carnot cycle.

EVI Technology (Intermediate Vapor Injection) as an Innovative Solution.

EVI technology is used to expand the operating range of heat pumps, reduce the temperature in the compressor, and increase the output power.

In conventional heat pumps, the process is as follows: the compressor compresses gaseous Freon, which condenses in the Freon/water heat exchanger, transferring heat to the heating system. The liquid Freon then passes through an expansion valve and evaporates in the air/Freon heat exchanger, absorbing heat from the outside.

In EVI systems, an additional expansion valve and heat exchanger are added. After the Freon condensation, part of it (about 20%) is directed to an additional expansion valve and an intermediate heat exchanger. The evaporated Freon then returns to the compressor for cooling.

The remaining 80% of the Freon, passing through the additional heat exchanger as a heater, enter the main expansion valve and, finally, the main evaporator. The additional heat exchanger supercools the main portion of the Freon, improving the efficiency of heat extraction from the environment. This allows the heat pump to operate effectively even at low temperatures, as the more cooled Freon ensures efficient heat exchange. Additionally, the intermediate injection of cold Freon also helps to cool the compressor, expanding its operating range.

The History of EVI Technology Development

Intermediate vapor injection technology (EVI) represents an important step in the evolution of heat pumps. Its development began in response to challenges associated with seasonal temperature changes affecting the efficiency of air heat pumps. To improve performance at low temperatures, engineers began seeking innovative methods to expand the operating range of heat pumps.

The concept of intermediate vapor injection was first introduced as a way to optimize the heat exchange process and increase efficiency in cold climatic conditions. The main principle involves using part of the Freon, which evaporated after the primary heat exchanger, for additional cooling of the compressor and supercooling of the main portion of Freon before entering the evaporator.

With the advent of EVI technology, heat pumps became more resistant to low temperatures, making them more attractive for regions with cold climates. This also led to an expansion of the use of heat pumps in areas where previously the use of this technology was limited.

Advantages of EVI Technology

EVI technology brings several significant advantages to the operation of heat pumps. Firstly, the expansion of the operating range and increased efficiency at low temperatures make these devices more versatile and effective in various climatic conditions.

Secondly, thanks to the use of intermediate vapor injection, heat pumps with EVI technology reduce the load on the compressor and improve heat exchange, which ultimately leads to increased longevity and energy efficiency of the equipment.

Thus, EVI technology continues to evolve, becoming an integral part of innovative solutions in the field of heating systems and climate equipment.


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