EVI Technology in Heat Pumps: An Engineering Solution for Extreme Conditions
In modern HVAC strategies, heat pumps are the most critical component of the sustainable energy transition. However, the success of the system depends on the engineering synergy between the compressor technology used and the selection of terminal units.
1. Technical Advantages of EVI (Enhanced Vapor Injection) Technology
Traditional heat pumps encounter capacity loss and high compressor discharge temperature issues as outdoor temperatures drop. EVI technology solves this problem by injecting refrigerant in the vapor phase at intermediate pressure into the compressor via an economizer.
• Thermodynamic Gain: EVI prevents compressor overheating, especially at temperatures of $-7$ °C and below, while increasing total heating capacity by 40% to 63% compared to standard systems.
• Efficiency (COP): Tests conducted on R32 refrigerant systems prove that the use of EVI directly improves the Seasonal Coefficient of Performance (SCOP) by a margin of 7%.
2. Terminal Unit Optimization: Underfloor Heating and Type 33 Radiators
The efficiency of a heat pump is inversely proportional to the flow water temperature. Therefore, the correct selection of terminal units is of vital importance:
• Underfloor Heating: By providing the opportunity to operate in the 35-40 °C range, it enables the system to reach COP values of 4.5. It extends the device's lifespan thanks to the thermal inertia of the screed layer.
• Panel Radiator Conversion: In a low-temperature regime (45/35 °C), the capacity of a standard Type 22 radiator drops significantly. To compensate for this loss, using Type 33 (600 times 1000) radiators with a larger surface area increases thermal capacity by 43%, ensuring the heat pump remains within its efficient operating range.
3. Energy and Capacity Analysis for a 150 m² Villa (Sample Table)
Comparison based on an annual heating load of 18,000 kWh for a 150 m² villa:
Heating System Type Terminal Unit Average SCOP Annual Consumption Savings Rate
Conclusion
From an engineering perspective; when a heat pump equipped with EVI technology is combined with underfloor heating or increased surface area (Type 33) radiators, it provides up to 70% energy savings and a lower carbon footprint compared to fossil fuels, even in the most demanding climate conditions.
This study was carried out in collaboration between Bursa Uludağ University and the COPA R&D Center.
Researchers:
Prof. Dr. Salih Coşkun – Bursa Uludağ University, Vocational School of Technical Sciences (ORCID: 0000-0002-6723-1992)
Lecturer Saffet Hakan Gül – Bursa Uludağ University, Vocational School of Technical Sciences (ORCID: 0000-0003-3775-3500)
Hüseyin Barış – Mechanical Engineer, COPA Heating Systems Industry and Trade Inc. (ORCID: 0009-0003-8874-3924)
Click here to examine COPA Trion S heat pump with EVI technology in detail.