Identifying the performance and losses of a scroll compressor with vapour injection and R1234ze(E)

Area of Science:

• Thermodynamics
• Mechanical Engineering
• Refrigeration Systems

Background:

• Heat pumps are crucial for efficient heating and cooling.
• Vapour injection scroll compressors enhance heat pump performance.
• R1234ze(E) is an emerging refrigerant for eco-friendly applications.

Purpose of the Study:

• Investigate the performance of a vapour injection scroll compressor heat pump using R1234ze(E).
• Identify the reasons for significant performance reduction at high temperature lifts.
• Develop and validate an improved semi-empirical model for compressor performance analysis.

Main Methods:

• Experimental testing of a water-to-water heat pump across a wide temperature range.
• Development of a semi-empirical compressor model incorporating vapour injection.
• Implementation of a novel suction pressure drop model considering laminar and turbulent flow regimes.
• Model validation against experimental data and parameter tuning for R1234ze(E).

Main Results:

• Heat pump performance drastically decreased for lifts exceeding 30 K, with COP below 2.
• Maximum second law efficiency reached only 28%.
• High suction pressure drop, attributed to friction and potential laminar flow, was identified as the primary loss mechanism.
• The developed model accurately captured performance degradation, unlike standard models.

Conclusions:

• Suction pressure drop is a critical factor limiting vapour injection scroll compressor efficiency in heat pumps, especially with R1234ze(E).
• The novel modelling approach provides better insights into compressor underperformance.
• Optimizing suction line design to mitigate pressure drop is essential for improving heat pump efficiency.