With increasing energy price and concern on environmental impacts, more attention has been paid to refrigeration and heat pump systems. Several regulations have already been applied on the choice of refrigerants and the search for more energy efficient system solutions has been intensified. Due to these reasons, CO2 as an environmental benign natural refrigerant has attracted great interest since 1990s.
Due to its low critical temperature (31.1 oC) and high critical pressure(73.8 bar), CO2 refrigeration cycle works as a transcritical cycle, which means part of the cycle is located in supercritical region, where the temperature is independent of the pressure. Depending on the heat sink fluid temperature profile the temperature glide of CO2 in the supercritical region makes it possible for the CO2 refrigeration cycle to have less irreversibility in a heat recovery process than traditional refrigeration cycles.
A new CO2 refrigeration/heat pump test rig is built at the division of Applied Thermodynamics and Refrigeration to investigate CO2 refrigeration/heat pump systems. With the newly built test rig following main tasks were performed in this project work,
- Overall system performance on various imposed operating conditions.
- Second law analysis of the system by exergy and entropy balance methods
- Basic components testing, namely the heat exchangers and the compressor.
- Uncertainty analysis.
Author: Anwar, Zahid