R744 efficiency improvements presented at Compressors 2013

Compressors 2013, the 8^th International Conference on Compressors and Coolants is organised in Papiernička Slovakia on the 2-4 September. A number of papers will be presented on the use of R744 as a refrigerant, with a focus on solutions and ideas to improve and maximise energy efficiency. R744.com presents an overview of this latest research.

Compressors 2013 is the 8^th in a series of conferences on compressors and coolants organised by Slovak Association for Refrigeration and Air-Conditioning Technology since 1995. With more than 70 abstracts and over 100 authors, the conference will feature the several research papers that look at different options for improving the energy efficiency of R744 refrigeration systems. The papers below will be included in the IIR’s Fridoc database.

High efficient 20-90 m³/h R744 compressor, Armin Hafner, Maria Justo Alonso, Petter Neskså, Christian Schmälzle

A gap in the market currently exists for single stage R744 compressors with variable volume flow rates in the range of 20 to 90 m³/h. To address this gap, the authors of this paper have developed a novel high efficient, 6 cylinder piston compressor. Initial experimental results show an overall efficiency significant higher than state-of-the-art compressor concepts with ordinary asynchronous motors. This research is the result of a close cooperation between SINTEF and OBRIST Engineering.

Pressure losses in the suction filter in reciprocating compressor with CO₂, Radovan Ruman, Jaroslav Šustek, Peter Tomlein

This paper investigates pressure losses in the refrigerant flow of CO₂ through the suction filter of a reciprocating compressor using Computational Fluid Dynamics (CFD) modelling. Results from the CFD simulation are compared with experimental measurements, covering different areas of the compressor’s working envelope, of pressure losses in the suction filter. On the basis of CFD simulations geometric and structural modifications of suction filter can be designed in order to reduce pressure losses in the refrigerant flow.

Analysis of application of the two-phase ejector as a booster compressor in subcritical and supercritical CO₂ systems, Piotr Baj, Dariusz Butrymowicz, Kamil Smierciew

One of the most promising directions for efficiency improvement in carbon dioxide refrigeration cycles is the application of two-phase ejectors in various cycle configurations. Throttling losses in the expansion device, caused by the high differences between condensation and evaporation pressures, may be effectively reduced by means of using expansion devices instead of throttling valves. Researchers suggest two possible solutions: expansion machines or ejectors. By using the latter, the ejector fluid expands in the motive nozzle allowing the use of the momentum of expanded fluids to compress the secondary fluid.

Efficiency improvements of CO₂ transcritical refrigeration systems by machine-made “subcooling”, Miroslav Petrák

Further cooling the transcritical refrigerant, to lower temperatures than those delivered by the gas cooler, can increase the efficiency of CO₂ refrigeration cycles. This can be done either by using an external chiller or by integration into the CO₂ cycle as a kind of multi-stage cycle.

Experimental evaluation of the seasonal energy efficiency rating for a transcritical R744 booster system in various climate conditions, Oliver Javerschek, Manuel Reichle

The energy efficiency of CO₂ booster systems, commonly used in commercial refrigeration, depends on the ambient temperature. Javerschek and Reichle analyse the Seasonal Energy Efficiency Rating (SEER) of a booster system in the three different climate zones of Athens, Strasbourg and Helsinki, using a state-of-the-art trans-critical CO₂ booster system with flash gas bypass is installed by BITZER at its Rottenburg site. A comparison of measured performance data suggests improvements that can be made for future third generation of CO₂ supermarket systems.

Background

Slovakia is one of the biggest compressors producers on the world, with leading manufacturers Embraco and Secop having long ago established manufacturing plants in the region. In fact, the ratio of Slovakia on the world production of compressors for household refrigerators and light commercial refrigeration is close to 10%. With its extensive links to the compressor industry, Slovakia is the ideal country to host the International Conference on Compressors and Coolants.