The trend to low-emission vehicles will be an increasing challenge for the automotive industry in the coming years. Therefore, the energy saving potential of all components in a vehicle must be investigated and exploited if possible. In the last ten years, the average fuel consumption of air conditioning in cars was reduced. This was achieved by optimizing components and applying controlled compressors and better control strategies. Recently an integrated heat exchanger indispensible in R744 systems was first used in a series vehicle for the refrigerant R134a. Another modification of the refrigeration cycle focuses on the expansion of the refrigerant. In todays automotive air conditioning systems the refrigerant leaving the condenser is expanded to the low system pressure without any work recovery. Whereas this potential is exploited in large-scale refrigeration equipment by expansion devices, it is still unused in automotive technology due to its (yet) disproportional effort. An ejector provides another approach to reduce the expansion loss. It is a jet pump that operates without moving parts and is robust and simple in construction. The energy of the refrigerant expansion is used to compress refrigerant vapor and relieves the compressor. The drawback of this technology however is its low efficiency so only a fraction of the improvement potential can be used. This paper aims to discuss the potential of ejector technology to improve the efficiency of R134a automotive air conditioning systems. Different design variations have been investigated using numerical simulations. A 1d-model of an ejector was developed and integrated in the simulation environment BISS (Behr Integrated System Simulation). This model calculates the ejector behavior through energy, mass and momentum balances. The ejector can be described in terms of geometric parameters and efficiencies of the ejector components. In combination with the simulation environment, even complex installations of the ejector in the system as it is the case in the ejector evaporator can be calculated. This allows the identification of a suitable ejector design so operation in all relevant operating conditions is provided. Furthermore the expected benefits can be predicted. First the thermodynamic potential inherent in the refrigerant expansion is derived for a number of characteristic operating conditions. Then the ejector and an ejector expansion refrigeration COP-Improvement of a Refrigerant Cycle by Ejector Expansion cycle are shortly introduced. The following part deals with the geometric design of ejectors and its consequences for overall performance of a refrigeration system with ejector. Finally a system with a compact ejector evaporator is presented and its expected potential is discussed.


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    Titel :

    COP-Improvement of a refrigerant cycle by ejector expansion


    Beteiligte:


    Erscheinungsdatum :

    2008


    Format / Umfang :

    11 Seiten, 6 Bilder, 2 Tabellen, 4 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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