Prototype of a thermally driven heat pump based on integrated Organic Rankine Cycles (ORC)

The concept studied in this work is a low power ORC–ORC heat pump system (providing about 20 kW heat at the condenser) and that is composed of an ORC power cycle driving a reversed ORC heat pump cycle, both cycles using the same fluid. The centrifugal compressor and the radial in-flow turbine are di...

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Bibliographic Details
Published in:Energy (Oxford) 2012-05, Vol.41 (1), p.10-17
Main Authors: Demierre, J., Henchoz, S., Favrat, D.
Format: Article
Language:English
Subjects:
air
Applied sciences
Energy
evaporation
Exact sciences and technology
Gas bearings
heat
heat exchangers
heat pumps
Oil-free
ORC
Residential heating
Supercritical evaporator
Thermally driven heat pump
vapors
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Summary:The concept studied in this work is a low power ORC–ORC heat pump system (providing about 20 kW heat at the condenser) and that is composed of an ORC power cycle driving a reversed ORC heat pump cycle, both cycles using the same fluid. The centrifugal compressor and the radial in-flow turbine are directly coupled on the same shaft rotating on self-acting refrigerant vapor bearings. The system has the advantage of being oil-free, fully hermetic and with low maintenance costs. The paper presents the development of an ORC–ORC prototype, with HFC-134a as working fluid. The main critical parts of the system are the compressor-turbine unit, the supercritical evaporator and the pump. The selected type of heat exchanger for the supercritical evaporation is the double tube coil (DTC). A first experimental setup has been built to test the pump and the supercritical evaporator. A comparison between the results obtained with an in-house supercritical evaporator simulation program and measurements made on the DTC is presented. The design steps of the compressor-turbine are briefly presented. The compressor-turbine unit has been balanced and tested, with air, at speeds up to 140,000 rpm. ► Development of a Rankine cycle driven heat pump for residential applications. ► A high speed oil-free compressor-turbine unit rotating on gas bearings is used. ► The evaporation of the ORC power cycle is supercritical. ► Measurements of R134a supercritical evaporation have been carried out. ► Validation of an in-house supercritical evaporator simulation tool.
ISSN:0360-5442
DOI:10.1016/j.energy.2011.08.049