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Invernizzi, Costante M. ; Iora, Paolo ; Preißinger, Markus ; Manzolini, Giampaolo:
HFOs as substitute for R-134a as working fluids in ORC power plants : A thermodynamic assessment and thermal stability analysis.
In: Applied Thermal Engineering.
Bd. 103
(2016)
.
- S. 790-797.
ISSN 1359-4311
DOI: https://doi.org/10.1016/j.applthermaleng.2016.04.101
Abstract
In this paper we investigate the potential replacement of HFC-134a in ORC applications by two low-GWP refrigerant fluids, namely HFO-1234yf and HFO-1234ze(E). After revising and discussing their main thermo-physical properties, we adopted in our calculations the Peng Robinson EOS available in Aspen Plus v7.3, integrated with literature data. By assuming as reference a geothermal plant operated with HFC-134a, we first consider the direct replacement of the original fluid by the two refrigerants. Results of such off-design simulations show a decrease of the net power of about 13 in case of HFO-1234yf and 1 in case of HFO-1234ze(E). Then, in case of heat recovery from a hot water source, from a comparison among the three refrigerants, with the hypothesis of a completely new design simulation, it turns out that the turbine power results lower than HFC-134a of about 20 and 28 for the cycles using HFO-1234yf and HFO-1234ze(E) respectively. We also show that in case of HFO-1234ze(E) the recuperative heat exchanger could be removed without tangible effects on the useful power and on the cycle efficiency. Finally we assess through an experimental thermal stability analysis that 200–250°C could be a feasible working temperature limit for HFO-1234yf.