Converting a commercial scroll compressor into an expander: Experimental analysis and analytical performance evaluation
Maurizio Cambi, Roberto Tascioni, Luca Cioccolanti, Enrico Bocci
Session: Poster session & Welcome drinks
Session starts: Wednesday 13 September, 17:30
Maurizio Cambi ()
Roberto Tascioni ()
Luca Cioccolanti (Università e campus)
Enrico Bocci ()
The core of the work is split in two parts, the first one regards an experimental analysis on a micro Organic Rankine Cycle lead to extrapolate the real compressor and turbine efficiency, then, in the second part of the work such data have been utilized as input to a mathematical model.
The experimental test founded by a HVAC company is based on a scroll compressor modified to work as scroll expander, a not regenerative cycle, a subcritical fluid regime, aimed at reducing in system cost and complexity. The scroll expander has been tested with its fluid R 410 in a real ORC cycle in order to get the isentropic efficiency of the scroll expander (0.5) and the pump (0.4).
On the basis of the experimental tests, a model accomplished by means of REFPROP has been carried out to evaluate the performance of the ORC group to achieve 10 kWe as target power output. Four operative fluids have been simulated, i.e. R 245fa, R 134a, R 1234yf, R 1234ze, fixing 100 °C as overheating temperature and considering condenser temperature in the range 20°-50°C.
The results have showed that 245fa is the most promising working fluid since it gives an higher expansion ratio within lower pressure values, as a consequence not only a lower mass flow rate is necessary but overall a lower pump consumption is needed, reaching greater overall conversion efficiency (about 6% with condensing temperature of 20°C).
Thus, a commercial heat pump scroll compressor can be effectively converted into an expander. The first fluid selection shows that the most used ORC fluid can be used within relative low performance but surely, low cost and easy management.