HFO-1336mzz(Z) and HCFO-1233zd(E) as alternatives to HFC-245fa in organic Rankine cycles for micro-scale low temperature applications.

The Organic Rankine Cycle is a power cycle for the valorization of low temperature heat sources, being similar to a conventional Rankine cycle, but using an organic working fluid rather than water. HFO- 1336mzz(Z) and HCFO-1233zd(E) have been recently presented as potential low global warming alternatives to HFC-245fa, a common working fluid used in micro-scale Organic Rankine Cycles. This paper compares the experimental results obtained using HFC-245fa, HFO-1336mzz(Z) and HCFO-1233zd(E) in a fully monitored ORC module, with a heat source inlet temperature of 155ºC and heat sink inlet temperature of 25ºC. The ORC module uses a regenerative configuration allowing heat recovery not only from the heat source but also from the expanded vapor, thus improving the cycle thermal and electrical efficiency. Similar global efficiencies are achieved, increasing a 3.15 % with the use of HCFO-1233zd(E) and decreasing a 21.72 % using HFO-1336mzz(Z). For a drop-in replacement, a superheating modification is needed.