Organic Rankine Cycle (ORC) unit

Подпись: Fig. 1 - Regenerative ORC scheme and T,s diagram representation of cycle points

The power block is based on a regenerative Organic Rankine Cycle according to the scheme and T — s diagram presented in figure 1.

R245fa is the substance considered as working fluid of the ORC in this work. Although this fluid yields lower values of the ORC thermal efficiency, when compared, e. g., to toluene or hexamethyldisiloxane [8], it presents zero ozone depletion potential or low flammability properties, environmental, health or safety issues accounted in the fluid selection process, considering the aim of the project.

Considering R245fa, the operating parameters that optimize ORC thermal efficiency in both cycles 2 and 3[5] top temperature conditions are given in Table 1. These values were determined considering typical values for regenerator effectiveness (0.80) [9-12] and vapour turbine efficiency (0.75). The latter is the estimated value for low power output ORC units (100-500 kW) [12]. Operating conditions presented in Table 1 are considered as full load ORC operating conditions.

Table 1. Optimized ORC operating parameters for cycles 2 (C2) and 3 (C3) (Л = 0.75; Vr = 0.75; eR = 0.80; Tcond = 30 °C)

TeVap [°C]/ Pevap [MPa]

T2 / Ty / Tx [°C]

T /

1 in, Solar y Tout, Solar [°C]

nR, net / nR, gross [%]

moRc / Wvt [kgh-1/kWm]

Qin. ORC WvT

[kWt/kWm]

QoutORC /Wvt

[kWt/kWm]

C2

134.6 / 2.56

145.0 / 55.4 / 39.7

127.6 / 150.0

15.72 / 16.74

92.1

5.97

5.03

C3

148.0 / 3.10

240.0 / 111.7 / 61.4

123.0 / 250.0

20.50 / 21.63

60.7

4.62

3.67