The saturation domes for R-134a and isopentane shown in Figures 13.4

and 13.18?

are quite asymmetric, with steep (R-134a) or even re curving (isopentane) saturation curves. Water, on the other hand, has a relatively symmetric saturation dome (Figure 12.9)

Explain why this feature makes R-134a and isopentane more suitable fluids for low-temperature heat extraction devices and engines than water. Why is water so widely used for higher-temperature systems such as steam turbines? What kind of shape for the saturation dome would be better for a phase-change fluid in a higher-temperature system?

Transcribed Image Text:

4.0 MPа 3.0MPA 100 80 2.0MPA 1.5 MPa 1.0MPA superheated 60 vapor 40 0.6 MPa 0.4MPA 20 0.2 MPa -20 0.1 MPa 1.4 entropy [kJ/kg K] 0.8 1.0 1.2 1.6 1.8 temperature [°C)