Page 61 - Fluid Mechanics and Thermodynamics of Turbomachinery

42 Fluid Mechanics, Thermodynamics of Turbomachinery
h P 1

01 02

P 2
1 2
C 1
2
1 1
1 2 C 2 2
2 C 2s 2

2
2s

(a) s

01 02
h
1 C 2 2
P 01 P 02 2 2

2s 1 2
2 C 1

P 2

1
P 1

s
(b)
FIG. 2.12. Mollier diagrams for the flow processes through a nozzle and a diffuser:
(a) nozzle; (b) diffuser.

Figure 2.12a shows the process on a Mollier diagram, the expansion proceeding
from state 1 to state 2. It is assumed that the process is steady and adiabatic such
that h 01 D h 02 .
According to Horlock (1966), the most frequently used definition of nozzle effi-
ciency, N is, the ratio of the final kinetic energy per unit mass to the maximum