Question 9:
A centrifugal pump is being designed to pump liquid refrigerant R-134a at room
temperature and atmospheric pressure. The impeller inlet and outlet radii are $r_1$= 100
and $r_2$ = 180 mm, respectively (Fig. 9). The impeller inlet and outlet widths are $b_1$ = 50
and $b_2$ = 30 mm (into the page of Fig. 9). The pump is to deliver 0.25 m³/s of the liquid
at a net head of 14.5 m when the impeller rotates at 1720 rpm. Design the blade shape
Term 231
Page 3 of 4
UHB
ME 427: Turbomachinery
HW2 - 231
for the case in which these operating conditions are the design conditions of the pump
($V_{t,1}$ = 0, as sketched in the figure); specifically, calculate angles $\beta_1$ and $\beta_2$, and discuss
the shape of the blade. Also predict the horsepower required by the pump.
