In a twostage reciprocating compressor if the inlet pressure

In a two-stage reciprocating compressor, if the inlet pressure to stage 1 is 4 bar and the outlet
pressure from stage 2 is 16 bar, then the intermediate pressure for optimum compressor work is
equal to

Select one:
a. 4 bar
b. 12 bar
c. 8 bar

Solution

c.8bar is the intermediate pressure

intermediate pressure is= sqrt((inlet pressure)(outlet pressure))

=sqrt(4*16)

=8 bar