Question

Subcooled liquid water flows adiabatically in a constant diameter pipe past a throttling valve that is partially open. The liquid can be modeled as an incompressible flow (i.e., specific volume (v) is constant, u=CAT). The subscripts i and e refer to the conditions at the inlet and exit of the valve, respectively.
Indicate whether each difference below is positive, negative, or zero.


hi-he __________


pi-pe __________


ui-ue __________


ti-te ___________

Answer 1

Answer:

hi-he = 0

pi-pe  = positive

ui-ue = negative

ti-te = negative

Explanation:

we know that fir the sub cool liquid water is

dQ = Tds = du +  pdv   ............1

and  Tds = dh - v dP         .............2

so now for process of throhling is irreversible when v is constant

then heat transfer is = 0 in irreversible process

so ds > 0

so here by equation 1 we can say

ds  > 0  

dv = 0 as v is constant

so that Tds = du    .................3

and du > 0

ue - ui > 0

and

now by the equation 2 throttling process  

here enthalpy is constant

so dh = 0

and Tds  = -vdP

so ds > 0  

so that -vdP > 0  

as here v is constant

so -dP =P1- P2

so P1-P2 > 0

so pressure is decrease here