Calculating Heat of Compression in a Fluid?

[ISX]

I have air figured out, but what about in a fluid? Say an injector that goes from 0psi to 4000psi. How would I calculate that? Also, when the fuel shoots out of the injector, does the instant expansion cause it to cool back down to the temp it was at 0psi?

 

[cjl]

If by fluid, you mean liquid, then typically, they are assumed to be incompressible, and as such, the pressure alone does not heat them up.