# Thermodynamics problem

1. Apr 20, 2005

### nineeyes

Having trouble with a thermodynamics problem

I'm having a bit of a problem with some of the homework in my thermodynamics class.
Question (Water at 20 C, 100 kPa is compressed isothermally to 50 MPa. Determine the work required per unit mass. )
using the tables I found:
State 1
$$T_1=20C$$
$$P_1=.100MPa$$
$$v_1=.001022$$ $$m^3/kg$$
State 2
$$T_2=20C$$
$$P_2=50MPa$$
$$v_2=.0009804$$ $$m^3/kg$$

However, according to the tables, both states are compressed/subcooled . The only method I found to solve for work in an isothermal process applied to ideal gases. I was thinking I needed to approximate this, I tried to plot as many points in between the states and do a curve fit to find function $$P(v)$$. Then integrate $$Work = \int_{v_1}^{v_2}P(v) dv}$$. If I can do it that way, what kind of line do I use? (2nd order polynomial, 3rd order polynomial, etc...)

Thanks for any help.

Last edited: Apr 21, 2005