phase changing process in subroutine..

mspark

Hi all I am studying the phase changing(heat exchanger problem) algorism in star-cd. Adapco-online.com shows the introduction of heat exchanger in detail. However, as you know, the calculation and change of QUALITY in each temperatures and pressure with the specific volume, enthalpy, entropy or mass. i just know the relationships below. How can i get QUALITY wit those properties

v=v_f+x*(v_g-v_f) or h=h_f+x*(h_g-h_f) or x=(m_g)/(m_g+m_f)

where x=quality v_g(specific volume of satureted vapor) v_f(specific volume of satureted luqiid) h_g(enphalpy of satureted vapor) v_f(enphalpy of satureted luqiid) m_g(mass of satureted vapor) m_f(mass of satureted liquid)