added Zvol corr (#1015)

Author: EvenSol

src/main/java/neqsim/thermo/phase/Phase.java

@@ -403,6 +403,13 @@ public double getZ() {
     return Z;
   }
 
+  /** {@inheritDoc} */
+  @Override
+  public double getZvolcorr() {
+    return getPressure("Pa") * getMolarMass() / neqsim.thermo.ThermodynamicConstantsInterface.R
+        / temperature / getDensity("kg/m3");
+  }
+
   /** {@inheritDoc} */
   @Override
   public void setPressure(double pres) {

src/main/java/neqsim/thermo/phase/PhaseInterface.java

@@ -2028,4 +2028,11 @@ public default boolean hasComponent(String name) {
    * @return String model name
    */
   public String getModelName();
+
+  /**
+   * method to return Z volume corrected gas compressibility
+   *
+   * @return double Z volume corrected
+   */
+  public double getZvolcorr();
 }