CPA Dew Point Calculator

This software is an outcome of the collaborative R&D project supported by GERG, the European Gas Research Group (, aiming to evaluate and compare carefully selected thermodynamic models used for calculating water and/or specific production chemical.

The industrial participants were Statoil (Norway), DGC (Denmark), Snam Rete Gas (Italy) and CERE/DTU (academic partner).

The water content of natural gas often poses problems during the production, transmission and distribution of the gas.

Small quantities of undesired dissolved water may condense leading to the formation of condensed water, hydrates and/or ice. Such condensed phases may result in corrosion, two-phase flow problems, safety hazards and flow assurance issues (slugging of the flow lines, valves and instrumentation resulting in reduced capacity and shutdowns; reduction of the reservoir permeability resulting in lower oil recovery factor).

Accurate thermodynamic models able to calculate the water vapor concentration in equilibrium with hydrate, ice and water in natural gas at pipeline operating conditions (253-323K and up to 250bar) are necessary both because experimental data are limited and difficult to obtain, and because the limits of dehydration techniques (physical adsorption and condensation) need to be defined. The latter techniques use chemicals (eg. glycols and alcohols), which also condense together with water, adding one more level of modeling challenge.

The main purpose of this project was to evaluate and compare the performance of the CPA (Cubic-Plus-Association) equation of state (EoS) and GERG-water calculation method (an ISO-standard model specifically designed to correlate water content and dew points of natural gas) with respect to the calculation of dew points of natural gas systems containing water and traces of selected production chemicals.

CERE CPA Dew Point Calculator

  • A user-friendly software, based on the CPA EoS, for calculation of dew point, frost point, and hydrate point temperatures was developed and disseminated to the participating companies.


GERG-Water CERE Dew Point Calculator

  • A user friendly software, based on the GERG-Water correlation as presented in GERG Technical Monograph TM 14, was developed for the calculation of water content in natural gas at specified pressure and temperature. The software is disseminated to the participating companies in order to compare it with CERE CPA Dew Point Calculator.



Alay Arya
DTU Chemical Engineering
+45 45 25 28 64


Georgios Kontogeorgis
DTU Chemical Engineering
+45 45 25 28 59