# WATER DEW POINT

Water dew point (or simply the dew point) of a gas mixture is the temperature, at a given pressure, at which any water vapours present in the gas mixture will start to condense into liquid water. The water dew point of a gas mixture, at a given pressure, is often referred to as the temperature at which the gas mixture is saturated with water vapours.

The term water dew point can be applied to air or any other gas. Commonly used equation of states (EoS) like Peng-Robinson cubic equation of state and Soave Redlich Kwong cubic equation of state can only calculate accurate values of vapour liquid equilibrium (VLE) properties for mixture of non-polar or mildly polar compounds like hydrocarbons and inorganic gases like oxygen, hydrogen sulphide, carbon dioxide, nitrogen and inert gases. These equations can not calculate accurate values of vapour liquid equilibrium (VLE) properties for mixture where highly polar compounds like water are present. However variants of commonly used equation of states (EoS) like Cubic plus Associative (CPA) equation of states can be used to find VLE properties like water dew point for a non-polar mixture of gases like air or natural gas. But variants of commonly used equation of states (EoS) like Cubic plus Associative (CPA) equation of states require suitable parameters for each of the non-polar or mildly polar compound present in the gas mixture. These parameters may not be available for all the compounds present in the gas mixture.

EQ-COMP software uses temperature dependent binary interaction parameters in commonly used Peng-Robinson cubic equation of state to find out water dew point temperature values. These temperature dependent binary interaction parameters were given by Prof. Jaubert and his team and these when applied in Peng-Robinson cubic equation of state form the Predictive Peng-Robinson 78 (PPR78) equation of state. As evident from the name, these temperature dependent binary interaction parameters used in Predictive Peng-Robinson 78 (PPR78) equation of state are predictive in nature. This means that the values of these temperature dependent binary interaction parameters can be predicted by group contribution method. The values of these temperature dependent binary interaction parameters can be predicted for any paraffinic, cyclo-paraffinic, olefinic, di-olefinic and aromatic compounds and inorganic gases like nitrogen, hydrogen sulphide, carbon dioxide, oxygen and argon with water. Predictive Peng-Robinson 78 (PPR78) equation of state gives reasonably accurate water dew point temperature values for a given pressure using these temperature dependent binary interaction parameters.

Water dew point software / water dew point calculator from EQ-COMP can be used to find water dew point curve and water dew point temperature value for a given pressure. Sample results of water dew point calculator are available at http://www.eq-comp.com/water-dew-point-temperatue-calculator-software/ webpage. The results of water dew point software / water dew point calculator of EQ-COMP can be requested through VLE CALCULATOR page.