To improve the transportation efficiency and reduce the supply cost

the liquefaction becomes an important technology to store and transport the natural gas. During the liquefaction

the various components (

e.g

. propane

ethane

methane

etc

.) undergo fractional condensation phenomenon due to their different boiling points. This means that when one component condenses

others play a role of non-condensable gas (NCG). In order to reveal the influence mechanism of NCG on this condensation process

a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures

namely the propane/methane (80%-95%)

ethane/methane (65%-85%) and methane/nitrogen (2%-13%) mixtures

on a vertical plate. The model was proposed based on the diffusion layer model

and the finite volume method was used to solve the governing equations. A user defined function was developed by cell iterative method to obtain the source terms in the condensation process. The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of hea

t transfer coefficient. And for the above three mixtures

there is a negative correlation between the NCG concentration and the heat transfer coefficient. Meanwhile

the results show a good agreement with the experimental data

meaning that the proposed model is reliable. Three mixtures within same non-condensable mole fraction of 20% were also investigated

indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient. As a result

the presence of the lighter NCG contributes to a thicker boundary layer.