The subject of the transport phenomena has a pivotal role in the performance of aqueous lithium bromide falling film absorbers. Although the thermodiffusion phenomenon appears inside the solution, very little is known about its influence on the mass transport. This study numerically analyses the influence of the thermal mass transfer mechanism on a vertical plate-type heat exchanger for different Reynolds numbers ([Formula: see text]). Results indicate that, in general, the mass transfer caused by the temperature gradient enhances the total absorption because of the negative Soret coefficient of the salt solution. This improvement is found to be higher at higher Reynolds numbers. Furthermore, the concentration and temperature profiles and, therefore, the absorption change significantly along the flow length. Overall, this analysis assists the understanding of the role of the thermal mechanism in this type of absorbers and it demonstrates that it should be considered in future studies.