Infra-red measurements of an evaporating meniscus with imposed contact angle

In this paper temperature profiles in a meniscus formed by ethanol at the mouth of a capillary tube with the meniscus' shape dependent on the liquid supply rate are studied as evaporation occurs. An Infra-Red camera is used to measure the meniscus interfacial temperature and the results are compared for four tube sizes and three tube materials. This work follows on from work on evaporating sessile drops which has attracted much scientific attention in recent years. It is found that when the meniscus is still inside the tube, the interface temperature profile is similar to that of previous work (Buffone and Sefiane [19]). The interesting finding is that as the meniscus becomes flat at the tube mouth, the temperature profile of the interface evens out to the temperature of the contact line region. When the meniscus is eventually pushed out of the tube, the temperature of the meniscus interface becomes non-uniform again (depending on the contact angle). We demonstrate that this phenomenon is consistent for different tubes sizes and tube materials (with different wettabilities). We develop a simplified model for the meniscus inside the tube and the meniscus outside the tube which agrees qualitatively with the experimental findings.