The temperature jump at water – air interface during evaporation Elizaveta Ya. Gatapova a,⇑ , Irina A. Graur b , Oleg A. Kabov a,c , Vladimir M. Aniskin d , Maxim A. Filipenko a,e , Felix Sharipov f , Lounès Tadrist b a Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 1 Lavrentyev Avenue, 630090 Novosibirsk, Russia b Aix-Marseille Université, CNRS, IUSTI UMR 7343, 13013 Marseille, France c National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk, Russia d Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch Russian Academy of Sciences, 630090 Novosibirsk, Russia e Novosibirsk State University, 630090 Novosibirsk, Russia f Departamento de Fisica, Universidade Federal do Parana, Caixa Postal 19044, Curitiba 81531-990, Brazil article info Article history: Received 6 April 2016 Received in revised form 31 August 2016 Accepted 31 August 2016 Keywords: Liquid–gas interface Temperature jump Evaporation Heat transfer Micro-thermocouple Temperature measurements Non-equilibrium abstract The temperature profiles are measured across a liquid–gas two-layers system at normal atmospheric conditions. A thin water layer is locally heated from the bottom substrate and it evaporates from the liquid–gas interface. A micro-thermocouple with sensor thickness of less than 4 lm has been specially manufactured for the accurate measurement of the temperature profiles. This micro-thermocouple is displaced with micro-steps near the interface, providing the detailed information on the temperature field. A temperature jump at the liquid–gas interface is clearly detected even for small evaporation rate. This jump is measured for heater temperature varying in the range 25–60 °C at normal atmospheric con- ditions. The temperature jump value is found to increase with increasing the temperature difference between heater and ambient gas, and, hence, with increasing of the evaporation rate. A specific evolution of the temperature profile with increasing of the heater temperature is obtained. Depending on the ambi- ent condition, the temperature in the gas phase near the liquid–gas interface can be higher or lower than that of the liquid. The temperature profiles with negligible temperature jump at liquid–gas interface are observed for some operating conditions. The temperature jump depends not only on evaporation rate, but also on temperature gradients in liquid and gas phases near the interface. The experimental results are found to be qualitatively in agreement with the kinetic theory and quantitatively with classical energy balance on the interface. The reported detailed data on the phase transition phenomena for relatively high heat flux are presented for the first time in the literature. However, more precise measurements of the temperature profiles at the liquid–gas interface should be done further. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction A detailed description of molecular transport across a liquid–gas interface during evaporation/condensation process is important not only for understanding surface chemistry [1,2] but also for many industrial applications involving the microsystems and dispersed phase systems (bubbles and microbubbles) with phase transition [3,4]. An evaporation of a liquid is accompanied by heat exchange between two liquid and gas phases as well as by other coupled phenomena as e.g. thermocapillary convection. A liquid–gas interface is usually far from its thermodynamic equilibrium state, which can lead to the development of different instability mechanisms. Two most important parameters, involved in the evaporation process according to the energy balance at a liquid–gas interface, are the mass and heat fluxes in both gas and liquid directions. A detailed information on the temperature profile across the liq- uid–gas layers is indispensable for determination of the heat flux by Fourier law. The investigation of the temperature profile across two different phases is an important issue for the thermal manage- ment of cooling systems, such as heat pipes, for the production of new materials as well as for design and manufacture of the microsystems with phase change. The correct definition of the boundary conditions is also an issue of fundamental importance which could be helpful for the better understanding of non-equilibrium phenomena, like for example, the Leidenfrost effect [5,6] and contact line dynamics [7,8]. Reliable and accurate measurements of the temperature and pressure near the liquid–gas interface and particularly in the Knudsen layer are a real http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.08.111 0017-9310/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: gatapova@itp.nsc.ru (E.Ya. Gatapova). International Journal of Heat and Mass Transfer 104 (2017) 800–812 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt