Heat Transfer During Evaporation of Binary Liquids from Wick Microstructures
Amaresh Dalal, Ram Ranjan, Jayathi Y. Murthy and Suresh V. Garimellaa
School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47906, USA.
asureshg@purdue.edu
ABSTRACT
The microscale heat and mass transfer from an evaporating meniscus of binary mixtures (water/propanol) formed inside a two-dimensional wick microstructure is explored. A numerical model is developed for the evaporation of a binary fluid under saturated vapor conditions. The Navier-Stokes equations coupled with the energy and species equations are solved in the liquid domain while the vapor is assumed to be saturated, consistent with typical heat pipe and vapor chamber conditions. Mass conservation of the secondary species is enforced. Liquid-vapor interface shapes in the wick microstructure are calculated using the program Surface Evolver and assumed to be static during the evaporation process. The evaporative mass flow rate and heat flux are evaluated for various concentrations of the secondary fluid in the mixture. The addition of 1-propanol, even in small quantities, is found to increase the overall evaporation rate, and correspondingly the heat transfer rate. The primary mechanism for this is found to be the thinning of the meniscus due to a decrease in contact angle.
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