the third term in the energy balance the latent heat carried away by the vaporization of the liquid 112 can be determined by measuring the mass transfer rate from the micro channel array 103 j m the latent heat transfer rate from the micro channels q l is then where h fg is the latent heat of vaporization of the liquid 112 micro channel vaporization efficiency u03b7 vap is defined to be the ratio of latent heat transfer rate by vaporization over the power into the vaporizer the driving force for liquid flow along the micro channel array 103 is the capillary pressure p c given by the equation where u03b3 is the surface tension between the liquid 112 and air u03b8 is the contact angle between the liquid 112 and the wall of the micro channel array 103 r is the smallest dimension of the micro channel array 103 the liquid flow rate can then be found using force balance by equating capillary pressure forces driving flow with liquid viscous force retarding flow with assumptions steady fluid flow in the micro channel array 103 neglecting temperature variation in liquid properties and fully developed laminar flow the following expression can be obtained where u is the liquid velocity u03bc is the liquid viscosity u03b9 is the distance over which liquid has traveled the mass flow rate of liquid 112 in the micro channel array 103 is then where u03c1 is the density of the liquid 112 a is the cross sectional area of the micro channel array 103 knowing the mass flow rate the vapor generating rate in the micro channel array 103 can be found v vap j m mr u t s p a 7 where m is the molecular weight of the average liquid 112 r.