Transient evaporation of n-heptane in heated micro tube with non-uniform wall temperature

Detailed numerical simulation using the VOF multiphase flow model with user defined function (udf) and the corresponding experiments were conducted to correlate the evaporation phenomena with the oscillation of micro diffusion flame. In experiments we observed that mass flow rate is less than 10µl/min, the flame shape is like a spherical ball, similarly in simulation two phase flow comprising of vapor and liquid domain with a distinct interface is observed. When the mass flow rate is greater than 20µl/min the flame shape was irregular and not periodic, similarly in simulation fuse or mix flow was observed with liquid bubble and streak of liquid in the vapor regime. For 30µl/min, the bubble formation occurs after consecutive 2msec, however when the mass flow rate was 70µl/min the bubble formation occur after every 0.625msec. When mass flow rate was 5µl/min and 70µl/min, maximum wall temperature was 1050K and 830K respectively. The numerical prediction of liquid-vapor interface is in good agreement with the experimental finding. The evaporation rate at interface is calculated and it is found that it depend on the pressure drop and interface back and forth movement.