Improvement on evaporation-condensation prediction of Lee model via a temperature deviation based dynamic correction on evaporation coefficient

Abstract

Lee model has been commonly accepted for modelling the mass transfer processes subject to both evaporation or condensation. However, severe concern caused by improper setting of mass transfer relaxation coefficient exists for the high-accuracy prediction. The complicated influence factor and variable parameters result in the failure of definition on the mass transfer relaxation coefficient. In this paper, the temperature deviation based dynamic modification model to define the evaporation mass transfer relaxation coefficient (MTRC) is proposed. The MTRC is no longer needed to be manually adjusted and numerous human and computation resources could be saved, with better prediction accuracy. The hyperbolic tangent function is applied to describe the relationship between the evaporation MTRC and the product of temperature deviation and volume fraction. Compared with the commonly used Lee model, better prediction accuracy at the evaporation section can be achieved with the prediction error lowered by 38.79%, 16.24% and 4.38% under power input of 100.65, 49.61 and 19.88 W, and the maximum relative error decrement by 44.74% and the average reduction by 14.26%, which could be attributed to the elimination of liquid temperature deviation. Note that the liquid temperature deviations are strictly restrained within acceptable range 0–2 K all the time with the dynamic correction model while the temperature deviation by common Lee model would up to 13 K. Meanwhile, the proposed model is found to effectively save the computational time with reduction around 83.3% because of the quick match of the mass transfer rate impacted by the modified evaporation coefficient.

Keywords

• Evaporation coefficient
• Phase change model
• Temperature deviation
• VOF