Numerical simulation on heat and mass transfer during multiple puffing in e-cigarette

To investigate the heat and mass transfer behaviors in the atomization process of e-liquid in a porous atomizer, a multi-puffing model was developed to simulate e-cigarette aerosolization process. The model was solved by using MATLAB software and its accuracy was verified. The multi-puffing model was used to simulate the heat and mass transfer characteristics and e-liquid composition variation in the phase change process of e-liquid, and the thermal efficiency of this phase transformation was calculated. The results showed that: 1) The e-liquid in the micro-pores of a porous atomizer was cooled down between the puffing intervals. However the temperature did not reduce to the ambient temperature within the interval of 30 sec. With the proceeding puffs, the temperature of the e-liquid at the beginning and end of the subsequent puff raised by 4.4% on average comparing with the previous puff. 2) For the 5 consecutive puffs simulated, the average vaporization mass rate of the e-liquid increased first and then decreased, peaking at the second puff with the maximum value of 2.80 mg/s. 3) With the proceeding puffs, the puff-by-puff energy consumption due to heating the total system decreased first and then increased, while the puff-by-puff energy consumption of the e-liquid vaporization showed an opposite trend. The puff-by-puff heat losses due to heat conduction, convection and radiation raised continuously, by 8.4%, 6.8% and 11.6% respectively when compared with the previous puff. The puff-by-puff thermal efficiency reduced gradually, from 93.3% to 90.9% when the puffing number increased from 1 to 5.