Characteristics of Homogeneous Nucleation Boiling in Ethanol during Rapid Linear Boundary Heating

The characteristics of homogeneous boiling in ethanol subjected to rapid heating with a linearly increasing boundary temperature condition have been studied by applying a theoretical model. A finite liquid control volume or cluster at the liquid boundary hasbeen considered in this model where energy is stored due to external heating while some energy is consumed due to bubble nucleation and subsequent growth. A particular state of liquid heating has been defined as the boiling explosion condition when massive scale vaporization causes the liquid sensible energy to decrease. As the size of liquid cluster, two different length scales have been adopted such as, size of a critical vapor embryo (2rc) and thermal penetration depth . For ethanol heating with initial and boundary conditions identical to those reported in the literature, the model predicts the time of the homogeneous boiling explosion with reasonable agreement with the experiments with the liquid cluster size being assumed to be that of a critical vapor embryo (2rc); while the consideration of the thermal penetration depth results in late prediction of the occurrence of boiling explosion. However, the temperature at the boiling explosion essentially corresponds to the same for both sizes of the liquid cluster. The obtained results have been presented and discussed in terms of the average liquid temperature rise inside the liquid cluster, maximum attainable cluster temperature and time to reach the boiling explosion condition for a wide range of boundary heating rates (10-109 K/s).