Use of the equivalent volumetric enthalpy variation in non-linear phase-change processes: freezing-zone progression and thawing-time determination

摘要: Abstract Unlike pure substances that melt and solidify at a fixed temperature, some materials, such as the Karlsruhe Test Substance (methyl cellulose gel) freeze thaw out over range of temperatures. In this paper, phase change process is studied using an equivalent volumetric enthalpy variation corresponding to thermal field in freezing or thawing zone instead latent heat appearing Stefan solution for substance. order determine variation, two different temperature distributions are assumed substance undergoing change. Results obtained from calculations applying approach compared with experimental measurements. Measurements freezing-zone progression were made course three experiments where first kind boundary conditions imposed on samples. addition, 35 values time have been taken literature presenting third conditions. Comparisons showed best agreement when quadratic distribution was adopted. The proposed method seems be useful many practical applications, particularly because it allows without necessitating use empirical parameters Plank's original equation