A novel method for measuring latent heat of low-temperature PCM phase transition by oxygen bomb calorimeter

Abstract

The method for the determination on the latent heat of phase change by oxygen bomb calorimetry of low-temperature phase change materials (PCMs) was feasible and validated. Experiments on the solidification of the variable boundary temperature of OP24 (the ratio was 57.5% caprylic acid + 42.5% myristic acid) low-temperature organic PCM, an energy storage medium, were carried out in a modified oxygen bomb calorimeter. In addition, a one-dimensional model of the solid–liquid two-phase cylindrical PCM solidification process was constructed by numerical simulation. Using the measured time-varying data of the PCM axial temperature, the oxygen bomb surface temperature, and the water temperature of the inner cylinder, the model was applied to approximate the latent heat of phase change of OP24 PCM using a cubic polynomial heat balance integration method. The calculated results were accurate for engineering applications when compared to the values obtained by differential scanning calorimetry. Moreover, the invisible phase interface moving with time could be obtained. The calculation process was relatively simple and convenient for engineering applications. Improving the accuracy of water temperature measurements in the inner cylinder could be the way forward to reduce experimental errors in the determination of the latent heat of phase change in low-temperature PCMs using oxygen bomb calorimetry.