Improving the operation and thermal response of multiphase coexistence latent storage system using stabilized organic phase change material

Abstract

Multiphase coexistence in the organic phase change material (PCM) leads to practical drawbacks. It causes partial charge/discharge behavior, which reduces the operational reliability of an active latent storage unit (LSU). The present work proposes stabilized OPCM (SOPCM) as a suitable method to promote a better phase transition performance. The stabilization is done by adding 10 wt% polymers (high-density polyethylene/HDPE) for the OPCM. The proposed method reduces the supercooling degree of PCM up to 4.2 °C. It makes the specific state of charge (SoC) for SOPCM increase by 18.8%/°C along with phase transition. The SOPCM has a lower temperature gradient (3.5 °C-4.5 °C) compared to PCM (5.2 °C-7.7 °C) during the solid-liquid transition. Dynamic heating and cooling tests with a rectangular shell and u-finned tube demonstrate the charging/discharging behavior of PCM and SOPCM, which varies significantly. The charging/discharging power profile of PCM is fluctuated, particularly in the phase change region. It implies that the phase change process causes severe disturbance in the heat transfer rate. Contrary to that, the SOPCM reduces the fluctuation, indicating a stable phase transition process. It gives the SOPCM a better storage efficiency (80.2%–90.2%) than PCM (72.5%–77.1%). The SOPCM discharges the stored heat effectively and reduces the residual power at the end of discharging process. Moreover, the SOPCM has a higher thermal conductivity in the liquid state (0.184 W·m−1·K−1–0.213 W m−1 K−1) which accelerates the average response time to reach the targeted nominal power during the discharging process.

Keywords

• Isothermal
• Partial behavior
• Phase transition
• Stabilization method
• State of charge