Maintaining high thermal response of carbon nanotubes after melting intensification in solid-liquid heat storage system

Abstract

The present work evaluates the proportional ratio of multi-walled carbon nanotubes (MWCNT) for improving the thermal conductivity (k) of paraffin wax (PW) and polymeric-paraffin with high-density polyethylene (PW/HDPE). The k value is assessed at 40 °C, 60 °C and 120 °C with different MWCNT content (0–10 wt% MWCNT). The measurement indicates the k value varies significantly at different temperatures. The study suggests that the ideal ratio of MWCNT content is limited to 6 wt%. The justification is based on the suitable average k value for PW (0.532–0.625 W·m-1·K-1) and PW/HDPE (0.595–0.641 W·m-1·K-1). Active thermal storage (ATS) evaluation shows significant improvement in the rating performance of PCM with MWCNT. The charge cycle increases by 39% with a peak power of 49.8 Watts for PW. Unfortunately, melting intensification for 240 h causes performance degradation due to precipitation which disturbs the dispersed MWCNT particle within the PW. In contrast, the composite PW/HDPE maintains suitable performance with unsubstantial change after melting intensification, where the peak power is obtained at 40.6 Watts and 40.1 Watts before and after melting intensification.