Thermal energy storage properties, thermal conductivity, chemical/and thermal reliability of three different organic phase change materials doped with hexagonal boron nitride

Abstract

Myristic acid (MA), Lauric Acid (LA) and Polyethylene Glycol (PEG) are promising organic Phase Change Materials (PCMs) for Thermal Energy Storage (TES). However, low thermal conductivity (TC) negatively affects their heat transfer efficiency during the heat storage/release periods in TES systems. In this regard, hexagonal Boron Nitride (h-BN) was chosen as a filler for TC enhancement. The present study targets to improve the TC of MA, LA and PEG by adding h-BN nanoparticle at different weight amounts, 0.5, 1.0, 1.5 and 2 %, along with a systematic examination of other chemical and thermal properties. Scanning electron microscopy (SEM)/Energy dispersive X-Ray spectroscopy (EDX), Fourier-transformed infrared (FTIR) and X-Ray diffraction (XRD) analysis results demonstrated that the dispersion of h-BN in the PCMs was fairly homogeneous and had no damaging influence on their chemical/crystalline structures. Differential scanning calorimetry (DSC) results indicated that the addition of h-BN (2wt%) marginally shifted their phase change temperatures and slightly decreased the LHS capacities compared to pure PCMs. The h-BN/PCM composites exhibited good chemical stability and thermal reliability after 500 heating/cooling cycles. The addition of h-BN (2 wt%) resulted in 1.40, 1.27 and 1.30 times-enhancement in TC values of MA, LA and PEG, respectively. This improvement was also displayed in the T-History curves. All findings revealed that 2 wt% h-BN addition could be enough for satisfactory TC enhancement without affecting the LHS properties of the selected PCMs significantly. Thus, h-BN enhanced PCMs could be used for thermal management of electronic equipment, solar collectors, solar PV systems and domestic water heating systems etc.