Optimization of the phase-change wallboard test method: Experimental and numerical investigation

Abstract

Abstract The application of phase change materials (PCMs) within building envelopes has been a topic of significant research in recent years. Conventionally, determination of the thermophysical properties of PCM-containing wallboard is achieved using the differential scanning calorimetry (DSC) and guarded hot plates method. The thermophysical parameters (phase change temperature, specific heat (Cp), and enthalpy-temperature curves (H(t))), however, of PCM wallboard (PCMW) determined using different methods present certain deviations. This has a significant impact on the reliability of corresponding numerical simulation investigations (e.g., EnergyPlus). Taking this into consideration, this study compares the temperature-dependent specific heats - Cp(T) - from both the DSC and guarded hot plates methods (in dynamic mode, steady mode, and step mode) via experimental investigation. Numerical simulation (using FLUENT software) was then employed to deduce the optimal test parameters for the phase change wallboard test, applying the guarded hot plates method (including dynamic/linear mode, steady mode, and step mode). These parameters include the heating/cooling rate, PCM content, wallboard thickness, and recommended thermal stability time (RST). Key results show that, using the dynamic mode, the heating/cooling rate should be set to 0.5°C/min or less, while for the step mode, the RST function was established. The purpose of this study was to propose an optimal phase-change wallboard test mode, using the guarded hot plates method, to accurately measure the thermophysical properties of PCMs within a full-scale specimen.