K18 is a paraffin phase-change material (PCM), consisting mostly of octadecane, with an average melt/freeze temperature of about 25.6 C (78.1 F). This study simulated peak and annual thermal loads through concrete sandwich walls, steel roofs and frame walls, both with and without the addition of K18. The loads were simulated using the explicit finite-difference method, modified to account for the latent heat storage properties of PCMs. The specific heats of the PCMs were measured using differential scanning calorimeter (DSC) tests. Loads were simulated with the indoor air temperature held constant and with two sets of outdoor boundary conditions: a single day in which the outdoor air temperature varied sinusoidally and using a year of typical meteorological data from Dayton, Ohio. The results indicate that the addition of K18 to building components measurably decreases both peak and annual cooling loads, even through high-mass building components such as concrete walls. Peak and annual thermal loads in a frame house and mobile home, with and without phase-change wallboard, were also simulated. The results indicate that phase-change wallboard would be more effective at reducing cooling requirements in lightweight mobile homes than in frame houses.
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