Graphite Foam Infused with Pentaglycerine for Solid-State Thermal Energy Storage

Abstract

The use of a solid-state phase change material, pentaglycerine, in thermal energy storage was investigated. The motivation for exploring a thermal energy storage system that relies on a solid-state phase transition is to eliminate phase change material leakage and sealing issues. Pentaglycerine was effectively injected into graphite foam, and this combination was studied for potential use in a thermal energy storage device. Graphite foam samples that contained pentaglycerine demonstrated a storage capacity that was close to the theoretical capacity. The graphite foam infused with pentaglycerine retained 100% of its storage capacity after 59 separate thermal cycles under various conditions, with many of those cycles contiguous. It was subjected to a 28% duty cycle of applied heat flux under active cooling conditions, and the duty cycle of the sample was not adversely affected by subcooling of the pentaglycerine. The onedimensional model developed for this study assumed a homogeneous mixture of pentaglycerine and foam which were in local thermal equilibrium with each other. The numerical results reasonably represented the effects of phase change as reflected by the temperature histories for several locations within a graphite foam-pentaglycerine sample. The current study showed that the graphite foam-pentaglycerine combination has potential for use in thermal energy storage devices. Nomenclature c p = specific heat, J∕g ·°C E = energy, J f = fraction of phase change material in a specified phase h = enthalpy, J∕g k = thermal conductivity, W∕m ·°C m = mass, g q = heat transfer rate, W T = temperature,°C t = time, s V = volume, cm 3 α = low-temperature phase of pentaglycerine γ = high-temperature phase of pentaglycerine ρ = density, g∕cm 3 φ = volume fraction Subscripts eff = effective f = foam i = ith component in = heated boundary of sample lat = latent heat out = cooled boundary of sample p = phase change material st = stored tr = transition/phase change

Thermal Properties of Alternative Phase Change Materials for Solar Thermal Applications

“…For PE, a density of 1.39 g cm -3 was given in some works [12,17], while Bushnell [22] provided a value of 1.107 g cm -3 . The following values were found for PG: 1.15 g cm -3 [42] and 1.22 g cm -3 [12,17]. Instead, only two studies reporting the density of the PE+PG mixture were found in the literature.…”

“…However, from Table 4, it can be noted that their thermal conductivity values are generally low. Consequently, this weakness was addressed in different studies that tried to enhance the thermal conductivity of the two PCs by combining them with materials with high thermal conductivity, such as graphite [42,43], graphene [40], alumina [26,[38][39][40], titanium nitride [46], copper nanoparticles [41], indium [25]. The results of these studies showed that an increase of the thermal conductivity of the studied composite PCMs was generally obtained.…”

Numerical modeling of heat transfer in open-cell micro-foam with phase change material

“…To increase the effective thermal conductivities, several thermal conductivity enhancers (TCE) such as fin or partition [2][3][4][5][6], packed particles [7], microor macro-encapsulation [8,9], and metal [10] or graphite foams [11] are used. Of these various PCM/TCE approaches, PCM/foam systems show great potential for use in TES devices particularly those requiring fast thermal transient response [12]. The foam helps to transport the heat from the source to the PCM and its large interfacial surface area distributes the heat more effectively in the PCM.…”

Multiscale Modeling of Multiphase Fluid Flow

“…To increase the effective thermal conductivities, several thermal conductivity enhancers (TCE) such as fin or partition [205][206][207][208][209], packed particles [210], micro-or macro-encapsulation [211,212], and metal [213] or graphite foams [214] are used. Of these various PCM/TCE approaches, PCM/foam systems show great potential for use in TES devices particularly those requiring fast thermal transient response [112]. The foam helps to transport the heat from the source to the PCM and its large interfacial surface area distributes the heat more effectively in the PCM.…”

“…Endothermic reactions represent novel opportunities for heat sinks and the implications and specific challenges they also present need further exploration. Ammonium carbamate has emerged as an expendable high energy density thermal management material in aircraft thermal management [111][112][113][114]. The reaction kinetics of the ammonium carbamate decomposition has proven to be elusive [115] and complex [116].…”