Advanced Energy Technologies
Mohammad Saleh Barghi Jahromi; Vali Kalantar; Mohammad Sefid; Masoud Iranmanesh; Hadi Samimi Akhijahani
Abstract
Paraffin waxes are widely used as commercial organic heat storage phase changes (PCM) for many applications due to their suitable properties. Significant heat from fusion, nonpoisonous and stable properties, no phase separation, and the phase process result in a small volume change. Meanwhile, they are ...
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Paraffin waxes are widely used as commercial organic heat storage phase changes (PCM) for many applications due to their suitable properties. Significant heat from fusion, nonpoisonous and stable properties, no phase separation, and the phase process result in a small volume change. Meanwhile, they are subject to low thermal conductivity. The thermal conductivity of PCMs can be increased by different techniques such as the use of dispersion of particles or nanomaterials with high conductivity in PCM and the use of metal foams. The use of nanoparticles has such disadvantages as high cost and particle deposition after various cycles. Hence, in this study, some experiments were carried out to investigate the effect of porous media like copper foam and iron wool as the filler instead of nanomaterials on improving the heat conductivity of PCM. The results show that the porous foam increases the heat transfer and during the charging operation, the temperature of the porous plate wall increases continuously at the same rate as the paraffin. At 2400 s, the temperature of pure PCM, iron wool, and copper foam reaches 67.3, 72.5, and 73.27℃, respectively. The optimal mode is the one in which the copper absorber plate is connected to the copper foam, thus reducing the charging time by 600 s compared to pure PCM and saving 75% of energy. Connecting the copper absorber plate to the iron wool has a good thermal performance and stores 70.83% of energy. Thus, iron wool has an acceptable performance and is suitable for storage systems.
Advanced Energy Technologies
Seyed Amir Hassan Bathaei; Masoud Iranmanesh; Hossein Amiri; Hajir Kourki
Abstract
Thermal Energy Storage (TES) for solar thermal systems has attracted great attention because of the intermittent availability of solar energy. In the current paper, new combinations of several Phase Change Materials (PCMs) including a type of paraffin and some mineral compounds like ammonium nitrate ...
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Thermal Energy Storage (TES) for solar thermal systems has attracted great attention because of the intermittent availability of solar energy. In the current paper, new combinations of several Phase Change Materials (PCMs) including a type of paraffin and some mineral compounds like ammonium nitrate and magnesium nitrate hexahydrate were exanimated and their thermophysical properties were compared. This study targets solar heating systems at different temperature intervals for the TES. Another new approach of this study is to determine the effect of Multi-Wall Carbon Nanotubes (MWCNTs) with two diameters (D) of 8 and 10-20 nm on paraffin's thermophysical property to improve these properties. An innovative method was used to measure Electrical Conductivity (EC) as it is easier to measure than thermal conductivity (K) to study the effect of nanoparticles on PCM behavior. The results showed that the highest values of improvement over paraffin properties were related to 5 % nanoparticle additive for both nanoparticle diameters among the percentages studied. The addition of 5 % nanoparticles with 10-20 nm and 8 nm to paraffin at 25 °C increased heat conductivity by 142 % and 156 %, respectively. The addition of nanoparticles to paraffin improved EC several times such that a diameter of 8 nm made a 300 % increase in EC compared to 10-20 nm.