Advanced Energy Technologies
Ala Moradi; Hajar Es-haghi; Seyed Hassan Hashemabadi; Majid Haghgoo; Zahra Emami
Abstract
Phase Change Materials (PCMs) have received much consideration as thermal energy storage systems due to their high storage capacity. However, their heat transfer rate is limited because of the low thermal conductivity. Incorporating of carbon-based nanoparticles into the matrix of PCMs with good dispersion ...
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Phase Change Materials (PCMs) have received much consideration as thermal energy storage systems due to their high storage capacity. However, their heat transfer rate is limited because of the low thermal conductivity. Incorporating of carbon-based nanoparticles into the matrix of PCMs with good dispersion can be an efficient way to solve their deficiency. In this research, graphite nanoparticles were homogeneously dispersed within the Eicosane PCM matrix to prepare a Nano-Enhanced PCM (NEPCM). The main objective is to determine the optimum amount of graphite to maximize the thermal properties of NEPCM composites. The Scanning Electron Microscopy (SEM) images of the prepared nanocomposites confirmed the excellent dispersion of graphite nanoparticles within the Eicosane layers through an ultrasonic bath-assisted homogenization procedure followed by solidification. In addition, Differential Scanning Calorimetry (DSC) and Thermal Conductivity Evaluation (TC) of the samples were conducted to determine their heat capacity and thermal diffusivity. The results illustrated that the more the number of graphite nanoparticles, the larger the number of collisions between graphite and Eicosane. As the nanoparticle content increased, the thermal conductivity and diffusivity were enhanced, as well. Numerically, the maximum thermal conductivity was 4.1 W/m K for the composite containing 10 wt% graphite, 15.66 times that of the pure Eicosane. Furthermore, increasing crystal growth and reducing heat capacity for the large number of nanoparticles in the composite were discussed. The significantly improved thermal properties of the prepared NEPCMs with an optimal nanoparticle content could make them applicable for different thermal management applications.
Renewable Energy Resources and Technologies
Seyed Amir Hossein Zamzamian; Mohsen Mansouri
Abstract
The enhancement of the thermal performance of Vacuum Tube Solar Collectors (VTSC) was studied by using alumina nanofluid as working fluid. VTSC is a simple and commonly utilized type of collector. This study established the heat transfer experimental model of all glass VTSCs used in a forced-circulation ...
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The enhancement of the thermal performance of Vacuum Tube Solar Collectors (VTSC) was studied by using alumina nanofluid as working fluid. VTSC is a simple and commonly utilized type of collector. This study established the heat transfer experimental model of all glass VTSCs used in a forced-circulation solar water heating system using alumina nanofluid as base fluid. Al2O3 (with an average particle size of 15 nm) nanoparticles were provided and utilized to prepare nanofluids at a low mass concentration (0.5–1 wt.%). The thermal performances of VTSC were 15.3%, 25.7%, and 27.2% for the deionized water and Al2O3/water nanofluids with 0.5 and 1.0 wt. % as the working fluid, respectively. Generally, for Al2O3/water nanofluids with mass concentrations of 0.5 and 1.0 wt. %, the thermal performance increased by 67.9% and 77.7%, respectively, superior to that of vacuum tube using deionized water as the working fluid. Experimental results also showed that, for all three experimental tests, the thermal efficiency of the VTSC would increase by enhancing the average solar radiation.
