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ABSTRACT
A mobile thermal battery operating under concentrated solar heating is considered and the performance analysis for assessment of thermal storage characteristics is presented. Aluminum meshes are incorporated to enhance heat conduction in the working fluid, water. A rotation of the thermal battery along the solar concentrator centerline is introduced in the analysis to realize almost uniform heating at the outer surface of the thermal battery. Governing equations of heat transfer and fluid flow, due to density variation and centrifugal force, are solved numerically. The predictions of numerical code are validated through the previous experimental data. The findings revealed that temperature predictions agree well with the experimental data reported earlier. The use of metallic meshes in the working fluid increases heat transfer and reduces the time needed to reach the desired temperature in the working fluid. The rotation of the thermal battery resulted in almost uniform temperature rise in the working fluid and reduced the difference between maximum and minimum temperatures in the thermal energy-storage medium. This behavior is more pronounced for the case when the rotational speed of the thermal battery increases.
Nomenclature
| cp | = | specific heat [J/kg-K] |
| D | = | diameter of pipe [m] |
| g | = | gravitational acceleration [m/s2] |
| Gr | = | Grashof number [-] |
| Pr | = | Prandtl number [-] |
| Ra | = | Rayleigh number [-] |
| T | = | Local temperature [K] |
| Tin | = | Initial temperature [K] |
| Tmax | = | maximum temperature [K] |
| Tmin | = | minimum temperature [K] |
| ΔTmax | = | temperature difference between maximum and minimum temperatures [K] |
| ΔT | = | temperature difference between local temperature and initial temperature [K] |
| V | = | velocity [m/s] |
| β | = | coefficient of thermal expansion [1/K] |
| k | = | thermal conductivity [w/m-K] |
| μ | = | viscosity [kg/m-s] |
| υ | = | kinematic viscosity [m2/s] |
| ρ | = | density [kg/m3] |
| φ | = | Temperature parameter [-] |
| ω | = | Angular velocity [rad/s] |
Nomenclature
| cp | = | specific heat [J/kg-K] |
| D | = | diameter of pipe [m] |
| g | = | gravitational acceleration [m/s2] |
| Gr | = | Grashof number [-] |
| Pr | = | Prandtl number [-] |
| Ra | = | Rayleigh number [-] |
| T | = | Local temperature [K] |
| Tin | = | Initial temperature [K] |
| Tmax | = | maximum temperature [K] |
| Tmin | = | minimum temperature [K] |
| ΔTmax | = | temperature difference between maximum and minimum temperatures [K] |
| ΔT | = | temperature difference between local temperature and initial temperature [K] |
| V | = | velocity [m/s] |
| β | = | coefficient of thermal expansion [1/K] |
| k | = | thermal conductivity [w/m-K] |
| μ | = | viscosity [kg/m-s] |
| υ | = | kinematic viscosity [m2/s] |
| ρ | = | density [kg/m3] |
| φ | = | Temperature parameter [-] |
| ω | = | Angular velocity [rad/s] |