Renewable Energy Resources and Technologies
Daryoosh Borzuei; Seyed Farhan Moosavian; Abolfazl Ahmadi; Rouhollah Ahmadi; Kourosh Bagherzadeh
Abstract
Energy plays a vital role in all human life activities. Due to the problems caused by fossil fuels in recent decades such as global warming, greenhouse gas emissions, ozone depletion, etc., the use of renewable and clean energy has been considered. An experimental facility for the acquisition of reliable ...
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Energy plays a vital role in all human life activities. Due to the problems caused by fossil fuels in recent decades such as global warming, greenhouse gas emissions, ozone depletion, etc., the use of renewable and clean energy has been considered. An experimental facility for the acquisition of reliable data from Parabolic Trough Solar Collectors (PTCs) was established to develop a robust analytical model. A wide range of Heat Transfer Fluid (HTF) flow rates (0.0372-0.1072 kg/s) and solar radiation (400-900 W/m2) were used to determine PTC parameters such as the outlet temperature of HTF loss and temperature distribution. Vacuum conditions in the receiver were considered effective in terms of thermal efficiency. Also, three types of HTF including two oil fluids (Syltherm 800 and S2) and water were examined. The temperature distribution showed that when Syltherm 800 or S2 passed through the absorber tube, the outlet temperature was higher than water: 2.84 % for Syltherm 800 and 3.72 % for S2. Since the absorber tube temperature was much higher than water, the heat loss in this condition was considered for oil HTF. Of note, the results demonstrated that use of the vacuum tube could diminish heat loss for the oil HTF. The effect of solar intensity increases from 600 W/m2 to 900 W/m2 on the maximum temperature of the receiver tube indicated that when Syltherm 800 was used as an HTF, this temperature increased by 35.1 % (from 167 °C to 219 °C), while this percentage was 32.7 % and 6.8 % for S2 and water, respectively.
Advanced Energy Technologies
Ehsan Hasan Zaim; Hadi Farzan
Abstract
Utilizing thermal storage units such as Phase Change Materials (PCMs) is a suitable approach to improving Solar Air Heaters (SAHs). The present study tries to assess the effects of PCM mass values on the heat dynamics and thermal performance of SAHs. To this aim, an analytical thermodynamic model was ...
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Utilizing thermal storage units such as Phase Change Materials (PCMs) is a suitable approach to improving Solar Air Heaters (SAHs). The present study tries to assess the effects of PCM mass values on the heat dynamics and thermal performance of SAHs. To this aim, an analytical thermodynamic model was developed and validated by available experimental data. This model provides a robust numerical framework to model the phase change phenomenon and analyze the heat dynamics and thermal performance of SAH using various PCM masses. Four scenarios were considered using the developed analytical model including SAHs using 0, 30, 60, 90 kg PCM. The obtained results illustrated that the maximum outlet temperature was reduced, approximately near 20 %, by increasing the PCM mass between 0 and 90 kg; however, heating time was extended to periods when solar energy availability was inadequate. The thermal performance improved by nearly 14.5 % in the SAH using 90 kg PCM mass compared to the SAH without using PCM. The thermal performance of the SAH with 90 kg PCM was slightly higher than the SAH using 30 kg of PCM; hence, a significant portion of stored thermal energy was lost during nighttime through heat exchange with ambient surroundings. The obtained results also showed that despite available latent thermal energy, the outlet air temperature profiles for the SAHs using different PCM mass were close after sunset due to the low thermal conductivity of paraffin.
