“…As a result, the thickness of the thermal boundary layer is less than the velocity layer, which makes the convective heat transfer coefficient substantially higher, and the maximum temperature lower. Moreover, the effect of thermal inertia is smaller for liquid sodium on the heat transfer process since it has less ( ρ·Cp ) [ 45 ]. Figure 33 Maximum temperature with different HTF, with constant Re & Q.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, the thickness of the thermal boundary layer is less than the velocity layer, which makes the convective heat transfer coefficient substantially higher, and the maximum temperature lower. Moreover, the effect of thermal inertia is smaller for liquid sodium on the heat transfer process since it has less (ρ⋅Cp) [45]. Using liquid sodium helps to reduce the heat losses from the receiver by reducing the temperature gradient between the receiver wall temperature and the mean fluid temperature [46], (as illustrated in Figure 34).…”
Section: The Effects Of Liquid Sodium and Hitec As Heat Transfer Fluidsmentioning
The solar receiver is considered the cornerstone of the solar tower power system. In particular, it receives hightemperature heat flux rays, and extracts the maximum heat energy to be transferred to the heat transfer fluid, while minimising any thermal and mechanical stresses. Reducing the solar receiver size helps to reduce the loss of spillage; consequently, the thermal stress increases. Using a solar receiver with inserted triangular longitudinal fins enhances the heat transfer as well as strengthens the receiver tube. This study aims to optimise the number of fins, heat flux aiming point, heat transfer fluid, nanoparticle effect with molten salt as the base fluid, and type of receiver material. Non-uniform heat flux with the cosine and Gaussian effects have been considered. When the number of fins (N) increases, the maximum temperature (T max ) decreases and the heat transfer is enhanced. When N ¼ 20, T max ¼ 656.4 K and when N ¼ 1, T max ¼ 683.55, while the efficiency for N ¼ 1 is greater by 3% compared to when N ¼ 20. The cosine distribution of heat flux has a higher maximum temperature than the Gaussian distribution by 29% and is 102% higher in receiver efficiency. The thermal efficiency when the heat flux is aimed at the middle point of the receiver is higher by 10% compared with a lower or upper aiming point. Using Al 2 O 3 nanoparticles with a concentration of 0.5 wt.% increases the thermal efficiency by 14% more than when using pure molten salt when Re ¼ 38000. Using liquid sodium is not required to monitor the peak heat flux, and by adding triangular fins the displacement and thermal stress are 6.5 % lower compared to a smooth receiver.
“…As a result, the thickness of the thermal boundary layer is less than the velocity layer, which makes the convective heat transfer coefficient substantially higher, and the maximum temperature lower. Moreover, the effect of thermal inertia is smaller for liquid sodium on the heat transfer process since it has less ( ρ·Cp ) [ 45 ]. Figure 33 Maximum temperature with different HTF, with constant Re & Q.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, the thickness of the thermal boundary layer is less than the velocity layer, which makes the convective heat transfer coefficient substantially higher, and the maximum temperature lower. Moreover, the effect of thermal inertia is smaller for liquid sodium on the heat transfer process since it has less (ρ⋅Cp) [45]. Using liquid sodium helps to reduce the heat losses from the receiver by reducing the temperature gradient between the receiver wall temperature and the mean fluid temperature [46], (as illustrated in Figure 34).…”
Section: The Effects Of Liquid Sodium and Hitec As Heat Transfer Fluidsmentioning
The solar receiver is considered the cornerstone of the solar tower power system. In particular, it receives hightemperature heat flux rays, and extracts the maximum heat energy to be transferred to the heat transfer fluid, while minimising any thermal and mechanical stresses. Reducing the solar receiver size helps to reduce the loss of spillage; consequently, the thermal stress increases. Using a solar receiver with inserted triangular longitudinal fins enhances the heat transfer as well as strengthens the receiver tube. This study aims to optimise the number of fins, heat flux aiming point, heat transfer fluid, nanoparticle effect with molten salt as the base fluid, and type of receiver material. Non-uniform heat flux with the cosine and Gaussian effects have been considered. When the number of fins (N) increases, the maximum temperature (T max ) decreases and the heat transfer is enhanced. When N ¼ 20, T max ¼ 656.4 K and when N ¼ 1, T max ¼ 683.55, while the efficiency for N ¼ 1 is greater by 3% compared to when N ¼ 20. The cosine distribution of heat flux has a higher maximum temperature than the Gaussian distribution by 29% and is 102% higher in receiver efficiency. The thermal efficiency when the heat flux is aimed at the middle point of the receiver is higher by 10% compared with a lower or upper aiming point. Using Al 2 O 3 nanoparticles with a concentration of 0.5 wt.% increases the thermal efficiency by 14% more than when using pure molten salt when Re ¼ 38000. Using liquid sodium is not required to monitor the peak heat flux, and by adding triangular fins the displacement and thermal stress are 6.5 % lower compared to a smooth receiver.
“…New type of HTFs are emerging, such as, molten salts, air, and CO 2 . In recent years, a lot of research has been focused (Bachelier and Jäger, 2019;Bachelier and Stieglitz, 2017) on the utilization of molten salts in LFR because these working will not only increase the working temperature of HTF from current 400 to 600 °C but can be also used as storage medium with high energy density.…”
“…The high-pressure CO 2 is then heated by the heat exchanger (HX2) and solar heater (SH1) (points 7−8−9) for power generation. Herein, SH1 and SH2 are also solar receivers which could be central receivers, 38 parabolic trough collectors, 39 solar parabolic dish concentrators, 40 or linear Fresnels 41 to further heat the CO 2 before entering the turbines (HT and LT). Then, the CO 2 exiting from the high-pressure turbine (HT) is divided into two streams: one is cooled to a liquid state to be stored in a CO 2 storage tank (points 9−10); the other is reheated by a solar heater (SH2) and then enters the low-pressure turbine (LT) (points 11−12−13).…”
It is important and urgent to overcome the intermittent nature of solar energy as a green substitute for fossil-based electricity. Concentrated solar power plants with thermochemical energy storage are considered as a potential option for costeffective electricity generation and dispatchability. This study aims to propose a novel concentrated solar power plant that uses thermochemical energy storage based on calcium looping with a flexible operation sequence to eliminate the dependence of power generation on the carbonation reaction under sunshine. The flexible operation involves two successive phases: energy charging in the sunshine mode and discharging in the night mode. A comprehensive exergy analysis was used to characterize the system performance based on its storage and power efficiencies. The results, which demonstrated a global storage exergy efficiency of more than 37% and a global power efficiency of around 48%, are comparable to those of the state-of-the-art systems. Moreover, it was also observed that the highest exergy loss is caused by the compressor and cooling process under the sunshine and night modes, respectively. In addition, a sensitivity analysis was performed to examine the thermodynamic laws of our system. The results indicated a technical contradiction between the storage and power efficiencies (net power) under sunshine mode, while no such contradiction was observed under night mode. Overall, the main contribution of this study is the design of a novel system with competitive performance, which is expected to serve as a useful guideline for the future development of efficient and flexible concentrated solar power plants.
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