Thermal performance analysis of a parabolic trough solar collector using supercritical CO2 as heat transfer fluid under non-uniform solar flux

Qiu, Yu; Sun, Qiuye; He, Ya‐Ling

doi:10.1016/j.applthermaleng.2016.09.044

Cited by 209 publications

(45 citation statements)

References 52 publications

(65 reference statements)

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“…For the solar collector, the data have been taken from [39,51]. It is essential to state that the solar irradiation has been kept constant during this study.…”

Section: Parametersmentioning

confidence: 99%

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Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Bellos

Tzivanidis

2017

Energies

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Abstract:The objective of this work was to optimize and to evaluate a solar-driven trigeneration system which operates with nanofluid-based parabolic trough collectors. The trigeneration system includes an organic Rankine cycle (ORC) and an absorption heat pump operating with LiBr-H 2 O which is powered by the rejected heat of the ORC. Toluene, n-octane, Octamethyltrisiloxane (MDM) and cyclohexane are the examined working fluids in the ORC. The use of CuO and Al 2 O 3 nanoparticles in the Syltherm 800 (base fluid) is investigated in the solar field loop. The analysis is performed with Engineering Equation Solver (EES) under steady state conditions in order to give the emphasis in the exergetic optimization of the system. Except for the different working fluid investigation, the system is optimized by examining three basic operating parameters in all the cases. The pressure in the turbine inlet, the temperature in the ORC condenser and the nanofluid concentration are the optimization variables. According to the final results, the combination of toluene in the ORC with the CuO nanofluid is the optimum choice. The global maximum exergetic efficiency is 24.66% with pressure ratio is equal to 0.7605, heat rejection temperature 113.7 • C and CuO concentration 4.35%.

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“…For the solar collector, the data have been taken from [39,51]. It is essential to state that the solar irradiation has been kept constant during this study.…”

Section: Parametersmentioning

confidence: 99%

“…In this study, this parameter is selected to be 1 m/s which leads approximately to h out = 10 W/m 2 K [39].…”

Section: Solar Field Modelingmentioning

confidence: 99%

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Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Bellos

Tzivanidis

2017

Energies

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“…For the radiation part, the sky temperature (T sky ) is estimated as [35] The heat convection coefficient between cover and ambient (h out ) is calculated according to Eq. 17 [34]. For wind velocity (V wind ) close to 1 m/s, this equation indicated that the heat convection coefficient is close to 10 W/m 2 K, Moreover, it is useful to give the way that the volumetric flow rate (V) is calculated using the mass flow rate (m).…”

Section: Mathematical Formulationmentioning

confidence: 99%

“…The thermal losses of the cover to the ambient are calculated as [34] These thermal losses have radiation and convection part. For the radiation part, the sky temperature (T sky ) is estimated as [35] The heat convection coefficient between cover and ambient (h out ) is calculated according to Eq.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Assessment of the thermal enhancement methods in parabolic trough collectors

Bellos

Tzivanidis

2017

Int J Energy Environ Eng

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Parabolic trough collector is an emerging solar technology for achieving the sustainability. Numerous studies have been focused on their performance evaluation and many techniques have been suggested for improving their thermal efficiency. The objective of this paper is to determine the impact of various thermal enhancement techniques on the thermal efficiency improvement of the PTC. The most usual techniques for increasing the thermal performance of parabolic trough collectors are the use of inserts, internal fins, metallic foams and the dimpled absorbers. A parametric analysis is conducted using different values of the thermal enhancement ratio (Nusselt number to the Nusselt number of the smooth absorber case). According to the final results, the thermal efficiency enhancement can reach up to 2% when the Nusselt number is about 2.5 times greater compared to the reference case and the inlet temperature is equal to 600 K. Moreover, in this case, the thermal losses are approximately 22% lower than in the respective reference case. For higher Nusselt number ratios, the thermal enhancement presents relatively small increase. This analysis is performed with a developed thermal model in Engineering Equation Solver (EES) which is validated with the literature results.

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Heat transfer analysis of receiver for large aperture parabolic trough solar collector

2019

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Summary Parabolic trough solar collector (PTSC) is one of the most proven technologies for large‐scale solar thermal power generation. Currently, the cost of power generation from PTSC is expensive as compared with conventional power generation. The capital/power generation cost can be reduced by increasing aperture sizes of the collector. However, increase in aperture of the collector leads to higher heat flux on the absorber surface and results in higher thermal gradient. Hence, the analysis of heat distribution from the absorber to heat transfer fluid (HTF) and within the absorber is essential to identify the possibilities of failure of the receiver. In this article, extensive heat transfer analysis (HTA) of the receiver is performed for various aperture diameter of a PTSC using commercially available computational fluid dynamics (CFD) software ANSYS Fluent 19.0. The numerical simulations of the receiver are performed to analyze the temperature distribution around the circumference of the absorber tube as well as along the length of tube, the rate of heat transfer from the absorber tube to the HTF, and heat losses from the receiver for various geometric and operating conditions such as collector aperture diameter, mass flow rate, heat loss coefficient (HLC), HTF, and its inlet temperature. It is observed that temperature gradient around the circumference of the absorber and heat losses from the receiver increases with collector aperture. The temperature gradient around the circumference of the absorber tube wall at 2 m length from the inlet are observed as 11, 37, 48, 74, and 129 K, respectively, for 2.5‐, 5‐, 5.77‐, 7.5‐, and 10‐m aperture diameter of PTSC at mass flow rate of 1.25 kg/s and inlet temperature of 300 K for therminol oil as HTF. To minimize the thermal gradient around the absorber circumference, HTFs with better heat transfer characteristics are explored such as molten salt, liquid sodium, and NaK78. Liquid sodium offers a significant reduction in temperature gradient as compared of other HTFs for all the aperture sizes of the collector. It is found that the temperature gradient around the circumference of the absorber tube wall at a length of 2 m is reduced to 4, 8, 10, 13, and 18 K, respectively, for the above‐mentioned mass flow rate with liquid sodium as HTF. The analyses are also performed for different HTF inlet temperature in order to study the behavior of the receiver. Based on the HTA, it is desired to have larger aperture parabolic trough collector to generate higher temperature from the solar field and reduce the capital cost. To achieve higher temperature and better performance of the receiver, HTF with good thermophysical properties may be preferable to minimize the heat losses and thermal gradient around the circumference of the absorber tube.

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Thermal performance analysis of a parabolic trough solar collector using supercritical CO2 as heat transfer fluid under non-uniform solar flux

Cited by 209 publications

References 52 publications

Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Assessment of the thermal enhancement methods in parabolic trough collectors

Heat transfer analysis of receiver for large aperture parabolic trough solar collector

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