اسعد ياسين علي الربيعي

The parabolic trough solar collector (PTSC) is mainly used for power generation. In this case, the system is used to produce hot water. The most important data (solar radiation, mass flow rate, temperature of the inlet and outlet of the collector) were measured, and energetic values (thermal power, efficiency) were determined. Copper and stainless-steel tube and glass cover tube was used with different diameter. The performance of PTSC system with glass covered copper receiver tube applied four ranges of mass flow rate. The best results obtained when glass covered copper tube was used as absorber and mass flow rate was (0.0036)kg/s

The parabolic trough solar collector (PTSC) is one of the most established solar concentrated systems in the solar thermal applications worldwide. The current paper presents experimental results on a PTSC designed and tested under Hungarian weather conditions in October and November 2020 regarding generation of hot water. The PTSC was made of aluminum sheet of parabolic shape to reflect and concentrate solar radiation into an absorber tube located at the focus point. The absorber tube was made of copper or stainless steel with diameters of 12 and 10 mm, respectively, with and without a glass cover tube. The efficiency of the PTSC was investigated depending on the time of the day at four flow rates under various conditions. The experimental results show that the copper tube coupled with the glass cover worked well at a mass flow rate of 0.0035 kg/s. Furthermore, the glass cover reduced the heat loss, and the performance of the PTSC was enhanced through improvement of the greenhouse effect between the glass and tube.

Parabolic trough solar collectors (PTSCs) are commonly used for applications that reach a temperature of up to 500 °C. Recently, improving the efficiency of PTSCs has been the focus of research because PTSCs have advantages, such as cost and size reduction and improved optical and thermal performance. This study summarizes relevant published research on the preparation, properties and experimental behavior of the optical and thermal properties of PTSCs. Analyzing of the thermal modeling method presents a steady and transient heat transfer analysis. Optical efficiency depends on material properties, such as mirror reflectance, glass cover transmittance, receiver absorption–emission, intercept factor, geometry factor and incidence angle. Also analyzed and discussed are the models used in computational fluid dynamics to study the physical properties of PTSCs. Lastly, studies on PTSC performance and enhancement, including novel designs, enhancement of passive heat transfer and laden flows of nanoparticles inside the absorber tube, are presented and examined separately. Nanofluids have illustrated their advantages and ability to increase heat transfer rates. Moreover, other works that aimed to enhance the optical and thermal efficiency of PTSCs are evaluated

Parabolic trough solar collector systems are the most advanced concentrating solar power technology for large-scale power generation purposes. The current work reviews various selective coating materials and their characteristics for different designs in concentrating solar power. Solar selective absorbing coatings collect solar radiation and convert it to heat. To promote higher efficiency and lower energy costs at higher temperatures requires, this study aims to analyse the fundamental chemistry and thermal stability of some key coatings currently being used and even under investigation to find reasons for differences, information gaps and potential for improvement in results. In recent years, several novel and useful solar absorber coatings have been developed. However, qualification test methods such as corrosion resistance, thermal stability testing and prediction of service life, which have essential technical value for large-scale solar absorbers, are lacking. Coatings are used to enhance the performance of reflectors and absorbers in terms of quality, efficiency, maintenance and cost. Differentiated coatings are required as there are no uniformly perfect materials in various applications, working conditions and material variations. Much more knowledge of the physical and chemical properties and durability of the coatings is required, which will help prevent failures that could not be discovered previously.

This paper presents the influence of the volume concentration (VC) and temperature on the viscosity and thermal conductivity (TC) of a graphene–Fe3O4/water hybrid nanofluid. The experiments were done for volume concentrations (VCs) of 0.1% to 0.5% at temperatures of 20°C to 60°C. The results show that the thermal conductivity ratio (TCR) increases with the VC and temperature. Moreover, the TCR grew more with the VC percent at higher temperatures. The maximum increase in the TC was 34% at a VC of 0.5% at 60°C. The viscosity got up with the VC and decreased with temperature growth. The maximum increase in the relative viscosity (RV) was 6% at a VC of 0.5% at 60°C. Therefore, the VC affects the viscosity and TC, and a new correlation was suggested according to experimental results with good accuracy

This experimental study discusses the thermal efficiency enhancement of a parabolic trough solar collector (PTSC) system using different absorber tube designs. Four different receiver tubes made from copper were designed and examined, including a single evacuated absorber tube, a double evacuated absorber tube, a loop evacuated absorber tube, and a double evacuated absorber tube with a flat plate. Two PTSC models, one representing the modified PTSC and the other for comparison, were fabricated and tested to compare the performance of absorber tubes under Hungarian weather conditions. A similarity test is verified prior the experiment to make sure that the two collectors give the same results. The results of the similarity test showed that the average efficiencies for the lower and upper collectors were 39.798% and 39.842%, respectively. The results showed that the maximum heat removal factor is obtained for 60 and 120 L/h mass flow rates were about 73.478% and 65.7048% for the case of a double evacuated absorber tube with a flat plate, respectively. Moreover, the maximum thermal efficiency of the PTSC with double-evacuated absorber tube and flat plate at 60 and 120 L/h was 52.7% and 59.05%, respectively. Conclusively, the PTSC's thermal performance using the loop-evacuated and double-evacuated absorbers with flat plates is superior to that of traditional tubes regardless of mass flow rate.