Thermal Efficiency Of Collector Research Articles

Analysis of parabolic trough solar collector thermal efficiency with application of a graphene oxide nanosheet‐based nanofluid

AbstractNowadays, clean energy production and reconciliation with nature is one of the best solutions known to rectify the global warming issue. Solar energy, as a clean and green one, has recently been drawing scientists' attention to itself more than ever. Applying parabolic trough solar collectors (PTSCs) is one of the state‐of‐the‐art ways to extract energy from the sun. As one of the most interesting research topics, the thermal efficiency enhancement of PTSCs is studied. The current study demonstrates how the thermal efficiency of PTSCs is enhanced through the application of graphene oxide (GO) nanosheets, as an inexpensive nanomaterial with superb thermal conductivity and unique structure, in thermal oil, namely, Behran oil, as heat transfer fluid, within the effective volume fraction range of 0.05. The above‐mentioned analysis is based on the theoretical calculations performed through a mathematical model based on the Taylor series approximation. All the calculations are performed with respect to a PTSC unit of a solar–thermal power plant situated in Shiraz, Iran, as the research case study. In addition, the Nan et al. model is used to analytically predict how the increase in the volume fraction of GO nanosheets raises the thermal conductivity and consequently increases the convection heat transfer coefficient of the nanofluid, leading to the thermal efficiency enhancement of PTSCs. The results reveal a maximum thermal efficiency of 71.10% for the volume fraction of 0.05. In comparison to the thermal efficiency of the real‐world case‐study mentioned above with pure thermal oil, that is, 67.71%, the thermal efficiency enhancement by about 5.5%, is achieved. Moreover, it is discussed how the thermal efficiency achieved from GO nanosheets surpasses the ones obtained from the application of particle shape nanomaterials, or carbon nanotubes in the same conditions.

Evaluation of the thermal efficiency of nanofluid flows in flat plate solar collector

In this research, flat plate solar collectors (FPSC) were studied due to their simplicity, low maintenance, and cost-effectiveness. The study focused on comparing FPSC thermal performance using CuO/H2O nanofluids. Experiments were conducted over three months during the Iraqi weather conditions (January, February, and March) with carefully selected nanoparticle concentrations. Data was collected from 9 A.M. to 3 P.M., using various mass flow rates (ranging from 0.003 to 0.076 kg/s). Results showed a direct correlation between temperature and nanoparticle concentrations, with the highest outlet temperature (50°C) observed at 3 P.M. for 1% CuO-water nanofluid. Notably, at 1 P.M. in March, the 1% CuO-water nanofluid exhibited a 32% increase in collector thermal efficiency, surpassing pure water by 11.3%. This would improve the performance of FPSC by achieving higher efficiency increments. These improvements were attributed to the unique physical properties of nanoparticles, their increased surface area, and higher thermal conductivity. The study determined that the optimum nanofluid concentration for superior collector efficiency was 1%.

Experimental and numerical investigation of parabolic trough solar collector thermal efficiency enhanced by graphene–Fe3O4/water hybrid nanofluid

This experimental study discusses and focuses on the working fluid because it is regarded as the most important factor influencing parabolic trough solar collector (PTSC) performance. To study the performance, two identical PTSCs were manufactured to use water and the graphene (G)–Fe3O4/water hybrid nanofluid (HNF) as working fluids with different concentrations. The two collectors were evaluated under the same conditions and based on experimental results that the average thermal efficiency and deviation between them not exceeding 0.11%. In addition, the HNF was prepared, and the effect of volume concentration and temperature on the viscosity and thermal conductivity of G–Fe3O4/water was studied. Test samples consisting of HNFs with volume concentrations of 0.01%, 0.05%, 0.1% and 0.2% were compared with water at a mass flow rate of 2 L/min. According to the results, the TE of the PTSC was improved by using a G–Fe3O4/water HNF. The thermal efficiency for G–Fe3O4 HNF was obtained for 0.2%, 0.1%, 0.05% and 0.01% VCs and reached 45.46%, 44.3%, 42.04% and 41.02%, respectively, while the collector efficiency with water was 40.41%. A numerical analysis of the performance of PTSC was also performed using ANSYS Fluent. The results obtained from the numerical and experimental work were in good agreement.

Heat pipes and nanofluids utilization for cooling photovoltaic panels: an application of hybrid machine learning and optimization models

Abstract This study explores the synergies between advanced cooling technologies and photovoltaic systems, seeking to improve their overall efficiency and contribute to the broader goal of mitigating greenhouse gas emissions. To cool photovoltaic panels in more efficiently maner, understanding heat pipes, nanofluids, and panels interaction play key roles. For analysis and optimization, hybrid models of convolutional neural network (CNN) and firefly optimization algorithm are employed. The firefly optimization algorithm is used to optimize the thermosiphon heat pipe’s operational conditions, taking into account inputs such as the filling ratio, nanofluid concentration and panel angle. The study compared the predicted outcomes of a classic CNN model to laboratory experiments. While the CNN model was consistent with experimental findings, it struggled to predict high power values with precision. The proposed model improved high power value predictions by 4.05 W root mean square error (RMSE). The proposed model outperformed the classic CNN model for values greater than 50 W, with an RMSE of 3.95 W. The optimal values for the filling ratio, nanofluid concentration and panel angle were determined after optimization with the firefly algorithm. The research contributes to the advancement of renewable energy technologies and the optimization of photovoltaic panel cooling and energy production. Nanofluid with 1% mass concentration improves photovoltaic collector thermal efficiency due to its higher thermal conductivity coefficient. The photovoltaic collector’s electrical efficiency peaks in the morning, drops at noon due to temperature and radiation and recovers by morning. Electrical efficiency is best with nanofluid at 0.86%. Exergy efficiency closely matches electrical efficiency, with nanofluid at the optimal percentage achieving the highest efficiency and water cooling the lowest.

Pulsating nanofluid-jet impingement cooling and its hydrodynamic effects on heat transfer

Unlocking optimum heat transfer is essential for enhancing solar thermal collector efficiency and advancing sustainable energy solutions. This experimental study investigates a simulated solar thermal collector's heat transfer behavior using jet impingement cooling, emphasizing hydrodynamic effects in pulsating nanofluid-jet impingement. Al2O3-MWCNT/water hybrid nanofluid is utilized, varying pulsating frequency (0.2 Hz ≤ F ≤ 20 Hz), amplitude (4 Vp ≤ A ≤ 20 Vp), waveform (sine, squared, triangular), wave offset (0 ≤ Ⴋ ≤ 4), and nanofluid volume fraction (0.05 vol% ≤ φ ≤ 0.3 vol%) to optimize heat transfer. Results show a significant influence on heat transfer performance for all parameters except waveform. A peak heat transfer enhancement of 24 % is observed for 0.3 vol% Al2O3-MWCNT/water compared to de-ionized water under continuous jet impingement. Additionally, a 20 % enhancement is achieved with a sine waveform at φ = 0.3 vol%, F = 0.2, A = 8, and Ⴋ = 2. Pulsating jet impingement generally yields higher cooling rates, as the cooling curves indicate. These findings provide crucial insights for optimizing heat transfer in solar thermal collectors through pulsating hybrid nanofluid jet impingement cooling.

Modeling and comparative assessment of solar thermal systems for space and water heating: Liquid water versus air-based systems

This work pertains to the transient modeling and comparative study of active solar thermal space and water heating systems using liquid and air-type solar thermal collectors as the main energy source. The study utilizes TRNSYS to simulate the two systems in the context of Taxila's weather data (located at 33.74°N, 72.83°E), with the goal of meeting peak space and domestic water heating demands of 20 kW and 200 lit/day, respectively. The liquid water-based system (S-1) is primarily composed of a liquid solar collector, thermal storage, an auxiliary heater, connections to the hot water supply, and the space heating load through a water–air heat exchanger. In contrast, the air-based system (S-2), employs a pebble bed storage to store heat extracted from the solar thermal air collector. The heated air is subsequently used directly for space heating and passed through an air–water heat exchanger for water heating. Dynamic simulations of both systems span the entire winter season, and various performance metrics, including solar fraction, primary energy savings, and solar collector thermal efficiency, are computed. The results revealed that at the same collector area, the liquid water-based system (S-1) shows a higher solar fraction than the air-based systems (S-2) while the primary energy savings of the S-1 resulted in lower values than S-2 at smaller collector areas (< ∼30 m2) but surpasses the S-2 with increasing collector size. The optimal collector tilt for both systems is determined to be 50°, while specific storage volumes corresponding to maximum primary energy savings are estimated to be 100 and 40 L/m2 for S-1 and S-2, respectively.

Improvement of the classical artificial neural network simulation model of the parabolic trough solar collector outlet temperature and thermal efficiency using the conformable activation functions

The outlet temperature and the thermal efficiency predictions of the PTSC are essential parameters in the solar thermal power system. Therefore, it is crucial to have a prediction model that can predict its spatiotemporal behavior to the greatest extent possible. For that, the present study provides improved models of the classical ANN model by using ELU, swish, softplus, logsig, and tansig functions through the exponential transfer function to improve the outlet temperature prediction performance and thermal efficiency of PTSC. The PTSC’s outlet temperature simulation showed that the ANN model of topology 6-2-1 with the conformable swish transfer function (cswish) was the best model among nine other studied models, with an R2 and Radj2 of 0.9988, and MAE of 0.0052. The simulation of PTSC’s thermal efficiency proved that the conformable functions logsig, tansig, ELU and the classical ELU function involved in the ANN model for 6-3-1 achieved better results with approximately 95% precision. With the non-integer activation functions, was reduced a neuron in the hidden layer, which leads to the simplicity of the prediction model compared to the use of the classical activation functions. The proposed activation functions do not require high-performance features according to their execution times. Therefore, it could be a good alternative for engineers to apply in other thermal energy systems to make their prediction models more accessible and practical in the control and optimization process.

Experimental Investigation of Parabolic Trough Solar Collector Thermal Efficiency Enhanced by Different Reflective Materials

Experimental Investigation of Parabolic Trough Solar Collector Thermal Efficiency Enhanced by Different Reflective Materials

Experimental investigation of parabolic trough solar collector thermal efficiency enhanced with different absorber coatings

The objective of this work is to investigate the thermal efficiency of a compound parabolic trough solar collector (PTSC) by using different absorber tube coatings. Two identical PTSCs were used to compare the different absorber coatings: one with matte coating (MC) and the other with nanocoating (NC) by adding Fe3O4 and graphene nanoparticles to the MC. In the beginning, similarity tests of the two collectors were carried out using the matte coating of the absorber tube under the same conditions and a mass flow rate of 120 L/h. The test results show the average thermal efficiency of collectors did not reach 0.11%. Then, the PTSC was compared with various mass flow rates: 30, 60, 90, and 120 L/h. The results show the maximum heat removal factor of PTSC for both nanocoating and matte acrylic coating at 120 L/h was 52.72% and 50.33%, respectively. And the maximum thermal efficiency of PTSC for both nanocoating and matte acrylic coating at 120 L/h was 41.58% and 40.37%, respectively. Finally, adding iron oxide and graphene nanoparticles to the matte acrylic coating has increased the amount of radiation absorption. As a result, PTSC's optical and thermal efficiency improved.

Effect of riser-pipe cross section and plate geometry on the solar flat plate collector's thermal efficiency under natural conditions

The current study aims to enhance the thermal performance of the Solar Flat Plate Collector (SFPC). To achieve that, four proposed models of (SFPC) were investigated in terms of thermal response under transient solar radiation using passive techniques. Two of these models simulate the influence of different riser-pipe configurations, namely models A and B, respectively representing semicircular and elliptical cross sections. While, the other two models, -C- and -D- represent the effect of plate geometry, which represent dimples and channel plates, respectively. All geometric models and the numerical simulations were created using ANSYS 19. R3. The results show that there is good conformity between numerical and experimental findings. Moreover, all four proposed models have been found to have a better thermal response than conventional model. Furthermore, model -D- is found to be the better model among all the other models under investigation due to the increased surface area of the collector, which leads to receive more solar radiation (heat flux) and hence increases the heat transfer to the working fluid within the riser pipe, which increases the temperature of the working fluid and the water inside the container. The thermal response of model -D- in terms of working fluid temperature inside the container and water temperature at the exit is approximately 13.2% and 12.3% higher, respectively, as compared to the traditional model. In addition, the overall thermal efficiency of the model -D- collector is approximately 13.7% higher than the conventional model.

Effects of carbon nanodots coating and airflow rate on the thermal efficiency of flat plate collector

ABSTRACT The application of nanoparticle coating in a collector could resolve the issues of lesser heat transfer rate and lower thermal efficiency associated with the flat plate collector (FPC). In this study, carbon nanodots (CNDs) synthesized from fish scales wwere coated over the black paint coating to enhance the thermal efficiency of FPC. The effect of various concentrations (0, 0.1, 0.2, and 0.5%w/v) of CND coatings and mass flow rates of air (0.011 kg/s (natural convection) and 0.015, 0.029, and 0.044 kg/s (forced convection)) on the collector outlet air temperature and efficiency of the FPC were evaluated with a control (black paint). Solar radiation ranged from 382 to 913 W/m2 on the experimental days, and the atmospheric temperature and relative humidity values varied from 26.2 to 34.8°C and 50–72%, respectively. Fourier transform infrared spectroscopic studies of absorber plate coating revealed that the CNDs interacted with the black paint surface through phenolic OH, C=O, and NH mainly by hydrogen bonding. It was observed that the exit air temperature of the collector varied from 55 to 65°C. The thermal efficiency of 59.97%, 62.72%, 71.87%, and 67.75% was obtained for control (black-paint), 0.1%, 0.2%, and 0.5% CNDs coating, respectively, at the airflow rate of 0.044 kg/s. The coating of 0.2% CNDs recorded a maximum thermal efficiency of 71.87% at 0.044 kg/s. Overall, the CNDs coating on the absorber surface enhanced the thermal efficiency of the collector by 19.84% over the black paint-coated surface (control). It can be concluded from the study that CNDs coating resulted in enhanced outlet air temperature and improved thermal efficiency, which can be utilized for low-temperature applications like the drying of food materials.

Experimental investigation of improved parabolic trough solar collector thermal efficiency using novel receiver geometry design

Experimental investigation of improved parabolic trough solar collector thermal efficiency using novel receiver geometry design

Investigation of tungsten halogen lamp for possible usage as heat source for testing solar collector

Artificial sunlight is a heat source in solar collector testing, where the light intensity and ambient conditions are controlled to provide uniformity in each test. In this study, twenty-five tungsten halogen lamps of 300 W 220 V were investigated for possible usage as the heat source. The experiment was conducted by varying the height of the lamps to the light field (Hd). The EN-12975–2 Standard was used to control the quality of the heat source on the light field. The results showed that the average light intensity (Iavg) decreased with an increase in Hd. When Hd was low, the %uniformity values (%uxy) met the criteria. The small light field area met the EN-12975–2 Standard better than the large area. A comparison of solar collector testing under a heat source from tungsten halogen lamps and natural sunlight was subsequently performed, and the experimental results were in accordance with the EN-12975–2 Standard. A single-channel flat plate solar collector was used as the test device and air was used as the working fluid. The experimental results revealed that the solar collector thermal efficiency (ηavg) trends were similar for both the heat source from tungsten halogen lamps and natural sunlight testing. A low %uxy resulted in a ηavg that was more similar to that of natural sunlight.

Numerical investigation of the effect of using louver baffles on thermal performance in solar air collectors

AbstractConventional flat plate solar air collectors have advantages such as low cost and simple design. However, their thermal efficiency is lower than that of other designs. The thermal efficiency of these collectors can be increased by detailed examination of parameters such as the shape, size, arrangement and material of the air duct. In this study, it is aimed to improve the thermal efficiency of solar air collectors. The effect of louver baffles, which were not previously used in solar air collectors, on thermal efficiency was investigated numerically via computational fluid dynamics. Three different solar air collectors with flat plates, segmented baffles, and louver baffles were compared in terms of thermal efficiency. In addition, pressure drops in solar air collectors were investigated. The mass flow rate of the air in all collectors is assumed to be 0.04 kg/s. Analyzes were carried out between 09:00 and 16:00. The thermal efficiency values obtained during the day for solar air collectors with flat plate, segmented baffles and louver baffles are 27.66%–56.35%, 29.57%–58.82% and 30.09%–59.47%, respectively. The daily thermal efficiency values obtained for solar air collectors with flat plate, segmented baffles and louver baffles are 46.98%, 49.18% and 49.87%, respectively. The pressure drop for solar air collectors with flat plate, segmented baffles and louver baffles were found to be 4.62, 18.82 and 5.96 Pa, respectively. Based on the data obtained from this study, louver baffles are recommended for use in solar heating applications due to their high thermal efficiency and low pressure drop.

Thermal efficiency of flat plate solar collector with TiO2-based nanofluid: synergistic effect of size and facet orientation

A solar collector is an important device for collecting and converting solar energy into thermal energy. It can be synchronized to work in combination with different power sources to provide stable and continuous power. In this study, TiO2 nanoparticles (NPs) with control on the size and the exposed facet orientation were prepared through a fluorine-free solvothermal synthesis process. The as-synthesized nanoparticles were analyzed using XRD and TEM techniques. The effect of size (about 6 and 17 nm) and facet orientation ([001] and [101]) for TiO2 NPs as nanofluid on the performance of the solar collector was investigated experimentally. In the experimental solar collector setup, the highest absorption efficiency was 71.75% for TiO2 NPs with the mixed effects of size and facet orientation, whereas the absorption efficiency was 71.37% for commercially available P25 NPs. Most importantly, the combination of the size and facet orientation effect led to a positive synergy effect. The obtained results represent that the performance of the solar collector was severely affected by the size and facet orientation of the NPs.

Optimizing Device Performance of Multi-Pass Flat-Plate Solar Air Heaters on Various Recycling Configurations

Various external-recycle configurations of multi-pass flat-plate solar air collectors were studied theoretically to examine the optimal thermal performance under the same working dimension and operation conditions. An absorber plate and insulation sheet were implemented horizontally and vertically, respectively, into an open rectangular conduit to conduct a recycling four-pass operation, which the device lengthens the air flow channel and increases the air mass flow rate within the collector, and thus, a more heat transfer efficiency is obtained. Four recycling types with different external-recycle patterns were introduced and expected to augment the heat transfer rate due to the turbulent convective intensity through four subchannels in the present study. Coupling energy balances into one-dimensional modeling equations were derived by making the energy-flow diagram within a finite element, which the longitudinal temperature distributions for each subchannel were obtained. The theoretical predictions show that the improved four-pass device is accomplished due to the multiple heating pathways over and under the absorber plate, from which the turbulence intensity augmentation results in the heat transfer rate as compared to that in the device without inserting the absorber plate and insulation sheet (say a downward-type single-pass solar air collector). The theoretical results also show that the external-recycle configuration (say Type C in the present study) acts as an optimal collector thermal efficiency and leading to a beneficial design in multi-pass solar air collectors for improving heat-transfer rate and increasing resident time under the same operation conditions. Theoretical predictions show a higher heat-transfer efficiency for the present recycling configurations up to a maximum 115% device enhancement in comparison to that of a single-pass device. Examination of implementing the absorber plate and insulation sheet on the heat-transfer efficiency enhancement as well as the hydraulic dissipated power increment were also delineated, and deliberated the suitable external-recycle configuration with respect to an economic consideration.

Design Parameters of Parabolic Solar Water Heater with Inbuilt Automatic Solar Tracking System

Abstract: This paper focuses on developing novel technique for a solar water heating system. The novel solar system comprises a parabolic dish concentrator, conical absorber and water heater. In this system, the conical absorber tube directly absorbs solar radiation from the sun and the parabolic dish concentrator reflects the solar radiations towards the conical absorber tube from all directions, therefore both radiations would significantly improve the thermal collector efficiency. The working fluid water is stored at the bottom of the absorber tubes. The absorber tubes get heated and increases the temperature of the working fluid inside of the absorber tube and causes the working fluid to partially evaporate. The partially vaporized working fluid moves in the upward direction due to buoyancy effect and enters the heat exchanger. When fresh water passes through the heat exchanger, temperature of the vapour decreases through heat exchange. This leads to condensation of the vapour and forms liquid phase. The working fluid returns to the bottom of the collector absorber tube by gravity. Hence, this will continue as a cyclic process inside the system. The proposed investigation shows an improvement of collector efficiency, enhanced heat transfer and a quality water heating system.

Experimental investigation of convective heat transfer performance of TiN nanofluid charged U-pipe evacuated tube solar thermal collector

The present study investigates the convective heat transfer performance of the U-pipe evacuated tube solar thermal collector with TiN nanofluid. TiN nanoparticles 40–50 nm in size dispersed in distilled water at 0 %, 0.025 %, 0.050 %, 0.075 %, and 0.1 % volume concentrations. The TiN nanofluid's stability and thermophysical properties are measured experimentally. ASHRAE standard 93-2003 evaluates collector thermal performance. The convective heat transfer coefficient, friction factor characteristic, and solar thermal efficiency are investigated experimentally at volume concentrations of 0 %, 0.025 %, 0.050 %, 0.075 %, and 0.10 %, and mass flow rates of 0.25, 0.50, 0.75, and 1 LPM. The solar thermal collector performance is tested in Sangamner at latitudes of 19.576°N and 74.2070°E under outdoor test conditions. The TiN nanofluid with a 0.1 % volume concentration at a 1.25 LPM flow rate gives a 109.6 % enhancement in the convective heat transfer coefficient compared to water. The friction factor penalty of TiN nanofluid at 0.1 % volume concentration is 2.58 and 1.82 for water. At 0.1 % volume concentration, the solar thermal collector efficiency reaches 70.9 %. The correlation is proposed to determine the Nusselt number, friction factor, and solar thermal efficiency in laminar flow. The TiN nanofluid is recommended for industrial solar thermal applications because of its notable improvement in convective heat transfer performance despite the friction factor penalty.

FPC thermal performance enhancement and reduction of greenhouse gas emissions: A sustainable approach using nanoparticles

Much research has been put into investigating and analyzing the performance of flat-plate collectors. The mathematical model of steady-state laminar conditions in a solar collector that was developed was done so with the assistance of Microsoft Excel. Researchers proved that the collector's thermal efficiency could be increased by 2% at a volume concentration of 4% when the working fluid was a Cu-water nanofluid rather than plain water. This was accomplished by using the nanofluid as the working fluid. In addition, the decrease in pressure resulting from pumping the nanofluid within the collection requires more electricity than the alternative method of dispersing the nanoparticles in water. According to the research conducted on collectors, the increase in pumping power and pressure drop was estimated to be around 29%. Compared to water, the use of nanofluid has been shown to result in a 3.8% greater reduction in the production of greenhouse gases.

Review of methods for improving the thermal performance of solar air collectors with flat plates

The latest research on improving the thermal efficiency of flat solar air collectors is carried out on the modification of the absorber surface, the organization of multiple air flow, the use of porous absorbers, the transfer of air flow to the absorber surface by impact, the integration of the absorber surface with heat accumulating materials. The formation of a laminar viscous layer on the surface of the absorber leads to the deterioration of heat transfer to the air stream. The main factor for increasing the heat transfer in flat solar air collectors is to increase the heat transfer surface and the air residence time in the collector, which is achieved by using fins, barriers, turbulizers and baffles. When installing turbulizers of different shapes on the surface of the absorber, the thermal efficiency of the collector increases from 71.4% to 93%. When the absorber surface is integrated with heat-accumulating materials and ribs, the daily thermal efficiency of the collector increases to an average of 0.4-4%. This review article presents an analysis of the scientific research conducted in the last decade on improving the thermal efficiency of flat solar air collectors.