Thermal Performance Of Collector Research Articles

Thermal analysis of five flat air solar collectors in Epinal (France) using modelling and simulation

ABSTRACT The purpose of this study is to investigate the effect of the position of the solar collector absorber and stagnant air relative to the airflow path on the thermodynamic properties of traversing air and the overall thermal performance of the collector. A numerical model was developed and validated using five different absorber design positions. Numerical results are validated using experimental data obtained from Epinal (France). The model was subsequently used to parametrically study the influence of these absorber positions on the density, temperature, velocity variations of the airflow through the collector and the thermal efficiency of each case scenario. The study showed the importance of stagnant air in solar collector thermal performance. Also, it showed that when one absorber is used, it is better to locate the absorber on the top of the airflow path than below the airflow path. Sandwiching the airflow path between double absorbers with the upper absorbers having stagnant air between it and the plexiglass cover and the down absorber having stagnant air between it and the bottom of the collector can produce a thermal efficiency of 31% which is 2% higher than the closest case and 13% higher than the worst-case design.

CFD modeling of a triple‐walled direct absorption evacuated tube solar collector based on hybrid nanofluid/microencapsulated PCM

AbstractNowadays, direct absorption solar collectors are a new concept of solar collectors which have attracted special attention. The type of heat transfer fluid (HTF) has a significant influence on the efficiency of this kind of collector. Therefore, in this study, a wide range of working fluids including mono nanofluid ( and CuO), binary nanofluid, and especially the incorporation of a new hybrid combination of nanofluid and microencapsulated phase change material (MPCM), are used as the working fluids of a triple‐walled direct absorption evacuated tube solar collector. The computational fluid dynamics (CFD) method is used for simulating the collector and investigating the effect of different parameters including volume fraction, base fluid, mass flow rate, and type of absorber tube structure (double‐ and triple‐walled) on collector thermal performance. Results show that binary nanofluids of 0.06% /0.002% CuO/water and 0.06% /0.002% CuO/ethylene glycol (EG) have the largest working fluid temperature differentials equal to 48.31 and 66.5 K, respectively. It was inferred that, at the mass flow rate of 2.7 , the efficiency is obtained to be 60.29% employing binary/EG nanofluid, which is 8.68% and 15.31% higher than CuO/EG and /EG nanofluids, respectively. Inserting the hybrid CuO nanofluid/MPCM leads to an improvement of 1.14% and 1.22% in the efficiency of triple‐ and double‐walled collectors, respectively, with respect to the individual usage of the nanofluid. The thermal efficiency of the double‐walled structure is higher than triple‐walled considering all HTFs.

Innovative new solar parabolic trough collector enhanced by corrugated receiver surface with PCM and turbulator inside

A solar trough parabolic collector (STPC) has a reflecting surface that is curved into the shape of a parabola. An implementation study on solar trough parabolic collector thermal performance with four different volumetric flow rate values showing the effect of the Reynolds number with multiple passive enhancement approaches was applied tothe solar collector. The first approach is to use a corrugated copper receiver tube, which increases the collector solar heat absorbed by increasing the receiver tube surface area and turbulence. The second enhancement method was done using paraffin wax PCM (phase change material). Phase change material is used as an athermal storage material for heat absorbed by the collector, increasing the outlet water temperature through the night while slightly affecting the day water outlet temperature. By applying this approach, the solar trough parabolic collector enhances the heat transfer rate by around 40 % for all the volumetric flow rates adopted in this work. The third solar trough parabolic collector enhancing method was done by adding a turbulator twisted tape inside the corrugated receiver copper tube. This approach method increases the solar trough parabolic collector performance by around 35 % for all selected volumetric flow rate values. Adopting the three enhancing techniques on solar trough parabolic collector increased the overall thermal efficiency to approximately 85 %. The solar trough parabolic collector heat transfer coefficient, pressure drop, and friction factor were also investigated. A comparison study with previous works was also adopted in this work, which proves a superior thermal performance of the Innovative solar trough parabolic collector of this work over the earlier studies work.

Thermal performance and experimental analysis of stainless steel flat plate solar collector with full-flow channels

The thermal performance of a flat plate solar collector (FPSC) is a critical indicator that depends on the environment, operational parameters, and dimensions. This study examines the impact of size on thermal performance improvement mechanisms. Firstly, numerical simulation models are introduced as the foundation for optimization research. This involves analyzing the flow resistance of microchannels and defining their structural parameters. Furthermore, experimental tests were conducted on a stainless steel flat plate solar collector (S/S FPSC) with the best design parameters to validate the accuracy of the mathematical model during the design phase. The results indicate that increasing the width of the microchannel and the height of corrugations can effectively enhance the thermal performance of the S/S FPSC. The momentary efficiency is projected to reach a remarkable 86.10% under ideal circumstances. Additionally, a mathematical expression was proposed to establish the relationship between the surrounding conditions and the momentary efficiency of the S/S FPSC. Moreover, the microchannel comprises S/S material, maintaining a homogeneous temperature distribution to maximize heat absorption. The use of stainless steel also extends the lifespan of the FPSC.

Thermal performance of a flat-plate solar collector using elliptical riser tubes and magnesium oxide nanofluid

In this research, a solar flat plate collector with a rectangular geometry with elliptical risers has was studied experimentally. The collector was designed and built by the authors and the studies and tests were based on the ASHRAE standard and were done in the south of Iran. Thermal performance for water fluid and magnesium oxide nanofluid was performed in different discharges and atmospheric conditions. Studies were performed based on the type of fluid including ordinary water and nanofluid of water-magnesium oxide with a concentration of 1% and the environmental conditions of the test site as well as the fluid flow. The results showed that using nanofluid increases the collector efficiency in all conditions, especially at higher flow rates of the working fluid. Also, the maximum efficiency obtained in the best conditions for water is about 62.7% and for water-magnesium oxide nanofluid is approximately 82.3%.

Thermal performance of solar flat plate collector using energy storage phase change materials

AbstractThe present study has been carried out to improve the overall efficiency of a conventional flat plate solar collector (FPSC) using two different heat storage phase change materials (PCMs). Two grades of paraffin wax—Paraffin‐P116 (PCM‐1) and Paraffin‐5838 (PCM‐2) as PCM are selected for the analysis based on their high heat fusion rate, low thermal conductivity, and suitable phase transition temperature. The present code has been validated with experimental results and it showed a maximum error of 6.43% in predicting the water outlet temperature. Absorber plate temperature, useful heat transfer rate, water outlet temperature and efficiencies are estimated to improve the performance of FPSC with and without PCM for various flow rates (15 lph and 30 lph) with two different weights of PCM (9 kg and 14 kg) for three different locations in India, [Chennai (13.0827° N, 80.2707° E), Bengaluru (12.9716° N, 77.5946° E), and Delhi (28.7041° N, 77.1025° E)]. The maximum increment in the efficiency of FPSC with the use of PCM‐1 is 19.59% and with the use of PCM‐2 is 16.53%. Using 14 kg of PCM‐1 with the conventional FPSC at water inlet flow rate of 15 lph increases the overall thermal efficiency up to 19.59% compared with conventional FPSC. The maximum increase in the percentage of efficiency with PCM‐1 from conventional FPSC for different cases of 15 lph‐09 kg is 16.34%, 15 lph‐14 kg is 19.59%, 30 lph‐09 kg is 14.57% and 30 lph‐14 kg is 18.45%. From the present study, it can be concluded that the overall efficiency of FPSC is increased with the use of 14 kg of PCM‐1 with conventional FPSC at the inlet water flow rate of 15 lph.

Thermal performance of Parabolic Trough Solar Collector

The research progress of numerical simulation of parabolic trough solar collector was introduced. Especially the numerical simulation studies of the internal flow field in the collector tube and the external flow field of the concentrator were reviewed. In the study of the internal flow field in the collector tube, the type of heat transfer fluids and the characteristics of optical concentration have a significant effect on the heat collection performance and thermal stress distribution, especially in the water/steam medium heat collection loop. The unique gas-liquid two phase flow superposition of the non-uniform heat flux distribution outside the tube may lead to serious thermal stress bending deformation of the collector tube. In the study of the external flow field of the concentrator, due to the high actual wind speed and the low structural strength of the ultra-thin lens, the concentrator is subjected to wind load deformation, resulting in the loss of optical efficiency, and even leading to the failure of the parabolic trough collector structure, which directly affects the normal operation of the whole collector field.

Thermal Performance of a Flat-Plate Solar Collector for Drying Agricultural Crops

In this study, the finite volume method was used to evaluate the thermal performance of a flat-plate solar collector used to dry agricultural crops. A 3D numerical model was created and used to predict the outlet air velocities and temperatures for three inlet air velocities. When compared with experimental measurements, the numerical predictions showed good agreement under all testing conditions. Then, the numerical model was used to predict the internal airflow and heat transfer characteristics of the collector. The internal baffles were found to increase the dwell time and efficiency but also promote flow separation, which resulted in flow loss. In addition, the collector has a transparent cover that results in a substantial heat loss, which can be mitigated by adding a vacuum gap between the flow inside the collector and the cover. Increasing the flow rate increased the heat loss and decreased the heat uptake, which decreased the temperature difference between the inlet and outlet of the collector. Because the heat was lost through long-wavelength radiation via the transparent cover and sidewalls, coating the absorber plate with black matte paint to increase the solar radiation absorption coefficient did not improve the drying performance.

Thermal Performance of Double Pass Solar Air Collector: Numerical and Experimental Investigation

Abstract In this research study, the development of a theoretical model to estimate the efficiency of a double pass solar air heater (DPSAH) was the main objective. The mathematical model was compared to experimental results and found to be in agreement, both qualitatively and quantitatively. The model used energy balance equations to determine the outlet temperature and could solve the temperature equations of each component of the heater simultaneously. A matrix inversion method was used for this purpose. The study found that increasing the Nusselt number led to an increase in energy efficiency, but also caused a drop in outlet temperature at any solar radiation. The mass flow rate (MFR), with larger flow rates resulting in better efficiencies, had a significant impact on the double pass air heater's efficiency. Thus, increasing of DPSAH’s length increases its thermal performances and reach its maximum values for L=9m. These findings could be beneficial in selecting the most efficient design parameters for DPSAH.

Optimization of gaseous working fluid and internally finned absorber tube for enhancing the thermal performance of parabolic trough solar collector

The current study examined the effect of various types of longitudinal finned absorber tubes with the gaseous working fluid on the performance of the parabolic trough collector. Conventional heat transfer fluids, such as water, thermal oils, molten salts, etc., have been limited when the parabolic trough collector works at very high temperatures. Gas may be used as heat transfer fluid when this collector may operate at very high temperatures. However, the heat transfer coefficient of gas is smaller than the conventional heat transfer fluid. Therefore, fins may be used to improve the parabolic trough collector's thermal performance when gas is used as heat transfer fluid. Hence, selecting the best suitable gas as heat transfer fluid and the optimum fin structure is essential to improve this collector's thermal performance. In this context, the current study has considered seven different gases, namely air, carbon dioxide, helium, nitrogen, oxygen, methane, and neon, and six longitudinal finned absorber tubes with different profiles, namely, rectangular, triangular, trapezoidal, T-shaped, and Y-shaped to select the best suitable heat transfer fluid and optimum fin structure. The best suitable gas and optimum fin profile have been chosen based on specific criteria (multi-objective optimization technique or the performance enhancement factor index). This problem has been simulated using commercial software ANSYS Fluent 2020 R2. The experimental and numerical data discovered in the literature are used to validate the results of the current investigation and found in good accuracy between them. The methane gas is found to be the most suitable heat transfer fluid based on both criteria. Then, the effect of mass flow rate and inlet temperature of methane gas on the average friction factor and Nusselt number have been investigated. It is found that the average friction factor decreases with the mass flow rate for the given inlet temperature, while the opposite trend has been observed for the average Nusselt number. For the first time, the T-shaped and Y-shaped finned absorber tube has been proposed in the present study and compared with earlier fin profiles utilized by the researcher. It is found that the increment in thermal efficiency for T-shaped and Y-shaped finned absorber tubes with methane gas is 8.9338 % and 10.1360 %, respectively. In contrast, the increment in exergy efficiency for T-shaped and Y-shaped finned absorber tubes is 8.942 % and 11.622 %, respectively. There is a significant improvement in the thermal and exergy efficiency of the proposed model compared to the models considered in the literature (air flow through absorber tube with the rectangular fin profile). Furthermore, the highest average Nusselt number of 480.4651 is found for the T-shaped finned absorber tube than other examined cases. However, the friction factor is also high for these fin profiles. As a result, the value of the performance enhancement factor for this fin profile is reduced, and the maximum value of the performance enhancement factor is obtained for rectangular fin profiles. Generally, increasing fin height and width increases thermal performance and pressure loss. Therefore, six different dimensions of rectangular fin have been studied and compared with smooth tubes. It is found that the optimum fin dimension of the rectangular fin is a height of 5 mm and a width of 4 mm. The present results can be utilized for designing an internally finned absorber tube to improve the collector's thermal performance with gas as heat transfer fluid.

Thermal performance and economic sustainability of flat plate solar collectors using MgO and ZnO nanofluids: A comparative analysis

Considering the higher outlet temperature, the present study assessed the performance of Zinc oxide (ZnO) and Magnesium oxide (MgO) nanofluid-based flat plate solar collector at a low volumetric flow rate, that is, 30 L/h. The lower solar irradiance results in a low percentage enhancement in collector efficiency; therefore, it constraints the use of the nanofluid-based collector at such conditions. The collector efficiency was nearly 67.98% and 65.22% for 1 vol% ZnO and 0.2 vol% MgO, respectively, almost 20.57% and 16.53% more than base fluid (ethylene glycol: distilled water). For 1 vol% ZnO and 0.2 vol% MgO, the heat absorption parameter intensified by 20.48% and 17.12%, respectively. The payback period at the optimum concentrations of ZnO and MgO nanofluid-based flat plate solar collector compared to electric heating was ∼2.97 and 3.69 years, respectively. In terms of present worth, the cost savings in a life span of 15 years was approximately 1918.18 and 1839.05 USD for 1 vol% ZnO and 0.2 vol% MgO, respectively. Such gains could be extended using large-sized areas of collectors. The 1 vol% ZnO at the flow rate of 30 L/h has the shortest payback period and highest cost-saving; hence, profoundly recommended in the flat plate solar collector instead of the base fluid.

Application of PEG-Fe3O4 nanofluid in flat-plate solar collector: An experimental investigation

In the present study, novel in-situ oxidation precipitation of ferrous hydroxide method is used to synthesized Fe3O4 nanoparticles and Polyethylene glycol 200 is used for covalent functionalization. Various characterizations tests (FESEM, EDX, XRD, FTIR, HRTEM) were performed, and the Polyethylene glycol treated Iron oxides functionalization was confirmed. Thermal conductivity, density, specific heat, and viscosity were experimentally assessed and validated using the correlations that were available. The corresponding improvements in thermophysical characteristics were 13.35%, 0.06%, 0.37%, and 20.9% at 0.1 wt% and 35°C. UV–vis spectroscopy and Zeta protentional was used to check the stability of nanofluids and found that nanofluid was stable for 30 days. A flat plate solar collector was experimentally installed, and the thermal performance of collector was calculated using ferrofluid under ASHRAE standard 93–2003 at different heat flux intensities (597,775,988 W/m2), mass flow rates ((0.0133, 0.0200, 0.0266 kg/s), inlet fluid temperature (30–50°C) and weight concentrations (0.025,0.05,0.075,0.1%). The highest thermal efficiency enhancement of 13.83% was noticed. Moreover, the ANSYS-CFD model was used for the numerical analysis of the thermal performance of flat plate collector at the same environmental conditions, and a maximum difference of 8.33% at 0.1 wt% was noticed in comparison with experimental data.

Innovative conceptual approach in concentrated solar PV/thermal system using Fresnel lens as the concentrator

ABSTRACT Photovoltaics (PV) is an ever-evolving field. Significant technological advancement in the PV field has been evident in recent years, including PV concentrators to enhance energy density. The present experimental study explores the viability of using a refractive Fresnel lens for electrical and thermal energy through a novel approach, i.e. irradiance bi-focussing method. Unlike in most of the concentrated PV (CPV) studies, real size PV module (polycrystalline) is used here, and its surface temperature was maintained well within 80°C with the help of a self-sustainable (burlap-based) passive cooling technique. Since the concentrated irradiance gets bifurcated and simultaneously received by both PV module (≈⅓) and the thermal collector (≈⅔), the power output from CPV is more than double compared to the reference module, and the maximum thermal efficiency recorded is 48%. Even the exergy analysis upheld the proposed system as the maximum exergy efficiency is ≈ 2.5 times compared to the reference module. Concerning the heat gain, the thermal collector performance is on par with a conventional solar water heater. Hence, such a combi system can entertain a variety of day-to-day energy applications. Further, as the distance between the concentrator and PV module changes the illumination level, it can be optimized based on the cooling and/or PV module type.

Experimental analysis of thermal performance of direct absorption parabolic trough collector integrating water based nanofluids for sustainable environment applications

Integration of nanofluids with solar collectors to enhance collector's thermal performance stands out as one of the most effective techniques owning to nanofluids favorable thermo-physical properties. By improving the thermo-physical properties of heat transfer fluids, nanofluids enhance the efficiency of thermal systems by improving the thermal energy storage capacity. This experimental study serves as a novel comparison between water-based Al2O3 (Alumina) and Multi-walled Carbon Nanotubes (MWCNTs) nanofluids in such mass concentrations (0.1%, 0.2%, and 0.3%) at fixed mass flow rates of 0.012 kg/s and 0.024 kg/s to investigate the impact on the performance of Direct Absorption Parabolic Trough Collectors (DAPTC) under the arid climatic conditions of Pakistan. The peak thermal efficiencies were found to be 40%, 56% and 58% for distilled water (DW), Al2O3-water and CNTs-water nanofluids, respectively. Thermal efficiency of DAPTC was improved by 18% in comparison with the basefluid alone on account of increased surface area, thermal conductivity and overall heat transfer capabilities. The CNTs-water nanofluids were observed to be more thermal efficient Heat Transfer Fluids (HTFs) owing to the black color and comparatively lower specific heat capacity. These thermal efficient fluids are of great use in the thermal energy storage systems. In addition, the use of nanofluids for heating and cooling purposes in industries is preferable as operational and manufacturing costs can also be lowered by reducing the systems size.

Optimization of Geometrical Parameters of a Solar Collector Coupled With a Thermal Energy Storage System

Abstract Solar thermal collector is a device that converts solar radiation into useful thermal energy (heat). This technology has become mature and cost-effective. However, because its input comes from an intermittent source (sun), its production is variable during the day; also it is vulnerable to climatic conditions. To adopt this technology, it is therefore necessary to invest in energy storage means or to use a secondary energy source. In this work, a solar thermal collector has been studied and modeled. The objective of this study consists of: first, analyze the impact of the geometrical form of the absorbing surface on the solar collector's thermal performance. Three geometries are tested, namely flat, triangular, and corrugated. The solar collector is evaluated under a hot climate considering the meteorological data of Er-rachidia city (Morocco). The second part of the present study consists of integrating a latent heat storage system using phase change materials (PCMs) to store part of the heat and exploit it during the night. Integrating PCM in this system is a relevant technique to overcome the problem of intermittency of solar energy. Moreover, according to the findings of this study, a significant improvement of the solar collector thermal performance has been reached. The reduction of the missed thermal energy is from 5.6485 kW h to 4.4566 kW h with the use of PCM and the corrugated surface.

Effect of argon concentration on thermal efficiency of gas-filled insulating glass flat-plate collectors

Insulating glass flat-plate collectors can save cost by being produced quickly and automatically in insulated glass production facilities, and they can be filled with argon to reduce heat loss. During its lifetime, the collector is likely to lose argon because of gradual material degradation of the sealing. However, information on the influence of the argon concentration on the collector efficiency is limited. Therefore, the objective of this research work was to analyse this effect. A theoretical material property calculation of argon-air mixtures was carried out to determine the convective losses with variable argon concentrations. Thermal collector performance was measured experimentally using an outdoor solar tracker test rig. The results strongly suggest, that the influence of argon concentration on both the convective losses and the thermal efficiency is non-linear. The measurements revealed that an argon concentration of 90 % can increase average thermal performance by 6.7±4.8 percentage points. An increase in argon concentration from 0 % to 50 % has almost twice the effect on average thermal efficiency as an increase from 50 % to 90 %. Concluding from these results, an argon leakage threshold of 2.5 percentage points per year is proposed to avoid disproportionate loss of efficiency over time.

Numerical investigation on the thermal performance of parabolic trough solar collector with synthetic oil/Cu nanofluids

Nanofluids as the advanced heat transfer fluids, could be used in the parabolic trough solar collector system because of the enhanced thermal transport properties. In this paper, the effects of the same nanoparticles with two different base fluids on the thermal performance of the collector are numerically investigated by finite element method. Moreover, the effect of nanofluids on the cross-sectional temperature distribution of the absorber tube, which is well-known to affect the collector performance is here investigated. The numerical study is divided into two groups according to the value range of inlet velocity and inlet temperature, which represents different application scenarios of the collector. The results show that the synthetic oil/Cu nanofluids could increase the convective heat transfer coefficient under wide working conditions, but more pumping work is required because of the increase in pressure drop. The cross-sectional temperature difference of the absorber tube is greatly decreased with synthetic oil/Cu nanofluids. Furthermore, it’s found that Cu nanoparticles could trigger thermal and exergetic efficiency increment, especially at a low flow rate and high working temperature. The thermal performance improvement of these two thermal oils by Cu nanoparticles is different, and Syltherm 800 is more suitable for being the base fluid of nanofluid.

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.

Thermal performance of asphalt solar collector by improving tube and slab characteristics

Thermal performance of asphalt solar collector by improving tube and slab characteristics

A Review of Enhancement of Thermal Performance of Flat Plate Solar Collectors through Nanofluid Implementation

Nanofluids have found widespread practical applications in heat transfer, including cooling oils for diverse uses like automobile radiators, solar and nuclear power systems, biomedical devices, ventilation, heating, air conditioning, refrigeration, engine cooling, and transformers. Extensive scientific studies have investigated the impact of exotic fluids when combined with traditional heat transfer fluids, revealing that this combination enhances heat transfer performance beyond that of conventional working fluids. Collectively, these studies demonstrate the impressive heat transfer abilities of nanofluids. To optimize the efficiency of flat plate solar collectors, a comprehensive approach integrating theory and experimentation is essential. The results of such research highlight that increasing both the mass flow rate and concentration of nanofluids can lead to significant efficiency improvements, with potential enhancements ranging from 20% to 85%.