Absorber Plate Research Articles

Heat Transfer Coefficient for a Glazed Transpired Solar Collector in Natural Convection Mode

A glazed transpired solar collector (GTC) was set up to operate in natural convection mode. Collector air temperature and velocity were measured at specific points in the collector. Solar radiation, ambient temperature, collector cover glass and absorber temperature were also measured. Using dimensional analysis and the measured data, a heat transfer correlation was obtained for the collector which will enable the heat transfer coefficient to be determined. The GTC heat transfer correlation based on influence of pitch is . The GTC absorber plate hole diameter was 3.0 mm and the pitches ranged from 15 mm to 35 mm. The Nusselt number correlation for influence of pitch, P for predicted all Nusselt numbers well with maximum error of 5.2%. The predicted Nusselt numbers using the correlation of this work were found to be in close agreement with a similar model which was developed based on the influence of absorber hole diameter. Furthermore, the correlation of this work is valuable for future studies on optimization of pitch for a given hole size in the application of the GTC for air heating and crop drying.

Energy and exergy analysis of a cross flow solar air heater for thermohydraulic performance augmentation

This study numerically examines the enhancement of thermo-hydraulic efficiency of a cross flow solar air heater (SAH) for Reynolds number ranging from 3000 to 21000. The thermal performance is investigated for various perforation hole diameters of absorber plate and varying number of rows of holes. Discrete Ordinates radiation model is used to simulate the solar radiation heat interactions within the computational domain. Maximum thermo-hydraulic efficiencies of 86.51% and 85.15% are observed for configurations with 3 rows and 4 rows of perforation holes with hole diameter ratio of 0.06 and 0.07 respectively. The maximum exergy efficiency is found to be 5.28%. The system's enviro-economic analysis shows that the CO2 mitigation rate is 1.12 t CO2/annum, whereas the environmental cost is 16.31 $/year. The exergo-economic parameter is computed as 1.18 kWh/$, while the energy cost is calculated as 0.049 $/kWh. Additionally, it is determined that the energy payback period is 5 months while the exergy payback period is 22 years. The heat map for the various configurations shows the economical operating range of the air heater. The envisaged SAH has the advantage of completely decimating the laminar sublayer throughout the absorber plate due to cross flow movement of air through the absorber plate unlike the conventional SAH.

Investigation of Solar Air Collectors with Carbon-Nanotube-Based Turbulators and Pin Fin Arrangements

This research attempts to investigate the thermal performance of solar air collectors with pin fins and turbulators. Incorporating carbon-nanotube-based fins and turbulators in solar collectors can enhance their performance due to their high thermal conductivity, low weight, and high aspect ratio. In the present study, numerical analyses of a solar collector with pin fins and turbulators are carried out to investigate its effect on the Nusselt number. The paper begins with the numerical analysis of conventional air collectors and compares them with theoretical results. This is followed by numerical analyses, which are carried out to examine different configurations of the absorber plate with pin fins of varying diameters (10 mm, 20 mm, and 30 mm) and turbulators of varying heights (20 mm, 40 mm, and 60 mm) in the base plate. The analyses include variations in the Reynolds number ranging from 3000 to 15,000. Subsequently, after the performance of the solar collector with pin fins is evaluated, the effect of turbulators of varying heights on the Nusselt number is analyzed, followed by the analysis of the combined effect of pin fins and turbulators. The results are compared with traditional solar collectors and show that the combined effect of pin fins and turbulators can significantly improve the thermal performance of solar air collectors. The findings of this study can contribute to the development of renewable energy-based air conditioning, ventilation, and heating systems.

Investigation of Performance of Stone Fin Solar Still Absorber by Water Depth Variations.

Passive Solar is still suitable for Indonesia's islands and coastal areas. Various attempts have been made to increase the performance of passive solar stills, including using porous materials, fins absorber models, and making water in the form of a thin layer. This study aims to increase the distillate output and Efficiency of Solar still. This study's method compares stone fin solar stills absorbers using water depth variations of 1 cm, 2 cm, and 3 cm with conventional solar stills at a water depth of 1 cm. The study resulted in the distillate output of stone fin solar still absorber of 3.35 (liter/m2.day) higher than the conventional solar stills 2.44 (liter/m2.day) at a depth of 1 cm. The highest Efficiency of solar stills using the stone fin solar still absorbers is 58.45% higher than conventional solar stills, 43.60% at a depth of 1 cm. Solar stills with lower water depths resulted in higher distillate output and Efficiency. Solar stills using stone fin absorbent plates produce higher productivity and Efficiency than conventional ones

Bone healing and stability after advancement genioplasty using a pre-bent absorbable plate and screws

This study aimed to compare the bone healing and stability of the chin with a pre-bent absorbable plate and a manually bent absorbable plate after advancement genioplasty.Patients with class II malocclusion who underwent genioplasty with bimaxillary surgery were included. After genioplasty, two absorbable bicortical screws were fixed on both sides. Then, a pre-bent absorbable plate and screws were used in the center area to fix the segment in advancement genioplasty (PB group). A manually bent absorbable plate was used for the remaining patients (MB group). Computed tomography (CT) was performed before surgery and 1 week and 1 year after surgery. Changes in the pogonion (Pog) and menton (Me) points, soft tissue points, and the ratio of bone squares under the plate were evaluated using lateral cephalometric images reconstructed with 3-dimensional CT data.32 patients were included in the study. There were no significant differences in the cephalometric measurements in the time interval from 1 week to 1 year. However, the bone square ratio in the PB group showed a significant increase after 1 year (P = 0.0021).Within the limitations of the study it seems that the use of a pre-bent absorbable plate is effective in promoting bone healing after advancement genioplasty.

Analysis Thermal Behavior of a Locally Heated Solar Chimney

This paper presents the thermal behavior of a partially heated solar chimney under hot-humid climate conditions. The solar chimney (SCH) is 2 m high and 0.8 m wide and consists of an absorber plate and a translucent plate. The SCH allows a cavity thickness variation from 0 to 0.28 m, an inclination angle variation from 0 to 90º, and allows varying the amount of energy absorbed by the absorber plate and translucent plate. These plates were heated by resistors, simulating a solar irradiance range of 225 to 900 W/m2 (absorber plate) and from 12.15 to 50 W/m2 (translucent plate). Twelve tests were conducted with different configurations varying the power supplied to both plates, the thickness of the absorber plate cavity, and the 90º inclination angle. The variables measured were temperature, air velocity at the inlet, and heat flow on the side walls and rear wall. As a result, a maximum air renewal of 51.43 ACH was obtained, equivalent to the air changes used in a paint booth. The results show that the partially heated solar chimney can be used as a passive ventilation system for air renewal.

Development of Nusselt number and friction factor correlations for double-pass solar air heater duct

A solar air heater exhibits a low heat transfer rate due to the formation of a laminar thermal boundary layer across the absorber plate. Furthermore, the artificial roughness contributes to the intensification of turbulence along the absorber plate, which interrupts and breaks the thermal boundary layer. Keeping in this view, a three-dimensional simulation is performed to investigate the heat transfer and frictional characteristics of a double-pass solar air heater with semicircular tubes and perforated baffles as artificial roughness. This numerical investigation is performed for the parameters considered in the study: tube amplitude ratios (a/H) from 0.2 to 0.5, baffle height ratios (e/H) from 0.4 to 0.8, open area ratios (β) from 13 % to 30 % and Reynolds number (Re) from 3000 to 19000. The experimental testing rig is designed to validate numerical results corresponding to e/H of 0.4, an open area ratio of 30 %, a/H of 0.3, and Reynolds number varying from 3000 to 15000. Numerical results are found to be in good agreement with the experimental results, with a maximum absolute percentage error of 1.82 % and 5.28 % for the Nusselt number (Nur) and friction factor (fr), respectively. The maximum Nusselt number is observed as 274.29 at Reynolds number of 19,000 and e/H of 0.8; however, the maximum friction factor is observed as 0.6290 at Reynolds number of 3000 and e/H of 0.8 at a constant value of open area ratio of 30 % and a/H of 0.3. Within the range parameters studied, the maximum THPP value is reported to be 2.51 at Reynolds number of 3000, β of 30 %, e/H of 0.4, and a/H of 0.3. Further, correlations for the Nusselt number and friction factor in the function of a/H, e/H, open area ratio, and Reynolds number have been derived based on simulation results.

Exergy based analysis of solar air heater duct with W-shaped rib roughness on the absorber plate

Exergy based analysis of solar air heater duct with W-shaped rib roughness on the absorber plate

Performance analysis of three sides solar air heater having roughness elements as a combination of multiple-v and transverse wire on the absorber plate

Performance analysis of three sides solar air heater having roughness elements as a combination of multiple-v and transverse wire on the absorber plate

Experimental investigation of augmented thermal and performance characteristics of solar air heater ducts due to varied orientations of roughness geometry on the absorber plate

Experimental investigation of augmented thermal and performance characteristics of solar air heater ducts due to varied orientations of roughness geometry on the absorber plate

Second law optimization and parametric study of a solar air heater having artificially roughened absorber plate

Second law optimization and parametric study of a solar air heater having artificially roughened absorber plate

Cooling and Heating a Greenhouse in Baghdad by a Solar Assisted Desiccant System

Modeling the microclimate of a greenhouse located in Baghdad under its weather conditions to calculate the heating and cooling loads by computer simulation. Solar collectors with a V-corrugated absorber plate and an auxiliary heat source were used as a heating system. A rotary silica gel desiccant dehumidifier, a sensible heat exchanger, and an evaporative cooler were added to the collectors to form an open-cycle solar assisted desiccant cooling system. A dynamic model was adopted to predict the inside air and the soil surface temperatures of the greenhouse. These temperatures are used to predict the greenhouse heating and cooling loads through an energy balance method which takes into account the soil heat gain. This is not included in conventional methods. The results showed satisfactory agreement with published papers. Also, the results of heating and cooling loads obtained revealed good agreement with those obtained from conventional methods when the soil heat gain is included. Two identical collectors in series of total area of 5.4m2 were employed as a heating system which provides an outlet air temperature of 30 o C at air mass flux of 0.06 kg/s.m2 at midday in January. While, a 65 oC outlet air temperature was achieved for the same mass flux at midday in August. The desiccant cooling system was operated in five operating modes; the ventilation mode and four recirculation modes with 20%, 50%, 70%,and 90% recirculation. The simulation results showed that a regeneration temperature of 60-70 o C is satisfactory for a cool supply air temperature of about 19.5 o C. Also, it was noted that 20-30 % recirculation of return air would result in suitable indoor greenhouse conditions for most periods of system operation. In addition, the coefficient of performance COP of the system was high compared with the conventional vapor compression systems.

The enhancement of energetic and exergetic performance of embedded twisted rib turbulator over absorber plate of solar air heater

Owing to present investigation, a stochastic analysis is conducted to numerically optimize the energetic and exergetic efficiencies of embedded twisted rib turbulator over absorber plate of solar air heaters (SAHs). These efficiencies are assessed taking into account temperature rise and design characteristics. The criterion in context to energy efficiency do not take into consideration the pumping force which is needed to blow the air from the duct. Therefore, estimating the energy distribution of solar air heaters becomes a difficult task when evaluating their exergetic or effective efficiency. The experimental work determined the Nu and fr correlations in the term of geometrical configurations which are considered for evaluating the thermal behavior and compared to prior findings with smooth plate. The Optimal turbulator parameters were defined by the exergetic efficiency criterion in terms of the Reynolds and insolation.Maximum improvements in energetic and exergetic efficiencies were reported as ηth=1.81;ηeff=1.79andηII=1.82 times over smooth plate for a geometric arrangement with P/e =8, α =60°, y/e = 3 and Re = 5000. The maximum differences between simulated and experimental results, when taken into account, resulted ±6%. The current methodology also tackles the methods to research novel artificial turbulator to increase the energetic and exergetic performance of a SAHs, making it feasible to develop a design plot for the turbulator parameter without having to spend a lot of money on actual trials.

Performance Investigation of a Solar Air Heater Artificially Roughened With Joukowski Airfoil Ribs

Abstract This paper investigates a solar air heater’s thermohydraulic and thermogeometric performances with an artificially roughened absorber plate with Joukowski airfoil ribs. The rib height and shape have a bearing on the overall performance of the air heater. Joukowski airfoil ribs of different sizes are generated from a circular rib of a radius of 1 mm using conformal mapping. Simulations are performed for the turbulent flow of air through the roughened duct in the Reynolds number (Re) range of 4000 ≤ Re ≤ 15,000 using ansys fluent version 2020. The renormalization group kinetic energy-turbulence dissipation rate (RNGκ−ε) model with enhanced wall treatment (EWT) has been employed to model the turbulent flow. The grid refinement study is performed to optimize the mesh size and estimate the numerical solution error. The proposed rib design is tested for both headwind and tailwind flow arrangements. The tailwind performance is better for smaller-size Joukowski ribs. However, the medium- and large-size Joukowski ribs perform better in headwind configurations. At low Re, heat transfer is more dominant than friction leading to higher thermohydraulic performance, whereas, at high Re, the reverse trend is observed.

Energy recovery from the enclosures between the glassing covers in a compact photovoltaic thermal collector

The awareness of bearing the cost due to the release of carbon dioxide in the atmosphere encourages people and governments to reduce their carbon emissions through the optimization of energy production devices. This research was performed for this purpose. Compact (Integrated) solar water heater (CSWH) is the most cost-effective collector due to its simple design. The use of two glass covers along with flat reflectors has increased the efficiency of this collector. In such system, energy recovery from the enclosures between the glassing covers was not reported. In this paper, the simulation for an enhanced compact photovoltaic thermal (PVT) system in EES software is conducted. The collector is a triple production in the form of hot water (stored in water storage tank), hot air (stored in multistage phase change materials (PCMs) due to energy released from the collector two air enclosures), and electricity (generated by a-Si semi-transparent module as an absorber plate). Simulation results show a 3.4% increase in the thermal efficiency of the proposed system compared to the previous passive systems. The minimum required masses for PCMs inside two cascade tanks were obtained 8.6 (kg) of BioPCMQ23 type, and 18.7 (kg) of Lithium Nitrate Trihydrate type.

Energy, exergy, economic and environmental evaluation of solar desalination system comprising different enhanced surface absorber plates

In the present work, energy, exergy, economic and environmental evaluation of single slope solar still (SS) using multiple enhancement techniques namely, sandblasting, milling, and shot-blast aided corrugation are investigated. Totally four SS types are considered, namely (1) conventional SS, (2) sandblasted surface absorber-SS, (3) milled surface absorber-SS, and (4) shot-aided corrugated surface absorber-SS. Among the methods employed, the shot-blasted aided corrugated-absorber SS produced a maximum yield of 3275 mL/m2/day, which was 1.46 times superior to that of traditional/conventional solar still (CSS) yield (2250 mL/m2/day). Activated carbon with black paint-based spray coating (14 vol%) improved mean absorptivity by 5 %, as a result, the thermal efficiency of the SS was increased up to 57.2 % as compared to traditional SS. The exergoeconomic factor of the SS with sandblasted, milling, and shot-blasted aided corrugation was SS was 25.2, 62.8, and 98.5 % respectively greater than CSS. More importantly, the energy payback time for CSS, sandblasted SS, milling SS, and shot-blasted SS were 1.49, 1.498, 1.396, and 1.065 years, respectively. Also, the exergy payback time for CSS, sandblasted SS, SS with milling, and SS with shot-blast aided corrugation were 5.99, 5.05, 3.90, and 3.23 years respectively.

Thermal performance assessment of an indirect solar dryer: A case study of Bananas

This study presents a design for an absorber used in a solar air collector for an indirect solar dryer. The absorber comprises two aluminium plates corrugated and joined together to form parallel cylinders, enabling airflow within the collector. This research aims to experimentally examine the drying process of two types of bananas, one from Morocco and the other from abroad, using the designed solar air collector. Additionally, the study aims to investigate the peculiarities of the drying process and the performance of the solar dryer employed. The experiments were conducted by subjecting the bananas to the designed solar air collector, and the evolution of drying was monitored. The initial mass of the bananas used was 631.6 g for the Moroccan banana and 713.6 g for the Export banana. After the drying process, the mass of the Moroccan banana reduced to 77.5 g, while the Export banana reduced to 137.3 g, indicating significant moisture removal. The percentage of the amount of water extracted (Q) from the bananas was found to be 87.7% for the Moroccan banana and 80.8% for the Export banana. These results demonstrate the effectiveness of the corrugated aluminium plate absorber in facilitating the drying process in the solar air collector. The significant reduction in the mass of the bananas and the high percentage of water extraction highlight the efficiency of the solar dryer in removing moisture from the agricultural produce. The findings of this study contribute to the understanding of the drying process of bananas and offer valuable insights for the design and optimization of solar drying systems for agricultural applications.

Energy and exergy study of a novel multi-mode solar dryer without and with sensible heat storage for Garcinia pedunculata

ABSTRACT In the present analysis, a novel four-mode solar dryer was developed and tested for the drying of Garcinia pedunculata. The four combinations considered were indirect-mode solar dryer without storage (ID-WOS), mixed-mode solar dryer without storage (MX-WOS), indirect-mode solar dryer with storage (ID-WS), and mixed-mode solar dryer with storage (MX-WS). The feature of this dryer that sets it apart is its capability to convert the drying cabinet into various modes simply by sliding the walls of the four sides of the cabinet. The storage system is made space efficient, by filling the gravel up to the surface of the absorber plate inside the solar air collector. For ID-WOS, MX-WOS, ID-WS, and MX-WS, respectively, the drying durations were 30 h, 25 h, 28 h, and 8 h, and the drying efficiencies were 18.55%, 24.03%, 20.32%, and 29.94%. In ID-WOS, MX-WOS, ID-WS, and MX-WS, the average exergy efficiency was determined as 47.08%, 65.10%, 52.46%, and 68.07%, respectively. Environmental impact was studied for all four cases. The energy payback periods for ID-WOS, MX-WOS, ID-WS, and MX-WS were 1.47, 1.61, 1.48, and 1.62 years, respectively. The study indicated that MX-WS outperformed the other three configurations in all aspects.

Effect of graphene nanopaint on performance of solar air heater attached with inclined and winglet baffles.

Solar air heater is widely used for drying and industrial processing application. Different artificial roughened surfaces and coatings over the absorber plates are used to improve their performance of solar air heater by increasing absorption and heat transfer. In this proposed work, the graphene-based nanopaint is prepared by wet chemical and ball milling method and the prepared graphene nanopaint is characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The prepared graphene-based nanopaint is coated on the absorber plate by conventional coating method. The thermal performance of the solar air heater coated with traditional black paint and graphene nanopaint is evaluated and compared. The day's maximum energy gain by the graphene-coated solar air heater is 972.84 W, whereas traditional black paint is only 808.02 W. The average energy gain of graphene nanopaint is 655.85 W, which is 12.9% higher than the traditional black paint. The maximum thermal efficiency for solar air heater coated with graphene nanopaint is 81%. Also the average thermal efficiency of graphene-coated solar air heater is 72.5%, which has a 13.24% higher average thermal efficiency when compared to conventional black paint-coated solar air heater. The average top heat loss for solar air heater coated with graphene nanopaint is 8.48% lower than solar air heater with traditional black paint.

Orbital box osteotomy in frontonasal dysplasia with severe hypertelorism: Our first experience

ABSTRACT Frontonasal dysplasia (FND) is a rare craniofacial deformity, including severe hypertelorism. We herein presented the case of a 6-year-old female patient with FND and Grade III hypertelorism who underwent a four-wall-orbital box osteotomy with a bicoronal approach. Orbital wall osteotomy was performed behind the lacrimal fossa. Central resection was done to allow for medial translocation of the orbits. At the last, the newly positioned orbitals were fixated using wire, absorbable plates, and screws. Neurosurgical assistance with the frontal bone flap before orbital osteotomy helps to leave the cribriform plate intact to preserve the olfactory. Finally, excessive median soft tissue was excised. The patient’s hypertelorism improved after surgery. Careful surgical procedures to correct the soft and bony tissue are beneficial treatments for improving the quality of life and general condition of patients with hypertelorism.