scholarly journals Numerical modeling of an innovative arc shape rib based solar air heater

2021 ◽  
pp. 095440622110395
Author(s):  
Hamid Kazemi Moghadam ◽  
Seyed Soheil Mousavi Ajarostaghi ◽  
Sébastien Poncet
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Thermal Efficiency ◽  
Reynolds Numbers ◽  
Heat Transfer Process ◽  
Coefficient Of Performance ◽  
Solar Air Heater ◽  
Air Heater ◽  
Arc Shape ◽  
Section Type

Solar air heating is a solar thermal technology wherein the sun energy is absorbed by an intermediate medium and utilized to heat air. In the present paper, a solar air heater equipped with innovative arc shaped ribs is considered. The heat transfer process in the proposed solar air heater is evaluated numerically for Reynolds numbers between 6000 and 12000. The influences of the rib cross section type, the inter-rib distance, the aspect ratio and the pitch of the ribs on the thermal efficiency of solar air heater are analyzed. Results indicate that firstly, ribs with quadrangular type of cross section exhibit the best coefficient of performance. Moreover, ribs with low pitch (40 mm) and aspect ratio equal to 0.5 show the highest thermal performance. Also, the effect of the distance between the ribs on the thermal efficiency of the considered solar air heater is insignificant. Finally, two correlations are obtained for the average Nusselt number and friction factor based on three dimensionless geometric factors.

Topology of vortex breakdown in closed polygonal containers

2017 ◽  
Vol 820 ◽  
pp. 263-283 ◽  
Author(s):  
Igor V. Naumov ◽  
Irina Yu. Podolskaya
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Vortex Breakdown ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Cylindrical Container ◽  
Stagnation Points ◽  
Aspect Ratios ◽  
Particle Visualization ◽  
Cross Section Geometry

The topology of vortex breakdown in the confined flow generated by a rotating lid in a closed container with a polygonal cross-section geometry has been analysed experimentally and numerically for different height/radius aspect ratios $h$ from 0.5 to 3.0. The locations of stagnation points of the breakdown bubble emergence and corresponding Reynolds numbers were determined experimentally and numerically by STAR-CCM+ computational fluid dynamics software for square, pentagonal, hexagonal and octagonal cross-section configurations. The flow pattern and velocity were observed and measured by combining seeding particle visualization and laser Doppler anemometry. The vortex breakdown size and position on the container axis were identified for Reynolds numbers ranging from 500 to 2800 in steady flow conditions. The obtained results were compared with the flow structure in the closed cylindrical container. The results allowed revealing regularities of formation of the vortex breakdown bubble depending on $Re$ and $h$ and the cross-section geometry of the confined container. It was found in a diagram of $Re$ versus $h$ that reducing the number of cross-section angles from eight to four shifts the breakdown bubble location to higher Reynolds numbers and a smaller aspect ratio. The vortex breakdown bubble area for octagonal cross-section was detected to correspond to the one for the cylindrical container but these areas for square and cylindrical containers do not overlap in the entire range of aspect ratio.

scholarly journals Various Designs of Solar Collectors for Enhancement of Thermal Performance

2011 ◽  
Vol 8 (1) ◽  
pp. 101-105
Author(s):  
M. K. Lalji ◽  
R. M. Sarviya ◽  
J. L. Bhagoria
Keyword(s):  
Thermal Performance ◽  
Thermal Efficiency ◽  
Energy Demand ◽  
Packed Bed ◽  
Wire Mesh ◽  
Solar Air Heater ◽  
Air Heater ◽  
The Matrix ◽  
Solar Heater ◽  
Economical Alternative

Solar energy is an economical alternative to the today's energy demand. Solar air heater is used for heating the air economically but produces low thermal efficiency. In this paper, an attempt has been made to study the design of solar heaters to increase the thermal efficiency. The matrix solar air heater with a wire mesh produces higher thermal efficiency over the conventional flat plate solar air heater. The evaluation of different methods for increasing efficiency of packed bed solar air heater has been done . Effect of different parameters on thermal efficiency of solar heater has also been studied.

scholarly journals Thermal Analysis of Solar Air Heater with Ventilator Turbine and Fins

2020 ◽  
Vol 8 (2) ◽  
pp. 510-523
Author(s):  
Arrad Ghani Safitra ◽  
Lohdy Diana ◽  
Denny Muhammad Agil ◽  
Julfan Hafiz Fareza ◽  
Nu Rhahida Arini
Keyword(s):  
Thermal Efficiency ◽  
High Performance ◽  
Outlet Section ◽  
Inlet Section ◽  
Solar Air Heater ◽  
Drying Process ◽  
Air Velocity ◽  
Absorber Plate ◽  
Air Heater ◽  
Measurement Tools

Solar air heater (SAH) is a renewable energy application for the drying process. SAH has a challenge to produce high performance under uncertain weather. The performance of SAH can be enhanced by providing the absorber plate by adding the fins. This study aims to evaluate the thermal performance of SAH with rectangular fins SAH at low air velocity. This study compares the performance of SAH without fins and SAH with rectangular fins. Two variations of a tilt angle of SAH are 0° and 30° which are observed in this study. The SAH uses a ventilator turbine to suck air into the collector box. The air velocity is 0.01 m/s. The method is experimental. The SAH is tested under real condition from 9 a.m. to 4 p.m. The measurement tools consist of  a pyranometer, an anemometer, a temperature sensor in the inlet section, 3 sensors in the absorber plate, a sensor in the outlet section,  6 temperature sensors in the drying cabinet. The result showed the thermal efficiency of SAH with rectangular fins is 29.67 % higher than SAH without fins at 0˚ tilt of angle at noon. The thermal efficiency of SAH with rectangular fins is 25.26 % higher than  that of without fins at 30˚ tilt of angle at noon.

Experimental Investigation on Thermal Performance in Three-Sided Solar Air Heaters Having an Alignment of Multi-v and Transverse Wire Roughness on the Absorber Plate

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Dhananjay Kumar ◽  
Laljee Prasad
Keyword(s):  
Thermal Performance ◽  
Thermal Efficiency ◽  
Roughness Height ◽  
Space Heating ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Absorber Plate ◽  
Air Heater ◽  
Relative Roughness ◽  
Operational Constraints

Abstract The use of artificial roughness is an efficient and commercial way to appreciate the thermal performance from the collector to the air in solar air heater ducts, for numerous applications such as space-heating, crop-drying, and seasoning of timber industrial purpose. In this paper, the tentative inquiry on thermal enactment using new-fangled of three-sided roughened quadrilateral duct solar air heater having an alignment of multiple-v and transverse wire is performed and compared the outcomes with smooth duct air heater under similar operational circumstances. The modification of an arrangement and operational constraints is inspected within the restrictions, the moral of four-sided duct aspect ratio (W/H) = 8, the Reynolds number occupied from 3000 to 12,000, fraction of pitch to roughness height, P/e in the range of 10–25; ratio of roughness height to hydraulic diameter, e/D in the range of 0.018–0.042; at flow attack angle, α = 60 deg for constant moral of relative roughness width, (W/w) = 6. The augmentation on thermal efficiency in three-sided rugged duct is found to be 23–86% when compared to smooth duct, and the maximum thermal efficiency can occur at P/e = 10 and e/D = 0.042. The enhancement in air temperature flowing under three-sided roughened duct is found to be 49.27% more than that of a smooth duct. The instant innovative form of three-sided roughened solar air warmer would be preferable to those of a smooth solar air heater with respect to heat assignment.

scholarly journals Thermal Evaluation of a Double-Pass Unglazed Solar Air Heater with Perforated Plate and Wire Mesh Layers

2020 ◽  
Vol 12 (9) ◽  
pp. 3619
Author(s):  
Afaq Jasim Mahmood
Keyword(s):  
Flow Rate ◽  
Thermal Efficiency ◽  
Air Flow ◽  
Wire Mesh ◽  
Inlet Temperature ◽  
Solar Air Heater ◽  
Outlet Temperature ◽  
Air Flow Rate ◽  
Double Pass ◽  
Air Heater

In this study, an experimental outdoor investigation of the thermal efficiency and outlet air temperature was conducted on an unglazed, double-pass, solar air heater with a perforated absorber plate and packing wire mesh layers as a supplemental absorbent area. This was done to observe their effects on the thermal performance of the solar air heater. The double-pass collector was constructed with a bed height of 0.05 m, and a collection area of 1.5 m2. The height of the upper channel was fixed at 0.015 m to improve the thermal efficiency, and the outlet temperature at air flow rates between 0.003 and 0.018 kg/s. The collector was mounted with a slope of 42° facing south, to maximize the intensity of solar irradiance during winter. The effects of the air flow rate, ambient temperature, inlet temperature, outlet temperature, and solar intensity were experimentally investigated. The results showed that thermal efficiency could be improved by increasing the air flow rate, where the highest thermal efficiency achieved was 86% at 0.018 kg/s. However, the temperature difference was increased to a maximum value of 38.6 °C, when the air flow rate was decreased to 0.003 kg/s. Furthermore, the results demonstrated a significant improvement in the thermal efficiency and outlet temperature; and when compared with previous research, the experimental results and the predictions for the outlet temperature using the theoretical model agreed.

Heat Transfer Characteristic Inside Two-Pass Variable Cross-Section Channels With Ribs and Bleed Holes

2004 ◽  
Author(s):  
Xiangyun Liu ◽  
Shuiting Ding ◽  
Zhi Tao ◽  
Guoqiang Xu
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Transfer Characteristic ◽  
Reynolds Numbers ◽  
Variable Cross Section ◽  
Heat Transfer Process ◽  
Variable Cross ◽  
Relative Roughness ◽  
Cross Section Area ◽  
Section Area

Heat transfer characteristics were experimentally studied for two-pass channels with variable cross-section with and without ribs. Rectangular ribs were placed symmetrically on two opposite walls with attack angles of 90° and 60° to the main flow. The bleed holes were only distributed on the rib roughened surface along the second pass. The cross-section area of the channel varied in the way that it increased along the first pass and decreased along the second. The relative roughness heights were 0.092 and 0.123; the relative roughness pitches were 10 and 20. The experiments were carried out at Reynolds numbers from 7100 to 60000. Analysis of the experimental results may lead to the following conclusions: (1) The heat transfer was enhanced by the presence of variable cross section. (2) The 60° ribs was not necessarily the optimistic option as published in the literature, test showed that 90° ribs produced a hither heat transfer for the relative roughness height of 0.092. (3) For up to 30% of bleeding were outlet, the existence of bleed holes enhanced the heat transfer process.

scholarly journals Nusselt Number and Friction Factor Correlations Development for Arc-Shape Apex Upstream Artificial Roughness in Solar Air Heater

2021 ◽  
Author(s):  
Mukesh Kumar Sahu ◽  
Manjeet Kharub ◽  
Mahalingam Murugesan Matheswaran
Keyword(s):  
Nusselt Number ◽  
Friction Factor ◽  
Roughness Element ◽  
Circular Cross Section ◽  
Solar Air Heater ◽  
Enhancement Ratio ◽  
Air Heater ◽  
Relative Roughness ◽  
Evaluation Of Performance ◽  
Arc Shape

Abstract In the present work an outdoor experimental investigation for solar air heater with arc-shaped apex-upstream flow by the use of circular cross section wires as roughness elements has been carried out. The roughness-element have been expressed in non-dimensionalizing geometric parameters as relative roughness-pitch (P/e), relative roughness-height (e/D) and flow attack-angle (α/60), and the range of these parameters varies from 8 to 15, 0.0454, and 0.75 to 1.25, respectively. For evaluation of performance of the roughened SAH, a novel parameter has been proposed and introduced in the present investigation which is Thermo-Hydraulic Improvement Parameter (THIP). With the use of present roughness geometry, considerably Nusselt number enhancement ratio (NNER) and friction factor enhancement ratio (FFER) have been observed. The maximum NNER and FFER values obtained experimentally is about 2.83 and 1.79 times, respectively. While, the maximum THIP has been obtained 157.49% higher than the smooth SAH. Using the experimental results correlations for the output parameters (Nusselt number and friction factor) as a function of input parameters (flow and roughness) have been developed.

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