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1
Content available Numerical assessment of solar air heater performance having a broken arc and broken S-shaped ribs as roughness
Haldia Shivam, Bisht Vijay Singh, Bhandari Prabhakar, Ranakoti Lalit, Negi Akashdeep
Archives of Thermodynamics
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2024
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Vol. 45, no 1
23--31
EN
This research article aims to provide a detailed numerical study of the multifaceted impact of S-shaped and broken arc roughness on solar air heaters. Therefore, a strong comparison was made between the modified heaters and smooth heaters for Reynolds numbers ranging from 2 00022 000. Also, the impact of two parameters, i.e. pitch and gap was analyzed to optimize the performance of the heater. The gap varies from 0.3 mm to 0.9 mm in both types of ribs with a step size of 0.2 mm. Afterwards, the pitch distance between both types of roughness was varied from 15 mm to 25 mm in the step size of 5 mm. Notably, it has been observed that among all the considered configurations, the gap length of 0.9 mm and pitch length of 25 mm have shown significant improvements in heat transfer characteristics. The specific combination of the gap of 0.9 mm and pitch of 25 mm has demonstrated better heat transfer capabilities at the expense of an increased friction factor. Lastly, the thermal performance factor of the systems was analyzed and reported. It was reported that the pitch length of 25 mm and gap length of 0.9 mm have shown a maximum thermal performance factor value from 2.9 to 3.3, while the pitch length of 25 mm and gap length of 0.3 mm have depicted the lowest thermal performance factor value. In terms of the overall performance, i.e. the thermal performance factor, the combination with a gap of 0.9 mm and pitch of 25 mm has shown the best performance, while a gap of 0.3 mm and pitch of 25 mm has yielded the worst performance.
2
Content available Effect of D-shaped, reverse D-shaped and U-shaped turbulators in solar air heater on thermo-hydraulic performance
Ghildyal Abhishek, Bisht Vijay Singh, Bhandari Prabhakar, Rawat Kamal Singh
Archives of Thermodynamics
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2023
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Vol. 44, no 2
3--20
EN
As the cost of fuel rises, designing efficient solar air heaters (SAH) becomes increasingly important. By artificially roughening the absorber plate, solar air heaters’ performance can be augmented. Turbulators in different forms like ribs, delta winglets, vortex generators, etc. have been introduced to create local wall turbulence or for vortex generation. In the present work, a numerical investigation on a solar air heater has been conducted to examine the effect of three distinct turbulators (namely D-shaped, reverse D- and U-shaped) on the SAH thermo-hydraulic performance. The simulation has been carried out using the computational fluid dynamics, an advanced and modern simulation technique for Reynolds numbers ranging from 4000 to 18000 (turbulent airflow). For the purpose of comparison, constant ratios of turbulator height/hydraulic diameter and pitch/turbulator height, of 0.021 and 14.28, respectively, were adopted for all SAH configurations. Furthermore, the fluid flow has also been analyzed using turbulence kinetic energy and velocity contours. It was observed that the U-shaped turbulator has the highest value of Nusselt number followed by D-shaped and reverse D-shaped turbulators. However, in terms of friction factor, the D-shaped configuration has the highest value followed by reverse D-shaped and U-shaped geometries. It can be concluded that among all SAH configurations considered, the U-shaped has outperformed in terms of thermohydraulic performance factor.
3
Content available remote Characterization of SiC particle reinforced copper matrix composite with copper wire structure
Singh Ashish, Srivastava Rajeev, Bisht Vijay Singh, Bhandari Prabhakar
Composites Theory and Practice
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2022
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R. 22, nr 3
178--183
EN
Composites have become a very important class of materials in our everyday life. In the present work, the effect of a copper wireframe structure in SiC particle reinforced copper matrix composites on the compressive strength and other physical properties was analysed. SiC particle reinforced copper matrix composites with and without a copper wireframe structure were fabricated by the powder metallurgy method and sintering was performed at 700°C in atmospheric condition. The copper wire used for making the wireframe structure has diameters of 0.2 and 0.3 mm. A scanning electron microscope (SEM) with magnification of 500X was used to characterize the sintered composites. In addition, hardness tests were performed on a Vickers hardness testing machine and compression testing was carried on a UTM machine. It was observed that the formation of Cu reinforced with 5-7 wt.% SiC and 0.1-0.2 wt.% copper wireframe structure composites was successful. It can be concluded that the hardness of the Cu-SiC composite rises with the increase in the wt.% of reinforcement, while the copper wireframe structure in the composite had a negligible effect on the hardness. However, the addition of the copper wireframe structure resulted in increased compressive strength.
4
Content available Numerical study of car radiator using dimple roughness and nanofluid
Thapa Robin Kumar, Bisht Vijay Singh, Bhandari Prabhakar, Rawat Kamal Singh
Archives of Thermodynamics
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2022
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Vol. 43, no 3
125--140
EN
Thermal augmentation in flat tube of car radiator using different nanofluids has been performed more often, but use of artificial roughness has been seldom done. Artificial roughness in the form of dimple is used in the present research work. Present study shows the impact of dimple shaped roughness and nanofluid (Al2O3/pure water) on the performance of car radiator. The pitch of dimples is kept at 15 mm (constant) for all the studies performed. The Reynolds number of the flow is selected in the turbulent regime ranging from 9350 to 23 000 and the concentration of the nanofluid is taken in the range of 0.1–1%. It has been found that the heat transfer rate has improved significantly in dimpled radiator tube on the expense of pumping power. Furthermore, the heat transfer rate also increases with increase in nanoparticle concentration from 0.1% to 1.0%. The highest heat transfer enhancement of 79% is observed at Reynolds number 9350, while least enhancement of 18% is observed for Reynolds number of 23 000.
5
Content available Thermodynamic analysis of combined ORC-VCR system with recuperator and reheater
Rawat Kamal Singh, Bhandari Prabhakar, Bisht Vijay Singh
Acta Innovations
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2022
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no. 44
34--44
EN
The trend of utilization of low-grade thermal energy gain huge attention due to increase in energy demand and depletion of conventional resources of energy. Low grade energy can be used in ORC-VCR cycle for refrigeration purpose. In the present work, to improve the performance a modified ORC-VCR cycle, recuperator and reheater are integrated in the cycle. The thermodynamic analysis of the modified system has been conducted with R600a, R600, R290 and R1270 as working fluids under various operating conditions viz. evaporator temperature, condenser temperature, boiler exit temperature. Different parameters evaluated to assess the performance are overall COP, mass flow rate per kW cooling capacity, expansion ratio and compression ratio. From the analysis, butane is found as a best choice for the modified ORC–VCR cycle. It was found that for the modified ORC-VCR cycle at boiler exit temperature of 90°C and condenser temperature 40°C has system COP of 0.5542 with butane, which is 7.1% and 18% higher than that of ORC-VCR cycle with recuperator and simple ORC-VCR cycle, respectively.
6
Content available Economic analysis of artificially roughened solar air heater with v-shaped ribs
Bahuguna Rahul, Chamoli Sunil, Barthwal Yogesh, Rana Sumit, Gupta Ashutosh, Bisht Vijay Singh
Acta Innovations
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2022
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no. 44
18--33
EN
Due to the minimal transfer of heat from absorber plate to moving air in the duct, solar air heaters have low performance. One of the procedures to augment the heat transfer by substantial amount is by utilizing artificial roughness, by which the performance can be improved considerably. In this study, an economic investigation of solar air heater embedded with artificial roughness is accomplished numerically employing v-shaped roughness, with the objective of optimising life cycle solar savings. The non-dimensional parameters of roughness, namely, angle of attack (α), roughness pitch (p/e) and roughness height (e/Dh) are examined by varying temperature rise over the solar air heater (∆T) and solar radiations (I) for different economic parameters values i.e., cost of collector, cost of roughness elements, and cost of conventional fuel.
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