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1

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.

2

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.

3

An experimental study of solar air heater using arc shaped wire rib roughness based on energy and exergy analysis

Ghritlahre Harish Kumar

Archives of Thermodynamics

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2021

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Vol. 42, no 3

115--139

EN

In the present study, energy and exergy analysis has been evaluated for roughened solar air heater (SAH) using arc shaped wire ribs. To achieve this aim, two different types of flow arrangement have been considered. These arrangements are: apex upstream flow and apex downstream flo. In addition to this, a smooth duct SAH has been used for comparative study. The experiments were performed using the mass flow rate of 0.007– 0.022 kg/s on outdoor condition at Jamshedpur city of India. The absorber plate roughness geometry has been designed with relative roughness height 0.0395, rib size 2.5 mm, relative roughness pitch 10 and arc angle 60◦ . The energetic and exergetic performances have been examined on the basis of the first and second law of thermodynamics. According to the results, there is observed to be the maximum thermal efficiency and exergy efficiency as 73.2% and 2.64%, respectively, for apex upstream flow SAH at 0.022 kg/s, while, at same mass flow rate the maximum thermal efficiency and exergy efficiency is obtained as 69.4% and 1.89%, respectively, for apex downstream flow SAH. In addition to this, results reported that the maximum outlet temperature and temperature difference observed at lower mass flow rate. Also examined the outlet air temperature of SAH with various mass flow rates is very important for both analysis.

4

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

Sahu Mukesh Kumar, Matheswaran M. M., Bishnoi Pardeep

Archives of Thermodynamics

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2020

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Vol. 41, no 3

147--182

EN

This paper presents the outdoor experimental results for thermal performance analysis of artificially roughened solar air heaters (SAHs). Circular wire ribs have been arranged to form arc shape geometry on the absorber plates and have been tested for two configurations of SAHs named as arc shape apex-downstream flow and arc shape apex-upstream flow SAH. Roughness parameters have been taken as relative roughness pitch in the range of 8–15, angle of attack 45°–75°, and for fixed relative roughness height of 0.0454, duct width to duct height ratio of 11. During the experimental analysis the mass flow rate varied from 0.0100 to 0.0471 kg/s. Based on the experimental results it was found that roughness with apexupstream flow SAH is having higher value of thermal efficiency, heat removal factor and collector efficiency factor as compared to roughness with apexdownstream flow SAH and simple absorber plate SAH. In the range of the operating parameters investigated the maximum of thermal efficiency, heat removal factor, and collector efficiency factor have been found.

5

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

Sahu Mukesh Kumar, Prasad Radha Krishna

Archives of Thermodynamics

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2019

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Vol. 40, no 2

107--135

EN

In present article a mathematical model of arc shape wire roughened solar air heater, on the basis of energy and exergy output rates, entropy generation rate and augmentation entropy generation number, has been developed. A parametric study leading to entropy generation minimization has also been performed. In the analysis the geometric and operating parameters which have been considered as variable are: inlet air temperature, duct depth, collector width to duct depth ratio, mass flow rate per unit collector area, and temperature rise parameter. Results have been presented to see the effects of these values on the energy and exergy output rates of the roughened solar air heater. Effect of different values of wire rib roughness parameters on entropy generation has also been presented. Finally, design curves and optimization for different rib roughness parameters on the basis of minimum entropy generation number with temperature rise parameter, have been presented and optimum values also have been found out 0.004 to 0.010 (Km2 )/W. The entropy generation rate obtained for the system, in the present work has been compared with those obtained for solar air heater with different roughness geometries on absorber plates available in the literature for common roughness parameters and operating parameters which validate the present results.