Performance analysis of triple-pass solar air heater system: Effects of adding a net of tubes below absorber surface

Jul 11, 2020

Journal Solar Energy

publisher Elsevier

DOI https://doi.org/10.1016/j.solener.2020.07.041

Issue 207

In this article, two triple-pass solar air heater (TPSAH) collectors have been experimentally investigated to analyse their performances through adding a net of tubes below the absorber surface and double glass cover on one of them for purpose of comparison. The first collector (TPSAH-1) has been covered with a single glass, whereas the second collector (TPSAH-2) has been covered with a double glass and adding a net of tubes below the absorber surface. The experiments for each system have been carried out in winter and compared under the same weather conditions. For all air mass flowrates, the results indicated that TPSAH-2 produces a higher efficiency as compared to TPSAH-1, where the maximum efficiency for high air mass flowrate have been obtained equal to 80.2% and 73.4%, respectively. A considerable temperature difference has been observed when using TPSAH-2 in comparison with that obtained using TPSAH-1. The improvement in the efficiency of TPSAH-2 compared to TPSAH-1 confirms that the adding of a net of tubes and additional glass cover have significant influence on heat transfer rate. The air mass flowrate has a substantially impact as compared to temperature difference. Thus, the performance of TPSAH is directly proportional to rise in air mass flowrate. For TPSAH-1, the glass, plate and outlet temperatures have been always found lower than TPSAH-2. Based on the outlet air temperature, it can be concluded that TPSAH-2 can be used for the applications that required large temperature difference and TPSAH-1 for the applications that required small temperature difference.

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Mixed convective of hybrid nanofluids flow in a backward-facing step

Dec 27, 2020

Journal Case Studies in Thermal Engineering

publisher Elsevier

DOI https://doi.org/10.1016/j.csite.2021.100868

Issue 25

Convective of hybrid nanofluids heat transfer flow over backward facing step in a heated rectangular duct under laminar flow is performed experimentally. It is used mixing of Al2O3 and TiO2 solid nanoparticles suspended in pure water. The preparation process of hybrid nanofluid for 1%, 2% and 3% mass fraction has been conducted. The test rig of this experimental study has been fabricated then both temperature and pressure drop along the duct have been measured. The duct is heated from the bottom by using an electrical heater and the other walls are being insulated. Results of heat transfer enhancement and pressure drop are indicated. It was observed that Nusselt number increases with increase of Reynolds number and mass fraction while, friction factor decreases as decrease of Reynolds number and increase of mass fraction. It is concluded that significant using the hybrid nanofluid through facing step. The enhancement of heat transfer and pressure drop are approximately 14% and 4% respectively.

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Impacts of adding porous media on performance of double-pass solar air heater under natural and forced air circulation processes

Aug 10, 2021

Journal International Journal of Mechanical Sciences

publisher Elsevier

DOI https://doi.org/10.1016/j.ijmecsci.2021.106738

Issue 210

This paper presents an experimental work on two trapezoidal double-pass solar air heaters (DPSAH) having double glass covers under natural and forced air circulation conditions to investigate their performances by adding packed beds above the absorber surface on one them for target of comparison. The DPSAH-1 has been operated with adding porous medium, whereas DPSAH-2 has been operated without adding porous medium. Experiments for each model have been performed in winter and compared under identical conditions. The results demonstrate that DPSAH-1 considerably enhances the system performance as compared to DPSAH-2. Results also indicate that the higher efficiency has been obtained when the systems are operated under natural convection. The peak efficiencies of DPSAH-1 and DPSAH-2 have been obtained equal to 87% and 82% for natural convection case and 81% and 67% for forced convection case for lower air mass flowrate, respectively. A considerable temperature difference has been found with natural process as compared to forced process. The advancement in performance of DPSAH-1 confirms that the adding porous medium and types of air circulation have considerable impact on heat transfer rate. Therefore, it can be concluded that DPSAH-1 is better than DPSAH-2, particularly for forced convection case including the applications that needs high temperatures and vice-verse.

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Experimental Investigation on the Effect of Sawdust Particles Size on Its Thermal Conductivity

Apr 2, 2023

Journal International Journal of Heat and Technology

publisher Edizioni ETS

DOI https://doi.org/10.18280/ijht.410224

Issue 2

Volume 41

The measurement of the thermal conductivity of the sawdust is one of the most difficult techniques due to its uniformed shape, by using this instrument, it gives the ability of measuring the thermal conductivity of the sawdust, without changing its physical properties, during the experiment, as well as, there are no necessity to use the additional materials in form of adhesive materials, that gives an identified shape of the specimen. In this study, wood sawdust is classified into three groups depending on the size of the wood pellets, namely; wo1.1.18mm, 1.18>wo2>0.6mm and wo3.0.6mm. To keep out the thermal properties of the sawdust as it is, no mechanical or chemical processes were carried out on sawdust specimens, such as compressing or bonding. The effect of moisture content on the thermal properties of sawdust is eliminated by drying the specimens, the procedure is carried out by heating it up to 100Ž for a 30 min. During this study, it can be seen that the thermal conductivity of all samples is inversely proportional to the working temperature. At a relatively low temperature less than 45Ž, it can be said that the first model (wo1) has the lowest thermal conductivity while the differences in the thermal conductivity of the samples are insignificant when the temperature exceed 50Ž, therefore; the first model (wo1) represents a good choice for flat plate solar collector insulation because it has the same activity as well as it is light and cheap.

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Impacts of geometric configurations on performance of discharge coefficient and wall pressure of Venturi meter under high Reynolds number

Apr 9, 2024

Journal INTERNATIONAL JOURNAL OF VENTILATION

publisher Taylor & Francis Group

DOI 10.1080/14733315.2024.2344992

Issue 4

Volume 23

The performance of discharge coefficient (Cd) and wall pressure of Venturi meter under various convergent and divergent cone angles have been experimentally investigated. Several models of tubes have been examined, where the tubes have been manufactured with two convergent angles (20� and 40�) and three divergent angles (7�, 11� and 15�). A pipe system along with ten tapping points distributed along the Venturi meter wall has been utilised to measure the static pressure. The examinations have been done for wide ranges of Reynolds number (Re). Results of Cd have been compared with the empirical solutions and they show a good agreement between them with a relative difference less than 3.5%. As Re is increased until Re¼15000, the results of Cd is substantially increased. Results display that the convergent angle has a less impact on Cd and a major influence on pressure drop as compared to divergent angle. Divergent angle has an inversely impact on Cd. The best value of Cd has been obtained when using the tube that has a convergent angle of 7� and divergent angle of 20�. Present results clearly demonstrate the necessity of choosing the required geometric parameters accurately while designing Venturi meter to achieve the optimum performance

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Impact of CuO+H2O nanofluid on the cooling towers performance with varying packing densities

Mar 17, 2025

Journal Results in Engineering

publisher Elsevier

DOI https://doi.org/10.1016/j.rineng.2025.104664

Issue 26

with varying numbers of layers have been employed to investigate the impacts of packing density on the CT performance when using Copper Oxide (CuO) nanofluid as a working fluid. Three different concentrations (1, 3, and 5 %) of CuO+H2O nanofluid have been evaluated to assess the influence of nanoparticle concentration on the CT performance. The results show that adding more packing layers improves the thermal performance of the CT, regardless of the use of pure water or nanofluid. The effect is more pronounced when CuO+H2O nanofluid is employed. Furthermore, at a volume concentration of 5 % CuO+H2O nanofluid, the water temperature differential, cooling tower characteristic, and cooling efficiency increased by 15.3, 7, and 12.5 %, respectively, compared to pure water. However, the tower characteristic tends to increase for lower concentrations (3 %), but may decrease for higher concentrations (5 %). Nonetheless, the tower characteristic may ultimately increase for all concentration levels. Additionally, the impact of CuO+H2O nanofluid on temperature difference becomes more pronounced as the packing density increases. For example, the temperature differential of the water increases by around 7.5 % and 24.3 % for 7 and 20-layer packing, respectively. These findings suggest that utilizing CuO+H2O nanofluid as a circulating fluid in place of pure water can lead to improved thermal performance of CTs.

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