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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.

2

Effect of artificial coarseness on the performance of rectangular solar air heater duct: a comparative study

Dubey Manoj Kumar, Prakash Om

Archives of Thermodynamics

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2023

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Vol. 44, no 3

325--358

EN

Solar air heater is regarded as the most common and popular solar thermal system and has a wide range of applications, from residential to industrial. Solar air heater is not viable because of the low convective heat transfer coefficient at the absorber plate which contributes to decreasing the thermal efficiency. Artificial coarseness on the plain surface is the most effective method to enhance heat transfer with a moderate rate of friction factor of flowing air in the design of solar air heater duct. The different parameters and different artificial coarseness are responsible to alter the flow structure and heat transfer rate. Over the years different artificial roughness and how its geometry affects the performance of solar air heater have been thoroughly studied. Various investigators report the correlations between heat transfer and friction factors. In the present study, a comparison of several artificial coarseness geometries and methods with a view to enhancing the performance of solar air heater has been made. A brief outline has also been presented for future research.

3

Analiza cieplno-hydrauliczna układu dolotowego i wylotowego silnika samochodowego

Frańczuk M., Nemś A.

Logistyka

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2015

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nr 3

1319--1328, CD 1

PL

W pracy przedstawiono odmienny od spotykanego sposób analizy sprawności jednostki napędowej samochodu. Analizowano sprawność jednostki napędowej jako wynik sprawności cieplnej silnika oraz strat wynikających z oporów hydraulicznych w układzie wlotowym i wylotowym. Zwrócono uwagę na występujące obecnie w motoryzacji trendy oraz wymogi emisyjne dotyczące współcześnie budowanych silników samochodowych. W pracy zestawiono spadki ciśnień występujące w poszczególnych elementach układu dolotowego i wylotowego znajdującego się w seryjnie produkowanym samochodzie osobowym. Przeanalizowano 21 elementów układu ssącego i 16 wydechowego. Zaprezentowano również możliwe do wykonania modyfikacje tych układów mające na celu zmniejszenie oporów przepływu. W artykule omówiono również wpływ występujących oporów hydraulicznych na sprawność jednostki napędowej dla całego zakresu prędkości obrotowych jednostki napędowej. W ostatniej części poddano rozważaniom konsekwencje wynikające z proponowanej analizy cieplno-hydraulicznej pojazdu.

EN

This paper presents a method of the car engine efficiency analysis which is different from that can be found in literature. The efficiency of the vehicle was analyzed both in terms of the engine thermal efficiency and losses resulting from hydraulic resistance in the inlet and exhaust system of the combustion engine. Development trends in the automotive industry and emissions requirements related to the modern automobile engines were pointed out. The pressure drops occurring in the different parts of the inlet and exhaust system of the series-production passenger car were also presented in this paper. Twenty-one elements of the inlet and 16 elements of the exhaust system were analyzed. The modifications, possible to implement in these systems, in order to reduce the flow resistance, were also presented. The impact of the hydraulic resistance on the performance of the engine was discussed for the entire rotational speed range of the drive unit. Also the consequences of the proposed thermal-hydraulic analysis of the engine were discussed in this paper.