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Evaluation of thermal performance factor for solar air heaters with artificially roughened channels

Siddique Waseem, Raheem Aneeq, Aqeel Muhammad, Qayyum Sualeh, Salamen Tareq, Waheed Khalid, Qureshi Kamran

Archive of Mechanical Engineering

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2021

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LXVIII, nr 2

195--225

EN

Heat transfer augmentation has become the utmost industrial desire. Turbulence promoters seems to be a better option for better heat transfer but at the expense of enormous pressure drop. In the current study, experimental optimization of heat transfer and pressure drop in various configurations of ribbed and corrugated surfaces on the bottom wall of the Solar Air Heater channel, having aspect ratio of 26:5 was performed. The results were evaluated in terms of enhancement in heat transfer (Nu/Nu s), friction factor ratio (f/f s) and thermal performance factor ( η). Three different cases and nine configurations with a pitch to rib/corrugation height ratio of 4.0 were studied. Case A consists of a smooth, continuous square rib, inline and staggered broken ribs. Case B comprises 30°, 45°, 60° and 90° trapezoidal corrugated geometries while Case C is the comparison of smooth, wavy corrugated and the best configurations of cases A and B. The results show that rectangular duct with staggered broken ribs and trapezoidal corrugation at 45° are the best configurations for case A and B, respectively. The 45° corrugated configuration is the best one amongst all, with values of 1.53, 1.5 and 1.33% for Nu/Nu s, f/f s and η respectively.

2

Modeling of thermal processes in the solar air heater

Zhelykh V., Kozak C.

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

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2014

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Z. 20 (170)

285--289

EN

The article sets out the place of solar energy in the world today. There are provided basic advantages and disadvantages of air quality heat capacity for solar heating system. Data for modeling heat flow system with passive energy use have been presented. Discussed methodology allows to determine the thermal characteristics of the air in the collector of the passive use of solar energy.

RU

Определено энергетическое положение в мире в настоящее время. Поданы основные преимущества и недостатки воздуха в качестве теплоносителя для солнечной системы отопления. Представлены данные по применению теории графов для моделирования тепловых потоков в пассивном солнечном воздухонагревателе. Приведена методика определения тепловых характеристик воздушного гелиоколлектора с пассивным использованием солнечной энергии.

3

Analysis of Heat Flow Distribution in the Room with Installed

Kozak C., Savchenko O., Zhelykh V.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

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2014

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T. 45, nr 9

359--362

EN

Regression equations are presented for finding the temperature of the heated air stream in a thermosiphon solar collector according to the intensity of the heat flux, the area of the collector holes and the inclination angle. It is proved that the greatest influence on relative temperature of the air stream has the angle of solar heater installation. The effectiveness of the flow turbulators installed along the coolant flow in the solar collector air channel is assessed. Availability of turbulators can improve the efficiency of the solar collector by 13%, as compared to a flat heat-absorbing plate.

PL

Przedstawiono równania regresji określające temperaturę strumienia ogrzanego powietrza w termosyfonowym kolektorze słonecznym w zależności od gęstości strumienia ciepła w obszarze otworów kolektora i jego kąta nachylenia. Zostało udowodnione, że największy wpływ na wartość względnej temperatury strumienia powietrza ma kąt montażu grzejnika słonecznego. Przedstawiono oszacowanie skuteczności turbulizatorów przepływu zainstalowanych wzdłuż przepływu powietrza chłodzącego w kanale kolektora słonecznego. Dostępność turbulizatorów może poprawić sprawność kolektora słonecznego o 13% w stosunku do płaskiej płyty absorbującej ciepło.