Natural circulation flow through water-in-glass evacuated tube solar collectors

Budihardjo, I.; Morrison, Graham; Behnia, Masud

doi:10.1016/j.solener.2007.03.002

Cited by 149 publications

(83 citation statements)

References 10 publications

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“…• In an integral all-glass collector, the solar-selective coated inner surface of a continguous inner glass tube within which the heat transfer fluid flow (Wang et al 1987(Wang et al , 1989Budihardjo et al 2007;Li et al 2010) • In a fluid-in-metal collector, a metal (usually copper) inner tube containing the heat transfer fluid (Window and Harding 1983;Window 1983;Zhigiang andHarding 1984, 1985;Harding and Zhiqiang 1985a, b) • A closed heat pipe (Tabassaun et al 1988). Several manifold arrangements for heat pipes are shown in Fig.…”

Section: Evacuated-tube Flat-plate Collectorsmentioning

confidence: 99%

Flat-Plate and Evacuated Tube Collectors

Norton¹

2013

Lecture Notes in Energy

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The sun has got his hat on Hip hip hip hooray! The sun has got his hat on, and he's coming out to play Gay and Butler (1932) 5.1 Overview Solar-energy collectors are devices employed to gain useful heat energy from the incident solar radiation. They can be of the concentrating or the flat-plate type. A simple flat-plate solar energy collector consists basically of an absorbing surface which absorbs the insolation and transmit it in form of heat to a working fluid commonly air or water. A general steady-state analysis for flat-plate collectors is shown in Fig. 5.1.Instantaneous efficiencies are plotted against (T fii ÀT a )/I and the intercept and the slope determined (7.1.5). The long-term performance of many solar heating collectors can be characterized by a thus determined intercept and slope as shown by the illustrative examples for different collector types given in Fig. 5.2. These parameters are not constant but depend on temperature and wind speed. Heat removed is also a weak function of overall heat loss. To account for these effects non-linear equations have been developed and together with an angular dependent "incident angle modifier" are used in various versions as the basis for rating tests. These are shown in Fig. 5.3.The absorber material in a flat-plate collector, in addition to having a high absorbance of the incident radiation should also have a low emissivity, good thermal conductivity, and be stable thermally under temperatures encountered during operation and stagnation. It should also be durable, have low weight per unit area and, most importantly, be cheap. Black coated metal sheets (in air heater) and fins in water heaters are used frequently as absorbers due to their effectiveness, ease of use, availability and relatively low cost. Wisely or not, a multitude of

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Section: Evacuated-tube Flat-plate Collectorsmentioning

confidence: 99%

Flat-Plate and Evacuated Tube Collectors

Norton¹

2013

Lecture Notes in Energy

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“…Este proceso de investigación llevó al desarrollo de un método que determina el tamaño y posición de la sombra sobre el área de cada tubo (Duffie y Beckman, 2013), se ha monitoreado el comportamiento típico del agua al interior de los tubos evacuados y en el precalentamiento (Budihardjo et. al., 2007).…”

Section: Introductionunclassified

Influencia del Angulo de Inclinación de los Tubos Solares Evacuados sobre la Temperatura del Agua

et al. 2015

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ResumenSe analizó el comportamiento de tubos evacuados ante la acción de la radiación solar incidente en la zona ecuatorial alto andina. Las pruebas se realizaron en cuatro días diferentes con tres declinaciones solares, cubriendo la época seca y la época lluviosa. Se trabajó con dos tubos evacuados, inclinados a 15º y 60º; 20º y 45º; 30º y 60º; 10º y 50º. Las mediciones demuestran que en las primeras horas del monitoreo la temperatura más alta del agua corresponde al tubo evacuado con el ángulo mayor y al acercarse el medio día el comportamiento cambia, a la inversa. Se concluye que para optimizar la incidencia de la radiación solar directa en el calentamiento de agua en la región ecuatorial se debe emplear tubos evacuados horizontales. Palabras clave: calentadores solares, ángulo de inclinación, colector solar, comportamiento térmico Effect of Tilt Angle of Evacuated Tubes on the Temperature of the Water AbstractThe behavior of solar evacuated tubes under the action of solar radiation in the Equator Andean high lands is presented. The tests were performed during four different days with three solar declinations, covering the dry season and the rainy season. In this study evacuated tubes at inclinations 15º and 60º; 20º and 45º; 30º and 60º; 10º and 50º were employed. The collected data shows that at the beginning of the monitoring experiment the highest temperatures was found for larger inclination angles. At noon, the behavior changes, to the inverse. It is concluded that solar evacuated tubes in the Equator Andean high lands must be in horizontal position to optimize the use of direct solar radiation.

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“…Investigações numéricas e experimentais foram realizadas para obtenção de uma correlação para a taxa de fl uxo de circulação natural em um coletor de tubos evacuados montado sobre um refl etor difuso por Budihardjo et al(2007). Neste trabalho, foi obtida a correlação da taxa de fl uxo de circulação natural em função da energia solar de entrada, da temperatura do reservatório, da inclinação do coletor e aspectos do tubo.…”

Section: Introductionunclassified