Natural Convection in Collector Cavities With an Isoflux Absorber Plate

Schinkel, W. M. M.; Hoogendoorn, C. J.

doi:10.1115/1.3266339

Cited by 4 publications

(4 citation statements)

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“…From this important result it can be concluded that their results are also applicable to upward flow in meander type absorbers. For downward flow the heat loss was increased by more than 10 % compared to upward flow, which is in qualitative agreement with the results of both Hellström et al (1988) and Schinkel and Hoogendoorn (1983).…”

Section: Heat Transfer In Gaps With Non-isothermal Boundariessupporting

confidence: 92%

“…In one experiment the strips were kept at the same temperature by individual heating. Because of the temperature stratification within the gap, the lowermost strip suffered a 5 times higher heat loss than the uppermost, which is in qualitative agreement with the numerical results of Schinkel and Hoogendoorn (1983).…”

Section: Heat Transfer In Gaps With Non-isothermal Boundariessupporting

confidence: 87%

“…Based on the hypothesis that the discrepancies between simulations and test results are caused by disagreement of boundary conditions, a number of experimental and numerical investigations have been undertaken. Schinkel and Hoogendoorn (1983) kept the cool upper plate isothermal while the lower plate was heated with constant heat flux. They measured an 11 % higher heat loss compared to isothermal conditions.…”

Section: Heat Transfer In Gaps With Non-isothermal Boundariesmentioning

confidence: 99%

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Accurate analytical modeling of flat plate solar collectors: Extended correlation for convective heat loss across the air gap between absorber and cover plate

Eismann

2015

Solar Energy

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The well-established correlation of Hollands et al. (1976), which is applicable to isothermal boundaries and Rayleigh numbers up to 10 5 , underestimates the convective heat loss across the air gap of flat plate solar collectors with tube-and-sheet type absorbers both in normal operation and at stagnation. Two reasons for this discrepancy were identified. 1) The Rayleigh number of the air gap above absorbers with highly selective coatings can be three times as high as the application limit. 2) The absorber is not isothermal during normal operation. Based on a literature study and theoretical considerations the application limit of the correlation was extended to Ra = 3•10 5. By means of an analytically derived correction parameter, the correlation was adapted to non-isothermal boundary conditions. For the cost-and efficiency optimization of flat-plate collectors an accurate analytical model was developed, based on the model of Duffie and Beckman (1991), enhanced by the new correlation for convective heat loss between absorber and cover plate and further correlations presented by Eismann (2015).The model was validated against data of standardized collector tests. It is able to predict both the thermal efficiency and the stagnation temperature within the uncertainty limit of the standardized test method EN 12975-2 (CEN 2006).

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Section: Heat Transfer In Gaps With Non-isothermal Boundariessupporting

confidence: 92%

Section: Heat Transfer In Gaps With Non-isothermal Boundariessupporting

confidence: 87%

Section: Heat Transfer In Gaps With Non-isothermal Boundariesmentioning

confidence: 99%

See 1 more Smart Citation

Accurate analytical modeling of flat plate solar collectors: Extended correlation for convective heat loss across the air gap between absorber and cover plate

Eismann

2015

Solar Energy

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“…The experimental setup consisted of two isothermal (cold and hot) plates of 0.2 • 0.3 m with variable distances. It has been described extensively in previous papers, Schinkel [15], [17] and [18]. Flow visualisation experiments and laser doppler anemometer measurements [17] were done to determine the effect of ~ on flow.…”

Section: Experimental Methodsmentioning

confidence: 99%

Core stratification effects on natural convection in inclined cavities

Schinkel

Hoogendoorn

1985

Appl. Sci. Res.

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A numerical and experimental study has been made on the flow and heat transfer in inclined air-filled cavities with aspect ratios 1-18 at Ra numbers from 2.104-5 9 105 and angles of inclination from 40 to 90 o. Core stratification influences the flow. Due to this there arises a torque with two components depending on angle of inclination. On basis of the two torques the computed effects on flow and temperature fields can be explained. For the heat transfer a scaling law could be derived. Experimental data validate the numerical studies.

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Numerical study of a ventilated facade panel

Mootz

Bézian

1996

Solar Energy

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Abstract-An energy-saving facade panel for non-residential buildings has been numerically investigated. Structured like a composite TrombeeMichel wall, the panel consists of a glazing, an absorber plate and insulation and contains a dead air space between glazing and absorber, as well as a convection channel between absorber and insulation. The influence of convection channel spacing on both recovery of solar energy during sunshine periods and on heat losses during night hours has been assessed. Two different options have been considered. First, the total panel thickness was maintained, which involves an increase of channel spacing having to be compensated by a corresponding decrease of the insulation thickness. Then, this constraint was removed so that an increase in channel spacing was allowed to entail an equivalent increase of the total panel thickness. The results indicate that large spacing favors energy recovery during sunshine periods for both options and reduces, although only slightly. heat losses during night hours for the second option. In the case of the first option, however, these losses tend to grow when channel spacing increases.

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Natural Convection in Collector Cavities With an Isoflux Absorber Plate

Cited by 4 publications

References 0 publications

Accurate analytical modeling of flat plate solar collectors: Extended correlation for convective heat loss across the air gap between absorber and cover plate

Accurate analytical modeling of flat plate solar collectors: Extended correlation for convective heat loss across the air gap between absorber and cover plate

Core stratification effects on natural convection in inclined cavities

Numerical study of a ventilated facade panel

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