Natural Convection and Radiation Heat Loss from Open Cavities of Different Shapes and Sizes Used with Dish Concentrator

Numerical three dimensional studies of the combined natural convection and radiation heat loss from downward facing open cavity receiver of different shapes is carried out in this paper. The investigation is undertaken in two categories: same inner heat transfer area and aperture area (case I) and same aspect ratio and aperture area (case II). These studies are carried out for five isothermal wall temperatures (523 to 923 K in steps of 100K). The effect of inclination is studied for seven inclinations from 0° (cavity aperture facing sideways) to 90° (cavity aperture facing down), in steps of 15°. The cavity shapes used are: cylindrical, conical (frustum of a cone), cone-cylindrical (combination of frustum of cone and cylindrical shape), dome-cylindrical (combination of hemispherical and cylindrical shape), hetro-conical, reverse-conical (frustum of a cone in the reverse orientation) and spherical. For both cases, conical cavity yields the lowest convective loss among the cavities investigated whereas spherical cavity results in the highest convective loss. Convective heat loss from cavities of different shapes and sizes are characterized by using different internal zone areas of the cavity (Acw, Acz, Acb and Aw). Acb is found to be better parameter for characterization of the convective heat loss. Nusselt number correlation is developed using convective zone area (Acb). It correlates 91% of data within ±11% deviation, 99% of data within ±16% deviation. Radiative losses (Qrad) have been determined numerically from cavities of both cases. The ratio of Qrad/Aap is found to be more or less constant (variation within 5%) for all types of cavities and for 0 ? epsilon ? 1. Thus radiative loss is dependent on aperture area and effective emissivity of cavity rather than the shape of the cavity. Further, it also matches well with the analytical formula based on effective emissivity.

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Three-dimensional analysis and numerical optimization of combined natural convection and radiation heat loss in solar cavity receiver with plate fins insert

Energy Conversion and Management ◽

10.1016/j.enconman.2015.05.061 ◽

2015 ◽

Vol 101 ◽

pp. 757-766 ◽

Cited By ~ 23

Author(s):

L.C. Ngo ◽

T. Bello-Ochende ◽

J.P. Meyer

Keyword(s):

Natural Convection ◽

Heat Loss ◽

Dimensional Analysis ◽

Numerical Optimization ◽

Three Dimensional ◽

Radiation Heat ◽

Radiation Heat Loss

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Numerical Simulation of Natural Convection in Solar Cavity Receivers

Journal of Solar Energy Engineering ◽

10.1115/1.4029106 ◽

2015 ◽

Vol 137 (3) ◽

Cited By ~ 12

Author(s):

James K. Yuan ◽

Clifford K. Ho ◽

Joshua M. Christian

Keyword(s):

Experimental Investigation ◽

Natural Convection ◽

Heat Loss ◽

Convective Heat ◽

Heat Losses ◽

Thermal Engineering ◽

Convective Heat Loss ◽

Software Packages ◽

Receiver Model ◽

Cubical Cavity

Cavity receivers used in solar power towers and dish concentrators may lose considerable energy by natural convection, which reduces the overall system efficiency. A validated numerical receiver model is desired to better understand convection processes and aid in heat loss minimization efforts. The purpose of this investigation was to evaluate heat loss predictions using the commercial computational fluid dynamics (CFD) software packages fluent 13.0 and solidworks flow simulation 2011 against experimentally measured heat losses for a heated cubical cavity receiver model (Kraabel, 1983, “An Experimental Investigation of the Natural Convection From a Side-Facing Cubical Cavity,” Proceedings of the ASME JSME Thermal Engineering Joint Conference, Vol. 1, pp. 299–306) and a cylindrical dish receiver model (Taumoefolau et al., 2004, “Experimental Investigation of Natural Convection Heat Loss From a Model Solar Concentrator Cavity Receiver,” ASME J. Sol. Energy Eng., 126(2), pp. 801–807). Simulated convective heat loss was underpredicted by 45% for the cubical cavity when experimental wall temperatures were implemented as isothermal boundary conditions and 32% when the experimental power was applied as a uniform heat flux from the cavity walls. Agreement between software packages was generally within 10%. Convective heat loss from the cylindrical dish receiver model was accurately predicted within experimental uncertainties by both simulation codes using both isothermal and constant heat flux wall boundary conditions except when the cavity was inclined at angles below 15 deg and above 75 deg, where losses were under- and overpredicted by fluent and solidworks, respectively. Comparison with empirical correlations for convective heat loss from heated cavities showed that correlations by Kraabel (1983, “An Experimental Investigation of the Natural Convection From a Side-Facing Cubical Cavity,” Proceedings of the ASME JSME Thermal Engineering Joint Conference, Vol. 1, pp. 299–306) and for individual heated flat plates oriented to the cavity geometry (Pitts and Sissom, 1998, Schaum's Outline of Heat Transfer, 2nd ed., McGraw Hill, New York, p. 227) predicted heat losses from the cubical cavity to within experimental uncertainties. Correlations by Clausing (1987, “Natural Convection From Isothermal Cubical Cavities With a Variety of Side-Facing Apertures,” ASME J. Heat Transfer, 109(2), pp. 407–412) and Paitoonsurikarn et al. (2011, “Numerical Investigation of Natural Convection Loss From Cavity Receivers in Solar Dish Applications,” ASME J. Sol. Energy Eng. 133(2), p. 021004) were able to do the same for the cylindrical dish receiver. No single correlation was valid for both experimental receivers. The effect of different turbulence and air-property models within fluent were also investigated and compared in this study. However, no model parameter was found to produce a change large enough to account for the deficient convective heat loss simulated for the cubical cavity receiver case.

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Numerical Simulation of Natural Convection in Solar Cavity Receivers

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91064 ◽

2012 ◽

Author(s):

James K. Yuan ◽

Clifford K. Ho ◽

Joshua M. Christian

Keyword(s):

Heat Flux ◽

Natural Convection ◽

Heat Loss ◽

Convective Heat ◽

Heat Losses ◽

Flat Plates ◽

Convective Heat Loss ◽

Software Packages ◽

Receiver Model ◽

Cubical Cavity

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Numerical Investigation of Convective Heat Loss from Upward Facing Cavity Receivers of Different Shapes at Different Inclinations and Temperatures

Journal of Energy and Environmental Sustainability ◽

10.47469/jees.2019.v08.100082 ◽

2019 ◽

Vol 8 ◽

pp. 7-11

Author(s):

Shivam Kumara ◽

Dadasaheb Jagannath Shendageb ◽

Prafulla Doke b ◽

Shireesh Balwant Kedare a ◽

Shridhar Laxman Bapat

Keyword(s):

Numerical Investigation ◽

Heat Loss ◽

Convective Heat ◽

Convective Heat Loss ◽

Different Shapes

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Conjugate Effects of Heat and Mass Transfer on Natural Convection Flow along an Isothermal Sphere with Radiation Heat Loss

Open Journal of Fluid Dynamics ◽

10.4236/ojfd.2013.32012 ◽

2013 ◽

Vol 03 (02) ◽

pp. 86-94 ◽

Cited By ~ 1

Author(s):

Salina Aktar ◽

Mahmuda Binte Mostafa Ruma ◽

Md. Abdul Alim

Keyword(s):

Mass Transfer ◽

Natural Convection ◽

Heat And Mass Transfer ◽

Heat Loss ◽

Convection Flow ◽

Radiation Heat ◽

Natural Convection Flow ◽

Radiation Heat Loss

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Effects of pressure work on natural convection flow around a sphere with radiation heat loss

Nonlinear Analysis Modelling and Control ◽

10.15388/na.15.3.14324 ◽

2010 ◽

Vol 15 (3) ◽

pp. 287-298

Author(s):

T. Akhter ◽

M. A. Alim

Keyword(s):

Natural Convection ◽

Heat Loss ◽

Nonlinear Partial Differential Equations ◽

Convection Flow ◽

Radiation Heat ◽

Natural Convection Flow ◽

Local Skin ◽

Pressure Work ◽

Boundary Layer Equations ◽

Radiation Heat Loss

The effects of pressure work with radiation heat loss on natural convection flow on a sphere have been investigated in this paper. The governing boundary layer equations are first transformed into a non-dimensional form and the resulting nonlinear partial differential equations are then solved numerically using finite-difference method with Keller-box scheme. We have focused our attention on the evaluation of shear stress in terms of local skin friction and rate of heat transfer in terms of local Nusselt number, velocity as well as temperature profiles. Numerical results have been shown graphically and tabular form for some selected values of parameters set consisting of radiation parameter Rd, pressure work parameter Ge, surface temperature parameter θw and the Prandtl number Pr.

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