Computation of surface radiation and natural convection in a heated horticultural greenhouse

Mezrhab, Ahmed; Farh, Larbi El; Naji, Hassane; Lemonnier, Denis

doi:10.1016/j.apenergy.2009.05.017

Cited by 20 publications

(24 citation statements)

References 10 publications

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“…The isotherms and streamlines are shown for various numbers of tubes (1≤Nt≤7) located in the bottom of greenhouse and for a Rayleigh number in the range 10 3 ≤Ra≤10 6 . We have seen that the shape of the arc largely explains the undulating profile of the air circulation inside the greenhouse, which directly affects the variations in air temperature and streamlines.…”

Section: Nb Ofmentioning

confidence: 99%

“…On the other hand, average Nusselt higher in 3D calculations, but still they are smaller compared to flat top enclosures. Mezrhab et al [6] reported on the computation of surface radiation and natural convection in a heated horticultural greenhouse. Results were reported in terms of isotherms, streamlines and average Nusselt number for Rayleigh number in the range 10 3 -10 6 .…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Natural Convection With Heated Tubes in Tunnel Greenhouse

Slatni

Djezzar

Messai³

2021

Journal of Thermal Engineering

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In this research, a numerical study was carried out on heat transfer by natural convection, in a closed tunnel greenhouse, in the range of the Rayleigh number (10 3 ≤Ra≤10 6 ). Were considered in the study, the number of heating tubes used (1≤Nt≤7), which were equidistant inside the greenhouse volume, when the bottom at an average temperature and cold Roof. The governing equations written in a bicylindrical coordinates were discretized using the finite volume method and vorticity-stream function formulation; the resulting algebraic equations were solved using successive over relaxation method (S.O.R). First, the effect of the Rayleigh number on heat transfer was examined for a fixed number of tubes as reference (Nt = 3) and the number of tubes was varied to investigate the influence on heat transfer in the greenhouse. Finally, the results obtained were summarized in the form of isotherms and streamlines, and for the average Nusselt number profile; in addition to the horizontal and vertical velocities and temperatures. However, in the reference case, for low Rayleigh numbers, the heat transfer is dominated by pure conduction.With the increase of the Rayleigh number and the number of tubes Nt, the natural convection becomes more dominant and the heat transfer increases, and in general the heat transfer increase with the increasing number of tubes.

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Section: Nb Ofmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Natural Convection With Heated Tubes in Tunnel Greenhouse

Slatni

Djezzar

Messai³

2021

Journal of Thermal Engineering

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“…Velusamy et al [6] performed a numerical study of the interaction effects of surface radiation with turbulent natural convection of a transparent medium in rectangular enclosures, covering a wide range of Ra numbers from 10 9 to 10 12 and aspect ratios of 1-200. Mezrhab et al [7] studied the problem of surface radiation and natural convection in heated greenhouses. In their work, it was found that the overall heat transfer within the greenhouse increases with the rise in the value of Rayleigh number.…”

Section: Introductionmentioning

confidence: 99%

Natural Convection Coupled with Radiation Heat Transfer in Slanted Square and Shallow Enclosures Containing an Isotropic Scattering Medium

Zhang

Ming

et al. 2015

Numerical Heat Transfer, Part A: Applications

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A finite-volume method (FVM) is used to address combined heat transfer, natural convection, and volumetric radiation with an isotropic scattering medium, in a tilted shallow enclosure. Numerical simulations are performed in the in-house fluid flow software GTEA. All the results obtained by the present FVM agree very well with the numerical solutions in the references. The effects of various influencing parameters such as the Planck number (0.0001 Pl 10), the scattering albedo (0 x 1), the inclination angle (À60 a 90 ), and aspect ratio (1 AR 5) on flow and heat transfer have been numerically studied. For a constant Pl number, flow is slightly intensified at the midplane as the Ra number increases from 10 6 to 5 Â 10 6 . As the scattering albedo increases, the effect of radiation heat transfer decreases on both slanted and horizontal enclosures. In positive tilt angles, the influence of a on heat transfer is quite remarkable. The highest Nu rad appears at a ¼ 30 (x ¼ 1)and 0 (x ¼ 0, 0.5), whereas Nu rad is maximum at a ¼ À 15 (x ¼ 1) and À45 (x ¼ 0, 0.5). At a ¼ À15 , the maximum and minimum values of Nu rad are presented for x ¼ 0, AR ¼ 1 and x ¼ 1, AR ¼ 5.

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“…Within the last decades, convection problems in cavities which are combined with internal or external heating have attracted much interest from researchers. The internal flow, according to the natural convection inside cavities, is particularly complex because of the interaction between the thermal boundary layer (near the cavity walls) and other fluid parts, where it has been studied numerically and experimentally due to various practical applications [1][2][3][4][5][6]. According to previous studies, natural convection that is combined with internal or external heating has many applications, such as solar energy collection-Singh and Eames [7], building and ventilation-DeBlois et al [8], cooling of electronic equipment-Bairi et al [9], and nuclear reactors-Tseng et al [10], and in many other applications.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Numerical Simulation of 2D Natural Convection in an Inclined Cavity with Internal Heat Generation Using Differential Quadrature Method

Alesbe

Aljabair

Jalil

2021

Walailak J Sci & Tech

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Natural laminar convective fluid flow has been simulated inside inclined rectangular cavities with and without internal heat generation for different aspect ratios and inclination angles. The most important basic dimensionless parameters for this problem are the external Rayleigh number (RaE) and the internal Rayleigh number (RaI), where RaE refers to the effects of the differential heating of the side walls and RaI refers to the amount of heat produced internally. Results were obtained for 4 cases with 192 tests: case (1), RaI = 0 without internal source generation, and cases (2, 3, and 4) with internal source generation for RaI = RaE, 10 RaE, and 100 RaE, respectively. In all cases, the parameters of study changed as 103 ≤ RaE ≤106, 0 ≤ RaI ≤ 107, inclination angle from 0 to 60 deg., and aspect ratios of the enclosure from 0.5 to 2. Results were represented graphically for flow and thermal fields as a streamline, isothermal contours, and Nusselt number. The computed results show that the strength of convection currents is measured by the internal energy. Finally, it is illustrated that by using a few grid points and a shorter CPU time for calculation, the present method can produce accurate numerical results. Also, increase in RaI leads to increasing heat transfer rate and its direction out from the cavity at both hot and cold walls. For lower values of RaI, heat transfer diffusion is more prominent, while for higher values of RaI, convection outweighs diffusion. HIGHLIGHTS Natural laminar convective fluid flow inside inclined rectangular cavities with and without internal heat generation for different aspect ratios and inclination angles has been simulated The most important basic dimensionless parameters, the external Rayleigh number (RaE) and the internal Rayleigh number (RaI) are studied DQ method performance was excellent The obtained computational results indicate that the strength of the convection currents depends on the internal energy Accurate numerical results can be obtained by the present method using a few grid points and shorter CPU time for calculation GRAPHICAL ABSTRACT

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Computation of surface radiation and natural convection in a heated horticultural greenhouse

Cited by 20 publications

References 10 publications

Numerical Investigation of Natural Convection With Heated Tubes in Tunnel Greenhouse

Numerical Investigation of Natural Convection With Heated Tubes in Tunnel Greenhouse

Natural Convection Coupled with Radiation Heat Transfer in Slanted Square and Shallow Enclosures Containing an Isotropic Scattering Medium

An Efficient Numerical Simulation of 2D Natural Convection in an Inclined Cavity with Internal Heat Generation Using Differential Quadrature Method

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