Convective Heat Transfer From a Desert Surface

The convective heat transfer relations for atmospheric flow over sparsely vegetated areas are reviewed and compared to existing relations for flow in rough ducts. Experimental convection coefficients obtained at four desert sites are compared to the analytical relations. The experimental equipment for measuring the heat transfer convection coefficient between air and ground in a desert environment consists of two electrically heated plates positioned flush with the ground. Measurements of power dissipation and surface temperatures allow direct calculation of the convection coefficient. The experimental heat transfer results are correlated with micrometeorological models from which a soil roughness height is calculated. This roughness parameter is shown to characterize air flow near the soil surface, and may be significantly different from the roughness parameter ordinarily determined from velocity profiles. A simplified heat transfer correlation is presented for desert surfaces.

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The Discrete Green's Function for Convective Heat Transfer—Part 1: Definition and Physical Understanding

Journal of Heat Transfer ◽

10.1115/1.4047515 ◽

2020 ◽

Vol 142 (10) ◽

Author(s):

John K. Eaton

Keyword(s):

Heat Transfer ◽

Green’S Function ◽

Convective Heat Transfer ◽

Convective Heat ◽

Green's Function ◽

Plate Boundary ◽

Direct Calculation ◽

Discrete Green’S Function ◽

The Matrix ◽

Flow Situation

Abstract The discrete Green's function (DGF) is a superposition-based descriptor of the relationship between the surface temperature and the convective heat transfer from a surface. The surface is discretized into a finite number of elements and the DGF matrix elements relate the heat transfer out of any element i to the temperature rise on every element j of the surface. For a given flow situation, the DGF is insensitive to the thermal boundary condition so it allows direct calculation of the heat transfer for any temperature distribution and noniterative solution of conjugate heat transfer problems. The diagonal elements of the matrix are determined solely by the local velocity field while the off-diagonals are determined by the spread of the thermal wake downstream of a heated element. An analytical DGF for the laminar flat-plate boundary layers is included as an example.

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Experimental Performance of Natural Convection of a Semitransparent Wall With Film Coating of a Cubic Enclosure Using Infrared Imaging

Advanced Energy Systems ◽

10.1115/imece2002-33152 ◽

2002 ◽

Cited By ~ 1

Author(s):

J. J. Flores ◽

G. Alvarez

Keyword(s):

Heat Transfer ◽

Convective Heat Transfer ◽

Convective Heat ◽

Infrared Imaging ◽

Convective Heat Transfer Coefficient ◽

Film Coating ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Experimental Heat ◽

Air Temperatures

This paper presents an experimental heat transfer study of the exterior side of a semitransparent wall (window) with film coating of a enclosure. The absorptance of the semitransparent wall with film coating was simulated using a film resistance on the glazing. A technique of infrared imagining thermography and a traversing system developed in Lawrence Berkeley National Laboratories (LBNL) were extended to measured from 1-D to 2-D local surface temperatures and boundary layer air temperatures of the exterior a glazing. From those measurements, the exterior heat flow and the exterior local convective heat transfer coefficients were calculated by applying a technique proposed by Truler [1]. The 2-D surface temperature distributions, the local convective heat transfer coefficient distributions and the average Nusselt number of the exterior side of the semitransparent wall with a simulated absorptance of 0.5 are presented.

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