The perforated nature of nets makes it impossible to measure the thermal radiative properties (emittance, εn, transmittance, τn, and reflectance, ρn) correctly by using any measuring device under natural conditions. In this study, a theoretical model was developed and validated to predict εn, τn, and ρn precisely by solving the model equations simultaneously. The net was tacked onto a wooden frame; thermal radiation balance was applied below and above the net surfaces and above a black substrate underneath the frame. The downward and upward thermal radiation fluxes were measured below and above the net to be used as input parameters to the simulation. Nets with different porosities (ϕ) and colors were used for the study. The results showed that the estimated εn ranged from 0.41 to 0.82 and τn ranged from 0.16 to 0.55 for the nets tested, whereas the reflectances were very low (ρn0.08). The color and porosity together affect the properties of the net. Even though under equilibrium conditions of a net with the surrounding environment, the emittance of the net is equal to its absorptance. However, the absorbed thermal radiation by the net dose not equal to the emitted radiation and the difference is a convected heat.

References

References
1.
Soni
,
P.
,
Salokhe
,
V. M.
, and
Tantau
,
H. J.
,
2005
, “
Effect of Screen Mesh Size on Vertical Temperature Distribution in Naturally Ventilated Tropical Greenhouses
,”
Biosyst. Eng.
,
92
(
4
), pp.
469
482
.
2.
Castellano
,
S.
,
Scarascia
,
G. M.
,
Russo
,
G.
,
Briassoulis
,
D.
,
Mistriotis
,
A.
,
Hemming
,
S.
, and
Waaijenberg
,
D.
,
2008
, “
Plastic Nets in Agriculture: A General Review of Types and Applications
,”
Appl. Eng. Agric.
,
24
(
6
), pp.
799
808
.
3.
Briassoulis
,
D.
,
Mistriotis
,
A.
, and
Eleftherakis
,
D.
,
2007
, “
Mechanical Behavior and Properties of Agricultural Nets, Part I: Testing Methods for Agricultural Nets
,”
Polym. Test.
,
26
(
6
), pp.
822
832
.
4.
Briassoulis
,
D.
,
Mistriotis
,
A.
, and
Eleftherakis
,
D.
,
2007
, “
Mechanical Behavior and Properties of Agricultural Nets, Part II: Analysis of the Performance of the Main Categories of Agricultural Nets
,”
Polym. Test.
,
26
(
8
), pp.
970
984
.
5.
Sethi
,
V. P.
,
Dubey
,
R. K.
, and
Dhath
,
A. S.
,
2009
, “
Design and Evaluation of Modified Screen Net House for Off-Season Vegetable Raising in Composite Climate
,”
Energy Convers. Manage.
,
50
(
12
), pp.
3112
3128
.
6.
Hemming
,
S.
,
Swinkels
,
G. L. A. M.
,
Castellano
,
S.
,
Russo
,
G.
, and
Scarascia
,
G. M.
,
2008
, “
Numerical Model to Estimate the Radiometric Performance of Net Covered Structure (AGRONETS)
,”
AgEng2008 Agricultural and Biosystems Engineering for a Sustainable World
, Crete, Greece, June 23–25, pp.
23
25
.
7.
Castellano
,
S.
,
Russo
,
G.
, and
Scarascia
,
G. M.
,
2006
, “
The Influence of Construction Parameters on Radiometric Performances of Agricultural Nets
,”
ISHS Acta Horticulturae International Symposium on Models for Plant Growth, Environmental Control and Farm Management in Protected Cultivation (HortiModel 2006)
, Vol.
718
, pp.
283
290
.
8.
Castellano
,
S.
,
Candura
,
A.
, and
Scarascia
,
G. M.
,
2008
, “
Relationship Between Solidity Ratio, Color and Shading Effect of Agricultural Nets
,”
ISHS Acta Horticulturae International Symposium on High Technology for Greenhouse System Management: Greensys2007
, Vol.
801
, pp.
253
258
.
9.
Castellano
,
S.
,
Hemming
,
S.
, and
Russo
,
G.
,
2008
, “
The Influence of Color on Radiometric Performances of Agricultural Nets
,”
ISHS Acta Horticulturae,
801
, pp.
227
236
.
10.
Abdel-Ghany
,
A. M.
, and
Al-Helal
,
I. M.
,
2011
, “
Analysis of Solar Radiation Transfer: A Method to Estimate the Porosity of a Plastic Shading Net
,”
Energy Convers. Manage.
,
52
(
3
), pp.
1755
1762
.
11.
Al-Helal
,
I. M.
, and
Abdel-Ghany
,
A. M.
,
2011
, “
Measuring and Evaluating Solar Radiative Properties of Plastic Shading Nets
,”
Sol. Energy Mater. Sol. Cells
,
95
(
2
), pp.
677
683
.
12.
Abdel-Ghany
,
A. M.
, and
Al-Helal
,
I. M.
,
2012
, “
Modeling Approach for Determining Equivalent Optical Constants of Plastic Shading Nets Under Solar Radiation Conditions
,”
Adv. Mater. Sci. Eng.
,
2012
, p.
158067
.
13.
Picuno
,
P.
,
Tortora
,
A.
, and
Capobianco
,
R. L.
,
2011
, “
Analysis of Plasticulture Landscapes in Southern Italy Through Remote Sensing and Solid Modeling Techniques
,”
Landscape Urban Plann.
,
100
(
1–2
), pp.
45
56
.
14.
Papadakis
,
G.
,
Briassoulis
,
D.
,
Scaracia
,
G. M.
,
Vox
,
G.
,
Feuilloley
,
P.
, and
Stoffers
,
J. A.
,
2000
, “
Radiometric and Thermal Properties of, and Testing Methods for, Greenhouse Covering Materials
,”
J. Agric. Eng. Res.
,
77
(
1
), pp.
7
38
.
15.
Nijskens
,
J.
,
Deltour
,
J.
,
Coutisse
,
S.
, and
Nisen
,
A.
,
1985
, “
Radiation Transfer Through Covering Materials, Solar and Thermal Screens of Greenhouses
,”
Agric. For. Meteorol.
,
35
, pp.
229
242
.
16.
Sica
,
C.
, and
Picuno
,
P.
,
2008
, “
Spectro-Radiometrical Characterization of Plastic Nets for Protected Cultivation
,”
ISHS Acta Horticulturae International Symposium on High Technology for Greenhouse System Management: Greensys2007
, Vol.
801
, pp.
245
252
.
17.
Andersson
,
N. E.
, “
Properties of Thermal Screens Used for Energy Saving in Greenhouses
,” http://www.pure.agrsci.dk:8080/fbspretrieve/4247455/REF403.pdf
18.
Kotey
,
N. A.
,
Wrigh
,
J. L.
, and
Collins
,
M. R.
,
2008
, “
Determining Long Wave Radiative Properties of Flat Shading Materials
,”
3rd SBRN and SESCI 33rd Joint Conference
,
Fredericton, NB
,
Canada
.
19.
Abdel-Ghany
,
A. M.
, and
Al-Helal
,
I. M.
,
2014
, “
Methods for Determining the Temperature of a Plastic Net Under Solar and Thermal Radiation Conditions
,”
Sol. Energy Mater. Sol. Cells
,
125
(
6
), pp.
1
7
.
20.
Abdel-Ghany
,
A. M.
,
Ishigami
,
Y.
,
Goto
,
E.
, and
Kozai
,
T.
,
2006
, “
A Method for Measuring Greenhouse Cover Temperature Using a Thermocouple
,”
Biosyst. Eng.
,
95
(
1
), pp.
99
109
.
21.
Gentle
,
A. R.
,
Dybdal
,
K. L.
, and
Smith
,
G. B.
,
2013
, “
Polymeric Mesh for Durable Infra-Red Transparent Convection Shields: Applications in Cool Roofs and Sky Cooling
,”
Sol. Energy Mater. Sol. Cells
,
115
(
8
), pp.
79
85
.
22.
Compaq Visual Fortran,
1999
, “
Professional Edition, Software Package
.”
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