A set of correlations for predicting the temperatures of inner and outer surfaces of the glass-cover of flat-plate solar collectors with single glazing is developed, enabling estimation of the heat-transfer coefficients. The temperatures of the inner surface of the glass-cover (Tgi) and outer surface of glass-cover (Tgo) are computed using the proposed relations and the results are compared with those obtained by numerical solution of heat balance equations. Using the proposed relations maximum computational errors in Tgi and Tgo are within 1.5 degrees and 3.0 degrees respectively: for the range of glass-cover thicknesses 3 mm to 5 mm.(Using the previously available relation in the literature computational error in glass-cover temperature is 9 to 11 degrees.) As a result the maximum errors in calculation of convective and radiative heat-transfer coefficients between the absorber-plate and the glass-cover are reduced from about 8.8 percent to 1.1 percent and from 3.7 percent to 0.5 percent respectively. With such low errors in computation of the heat-transfer coefficients, numerical solution of heat balance equations is not required. The proposed method can also take into account absorption in the glass-cover.

1.
Buchberg
H.
,
Catton
I.
, and
Edwards
D. K.
,
1976
, “
Natural Convection in Enclosed Spaces—A Review of Application to Solar Energy Collection
,”
ASME JOURNAL OF HEAT-TRANSFER
, Vol.
98
, No.
2
, pp.
182
188
.
2.
Duffle, J. A., and Beckman, W. A., 1991, Solar Engineering of Thermal Processes, Second Edition, John Wiley and Sons, New York,
3.
Francey
J. L.
, and
Papaioannou
J.
,
1985
, “
Wind-Related Heat Losses of a Flat-Plate Collector
,”
Solar Energy
, Vol.
35
, No.
1
, pp.
15
19
,
4.
Hollands
K. G. T.
,
Unny
T. E.
,
Raithby
G. D.
, and
Konicek
L.
,
1976
, “
Free Convective Heat-Transfer Across Inclined Air Layers
,”
ASME JOURNAL OF HEAT TRANSFER
, Vol.
98
, pp.
189
192
.
5.
Mullick
S. C.
, and
Samdarshi
S. K.
,
1988
, “
An Improved Technique for Computing the Top Heat Loss Factor of Flat-Plate Collector With a Single Glazing
,”
ASME JOURNAL OF SOLAR ENERGY ENGINEERING
, Vol.
110
, pp.
262
267
.
6.
Nagar
V. K.
,
Vaishya
J. S.
, and
Bhide
V. G.
,
1984
, “
Emittance from Stagnation Temperature Study
,”
Solar Energy
, Vol.
32
, No.
5
, pp.
633
636
.
7.
Swinbank
W. C.
,
1963
, “
Long-Wave from Clear Skies
,”
Quarterly Journal of Royal Meteorological Society
, Vol.
89
, p.
339
339
.
This content is only available via PDF.
You do not currently have access to this content.