Abstract
The paper aims at establishing the theoretical efficiencies of flat plate solar thermal collector with improved properties regarding the absorption and the transparency of the collector plate and that of the transparent element. The paper presents the thermal balance equations corresponding to the plate of the solar collector and to its transparent element. The mathematical model developed was implemented in an automated computational tool and it was used in order to determine the energy performance. The graphical variation of the efficiencies as a function of the outdoor parameters offers a synthetic image of the energy performance for this type of solar collectors.
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- tm :
-
Average temperature of the thermal agent in the flat plate solar thermal collector (oC)
- te :
-
Outdoor temperature (oC)
- tE :
-
The sol-air temperature (oC)
- I:
-
Global intensity of solar radiation (W/m2)
- αap :
-
Absorption coefficient of the absorption plate, in visible spectrum (-)
- αag :
-
Absorption coefficient of the glazing, in visible spectrum (-)
- αrg :
-
Reflexing coefficient of the glazing, in visible spectrum (-)
- τ:
-
Glass transparency (-)
- αi :
-
Convection coefficient inside the pipe for the thermal agent [W/(m2 K)]
- αe :
-
Convection coefficient outside the solar panel [W/(m2 K)]
- ki :
-
Descending heat transfer coefficient of the solar panel [W/(m2 K)]
- ks :
-
Upward heat transfer coefficient of the solar panel [W/(m2 K)]
- qs :
-
Surface specific heat flux for the upward of the solar panel (W/m2)
- qi :
-
Surface specific heat flux for the downward of the solar panel, (W/m2)
- l:
-
Half the distance between two consecutive pipes of the solar panel (m)
- di :
-
The inside diameter of the solar panel pipes (m)
- de :
-
Outside diameter of the solar panel pipes (m)
- Rc :
-
Contact thermal resistance between the pipes and the absorbent panel, (m K/W)
- λp :
-
Thermal conductivity of the absorbent panel [W/(mK)]
- δp :
-
Width of the absorbent panel (m)
- δiz :
-
Width of the insulation layer (m)
- λiz :
-
Thermal conductivity of the insulation layer [W/(mK)]
- εp :
-
Emissivity of the absorber panel (-)
- εg :
-
Emissivity of the glazing (-)
- tg :
-
Glazing temperature (oC)
- tp :
-
Absorber panel temperature (oC)
- S:
-
The flat plate solar thermal collector surface (m2)
- αcv :
-
Convective heat transfer coefficient between panel and glass [W/(m2K)]
- αr :
-
Radiant heat transfer coefficient between panel and glass [W/(m2K)]
- αpg :
-
Radiant and convective coefficient between panel and glass [W/(m2K)]
- φI :
-
Heat flux incident on the solar panel (W)
- φU :
-
Heat flux absorbed by the thermal agent (W)
- Φo :
-
Optic flux loss (W)
- F′:
-
Geometric-structural factor for the solar panel (-)
- β:
-
Outdoor parameter, ratio between the average logarithmic difference of the temperatures and the solar intensity radiation (m2 K/W)
- γ:
-
Temperature difference ratio (-)
- η:
-
The efficiency of the flat plate solar thermal collector (%)
- kc :
-
Heat loss global coefficient of the flat plate solar thermal collector (W/m2 K)
- kc1 :
-
The first heat loss global coefficient of the flat plate solar thermal collector (W/m2 K)
- kc2 :
-
The second heat loss global coefficient of the flat plate solar thermal collector (W2/m4 K2)
References
Duffie, J. A., & Beckman, W. A. (1980). Solar engineering of thermal processes. New York: Wiley.
Iordache, F. (2010). Energy aspects of the thermal device and systems in buildings. Bucharest: Conspress (in Romanian).
Iordache, F. (2014). Flat plate solar thermal collectors. Energy aspects—revista romana de inginerie civila—2014 (in Romanian).
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© 2014 Springer International Publishing Switzerland
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Iordache, F., Iordache, V. (2014). Efficiency of the Flat Plate Solar Thermal Collector. In: Visa, I. (eds) Sustainable Energy in the Built Environment - Steps Towards nZEB. Springer Proceedings in Energy. Springer, Cham. https://doi.org/10.1007/978-3-319-09707-7_20
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DOI: https://doi.org/10.1007/978-3-319-09707-7_20
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Publisher Name: Springer, Cham
Print ISBN: 978-3-319-09706-0
Online ISBN: 978-3-319-09707-7
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