10.07.2015   EUROSUN 2008

Discharging processes

DTf • T + T

J. 1^*0 )

fCPf TT = mCPf (T — To ) + ha-f[3] [4]a (Ta —

m

dt

2

(eq.13)
Подпись: m Подпись: dt Подпись: 2 Подпись: (eq.13)

The differential equation governing the heat transfer into the fluid during the discharging process is given by equation 13.

Time (s)

Fig.6: Comparison between experience (interface absorber/polymer (o) and outlet (□) temperatures) and simulation (interface absorber/polymer (—) and outlet (—) temperatures) in discharging process
Подпись: Time (s) Fig.6: Comparison between experience (interface absorber/polymer (o) and outlet (□) temperatures) and simulation (interface absorber/polymer (—) and outlet (—) temperatures) in discharging process

This expression links the outlet temperature to the absorber temperature via a heat transfer coefficient hf-a calculated previously during preliminary absorber efficiency test (hf-a=70 W. m-2.K-1). Entering the experimental conditions (mass flow of 40L. h-1 and inlet temperature of 298 K) we obtain the profile temperatures plotted in figure 6.

G

Solar global irradiation (W. m-2)

h

Heat transfer coefficient (W. m-2.K-1)

m

Mass flow (kg. s-1)

m

Mass (kg)

T

Temperature (K)

Greek symbols

a

Absorbance

T

Transmittance

X

Thermal conductivity (W. m-1.K-1)

є

Emissivity

n

Efficiency

p

Reflectivity

Subscript

amb

Ambiant

c

Composite

e

End

f

Fusion, Fluid

i

Inlet

in

Initial

l

Liquid

o

Outlet

s

Solid

sky

Sky

Acknowledgement

Saunier Duval industry part of Vaillant Group and the French Government (trough the ANRT) are

acknowledged for financial support.

References

[1] J. Tey, J. I. Rosell, M. Ibanez, R. Fernandez, “Solar collector with integrated storage and transparent insulation cover”, poster at Eurosun 2002, Bologna, Italy, June 2002.

[2] Y. Rabin, I. Bar-Niv, E. Korin, B. Mikic, Integrated solar collectors storage system based on a salt hydrate phase change material, Solar Energy, Vol.55, No 6, pp. 435-444, 1995.

[3] D. Haillot, X. Py, V. Goetz, M. Benabdelkarim, Storage composite for the optimisation of solar water heating systems, Chemical Engineering Research and Design, Vol.86, Issue 6, pp. 612-617, 2008.

[4] Installations solaires thermiques et leurs composants — Capteurs solaires — partie 2: Methode d’essai, Norme europeenne prEN 12975-2, 2005.

[5] D. Faiman, Towards a standard method for determining efficiency of integrated collector-storage solar water heaters, Solar Energy, Vol. 33, No. 5, pp. 459-463, 1984.

[6] J. Duffie, W. Beckman, Solar engineering of thermal processes, Third edition, Wiley, 2006.

[7] J. Bernard, Energie solaire calculs et optimisation, Ellipses, 2004.

[8] C. Plantier, Etude numerique et experimental d’un prototype de chauffe eau solaire equipe d’un stockage a chaleur latente, these de doctorat, universite de Savoie, 2005.