The 4th order Runge-Kutta method allowed the numerical solution of the system of equations governing the collector loop. The development of a program for computing the thermodynamic properties of the working fluids was necessary for the theoretical analysis of the cooling cycle.

• Results and discussion

It is obvious that the global performances of the studied system depend on the levels of temperature of the heat sources and sinks (Coefficient of Performance of the endoreversible cooling system) and the efficiency of the solar collector.

The theoretical parametric study of the three heat reservoir cooling system showed the influence:

— of the site (Algiers (north algeria), Hassi-Messaoud, Tamanrasset (south algeria))

— of the geometrical parameters of the collector (thickness of the absorber, spacing between tubes, diameter of tubes) and of the characteristics of material of the absorber.

— of the nature of the working fluid (R134-a and R123).

As shown in Figures 5, 7, 8, 9, the performances obtained with the refrigerant R123 are sharply better than those obtained with the R134-a but the coefficient of performance COPF, Q remains relatively low for both fluids compared to conventional cooling systems. For an ambient temperature of 40°C and a cold reservoir temperature of 0°C, the coefficient of performance COP varies from 0.1 to 0.6 in average.

R 134a

(XY) I 31 M ar 2004 T TSV Fig.4 The cooling load vs the solar time for different sites (R134a)

TSV

R123

03

R123

TSV Fig.7 The cooling power ys the solar time for different sites (R123, mean day)

R134a

(XY) I 31 Mar 20 04T TSV Fig.6 The cooling power ys the solar time for different sites (R134a, mean day)

SHAPE * MERGEFORMAT

(XY) I 31 Mar2004 l’

TAMANRASSET 24 AOUT (jour moyen) Latitude 22 47′ N TSV

TAMANRASSET 24 AOUT (jour clair) Latitude 22 47′ N TSV Fig.8′ The cooling power vs the solar time for different working fluids

• Conclusion

The main objective of this paper is to present the results of theoretical performances of a solar powered ejector cooling system using R123 or R134a as the working fluid. We have developed a program that allows calculation of the cooling power. It is maily composed of four subroutines computing the solar radiation, the thermodynamic properties of working fluids, the vapour driving massflowrate and the cooling power respectively.

The parametric study, based on the cycle analysis, shows the influence of the working fluid, the site, the day, the ejector geometry, the solar collector type, the system configuration, etc…

In the comparative study of the cooling performances for the two working fluids, it comes out to be the R123 which leads to better results. The cooling power is about 4 kW in average. However, due to the low massflowrate at the collector exit, the coefficient of performance is relatively low for both fluids compared to conventional cooling systems. That makes this cycle more suitable for air conditioning applications than refrigeration but one can for example, use it with hybrid cycles to improve the efficiency of conventional [4] and non conventional refrigeration systems.