BSME-ASME International Conference on Thermal Engineering
31 December 2001 – 2 January 2002, Dhaka
Optimal Performance of an Endo-reversible Solar Driven
Sorption Refrigeration System
K.C.A. Alam and M. M.A. Sarker
Department of Mathematics,
Bangladesh University of Engineering and Technology
Dhaka-1000, Bangladesh
Abstract:
This article deals with the thermodynamic optimization of a solar driven sorption
refrigeration system. An externally irreversible but internally endo-reversible model has
been emp loyed to analyze the optimum conditions of a sorption cooling system driven by
a solar collector. The operating conditions for maximum refrigeration load are
determined. It is shown that the system gives its highest capacity if the thermal
conductances of the heat exchangers are distributed properly. Results also show that
optimum refrigeration load increases with the increase of collector stagnation and
required room temperature increase and decreases as the ratio of collector size to the
cumulative size of all four heat exchangers increases. It may also see that the optimal
thermal conductance of the evaporator expands with the expense of the optimal thermal
conductance of solar collector as collector stagnation temperature, refrigerated room
temperature increase.
1. Introduction
In recent years, heat driven sorption refrigeration system have drawn considerable
attention due to its lower environmental impact and large energy saving potential.
Another interesting feature of this system is that, the chiller/heat pump can be operated
by thermal heat such as waste heat from industries or by solar heat. From this context, a
number of researchers investigated the performance of sorption heat pumping/
refrigeration system driven by waste heat or by renewable energy sources. Among these,
for solar cooling, worked by Pons and Guilleminot(1986 ), Zhang and Wang (1997) for
automobile cooling and Saha et. al (2000), Alam et. al. (200a,b) for waste heat utilization.
While the feasibilty of the system performance has been studied, the investigation on
optimum design of a heat driven refrigeration system is scare. In 1993, Sokolov and
Hersagal (1993) apply optimization techniques to optimize the system performance of a
solar driven year round ejector refrigeration. Vargas
et. al. (1996) investigated the
optimal condition for a refrigerator driven by solar collector considering the three heat
transfer irreversibilites. Later, Chen and Schouten (1998) discussed the optimum
performance of an irreversible absorption refrigeration cycle in which three external heat
transfer irreversibilities have been considered.
Recently, Alam et. al. (2001) modeled and optimized a solar driven endo-reversible
adsorption refrigeration system by considering the four heat transfer irrevesibilities. In
that article, authors showed that the maximum refrigeration effect could be achieved by
allocating the heat exchangers inventory properly. They also showed that the optimal
thermal conductance of the heat exchangers that take heat from the heat source is almost
equal to the thermal conductance of the heat exchangers that release to the external
ambient. In the present study, the model of Alam et. al. (2001) has been utilized to
investigate the optimum refrigeration load in different conditions. The primary objective
of this study is to determine the optimum allocation of thermal conductancee between the
collector and evaporator.
2. Mathematical Model
The main components of a solar driven sorption refrigeration system are a solar collector,
a desorber, a sorber, a condenser and an evaporator, as shown in Fig. 1. In a sorption
cycle, the working fluid execute a cycle and exchange heat to the heat exchange
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