irradiance, inlet concentration of the solution, and ambient humidity. There is an optimum flow rate for a
particular length of collector where the rate of evaporation is maximum. A high wind speed reduces
evaporation especially at the higher ambient humidity ratios. The experimental results showed a
regeneration efficiency varying between 38 and 67%. and the corresponding cooling capacities ranged from
31 to 72 kW (8.8 to 20 tons).
Erhard and Hahne (1997) built a solar cooling machine for demonstration purposes. The main principal part
of the device is an absorber / desorber unit which is mounted inside a concentrating solar collector. The
working pair consists of NH3 and &Cl?. The overall COP of the cooling system had been calculated as
0.049, using data of 1994. In 1995, a better overall COP (0.045-0.082) was attained. Their simulation
program was a highly capable tool for the planning of solid absorption cooling machines and their
components.
Bansal et al., (1997), designed and fabricated a solar cooling unit on solid-vapour intermittent absorption
system, which utilises thermal energy supplied by the heat pipe vacuum tube solar collectors through
thermosyphonic flow water. The unit of I .5 kWh/day cooling capacity uses ammonia as a refrigerant and
IMPEX material (80% SKI2 and 20% Graphite) that has high heat and mass transfef coefficient as well as
high absorption capacity. Theoretical maximum overall COP of the unit was 0.143, and it depends upon the
climatic conditions. Under field conditions, it was found that if the maximum daytime ambient temperature
was 30°C and night-time temperature 20°C. The overall COP was found to be only 0.081.