| dc.description.abstract | An experimental intermittent solar refrigerator
using ammonia-water as the refrigerant-absorbent
combination and powered by two flat-plate collectors
has been designed, fabricated and tested under
outdoor conditions in Nairobi, Kenya. The research
was conducted in order to study the performance of
the system in the Kenyan climate and to determine the
prospects of the system in the climatic region. It
was also carried out with a view of investigating how
variations in the initial solution mass, the initial
ammonia concentration in the solution and the final
generator temperature affect the system performance.
The generator-absorber consisted of two copper
flat-plate collectors, each having eight 12.7 mm
diameter steel furniture tubes soldered onto it at
100 mm intervals and glazed by two glass covers. The
total effective collecting surface area of the two collectors was 1.463 m2. The condenser-evaporator
was a one shell pass, one tube pass, multi-tube
vertical heat exchanger, with condensation-inside the
tubes .and refrigerant storage in the-condenser tubes.
The condenser was water cooled.
Tests were performed with different
concentrations in the range 0.35 to 0.58 kg NH / 9
kg solution with different solution masses. System
parameters during regeneration and refrigeration
proceses were measured, and the cooling effect and
the system coefficient of performance computed.
The maximum generator temperature attained was
100°C with an initial solution mass of 10.65 kg and
an initial concentration of 0.37 kg NH9/kg solution.
Cooling ratios in the range of 0.24 to 0.49 were
obtained and the overall coefficient of performance
was found to be in the range of 0.07 to 0.17. The
effective cooling per unit area of collector surface
per day for the experimental refrigerator was in the
2 range of 825.4 kJ/m , for an initial solution
concentration of 0.37 kg NH /kg solution and initial ;)
solution mass of 10.65 kg, to 2463.4 kJ/m2
for an
initial solution concentration of 0.58 kg NH /kg 1)
solution and initial solution mass of 13.8 kg, for
clear sunny days.
The results obtained herein compare favourably
with those obtained by El-Shaarawi and Ramadan (1986)
from their investigation carried out in Egypt, which
is an example of a tropical climatic region. Hence
the good performance of the system demonstrates the
applicability of the system in the Nairobi climatic
conditions. Although the performance is limited by
the characteristics of the intermittent cycle as
compared to the continuous cycles, the simplicity of
the unit makes it adequate for use in small household
and other food chillers in the rural areas where
there is no electricity | en |
