The design, construction and testing of a solar operated refrigeration unit

Abstract

The project consisted of the design, construction, and testing of an exclusively solar operated refrigeration unit. Direct application of solar energy to refrigeration involved the use of an intermittent absorption refrigeration system. Design specifications were:-

1/8 ton of refrigeration at - 200C evaporator temperature refrigeration process to last 3 hours. Ambient temperature variation from 200C to 350C. Minimum generation period of 3 hours. For the unit, the design procedures to meet system specifications have been explained, and component fabrication processes outlined.

Due to availability of ammonia gas, ammonia-water combinations of concentrations ranging from 0.48 to 0.70 were used. Tests were carried out to measure the refrigeration temperatures obtainable, when a solar concentrator is used, for an all solar simple absorption refrigeration unit having an air cooled condenser and absorber.

Tests were initially carried out with electrical heating to simulate solar insulation. In some of these tests, a constant power was applied throughout the generation period whereas in others, the power was varied during experimentation. Later, actual generation with solar insulation was carried out, and the results of the two generation methods compared.

System parameters during refrigeration and regeneration processes were measured, and the cooling effect computed and discussed.

Poor rectification, low values of solar intensities, poor vapor condensation, together with the non-provision of auxiliary equipment on the unit e.g. pumps etc, were noted as setbacks to reasonable system performance. Improvements to such a system have been recommended.