Solar refrigeration (1986)
Type of ContentTheses / Dissertations
Thesis DisciplineChemical and Process Engineering
Degree NameDoctor of Philosophy
PublisherUniversity of Canterbury
AuthorsPrasad, Tadipatri Srinivasashow all
Solar refrigeration is a natural application of solar energy as the demand and supply match very well. Electrolux refrigerators have considerable appeal as solar driven devices because they do not require any electrical connections or mechanical drivers. The aim of the present investigation was to develop a solar refrigeration system based on an Electrolux refrigerator.
Because of the lack of adequate information two Electrolux refrigerators were tested and their performances evaluated. The optimum generator temperature and the optimum generator energy input were 175°c and 100 W respectively.
The temperatures required by an Electrolux refrigerator are beyond the range of most flat plate collectors. A novel hybrid nontracking collector was developed in which the desirable characteristics of a flat plate heat pipe solar collector are used in conjunction with a semi-cylindrical reflector and a special glazing arrangement to achieve a collector which works in the range suitable for the Electrolux system.
A detailed computer model of the collector was developed to predict the performance curve of several versions of the basic collector design. Two collectors were fabricated, the second one incorporating several improvements over the first one. The second panel attained a stagnation temperature of 215°c as against the model prediction of 222°c, at an insolation of 946 W.m-2 and an ambient of 26°c. With the heat transfer oil circulating, the collector attained a thermal efficiency of 21% at an average oil temperature of 147°c.
In order to link the collector with the refrigerator, the latter had to be modified. A jacket with internal fins was fitted to the generator tube and the performance of the refrigerator operating on hot oil was evaluated. At a generator temperature of 144°c and an ambient of 14°c it attained a real COP of 0.47 with the freezer operating at -9°c and cabinet at 2.5°c.
The collector was then linked to the refrigerator and the heat losses from various parts of the system were evaluated. Only 16% of the total energy input to the system was utilized by the refrigerator, while the rest was lost to the surroundings via the secondary circuits used in the measurements. Recommendations are made to reduce the heat losses and to link the collector to the refrigerator in different ways.