The principle of working an ordinary solar ice maker
Solar Icemaker operates in two modes ,first mode works in the day and second one in the night.
During the day, solar energy is used to generate liquid ammonia refrigerant.
During the night, the generator is cooled and ice is formed in the evaporator compartment as ammonia is reabsorbed to the generator.
Operation of the Intermittent Ammonia-water System
The operation of the intermittent aqua-ammonia system can be divided into two phases.
The regeneration phase
During the regeneration phase heat is supplied to the generator-absorber which contains an ammonia solution of high concentration, As the solution is heated the pressure rises and once condensation pressure is reached ammonia distills off and condenses in the evaporator-condenser which is immersed in a bucket of water, Fig. 2.1
The refrigeration phase
During the refrigeration phase the heat source is removed and the generator-absorber is allowed to cool. The pressure drops and the ammonia starts evaporating drawing heat from the surroundings thus producing cooling. The weak ammonia solution in the generator-absorber absorbs the evaporated ammonia and the process continues until all the ammonia in the condenser is evaporated, Fig. 2,2,
It consists of a solar collector, a condenser/heat-exchanger and an evaporator that is placed in a refrigerator box.
The inside of the collector is lined with an adsorption bed packed with activated carbon absorbed with methanol.
The refrigerator box is insulated and stocked with aluminum trays filled with water. The activated carbon can adsorb a large amount of methanol vapor in ambient temperature and desorbs it at a higher temperature (around 100 degrees C).
The schematic diagram of the solar refrigeration system is shown in Fig.1
The procedure of working of the solid-adsorption ice-maker
It also works in two modes i.e. the day mode and night mode.
During the daytime, the sunshine irradiates the collector, so the collector is heated up and the methanol is desorbed from the activated carbon. In desorption, the liquid methanol adsorbed in the charcoal heats up and vaporizes. The methanol vapor condenses and is stored in the evaporator
At night, the collector temperature decreases to the ambient temperature, and the charcoal adsorbs the methanol from the evaporator.
The liquid methanol in the evaporator vaporizes and adsorbs the heat from the water contained in the trays.
The methanol evaporates at a temperature of about –10 degrees C, so the water temperature can be as low as –5 degrees C and becomes icy.
The ice maker operates in an intermittent way to produce the refrigerating effect.